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Spectroscopic properties of gamma irradiated TiO2 doped lithium phosphate glasses
Abstract
Optical absorption spectra of undoped and TiO2-doped lithium phosphate glasses were measured before and after successive gamma irradiation. Undoped lithium phosphate glasses show strong UV absorption, while TiO2-doped samples exhibit surplus two broad visible bands due to the presence of Ti3+ ions in predominant ratio. Gamma irradiation produces UV and visible induced bands but the presence of TiO2 seems to cause some shielding effects towards successive gamma irradiation. Infrared absorption spectral measurements indicate the presence of characteristic phosphate groups and the effect of gamma irradiation is limited to small changes in the intensities of some absorption bands. The experimental results are interpreted on the bases of current views on the structure of the studied host glass in relation to properties studied.
... Vanadium ions are accepted to be able to exist in three valence forms in glasses, namely the trivalent, tetravalent and pentavalent states [10,21,22]. The trivalent vanadium (V 3+ ) ions exist in distorted octahedral coordination with oxygens and exhibit two characteristic absorption bands at 350-400 nm and 580-600 nm. ...
... The extra visible peak at 580 nm can be related to the presence of trivalent vanadium. These results are also identified in V 2 O 5 -doped sodium borate glass [21]. Upon gamma irradiation, no distinct changes in the observed peaks before irradiation and no extra induced bands are observed. ...
... Upon gamma irradiation, no distinct changes in the observed peaks before irradiation and no extra induced bands are observed. This result indicates that the presence of vanadium ions is assumed to cause some shielding effect towards gamma irradiation as observed in vanadium ions doped in various glasses [10,21]. ...
Optical and FT infrared absorption spectroscopic studies were carried out to investigate the spectral properties of prepared undoped and 3d transition metal oxides-doped-strontium borate glasses. The same measurements were repeated after gamma-irradiation of the samples with a dose of 8 Mrad (8 10 4 Gy). The undoped strontium borate glass before irradiation exhibits a broad strong UV absorption which is related to unavoidable trace iron (Fe 3+ ions) impurities contaminated within the raw materials used for the preparation of this glass. Examination of the optical spectra of TMs-doped glasses reveals extra characteristic UV-visible bands due to the respective doping 3d transition metal ions. Gamma irradiation of the undoped strontium borate glass produces induced defects within the UV and visible regions while the TMs-doped glasses reveal limited variations due to shielding effects of some TM ions in this specific host strontium borate doped glasses towards gamma irradiation. Infrared absorption spectra of the prepared glasses reveal characteristic vibrational bands due to both triangular and tetra-hedral borate groups within the wavenumber range 1200-1600 cm-1 and 800-1200 cm-1 , respectively. The addition of 3d TM dopants (0.2 %) causes no distinct variations in the main IR vibrational bands because of the low level of TM ions and their housing in the glass network structure as modifiers. Also, gamma irradiation causes no changes in the number or position of the main characteristic IR vibration bands due to the quite stability of the base glass containing high content of heavy metal (Sr 2+) cations.
... Li 2 CO 3 in low and high ceramic glaze acts as a common ingredient. ZnO performs as a cross-linker among different phosphate ions during the initiation of hydration reaction [4,5]. By the addition of lithium carbonate and zinc oxide, the breakage of P-O-P bonds and creation of non-bridging oxygen atoms occur, which increase significantly the chemical durability of prepared glasses [6][7][8][9][10]. ...
The transition metal ion-doped lithium phosphate glasses are prepared with a novel composition by melt quenching method, XRD patterns revealed their characteristic amorphous nature. The structural and physical properties of the prepared glasses are significantly varying with the increased concentration levels of dopant. Optical absorption and transmission spectra of the glass samples are analyzed. The absorption peaks are observed in ultraviolet, visible and infrared regions.The direct and indirect energy band gap values are decreasing while Urbach's energy values are increasing as the concentration levels of dopants are increasing. The obtained energy band gap values are in the range of semiconductor materials. The optical transmission spectra of these transition metal ion-doped glasses reveal their application as bandpass filters with filtering ability in UV or Visible regions at double and triple wavelengths and hence useful as dual band-pass filters. The glasses with <10 full width half maximum(FWHM) values are useful for narrowband lasers.
... It is worth mentioning that despite the absence of boron in the sample B0, the appearance of peaks in the range from 800 to 1400 cm À1 might be due to the interlocking between the peaks of phosphate and boron [33], while the band at about 1600 cm À1 is related to PeOeH bridges [34]. ...
Preparation of LiTi2(PO4)3 (NASICON-type) glass ceramic from LiF.(2-x)TiO2.xB2O3.P2O5 system were achieved via melt-quenching technique. The effect of gradual replacement of Ti⁴⁺ ions with B³⁺ ions was investigated. The prepared samples were characterized using differential thermal analysis, X-ray diffraction, Fourier transform infrared spectroscopy and High-Resolution transmission electron microscope. The results revealed crystallization of LiTi2(PO4)3 as the major phase with traces of Li2TiF6 phase in the quenched samples. The quantities of these phases decreased with increasing B³⁺ ions until x = 1; beyond this value, B2O3 and β-Li4B2O5 were the dominant phases. After heat treatment at 800 °C/2 h, pure LiTi2(PO4)3 was detected till x = 1 then BPO4 appeared and increased with increasing B³⁺ ion. At x = 2, pure BPO4 was achieved. TEM revealed nanocrystalline size for the formed phase. In deduction, the substitution of Ti⁴⁺ ions by B³⁺ ions in the glass matrix improved the dc-conductivity at room temperature from 1.29 × 10⁻¹⁰ Ω⁻¹ cm⁻¹ in boron-free sample to 3.41 × 10⁻³ Ω⁻¹ cm⁻¹ for x = 2 sample due to the precipitation of β-Li4B2O5 in addition to B2O3. However, after heat treatment free boron sample (B0) showed the highest dc-conductivity at room temperature ∼1.23 × 10⁻⁴ Ω⁻¹ cm⁻¹ and lowest activation energy 0.032 eV. Therefore, the high conductivity, low activation energy and high diffusion coefficient (1.8 × 10⁻⁷ cm²/s) suggesting the use of the prepared materials in Li-ion battery applications.
... Also, the same behavior was observed for the refractive index. According to Singh et al. [19] assumed that the decrease in optical band gap and increasing behavior in both Urbach and refractive index were correlated to the structural changes occurred as a result of different site occupation in the building structure of the glass network [18,[30][31][32]. The and Bi 3+ allows increasing the growth of non-bridging oxygens instead of bridging oxygen that causes the shift in the valence band to high energy and reduces the energy gap and increases the Urbach energy and refractive index. ...
The current research focuses on studying the photoluminescence and phosphorescence performance of some types of undoped zinc borosilicate glasses together with BaO or Bi2O3. The effects of addition transition metal oxide (MnO2) and/or rare—earth oxide (Sm2O3) on the behavior of mentioned characteristics were also studied. The glasses were prepared through the usual method of melt and annealing technique. X-ray diffraction (XRD) analysis proved the amorphous nature of the prepared glasses. The optical properties including the absorption in the UV–Visible NIR region and estimation of the optical band gap, Urbach energy, and refractive index have been studied. Both undoped zinc borosilicate and BaO glasses exhibit UV absorption and Bi2O3 doped glass exhibit an extended near—visible absorption. The characteristic absorption bands of MnO2—doped glasses in the visible region beside UV absorption were identified while the extended absorptions in the NIR region appeared for glasses containing Sm2O3. According to the progressive changes in the optical absorptions, variations in the optical parameters (Eopt, ∆E, n) were identified depending on the composition. The photoluminescence measurements revealed characteristic emissions of MnO2 and/or Sm2O3. The prepared glasses show good photoluminescence responses that gave the chance to estimated the phosphorescence performance of the prepared glasses. The phosphorescence measurements show different emissions related to reddish orange emission. The CIE chromaticity coordinates also indicated the appearance of a clear observable reddish orange color produced as a result of phosphorescence in the presence of MnO2 and/or Sm2O3 as a dopant in the glass matrix. The FTIR measurements represent the building structure of the studied glass network. Both tetrahedral BO4 and triangle BO3 beside SiO4 groups were shared as the basic building blocks of the glasses. Heavy metal ions Ba²⁺ and Bi³⁺ show characteristic changes in the FTIR absorption which reflect their effect on the building structure. The thermal properties of the prepared glasses have been identified by differential thermal analysis (DTA) and thermal expansion measurements. The thermal analysis was correlated to the change of heavy metal ion Ba²⁺ or Bi³⁺ in the glass network and indicating the crystallization conductance of the prepared glasses.
... In addition to that, phosphate glasses are fascinating materials to accommodate with other modifier such as oxide materials [3]. One of the disadvantages of phosphate glass is poor chemical durability which can be addressed by the addition of transition metal oxides like chromium oxide [4,5]. They persist in broad arenas of structural probabilities and their physical and chemical properties leads to technological applications like polymer composites and solid state lasers [6,7]. ...
Cr ³⁺ metal ion doped Zinc-Lead-Lithium-Phosphate glass samples are made by melt quenching technique, by varying 0.2% mol (20-x) Li 2 CO 3-x Cr 2 O 3 in glass mixture composition. To identify basic structural units in these glasses, to investigate structural changes with the change in glass composition and to relate structural changes with the difference in properties of glasses, the samples subjected to spectral studies of XRD, UV-vis, EPR and FTIR. The physical properties of the glass samples like average molecular weight, Cr ³⁺ ion concentration, density, refractive index etc, were calculated. Spin-Hamiltonian parameters are evaluated from EPR spectra which exhibit two resonance intense signals representing coupled pair and free state of Cr ³⁺ ions. The breakage of Phosphorous - Oxygen - Phosphorous (P-O-P) link and the development of cross ionic bonding among the chains of phosphate are identified in FTIR spectra. From optical absorption spectra, crystal field parameters and optical band gap values have been calculated. The optical band gap value of the prepared phosphate glasses is found to lie in the range 1.60-1.63 eV, which fined immediate applications in the fabrication of ultra high speed Integrated circuits, IR photon detectors and thin films.
... The two glasses containing only MoO 3 as dopant ions show extra or additional distinct UV band at 380-390 nm within the optical spectra of the two systems containing MgO or MgF 2 . [29][30][31][32] that the additions of the transition metal ions caused changes in the building structure of the glass network. In more detail view, additions of trivalent or divalent metal ions are assumed to allow the breakdown of bridging oxygens in the glass network with forming new non-bridging oxygens (NBOs). ...
Glasses from the two basic systems (Na2O–P2O5–MgO) and (Na2O–P2O5–MgF2) doped with either MoO3 or MnO2 or both of them were obtained by melting–annealing method. Characterization of both the optical and FTIR spectra for the prepared glasses were carried out together with deriving the optical band gaps and refractive indices. DTA and thermal expansion properties were investigated to reach suitable nucleation and crystallization temperatures to convert the glasses to their corresponding glass–ceramic derivatives. X-ray diffraction investigations of the glasses were primarily done to confirm their amorphous nature and then to identify the formed crystalline phases formed upon controlled thermal heat treatment with two step regime within the glass–ceramic derivatives. Optical spectra of the studied glasses reveal distinct UV absorption bands due to contaminated trace iron impurities together with the appearance of characteristic absorption bands due to molybdenum or manganese ions or both in the mixed dopants samples. FTIR spectral data indicate the appearance of vibrational peaks of phosphate groups with the interference of MgO4, MgF2 or PO3F groups. The dopants cause minor effects on the FTIR spectra. DTA and thermal expansion data support the voluminous crystallization behavior and indicating the different roles of MgO than MgF2 as reflected on the identified crystalline phases. In MgO containing glass–ceramics, the identified crystalline phase is sodium magnesium phosphate of the formula (Na3Mg2P2O16) while with MgF2–glass, two crystalline phases are identified: sodium magnesium pyrophosphate (Na2MgP2O7) beside sodium magnesium fluoride crystalline phase (NaMgF3). This refers to the compactness of the network of glasses with MgO due to its refractoriness and possibility of the formation of structural MgO4 groups. On the other hand, MgF2, is assumed to act in glass during crystallization as efficient nucleating agent as CaF2 and it is assumed to lower the melting temperature and ease of crystallization.
... Due to large band gap [3][4][5], the indium oxide thin films also appear to be quite promising material for the development of gamma radiation sensors and dosimeters. On passing through any metal oxide thin film, gamma radiation produces structural defects such as colour centres, oxygen vacancies, grain size and grain boundary modifications [6][7][8][9][10][11][12]. Correspondingly, the defect density undergoes a change that depends upon the level of the gamma irradiation. ...
Effects of gamma irradiations on structural and electrical properties of the post-annealed indium oxide thin films of thickness 750 nm, prepared by thermal evaporation in vacuum, were studied. The thin films, exposed to various levels of the gamma radiation dose, were characterized by XRD, SEM and I-V measurements. Results show that the average grain size and the degree of crystallinity increase with the gamma radiation dose up to a certain dose and decrease thereafter. Results also show that the conductivity Increases with the gamma radiation dose up to the same value of the dose and decreases thereafter. The dislocation density, however, shows the opposite trend of the dose dependence.
... The irradiation effect generates changes in the optical properties of glasses in the form of creation of some new induced absorption bands. In recent times a chain of studies have been accounted on γ-irradiation effect on diverse types of glasses such as soda lime phosphate, cabal, bioglass, borosilicate, lithium borate and phosphate glasses [13][14][15], where intrinsic defects are found due to occurrence of dopants or impurity in the glass. The www.ijntr.org ...
... Indeed, if ionizing radiation strikes glasses, physical properties may alter remarkably. Among the possible changes, color centers have great significance [19,25,26]. However, G T is the sole sample without considerable change in appearance. ...
In this study, the parent photosensitive glass and glass-ceramic in the system of lithium silicate containing AgCl under radiation of ultraviolet (UV) light were successfully prepared by melting process. Besides, the effects of adding TiO2 and P2O5 as nucleating agents on the solarization and crystallization of lithium silicate photosensitive glass were studied. The characteristics of the samples were identified by ultraviolet-visible absorption spectroscopy (UV-Visible), simultaneous thermal analysis (STA-TG/DTA), X-ray powder diffraction (XRD), and scanning electron microscopy (SEM). The results showed that adding P2O5 in the amount of 2 wt.% to this system could be an acceptable nucleating agent, while adding 4 wt.% TiO2 to it resulted in shielding behavior against the UV light. Therefore, this amount of TiO2 is not successful in both solarization improvement and nucleation process. In addition, lithium disilicate crystalline phase formed only in the samples containing P2O5.
... EPR, UVeVIS and FTIR spectroscopies are very useful experimental techniques because they can provide valuable information related to the local symmetry, nature of the chemical bonds and other structural properties of glasses (Wong & Angell, 1976). Glasses doped with transitional metal ions (TMI) attract much attention because of their interesting electrical (Abd El All and Ezz-Eldin, 2010;Bahgat, Makram, Shaisha, & El-Desoky, 2010;Sankarappa, Devidas, Kumar, Kumar, & Kumar, 2009; Santi c, Kim, Day, & Mogu s-Milankovi c, 2010), optical (Ghoneim, Marzouk, Daoud, & Ezz-Eldin, 2013;Kesavulu, Chakradhar, Muralidhara, Rao, & Anavekar, 2010;Moustafa, Fayad, Ezz-Eldin, & El-Kashif, 2013;Muralidhra, Kesavulu, Rao, Anavekar, & Chakradhar, 2010;Subhadra and Kistaiah , 2010) and magnetic properties (Elahdal, Antar, Mahmoud, & Ezz-Eldin, 2011;Kumar, Kishan, Rao, & Awana, 2010;Nagarjuna, Venkatramaiah, Satyanarayana, & Veeraiah, 2009;Pascuta, Borodi, Popa, Dan, & Culea, 2010;Pascuta, Bosca, Borodi, & Culea, 2011;Singh & Srinivasan, 2010). These properties are determined by the presence of TMI in multivalent states, by the environment of TMI as well as by the TMI content and its distribution in the glass matrix. ...
Combined optical, FTIR and photoluminescence spectra of varying Sm3+ ions in NaF–AlF3–phosphate glasses were investigated before and after successive gamma irradiation. Optical (UV–visible) absorption of the base undoped glass reveals UV absorption which becomes broadened and strong with progressive gamma irradiation. The UV absorption of the undoped glass is related to unavoidable trace iron impurity (Fe3+) contaminated within the chemicals used for its preparation. Upon gamma irradiation, ferrous ions present in noticeable percent within the impurity due to the reducing nature of phosphate glass interact with positive holes during the irradiation process and are transformed to ferric ions through photochemical reactions and the additionally formed Fe3+ ions impart their characteristic strong absorption in the UV region. Sm3+ containing glasses show characteristic small peaks arranged into two regions from about 350 to 900 nm and from about 1000 to 1600 nm. Such absorption peaks are more distinct with the increase of Sm2O3 content. Most of the limited number of absorption peaks are due to transitions from the 6H5/2 level to the various excited 2s+1LJ levels. The majority of the transitions in the spectra are assumed to originate from induced electric dipole (ED) interactions with the selection rule ∆J≤6. The intense band 6P3/2←6H5/2 around 25,000 cm−1 (~400 nm) is spin-allowed. The emission spectra of Sm2+ ions were recorded under the excitation wavelength of 402 nm for all prepared Sm2O3-containing glasses. The photoluminescence spectra show four emission lines, of which three consist of strong bands while the last line is a weak band. The wavelengths of the four luminescence peaks occur at about 560, 596, 642 and 702 nm and they are assigned to transitions from 4G5/2 to 6H5/2, 6H7/2, 6H9/2 and 6H11/2, respectively. The intensity of the emission spectra is observed to increase with the increase of Sm2O3 content. The optical spectra within the visible–near IR region and photoluminescence spectra of Sm2O3-doped glasses are found to be stable and show almost no variations after gamma irradiation especially when rare-earth ions are present in noticeable contents (1–3%). FTIR spectra of all the studied glasses reveal repetitive and characteristic vibrational bands mainly due to phosphate groups with abundant of Q2 and Q3 groups due to the high content of P2O5 (70 mol%). The introduction of 10% NaF and 20% AlF3 is observed to cause formation of mixed fluorophosphate groups (PO3F)2−. The formation of (AlPO)4 and/or (AlPO6) groups needs further justification by combined techniques. The increase of Sm2O3 content to 3% causes obvious increase of the IR absorption bands within the wavenumbers range of about 850–1400 cm−1 due to suggested depolymerization effect. Gamma irradiation causes no distinct variations in the FTIR spectra due to suggested compactness through the formation of additional structural groups from AlF4 or AlF6.
... EPR, UVeVIS and FTIR spectroscopies are very useful experimental techniques because they can provide valuable information related to the local symmetry, nature of the chemical bonds and other structural properties of glasses (Wong & Angell, 1976). Glasses doped with transitional metal ions (TMI) attract much attention because of their interesting electrical (Abd El All and Ezz-Eldin, 2010;Bahgat, Makram, Shaisha, & El-Desoky, 2010;Sankarappa, Devidas, Kumar, Kumar, & Kumar, 2009; Santi c, Kim, Day, & Mogu s-Milankovi c, 2010), optical (Ghoneim, Marzouk, Daoud, & Ezz-Eldin, 2013;Kesavulu, Chakradhar, Muralidhara, Rao, & Anavekar, 2010;Moustafa, Fayad, Ezz-Eldin, & El-Kashif, 2013;Muralidhra, Kesavulu, Rao, Anavekar, & Chakradhar, 2010;Subhadra and Kistaiah , 2010) and magnetic properties (Elahdal, Antar, Mahmoud, & Ezz-Eldin, 2011;Kumar, Kishan, Rao, & Awana, 2010;Nagarjuna, Venkatramaiah, Satyanarayana, & Veeraiah, 2009;Pascuta, Borodi, Popa, Dan, & Culea, 2010;Pascuta, Bosca, Borodi, & Culea, 2011;Singh & Srinivasan, 2010). These properties are determined by the presence of TMI in multivalent states, by the environment of TMI as well as by the TMI content and its distribution in the glass matrix. ...
In the present radiolytic study, we report the formation of Cu+2 ions in a sol-gel SiO2 thin film via γ-irradiation. The optical and magnetic properties of Cu/SiO2 film are discussed in relation to the mechanism of the formation of Cu+2 ions through irradiation. The color of the treated Cu/SiO2 films swinging from faint green to dark blue as the concentration of Cu(NO3)2 solution was increased from 0.2 to 0.6 and then decreased at 1.2 mol/L. The absorption spectra of the samples revealed many identified broad absorption bands in both, UV (∼190-280 nm) and, in the visible region (∼360-530 and ∼600-740 nm) beside a shallow broad ones in near infrared (∼800-880 nm). Also, there are remarkable increases in the absorption intensities accompanying with red shift for the heat-treated samples soaked in 1.2 mol/L. In order to study the state of Cu2+, and confirm the influence of the matrix, by investigating their EPR and XRD spectroscopy, respectively.
... EPR, UVeVIS and FTIR spectroscopies are very useful experimental techniques because they can provide valuable information related to the local symmetry, nature of the chemical bonds and other structural properties of glasses (Wong & Angell, 1976). Glasses doped with transitional metal ions (TMI) attract much attention because of their interesting electrical (Abd El All and Ezz-Eldin, 2010;Bahgat, Makram, Shaisha, & El-Desoky, 2010;Sankarappa, Devidas, Kumar, Kumar, & Kumar, 2009; Santi c, Kim, Day, & Mogu s-Milankovi c, 2010), optical (Ghoneim, Marzouk, Daoud, & Ezz-Eldin, 2013;Kesavulu, Chakradhar, Muralidhara, Rao, & Anavekar, 2010;Moustafa, Fayad, Ezz-Eldin, & El-Kashif, 2013;Muralidhra, Kesavulu, Rao, Anavekar, & Chakradhar, 2010;Subhadra and Kistaiah , 2010) and magnetic properties (Elahdal, Antar, Mahmoud, & Ezz-Eldin, 2011;Kumar, Kishan, Rao, & Awana, 2010;Nagarjuna, Venkatramaiah, Satyanarayana, & Veeraiah, 2009;Pascuta, Borodi, Popa, Dan, & Culea, 2010;Pascuta, Bosca, Borodi, & Culea, 2011;Singh & Srinivasan, 2010). These properties are determined by the presence of TMI in multivalent states, by the environment of TMI as well as by the TMI content and its distribution in the glass matrix. ...
a b s t r a c t
In the present radiolytic study, we report the formation of Cuþ2 ions in a solegel SiO2 thin
film via g-irradiation. The optical and magnetic properties of Cu/SiO2 film are discussed in
relation to the mechanism of the formation of Cuþ2 ions through irradiation. The color of
the treated Cu/SiO2 films swinging from faint green to dark blue as the concentration of
Cu(NO3)2 solution was increased from 0.2 to 0.6 and then decreased at 1.2 mol/L. The absorption
spectra of the samples revealed many identified broad absorption bands in both,
UV (~190e280 nm) and, in the visible region (~360e530 and ~600e740 nm) beside a shallow
broad ones in near infrared (~800e880 nm). Also, there are remarkable increases in the
absorption intensities accompanying with red shift for the heat-treated samples soaked in
1.2 mol/L. In order to study the state of Cu2þ, and confirm the influence of the matrix, by
investigating their EPR and XRD spectroscopy, respectively.
In this paper, nanostructured TiO2 thin film has been investigated under gamma irradiation source(Co-60) at eight, sixteen and twenty four hours duration. The TiO2 thin film was synthesized by spin coated sol-gel method. The irradiation was performed by using the facility of Gammacell-220 No.246 with cobalt-60 as gamma source. The structural morphology and modifications were analyzed with scanning electron mircroscopy(SEM) and X-ray diffraction(XRD) techniques. The results including the obsorption and emission spectra were acquired with JASCO spectrometer and flourospectrometer. The obtained data showed the decrease in particle size while increasing gamma irradiations exposure time at certain level of sixteen hours but then increase with further exposure upto twenty four hours duration. The analysis gives the understanding that the optical gap has decreased linearly with exposure time. This research predicts the variation in optical and morphological properties of TiO2 thin films with gamma exposure and thus gives an indication of developing radiation shielding materials for nuclear applications.
Collective characterizations of prepared binary barium borate glass (50 mol % BaO - 50 mol % B2O3) together with samples containing increasing added TiO2 contents (5% → 30%) were carried out by optical and FT infrared absorption measurements. FT infrared and X-ray diffraction analysis were done for heat treated glass - ceramic derivatives prepared through two step regime process. Optical spectra of the glasses reveal the presence of titanium ions mainly in the tetravalent state imparting additional UV band beside strong UV absorption due to trace iron impurity. IR spectral studies indicate the presence of triangular and tetrahedral borate groups through the modification of BaO to some BO3 to BO4 groups beside the presence of titanium ions as interfering or overlapping TiO4 or B-O-Ti groupings in the glassy network. Crystalline X-ray diffraction results indicate the separation of crystalline barium borate of the composition (2BaO.5 B2O3) as a main constituent together with some crystalline alkali titanates confirming the role of TiO2 of both as nucleating agent beside acting as structural forming through reaction with alkali oxides to form crystalline titanates. The optical band gap values reveal progressive decrease and increase of Urbach energy with TiO2 content and the same for the refractive index values and all these parameters are correlated with the proposed changes in the glass constitution with the introduction of TiO2. The additional thermal expansion measurements indicate the peculiar characteristic negative expansion up to 300 °C and after which an increase in the coefficient of thermal expansion is identified with the increase in temperature. The thermal parameters are also correlated with the modification of the glass structure by the introduction of titanium ions.
This work reports the preparation of glasses of binary cadmium borate with the basic composition (mol% 45 CdO 55 B2O3) and samples of the same composition containing 0.2 wt% dopants of 3d transition metal (TM) oxides (TiO2 → CuO). The glasses have been investigated by combined optical and Fourier Transform infrared spectroscopic measurements before and after being subjected to gamma irradiation with a dose of 8 Mrad (8 × 104 Gy). Optical absorption of the undoped glass before irradiation reveals strong charge transfer UV absorption which is related to the presence of unavoidable contaminated trace iron impurities (mainly Fe3+) within the raw materials used for the preparation of the base cadmium borate glass. The optical spectra of the 3d TM ions exhibit characteristic bands which are related the stable oxidation state of the 3d TM ions within the host glass.
Gamma irradiation produces some limited variations in the optical spectra due to the stability of the host glass containing high percent 45 mol% of heavy metal oxide (CdO) which causes some shielding effects towards irradiation. From the absorption edge data, the values of the optical band gap Eopt and Urbach energy (∆E) have been calculated. The values of the optical energy gap are found to be dependent on the glass composition. Infrared absorption spectral measurements reveal characteristic absorption bands due to both triangular and tetrahedral borate groups with the BO3 units vibrations more intense than BO4 units due to the known limit value for the change of BO3 to BO4 groups. The introduction of 3d TM ions with the doping level (0.2 wt%) causes no changes in the number or position of the IR bands because of the presence of TM ions in modifying sites in the glass network. It is observed that gamma irradiation causes some limited changes in the FT-IR spectral bands due to the stability of the host heavy cadmium borate glass.
Heavy metal oxide glasses (composition 60 PbO, 20 Bi2O3 mol%) and containing 20 mol% conventional glass formers SiO2, B2O3, and P2O5 were prepared. Combined optical and Fourier transform infrared absorption spectra were measured for the prepared glasses to justify the role of glass formers in the optical spectra together with the network structural groups in such glasses. Also, the density and molar volume values were calculated to obtain some insight on the compactness and arrangement in the network. Optical measurements have been used to determine the optical band gap (Eg), Urbach energy (ΔE) and the refractive index (n). Optical spectra of all the samples reveal strong UV absorption which is related to the presence of unavoidable trace iron impurities (Fe 3+ ions) contaminated within the raw materials which were used for the preparation of the studied glasses. Additional near visible bands are observed in all prepared glasses due to characteristic absorption of Pb 2+ and Bi 3+ ions. Furthermore, The variations of the luminescence intensity, values of the optical band gap, band tail, and refractive index can be understood and related in terms of the structural changes that take place in the glass samples. The infrared absorption spectra of the prepared glasses show characteristic absorption bands related to the borate or silicate or phosphate network (BO3, BO4, SiO4, PO4 groups) together with vibrational modes due to Bi-O and Pb-O groups.
BaO–Ga2O3–P2O5 glasses containing different concentrations of MoO3 ranging from 0 to 0.5 mol% have been prepared. Spectroscopic studies viz., infrared, optical absorption and ESR spectra of these glasses have been carried out as a function of molybdenum ion concentration. The results suggest that molybdenum ions exist in Mo5+ state with Mo(V)O3− complexes that act as modifiers in addition to Mo6+ state with MoO4 and MoO6 structural groups in these glasses.
Present work reports a comparative study of spectroscopic and magneto-optic properties of Fe3O4 based ferrofluids prepared with two different carrier fluid namely milli-Q-water and kerosene. The ferrofluids are labelled as FFW and FFK respectively. Both ferrofluids are subjected to gamma-irradiation of dose: 2,635 Gy. Transmission electron microscopy and dynamic light scattering studies reveal that gamma-photon interaction could lead to substantial growth of the dispersed nanoparticles of ferrofluids. In case of FFW, particle sizes are similar to 9 nm (pristine) and similar to 48 nm (irradiated) whereas, in FFK unirradiated particles of size similar to 9 nm show growth to similar to 18 nm after the irradiation. The role of different physical parameters (viz. viscosity, density) of carrier fluid on the growth process is considered in this regard. Viscosity of the carrier fluid is found noteworthy in the measurement of Faraday rotation response of the ferrofluids. In addition to low viscosity of water, irradiation induced particle growth as well as improved size distribution with larger particles leads to a comparatively larger enhancement of Faraday rotation of FFW than that of FFK. Consequently, as a result of gamma-irradiation, Verdet constant is modified by similar to 70 % in the former case and by similar to 60 % in the latter case.
X-Ray diffraction, energy dispersive X-ray, Fourier transform infrared, Raman spectroscopy, differential
scanning calorimetry, UV–Visible spectroscopy and electron paramagnetic resonance spectroscopic studies have been carried out on alkali earth lead zinc phosphate glasses doped with 0.1 % chromium ions. The energy dispersive X-ray spectra reveal fundamental compositional information of the glasses. Infrared spectra indicate that phosphate network is depolymerized with progressive substitution of alkali earth content and inform the characteristic vibrations of PO4 3- units.Raman spectra suggest that these glasses are consisting of metaphosphate [Q2] units along with some bands related to pyrophosphate [Q1] and orthophosphate [Q0
] units. The crystal-field parameter and inter-electronic repulsion parameters
have been evaluated from optical absorption spectral data. Electron spin resonance spectra of Cr3? systems indicate that gk[g\ and Cr3? ions are located at sites with lower symmetry. It is obtained that the glass transition temperatures fall in region of 377–360 C. Increase in density of the glass system brings changes in structure of the glasses on replacement of alkali earth content
The effect of Bi2O3 and PbO on the physical and luminescence properties of Eu3+:PbO–Bi2O3–WO3–B2O3 glasses is presented. The increase in the concentration of Bi2O3 causes UV shift in the optical absorption spectra and increase in the intensities in the photoluminescence spectra (excitation and emission) of these glasses. The spectroscopic ratio factors of the integrated luminescence intensities 5D
0 → 7F
J
/
5D
0 → 7F
1 (j = 0, 1, 2, 3) are reported. The experimental branching ratios of the 5D
0 → 7F
J
(j = 0, 1, 2, 3) are presented. The 5D
0 → 7F
2 exhibits high β
R
(>60 %) values for all glasses reflecting their potential lasing application in the development of red laser and optical devices. The σ
e
for 5D
0 → 7F
2 and 5D
0 → 7F
4 transitions are reported. The observed 5D
0 → 7F
0 in the emission spectra confirms low symmetry around Eu3+ ion for all glass compositions.
Infrared absorption spectra of sodium phosphate glasses, Na2O=30–50 mol%, have been studied in the region of 400–2000 cm−1. Spectra were analyzed to determine the relative intensity of the IR bands responsible for the different phosphate units. Spectral analyses has shown that the substitution of P2O5 by Na2O influences the intermediate range order of the glass matrix. Increasing Na2O content leads to a gradual degradation of the phosphate ring type structures, with consequent depolymerization causing compaction of the glass matrix. Analyses of IR spectra illustrates the reorganization effects of Na2O in the phosphate matrix.
The nonlinear optical properties for the PbO, TiO 2 , K 2 O , and SiO 2 system have been measured by the Z -scan method. The magnitude and sign of the nonlinear refractive index n2 were determined, as was the negative sign, which indicated a self-defocusing optical nonlinearity. Two optical absorption bands at 540 and 660 nm, respectively, are observed in the optical absorption spectra. The sources of the absorption bands are attributed to the 3d -shell electronic transitions of Ti 3+ ions from the ground state to the excited states. The origin of the negative nonlinear refractive index was the contribution of resonant electronic transition processes, which can cancel the positive nonresonant refractive index that mainly resulted from the hyperpolarizabilities of the Pb–O and Ti–O pairs. © 1997 American Institute of Physics.
Undoped and TiO2-doped soda lime-phosphate glasses were prepared. UV-visible, infrared, Raman and electron spin resonance spectroscopic studies of the prepared samples, with varying compositions and increasing TiO2 contents, were measured before and after successive gamma irradiation. The parent undoped glass reveals strong UV absorption originating from trace iron impurities. Experimental data indicate that titanium ions are involved in two valencies in such glasses, namely the trivalent and pentavalent states. The trivalent titanium (Ti3+) ions are characterized by its purple colour and showing characteristic two visible absorption bands and paramagnetic ESR character. The tetravalent titanium (Ti 4+) ions belong to the d° configuration and possess only charge transfer ultraviolet absorption interfering with the UV bands due to trace iron impurities as evidenced in the undoped specimen. Glasses with high TiO2 contents show retardation or shielding effect towards successive gamma irradiation. The changes in the UV, visible and infrared absorption spectra are interpreted in relation to the generation of induced defects by irradiation and the response of the change in glass composition or TiO2 content. Raman and ESR measurements support the proposed interpretations of the experimental results.
Undoped and V2O5-doped sodium phosphate glasses of various compositions and with varying progressive
V2O5 contentswere prepared. UV–vis and infrared, Raman and electron spin resonance spectroscopic
studies were measured before and after successive gamma irradiation. Experimental results indicate that
vanadium ions exist in three possible valencies in sodium phosphate glasses, namely, the trivalent, tetravalent
and pentavalent states. The first two lower valencies are predominant in this glass system. The changes
in UV–vis and infrared spectral data are discussed in relation to the structural evolution caused by the
change in the V2O5 content or glass composition. Raman and ESR measurements are taken as confirmative
tools to support our assumptions relating to the states of vanadium and structural groups arrangements
in the studied glasses. Gamma irradiation produces induced defects depending on the host glass and
the concentration of V2O5 content together with the sharing of unavoidable trace iron impurities. Vanadium
ions when present in high doping level, have been found to exhibit a shielding behaviour towards
the effects of progressive gamma irradiation causing a retardation of the growth of the induced defects
caused by irradiation.
A study of energy transfer from samarium to erbium ions in zinc phosphate glass has been performed for a range of donor (1.0 wt% fixed) and acceptor concentrations ranging from 0.2 wt% to 1.2 wt%. The intensity of emission spectra of Sm 3+ ions in the presence of Er 3+ ions shows an overall decrease, thereby suggesting a non radiative energy transferiram Sm 3+ions to Er 3+ ions. The interaction mechanism between the donor and acceptor ions is found to be mainly electric dipole-dipole in nature. The parameters required for the quantitative study of energy transfer e.g. energy transfer efficiencies, transfer probabilities, critical transfer distances have been computed.
Optical absorption spectra of 3d transition metals have been measured in a bioglass host before and after successive γ-irradiations. In general, transition metals exhibit predominantly the higher oxidation state or tetrahedral coordination in this host glass, which possesses abundant alkali and alkaline earth oxide contents. Transition metals-doped bioglasses reveal varying response to the effect of successive γ-irradiation. The intensity and growth behaviour of the radiation-induced bands are seen to depend on the type of the transition metal ion. The change in the growth behaviour is related to the annihilation or approach to saturation of characteristic induced bands.
Conventional quenching methods were used to prepare (50-x/2)Na2O.xBi2O3. (50-x/2) P2O5, system phosphate glasses for x≤16.0. The glass structure was then analysed with infrared and 31P MAS NMR spectroscopy. The main phosphate species formed by the depolymerisation of the sodium metaphosphate chains by Bi2O3 are firstly chain end groups and then mixed sodium bismuth pyrophosphates. Analysis of the phosphate species shows that some meta and orthophosphates are formed by the equilibrium 2Q1=Q2+O0. Infrared and NMR data are in accordance with the covalent character of Bi-O-P bonds. The stereochemically active 6s2 lone electron pair and the high polarisability of Bi3+ lead to a highly distordedcoordination sphere, with one sided shorter covalent Bi-O bonds and longer ionic Bi-O bonds. The former bonds are the origin of the partial glass forming ability of Bi3+.
Over the last several decades, many investigators have found that the analysis of vibrational spectra of glasses can be applied to the solution of both industrial and basic research problems. In an applied industrial study, the vibrational spectra can be used to identify glasses or specific groups which are present in glasses. However, in a theoretical study, information can be obtained concerning the fundamental structural nature of glasses on which their external properties are dependent.
PbO-Sb2O3-As2O3 glasses
containing small concentrations of TiO2 ranging from 0 to 0.5
mol% were prepared. A number of studies viz. differential scanning
calorimetry, infrared spectra, optical absorption, ESR spectra and
magnetic susceptibility have been carried out as a function of titanium
ion concentration. The interesting changes observed in these properties
are discussed in the light of different oxidation states of titanium
ions.
In the present work, measurements are made on the intensity and angular distribution of Compton scattered gamma rays of energy 279 keV from K-shell electrons of tin at scattering angles ranging from 30° to 150° and also determined the K-shell to free electron differential collision, absorption and scattering cross section ratio. For this purpose, two NaI(Tl) scintillation detectors working in coincidence with 30 nsec resolving time are used to record the events. The experimental results are compared with the available experimental and theoretical data.
Li2O–CaF2–P2O5 glasses mixed with different concentrations of TiO2 (ranging from 0 to 0.8 mol%) were crystallized at 500 °C. The photo luminescence spectra of these samples excited with the wavelengths corresponding to their absorption edges have been recorded at room temperature. The spectra exhibited an emission band in the wavelength region 470–500 nm. The emission band is identified due to the charge transfer from O2− ion in to empty 3d orbital of octahedrally positioned Ti4+ ions. The analysis of the results further indicates the highest luminescence efficiency for the glass ceramic sample crystallized with 0.6 mol% of TiO2.
In this paper, studies on various physical properties, viz., dielectric properties (dielectric constant, loss tan {delta}, a.c. conductivity {sigma}) over a wide range of frequency and temperature, optical absorption, ESR at liquid nitrogen temperature and magnetic susceptibility at room temperature of Li{sub 2}O-CaF{sub 2}-P{sub 2}O{sub 5}: Cr{sub 2}O{sub 3} glass ceramics, have been reported. The optical absorption, ESR and magnetic susceptibility studies indicate that the chromium ions exist in Cr{sup 5+}, Cr{sup 4+} and Cr{sup 6+} states in addition to Cr{sup 3+} state in these samples. The dielectric constant and loss variation with the concentration of Cr{sub 2}O{sub 3} have been explained on the basis of space charge polarization mechanism. The dielectric relaxation effects exhibited by these samples have been analysed by a graphical method and the spreading of dielectric relaxation has been established. The a.c. conductivity in the high-temperature region seems to be connected both with electronic and ionic movements. - Graphical abstract: The optical absorption spectroscopic studies on Li{sub 2}O-CaF{sub 2}-P{sub 2}O{sub 5}: Cr{sub 2}O{sub 3} glass ceramics indicate that a part of Cr{sup 3+} ions oxidized into Cr{sup 6+} ions during the crystallization. These ions enter the glass network with CrO{sub 4}{sup 2-} structural units, alternate with PO{sub 4} units and increase the rigidity of the glass-ceramic sample.
Measurements are reported for the electrical dc conductivity of the semiconducting vanadium tellurite glasses containing P2O5, Sb2O3, or Bi2O3 in the temperature range 80–450 K. The experimental data have been analyzed in the light of existing theoretical models. It has been observed that the general behavior of the electrical conductivity is similar for all glass compositions. The high temperature conductivity data are consistent with Mott’s models of phonon-assisted polaronic hopping in the nonadiabatic regime, while at low temperatures variable range hopping is valid. The small polaron hopping model of Schnakenberg is the best model to interpret the temperature dependence of the activation energy and the conductivity in the entire temperature range. The percolation model applied to the polaron hopping regime is also found to be consistent with the temperature dependence of the conductivity data at high and low temperatures. The various parameters obtained by fitting these models to the experimental data are found to depend on glass forming oxides other than the vanadium oxide.
A study of energy transfer from samarium to erbium ions in zinc phosphate glass has been performed for a range of donor (1.0 wt% fixed) and acceptor concentrations ranging from 0.2 wt% to 1.2 wt%. The intensity of emission spectra of Sm3+ ions in the presence of Er3+ ions shows an overall decrease, thereby suggesting a non radiative energy transfer from Sm3+ ions to Er3+ ions. The interaction mechanism between the donor and acceptor ions is found to be mainly electric dipole-dipole in nature. The parameters required for the quantitative study of energy transfer e.g. energy transfer efficiencies, transfer probabilities, critical transfer distances have been computed.
MoO3-doped lithium phosphate glasses with varying molybdenum contents were prepared and characterized. Combined UV-visible and infrared (FT/IR) spectroscopic studies were measured before and after gamma irradiation. Experimental results indicate that molybdenum ions occupy different local sites including presence of Mo3+, Mo4+ and Mo5+ with different ratio depending on the host lithium phosphate glass composition and concentration of molybdenum ions. Undoped lithium phosphate glass reveal UV absorption which is related to the presence of unavoidable trace iron impurities. FT/IR spectra were used to identify the main building structural groups present in the studied lithium phosphate glass. The same spectroscopic reutilized techniques were reutilized to identify the induced defects generated after successive gamma irradiation and the influence of molybdenum ions on the irradiation process. Experimental results indicate that molybdenum ions occupy two valences: Mo5+ and Mo3+ with the first in dominant percent. The change in the UV, visible and infrared spectral data are discussed in relation to the change in the state of molybdenum ions with glass composition or dopant concentration or network structure evolution caused by the change in glass constituents.
Undoped lead borate glass of the composition PbO 70%–B2O3 30% together with samples of the same composition and doped with varying V2O5 contents were prepared. UV–visible absorption spectra were measured out in the range 200–1500nm before and after successive gamma irradiation. Infrared absorption measurements within the range 4000–400cm−1 were carried out for the undoped and V2O5 doped samples before gamma irradiation and after being irradiated with a dose of 6Mrad. All the glass samples are observed to absorb strongly in the UV region due to the combined contributions of absorption due to trace iron impurities and that from the divalent lead Pb2+ ions. The V2O5-doped glasses reveal extra visible absorption bands which are attributed to the existence of V3+ ions in measurable content but not neglecting the other valence states of vanadium ions (V4+, V5+). Infrared absorption spectra indicate the presence of both triangular and tetrahedral borate groups besides the sharing of lead ions in network forming and network modifying sites.
Dc and ac conductivities of Li2O–BaO–Bi2O3 glasses have been studied in a temperature range of 263–523 K and a frequency range of 10 Hz–2 MHz and have been compared with those of binary Li2O–Bi2O3 glasses. The frequency dependent conductivity has been studied employing both the modulus and conductivity formalisms. We have observed small changes in the dc conductivity and its activation energy from those of the binary glass when content of BaO is small. However we have observed noticeable changes in the conductivity and the activation energy when BaO content is large. The significant changes in the values of the non-exponential parameter and the power-law exponent of the ac electrical properties have been observed due to introduction of BaO in the lithium bismuthate glasses. The existing relation between the power-law exponent and the non-exponential parameter was also violated in the present glass compositions.
Dc and ac conductivities of Li 2 O–BaO–Bi 2 O 3 glasses have been studied in a temperature range of 263–523 K and a frequency range of 10 Hz–2 MHz and have been compared with those of binary Li 2 O–Bi 2 O 3 glasses. The frequency dependent conductivity has been studied employing both the modulus and conductivity formalisms. We have observed small changes in the dc conductivity and its activation energy from those of the binary glass when content of BaO is small. However we have observed noticeable changes in the conductivity and the activation energy when BaO content is large. The significant changes in the values of the non-exponential parameter and the power-law exponent of the ac electrical properties have been observed due to introduction of BaO in the lithium bismuthate glasses. The existing relation between the power-law exponent and the non-exponential parameter was also violated in the present glass compositions.
Borosilicate and disilicate glasses doped with 0–2mol% of TiO2 have been irradiated with 2MeV electrons. Reduction of Ti4+ is attested by the presence of an intense electronic paramagnetic resonance (EPR) signal around g=1.92 corresponding to Ti3+, not observed in samples that were not irradiated. Moreover, two distinct sites of Ti3+ have been detected in each glass composition. Ti–K-edge X-ray absorption near edge structure (XANES) experiment and more precisely the pre-edge analysis of non-irradiated samples indicates the presence of four, five and six coordinated Ti(IV) in borosilicate glass compositions. In contrast, the average Ti(IV) coordination in DS composition is a mixture between fivefold and sixfold. In irradiated glasses, the Ti–K-edge energy (as well as the pre-edge position) shows a shift to smaller energies, which we suggest is caused by Ti3+. Comparison between EPR, Raman and XANES results in a coherent description of Ti4+ reduction process in the glass samples.
This paper presents a Raman investigation of glasses of the system MX:M2O:B2O3:P2O5 (M = Li, Ag; X = Cl, 1). For the phosphate glasses, we discuss in detail the relationship among glass composition, density of the different phosphate (PO4) units, and Raman spectra. For the borophosphate glasses, we analyze how the oxygens introduced with the modifier oxide M2O are shared among borate and phosphate units. When P2O5 is partially substituted by boron oxide, and the M2O content remains constant, the negative charge of the phosphate units increases, on average. Comparison with the results of a companion 31P NMR-MAS study allows identification of bands associated with structures containing the P-O-B motives. A discussion is also given of the changes induced into the borophosphate glass network by addition of a “doping” MX salt.
We have reported the ionic relaxation for different compositions of xAg2O−(1−x)TeO2 conducting glasses in wide temperature and frequency ranges. We have explained the composition dependence of the conductivity and the activation energy in terms of composition-dependent network structure of these glasses. We have compared the results for silver tellurite glasses with those for the alkali (Li,Na) tellurite glasses and observed that the migration of Ag+ ions in glasses, in general, appears to be anomalous. We have analyzed the frequency-dependent electrical data in the framework of the power-law conductivity formalism. We have explained the decreasing trend of the relaxation time with increasing Ag2O content in terms of structural transformation of tellurite network. Interestingly, we have observed that the concentration of mobile Ag ions is less than the concentration of total Ag ions and decreases with the increase of silver oxide content in the compositions, while the conductivity increases. We have shown that the scaling of the conductivity spectra is independent of temperature, but depends on composition.
The extent of solarization is strongly influenced by many factors such as glass matrix, dopants, or irradiation source. Typical irradiation induced effects are illustrated in a series of glasses doped with a selection of polyvalent ions. Intrinsic and extrinsic defects, consisting of electron and hole centers, are characterized with optical and EPR spectroscopy. Used in combination, both spectroscopic methods allow to detect a wide range of defects. UV-lamp irradiation causes in fluoride-phosphate glasses the photoreduction of Ni 2þ , Pb 2þ and Ag þ while Co 2þ , Ce 3þ , Fe 2þ and Mn 2þ are photooxidized. The influence of the glass matrix is evident for Ni 2þ which is photooxidized in borosilicate, but reduced in fluoride-phosphate glasses. Iron ions also show different redox reactions depending on the glass matrix, as well as on the melting conditions, which will be shown for low alkaline borosilicate glasses doped with iron or tin. Changes in the nature and the rate of defect formation could be observed within the irradiation process of a fluoride-phosphate glass co-doped with Mn 2þ and Fe 2þ and during thermal annealing of a lamp irradiated phosphate glass containing Co 2þ . The series Mn 2þ , Fe 2þ , Co 2þ and Ni 2þ shows a trend of increased photooxidation with increasing electro-negativity or decreasing mass of the ions.
Spectrophotometric, magnetic susceptibility and density molar volume studies on a number of alkali borate glasses containing nickel and titanium oxides were carried out to obtain information on their structure. The effect of replacing one of the main constituents of the glasses by one of the mono, di, tri or tetravalent metal oxides was studied and the effect of nickel and titanium oxide concentrations also investigated. The experimental results are analysed and explained by assuming that nickel exists in glass as divalent nickel ions in two different states of coordination, i.e. octahedral and tetrahedral while titanium ions exist mostly in octahedral environments with some tetragonal distortions. The states of transition metal ions in the glasses are considered to depend on several factors such as: (i) the polarisability of the oxygen ligands surrounding the transition metal ion; (ii) the mobility of the alkali ions and their field strengths; and (iii) the opportunity of forming network units such as MO3 or MO4 for some of the di, tri and tetravalent metal oxides.
Ultraviolet and visible spectroscopic measurements were used to investigate prepared undoped and Mn-doped sodium phosphate glasses before and after successive gamma irradiation. The effects of both glass composition and MnO2 content on the generation of radiation-induced defects were investigated. Undoped sodium phosphate glass shows strong UV absorption, which is attributed to the presence of trace iron impurities present in the raw materials. Mn-doped glasses reveal an additional visible broad band centered at about 500 nm due to Mn3+, which has recently been related to the 5Eg →5T2g transition. The radiation-induced bands are correlated with the generation of liberated electron–hole pairs during the process of gamma irradiation and the possibility of photochemical reactions especially with trace iron impurities and manganese ions. The intensity and the position of the induced bands are observed to depend on the type and composition of glass, concentration of the dopant and also on the irradiation dose. Manganese ions when present in relatively higher content have been found to show a shielding behavior towards the effects of progressive gamma irradiation causing a retardation of the growth of the induced defects. Infrared and Raman spectra of the undoped and Mn-doped glasses were measured to investigate the structural phosphate groups present and the effect of MnO2 on the network structure. An ESR investigation was carried out to confirm the state of manganese ions in the prepared sodium phosphate glasses.
Glass formation and structural properties of the unconventional lead cuprate glasses of compositions (CuO)x(PbO)100-x (mol %), are reported for the first time. X-ray diffraction and electron microscopic studies show that the glass formation occurs for x = 15-50 mol %. The compositional dependence of the density, molar volume, and glass transition temperature suggests that all glass compositions in this domain have the same topology and network connectivity. The glass structure is built up of [PbO4] tetrahedral units. On heat treatment above glass transition temperatures, the glasses crystallize to CuO and PbO. Electron Spin Resonance (ESR) spectra of the glass compositions consist of broad resonance lines.
Ultravoilet (UV)–vis absorption spectra of undoped and transition metal (TM)-doped borosilicate glasses before and after successive gamma rays irradiation are reported. Before irradiation, the undoped glass reveals UV absorption due to trace iron impurities and no visible bands whereas the TM-doped glasses show the absorption bands which are characteristic for each TM ion in the UV and visible regions. The induced absorption bands are examined and related to either intrinsic radiation-induced defects from the host base borosilicate glass or extrinsic induced defects generated from TMs. The response of the glasses to gamma irradiation is related to the creation of defect color centers, the approach of a saturation condition and/or the possible photochemical effect on TM.
Temperature and compositional dependences of electrical conductivity in lead - iron glasses are reported. The experimental results are analysed in the light of existing theories. It has been observed that the electrical conduction in these glass compositions at high temperatures is best described by Mott's phonon-assisted hopping model, while the low-temperature data are consistent with the variable-range hopping model. Hopping at high temperatures occurs in the non-adiabatic regime. The generalized hopping model of Schnakenberg is the best to interpret the temperature dependences of the conductivity and activation energy over the glass compositions studied. Values of the physical parameters obtained by the best fits of the experimental data are consistent with the glass compositions.
We have developed a new scaling property of the conductivity spectra of fluoride glasses. This
property predicts the existence of a universal ionic relaxation in these glasses. The relaxation
process in fluoride glasses is observed to be independent of temperature as well as the nature and
concentration of the ionic charge carriers.
Li2O–CaF2–P2O5 glasses mixed with different concentrations of NiO (ranging from 0 mol% to 2.0 mol%) were crystallized. The samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy and differential thermal analysis. Studies were extended to optical absorption and magnetic susceptibility of these glass ceramic samples. The XRD and SEM studies reveal the presence of lithium phosphate, calcium phosphate and nickel phosphate crystal phases. The optical absorption studies together with magnetic susceptibility measurements indicate a gradual transformation of nickel ions from tetrahedral sites to octahedral sites (lasing sites) as the concentration of NiO is increased beyond 0.8 mol%. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
The optical absorption spectra of nominally pure and V-doped sodium phosphate glasses have been measured from 200 to 1100 nm before and after gamma-ray irradiation. The induced absorption spectra, calculated as the difference between the spectra of the irradiated and the unirradiated glasses, exhibit three absorption bands at about 400 nm (3.10 eV), 500 nm (2.48 eV) and 550 nm (2.23 eV) in the parent sodium phosphate glass, while the V-doped glasses show a broad composite ultraviolet cut-off extending to 400 nm (3.10 eV) and two other visible bands with peaks at about 680 nm (1.82 eV) and 830 nm (1.49 eV). The intensity of the induced bands depends on the irradiation dose, the glass composition and also on the V2O5 content. The response of the phosphate glass to gamma-ray irradiation is related to the formation of characteristic defects and colour centers, to the possible photochemical effect of the transition metal in the glass, and also to the possible approach of saturation after a certain irradiation dose. The suppression or retardation of the vanadium present in phosphate glasses in the creation of induced defects is also considered.
The addition of up to ∼16 mol% Cs2O to vitreous P2O5 reduces the glass transition temperature (Tg) by 150 K, whereas further additions up to 60 mol% increases Tg by ∼20 K. 31P magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra indicate that the phosphate network is progressively depolymerized over the entire range of compositions. The property trend is explained by a transition in the Cs+ coordination environment, from isolated Cs-polyhedra below ∼16 mol% Cs2O to a corner-sharing Cs-polyhedral sub-structure in the glasses with greater Cs2O contents. This ‘modifier transition’ does not occur in Al phosphate glasses. 27Al MAS NMR spectra indicate that the average Al coordination number decreases with increasing Al2O3 content to avoid the formation of Al–O–Al bonds in these binary phosphate glasses.
Ultraviolet transmission characteristics of LG-810 fluorophosphate laser glass were investigated as a means of diagnosing transition metal contamination. Absorption bands normally exhibited by this glass were shown to derive primarily from metallic impurities. Uv-transparent glasses were produced having absorption cut-offs close to those reported for BeF2-based glasses.
Ultraviolet, visible, and infrared spectroscopic measurements have been employed to investigate undoped binary bismuth borate
glass (60mol% Bi2O3, 40mol% B2O3) and doped samples with 0.2% 3d transition metal oxides in order to obtain information about the role of all the constituents
oxides including the dopants on the measured properties. The undoped sample shows strong extended UV-near visible absorption
bands which are attributed to both trace iron impurities from raw materials used for glass preparation and Bi3+ ions. The TM-samples show the same strong UV-near visible absorption as the undoped sample beside characteristic visible
bands because of TM ions. The prepared samples show obvious shielding behavior toward the effect of successive gamma irradiation
especially in the visible region. The infrared absorption spectra of the prepared samples show characteristic bands related
to the sharing of triangular and tetrahedral borate groups together with Bi–O groups. The IR spectra are slightly affected
by gamma irradiation indicating the stability of network forming units while the modifier, OH and water bands show obvious
changes in their intensities.
The optical absorption and infrared (IR) spectra of mixed alkali silicate glasses in the system 3SiO2–(1 − x)Na2O–xK2O + 2.5–20 g of TiO2 were measured. Absorption bands due to Ti3+ ions, at 500 and 570 nm, were observed in the spectrum of Na2O-free glasses. The intensities of such bands were followed with the variation in TiO2 content from 2.5 to 20 g (per 100 g of glass). The incorporation of titanium oxide as Ti3+ in the Na2O-free glass, conferring a violet hue to it, was explained on the basis of the acidity–basicity character of the glass. The
IR measurements have been used to explore the structural changes throughout the compositional variations.
Copper-doped sodium phosphate glasses of various compositions and with varying copper contents were prepared. UV-visible and
infrared spectroscopic studies were measured before and after successive gamma irradiation. Experimental results indicate
that copper ions occupy different local sites depending on the host glass composition and concentration of copper ions. The
changes in UV, visible and infrared spectral data, are discussed in relation to the structural evolution caused by the change
in composition and states of copper ions. Copper ions have been found to show a shielding behavior toward the effects of progressive
gamma irradiation causing a retardation of the growth of the induced defects caused by irradiation.
The temperature dependence of the thermoelectric power of the semiconducting bismuth‐vanadate glasses was presented in a range of compositions. The high‐temperature thermoelectric power was satisfactorily explained by Heikes’ relation [R. R. Heikes and R. W. Ure, Eds., Thermoelectricity (Interscience, New York, 1961), p. 81]. The thermoelectric power data also showed evidence of small polaron formation in the glass and revealed that the disorder energy happened to increase with the increase of V 2 O 5 content in the glass. An estimate of the disorder energy was made from the low‐temperature thermoelectric power data.
The structures of xCuO · (1 − x)P2O5 glasses (0 ⩽ x ⩽ 0.50) prepared in vacuum sealed silica ampoules were investigated using vibrational spectroscopies. With the addition of CuO, both infrared and Raman spectra indicate a systematic transformation from a three-dimensional ultraphosphate network dominated by Q3 tetrahedra into a chain-like metaphosphate structure dominated by Q2 tetrahedra. IR spectra clearly show two distinct Q3 sites with bands at 1378 and 1306 cm−1, assigned to PO bonds on isolated Q3 tetrahedra and PO bonds on tetrahedra that participate in the coordination environments of the Cu-octahedra, respectively. As CuO content increases, the intensity of the PO band associated with the tetrahedra increases to a maximum x ∼ 0.33, then decreases with a concomitant increase of the intensity of the band at 1265 cm−1, due to the asymmetric vibration of the PO2 groups on Q2 tetrahedra. When x > 0.33 the isolated Cu-octahedra begin to share common oxygens to form a sub-network in the phosphate matrix. The effects of glass structure on the glass properties, including density, refractive index, and glass transition temperature, are discussed.
The local environment around iron ions in iron phosphate glasses of starting batch composition 40Fe2O3–60P2O5 (mol%) melted at varying temperatures or under different melting atmospheres has been investigated using Fe-57 Mössbauer and X-ray absorption fine structure (XAFS) spectroscopies. Mössbauer spectra indicate that all of the glasses contain both Fe(II) and Fe(III) ions. The quadrupole splitting distribution fits of Mössbauer spectra show that Fe(II) ions occupy a single site whereas Fe(III) ions occupy two distinct sites in these glasses. When melted at higher temperatures or in reducing atmospheres, the Fe(II) fraction in the glass increases at the expense of Fe(III) ions at only one of the two sites they occupy. The pre-edge feature in the XAFS data suggests that the overall disorder in the near-neighbor environment of iron ions decreases with increasing Fe(II) fraction. The XAFS results also show that the average iron–oxygen coordination is in the 4–5 range indicating that iron ions have mixed tetrahedral–octahedral coordination.
This paper discusses, in some detail, the nature of color centers induced by radiation in different borate, silicate and phosphate glasses; using optical and ESR techniques. The role of cerium and other multivalent ions in suppression of some of these centers and in studying their nature is also discussed. In most glasses, the visible induced absorption was associated with positive hole centers. However, at certain compositions, an electron trap center which absorbs in the visible is also induced by radiation, and was associated with certain structural defects, e.g. a non-bridging oxygen ion vacancy neighboring the alkai ions in diborate or disilicate glasses, Pb2+ ions (or other isoelectronic ions) taking network modifying positions, or Ce3+ ions in relatively high concentrations. Some examples of the use of radiation induced optical absorption and electron spin resonance as a tool for studying structural changes are also discussed.
Transparent glasses composition of which can be expressed by the formula: (100−x) · (K2O · 2TiO2 · P2O5) · x(K2O · 2B2O3 · 7SiO2), where x=5, 10, 15 and 20 mol% (KTP–xKBS), were obtained by melt quenching technique. The structure and crystallization behavior of these glasses have been examined by Fourier transform infrared spectroscopy, differential thermal analysis and X-ray diffraction. In spite of their nominal composition, the studied glasses exhibit a similar oxygen polyhedra distribution. However, significant differences were found in the trigonal BO3 units amount. During DTA runs all the examined glasses devitrify in two steps. In the former, very small crystals of an unknown crystalline phase are produced. In KTP–5KBS and KTP–10KBS glasses anatase phase was also detected. Attempts were made in order to identify the unknown phase (UTP) for which a AB3(XO4)2(OH)6 Crandallite-type structure was proposed where the A, B and X sites were occupied by K, Ti and/or Al, and P, respectively. In the second devitrification step the crystallization of the KTiOPO4 phase occurs while the UTP phase previously formed disappears. Isothermal heat treatments performed at temperature just above Tg have allowed one to obtain transparent crystal–glass nanocomposites, formed by crystalline nanostructure of the UTP phase uniformly dispersed in the amorphous matrix.
The IR reflection spectra of mixed zinc alkali pyrophosphate glasses in the broad frequency ranges are reported and the quantitative treatment of these with a version of the dispersion analysis method was conducted based on the specific analytical model of the complex dielectric constant of glasses. Numerical data on the optical constants, band frequencies, and band intensities are calculated. Results obtained are interpreted in terms of vibrations of the (PO3)2− and (PO2)− terminal groups, (PO4)3− anion, and P–O–P bridge. The presence of all these groups in the structures of glasses under study is confirmed and the formation of the (P3O9)3− ring metaphosphate anion rather than the chain polymeric phosphate anions is suggested. The gradual decrease in the width of the anion distribution toward the pyrophoshate anion with the Me2O for ZnO substitution is also confirmed. It is shown that this decrease determines the IR spectrum variations observed in the 0 to about 27 mol% Na2O composition range. The amounts of the (PO4)3− and (P3O9)3− anions are shown to become negligible in the structures of glasses with Na2O content greater than 30 mol%, and the IR spectrum variations observed in the 27–45 mol% Na2O composition range are shown to be mostly due to the intensity redistribution from the low-frequency component of the asymmetric stretch of the (PO3)2− terminal group to the high-frequency component of the same stretch.
The essential features of the I.R. spectra of orthosilicates and orthogermanates may be explained by the systematic use of a new method, namely the method of isomorphic substitution. By the study of solid solutions of the type X2(Si,Ge)O4, (X,Y)2SiO4 and (X,Y)2GeO4, it is possible to observe separately the contribution of the main factors which are responsible for the complexity of the spectrum: (a) the vibrations of SiO4 or GeO4 tetrahedra and the vibrations of XOn or YOn co-ordinated groups; (b) the departure of the tetrahedra, octahedra … from the perfect Td, Oh … symmetry; (c) the interactions between similar groups in the unit cell.The detailed treatment is given for the I.R. spectrum of willemite Zn2SiO4, where the ZnO4 tetrahedra have been found to have fairly strong absorption bands in the 600 cm−1 region. The main possibilities and limitations of the method are briefly discussed.
(Fluoride)phosphate and borosilicate glasses of high intrinsic transparency in the deep ultraviolet (UV), were doped with 50–5000 ppm of the 4d- and 5d-ions Zr, Nb, Ta, Mo, or W. All of these ions absorb strongly in the UV. Samples plates were irradiated by UV lasers and the as a consequence generated various extrinsic and intrinsic defects were characterized by optical and EPR spectroscopy. The laser induced transmission changes depend not only on the glass matrix, but also on the valence of the dopants. Only fully oxidized d0-ions are observed in fluoroaluminate glasses. Laser irradiation photoreduces the d0-ions to extrinsic electron-centers (EC). Laser induced transmission changes extend from the UV up to 600 nm in the visible. The dopants are easily reduced to lower valences in metaphosphate glasses. Extrinsic hole centers (HC) replace intrinsic HC in samples containing the reduced transition metal ions. The strong transmission changes seen below 300 nm arise from intrinsic EC and extrinsic HC. The few remaining intrinsic HC (300–600 nm) recombine rapidly with EC or transform into more stable extrinsic HC. Borosilicate glasses show the formation of intrinsic boron oxygen hole center in the EPR spectra and of intrinsic HC and EC in the optical spectra. The d1-ion Mo5+ is the only identified reduced dopant species in the borosilicate glasses. The band intensity of intrinsic EC in relation to intrinsic HC is correspondingly highest for the Mo-doped samples, in which extrinsic HC are generated.
The relationship between intrinsic and extrinsic ultraviolet (UV) transmission and UV lamp- and laser radiation-induced defects produced in phosphate glasses has been investigated. The composition was varied from simple binary metaphosphate glasses (MPs) to multicomponent ultraphosphate glasses (UPs), which can be melted on a commercial scale, to small amounts of mono- and diphosphates in fluoroaluminate glasses. The effects of the structure-dependent band gap (intrinsic effect) and the Fe2+/Fe3+ and P5+/P3+/P0 concentration ratios (extrinsic effect) on the UV absorption, and on the formation and recombination of radiation-induced defects were studied. A correlation has been inferred with the optical basicity of the glass matrix. The kinetics of the photoionization of Fe2+ to (Fe2+)+ were measured and simulated. This process is single photon, whose rate depends on the phosphate content and increases with increasing phosphate content (increasing basicity). Single and two photon mechanisms were indicated by the excimer laser radiation forming electron and hole defect centers, which were attributed to phosphorus species based on their electron paramagnetic resonance spectra. These defects cause additional absorption bands in the UV-visible region. Differences were detected between phosphate and fluoroaluminate glasses with a phosphate content ⩽20 mol%. The fluoroaluminate glasses have the lowest optical basicity and are stable against UV radiation, but crystallize. The optical basicity increases, the crystallization tendency decreases, and the UV radiation-induced defects increase with increasing phosphate content.
Tungsten-doped sodium phosphate glasses of various compositions and with varying WO3 contents were prepared. UV–visible and infrared spectroscopic studies were measured before and after successive gamma irradiation. Raman and ESR studies were conducted for some selected glass samples. Experimental results indicate that tungsten ions occupy two possible valences W6+ and W5+ with different local sites depending on the host glass composition and concentration of tungsten ions.The changes in UV, visible, infrared and Raman spectral data are discussed in relation to the structural evolution caused by the change in glass composition and state of tungsten ions. Electron spin resonance studies confirm the presence of unpaired W5+ ions.Tungsten ions have been found to show a shielding behavior towards the effects of progressive gamma irradiation causing a retardation of the growth of the induced defects caused by irradiation.
UV–visible spectroscopy of undoped and TM-doped (Ti–Cu) lithium diborate glasses have been measured before and after successive gamma irradiation. In the undoped borate glass, strong charge transfer UV bands are observed at 235 and 280 nm which are related mostly to trace iron impurities (Fe3+) ions.In the TM-doped glasses, characteristics absorption bands are obtained due to each specific TM ion in addition to that due to the base glass.Gamma irradiation produced induced bands due either to the intrinsic host borate glass in the UV region at about 210, 230, 280 nm and one visible band at 540 nm or extrinsic bands which are different according to the added TM ions and initiated by photochemical processes. The rate of induced color centers formation is fast at first and then becomes slower or reaches saturation and some TM ions (V, Cr, Co, Ni, Cu) show retardation or shielding to gamma ray but with varying degrees. Infrared absorption measurements of the undoped and TM-doped glasses are measured to justify the structural groups of the host lithium borate glass and the effects of TM ions on their arrangement.Gamma irradiation causes a decrease in the intensities of the IR bands accompanied by losing sharpness. These features are related to more amorphicity or disorder by irradiation or to the possible changes in bond angle or bond length in the building groups arrangement.
Glass systems with composition xTiO2.(30 - x)Na2O.70B2O3 (series I) and xTiO2.(70 - x)B2O3.30Na2O (series II) containing 2 mol% V2O5 have been prepared (0 < or = x < or = 7, mol%) by normal melt-quenching. The electron paramagnetic resonance (EPR) spectra of VO2+ ions have been recorded in the X-band (approximately 9.13 GHz) at room temperature. Spin Hamiltonian parameters, gparallel, gperpendicular, Aparallel, Aperpendicular, the dipolar hyperfine coupling parameter (P) and the Fermi contact interaction parameter (K) have been calculated. The increase in Deltagparallel/Deltagperpendicular with increase in TiO2 content in series I shows that the octahedral symmetry of V4+O6 complex is reduced, whereas in series II the octahedral symmetry is improved with increase in x. The decrease in P, in both the series, indicates that the 3dxy orbit expands with increase in mol% of TiO2. The molecular orbital coefficients, alpha2 and gamma2 have been calculated by recording the optical transmission spectra in the range 500-850 nm. alpha2 and gamma2 increase with increase in x in both the series, which indicates that, the covalency of the vanadium oxygen bonds decreases. The dc conductivity sigma, decreases and activation energy, W increases with increase in TiO2:Na2O ratio whereas with increase in TiO2:B2O3 ratio the variation in sigma and W is within experimental error.
Colour Generation and Control in Glass
- C R Bamford