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In this study, Li6 Y1-x Eux (BO3 )3 phosphor was successfully synthesized using a modified solid-state diffusion method. The Eu(3+) ion concentration was varied at 0.05, 0.1, 0.2, 0.5 and 1 mol%. The phosphor was characterized for phase purity, morphology, luminescent properties and molecular transmission at room temperature. The XRD pattern sugges...
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... excitation spectrum of Li 6 Y 1-x Eu x (BO 3 ) 3 phosphor was re- corded in the spectral range of 220-500 nm (see Fig. 4 The excitation spectrum also shows a series of peaks at 363, 380, 395 and 466 nm, which are assigned to characteristic f-f transitions of Eu 3+ ions (17). The excitation wavelength range of Eu 3+ in the UV and blue spectral regions matches well with the output wave- lengths of InGaN-based LED chips indicating that the phosphor has ...
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... The lithium borate [9,10], gadolinium borate [11], lithium aluminate [12] and lithium gadolinium borate [13] phosphors have shown exceptional UV and/or NUV absorption, strong luminescence efficiency and improved temperature dependent luminescence. The inclusion of aluminate to the lithium gadolinium borate host stimulates the RE active ions to produce high intense and unwavering luminescence leading to potential applications in the fields of lighting, optoelectronic and biosensors [14][15][16]. ...
... The IR absorption band in the region 1102-1108 cm -1 is attributed to asymmetric stretching vibrations of Al-O bond [12]. A group of IR absorption bands perceived in the regions 985-994, 948-961, 933-939, 905-911 cm -1 have been ascribed to the symmetric stretching vibrations of B-O bond [9,10]. The IR absorption band in the region 867-874 cm -1 is credited to stretching vibrations of Li-O bond [24]. ...
The Li6AlGd(BO3)4:xEu³⁺ phosphors were synthesized by solid phase reaction technique. The crystalline phase, morphology and photoluminescence properties were investigated using X-ray diffractometer, scanning/transmission electron microscope and fluorescence spectrophotometer, respectively. Up on 395 nm near ultra violet excitation, the Li6AlGd(BO3)4:xEu³⁺ phosphors exhibit intense red emission through ⁵D0 → ⁷FJ (J = 0, 1, 2, 3, 4) transitions. The concentration of Eu³⁺ ions was optimized as 4.0 mol% for efficient red emission at 395 nm excitation. The CIE colour coordinates (0.647, 0.352) are very close to the National Television System Committee red coordinates and commercial red phosphors. The luminescence thermal resistance was examined by studying the temperature dependence luminescence at 395 nm excitation. The quantum efficiency was estimated using the integrated intensity of emission peaks and decay time. The experimental observations show that the Li6AlGd(BO3)4:xEu³⁺ (x = 4.0 mol%) phosphor has greater proficiency as red component in the design of white LEDs and display devices.
... The FTIR spectral profile of LAGBSm0.5 phosphor in the region 400-1600 cm − 1 presented in Fig. 5a is identical to that of LAGBPr0 phosphor [22]. This spectrum reveals nineteen FTIR absorption bands corresponding to different symmetric/asymmetric stretching and/or bending [26][27][28][29][30][31][32][33][34][35][36] and their assignment is abridged in Table 1. ...
A new class of Li6AlGd(BO3)4: Sm³⁺ phosphors were prepared via solid-state-reaction method and analyzed for orange-red light sources. The structure, morphology, distribution of particles, presence of various bonds responsible for optical properties, energy-transfer among the excited Sm³⁺ ions and decay properties were broadly studied. Most of the intense and sharp excitation transitions of Sm³⁺ in LAGBSmx phosphors appear in n-UV region and the emission spectra reveal ⁴G5/2 → ⁶H5/2, 7/2, 9/2, 11/2 transitions upon 408 nm n-UV wavelength excitation. The concentration was optimized to be 1.0 mol% for efficient orange-red emission. The CIE colour coordinates were obtained as (0.611, 0.388) for LAGBSmx phosphors with a negligible change with variation in concentration of Sm³⁺ ions. The decay profiles were well fitted to double-exponential function showing the occupation of Sm³⁺ in two different sites. The transfer of energy among the excited Sm³⁺ ions was possible through exchange interaction at higher concentrations. The emission of orange-red light shows its proficiency for solid-state lighting devices as well as red light source replacement in the design of white-LEDs.
... As seen the FTIR patterns one can notice various vibrational bonds which have been ascribed to borate, aluminate, lithium and gadolinium modes [20][21][22][23][24][25][26][27][28][29][30] . The assignment of these vibrational bonds is summarized in Table 1 . ...
New and low energy consumption Li6AlGd(BO3)4: Dy³⁺ phosphors were fabricated through solid-state-reaction technique and characterized for lighting applications. The crystalline phase was confirmed from the powder X-ray diffraction technique. The Fourier transform infrared analysis was employed to investigate the presence of different bondings. The distribution of particles and their agglomeration was examined via morphological studies. Photoluminescence excitation, emission and decay studies were employed to study the luminescence properties. The excitation wavelength was optimized as 350 nm for efficient and strong luminescence from Li6AlGd(BO3)4: Dy³⁺ phosphors. They emit efficient luminescence through ⁴F9/2 → (⁶H15/2, ⁶H13/2, ⁶H11/2) transitions when excited at 350 nm near-UV wavelength. The photometric parameters such as chromaticity coordinates, colour purity and correlated colour temperature were determined using the emission spectral results. The quantum efficiency and the quantum yield parameters of studied phosphors show their applicability for lighting devices. The Li6AlGd(BO3)4: xDy³⁺ phosphor with x = 1.0 mol% has highest proficiency for lighting applications.
... It is made up of agglomerated particles and has a granular polycrystalline shape, as per FESEM images at different magnifications. They are certainly useful in a wide range of scientific and solid-state lighting device manufacturing applications [18]. ...
A series of NaBaBi(2-x)(PO4)3:xDy3+ eulytite type phosphors with varying doping concentrations were synthesized using a conventional solid-state reaction. The crystalline nature and phase formation of the phosphor were confirmed by the PXRD technique. FESEM was used to examine the surface morphology. UV-DRS measurements were used to quantify the band gap of the host and Dy3+ ion doped phosphors. The phosphors’ photoluminescence properties were thoroughly investigated. According to the excitation spectra, these phosphors show a strong absorption band in the near-ultraviolet (NUV) region, extending from 250 to 450 nm. Under the excitation of 352 nm, the peaks of the emission spectra of Dy3+ ions are located at 485 nm (blue), 575 nm (yellow) and 666 nm (red), corresponding to the magnetic dipole 4F9/2→6H15/2 transition, the electric dipole 4F9/2→6H13/2 transition and the 4F9/2→6H11/2 transition. The optimal concentration of Dy3+ doped phosphor is x = 0.075 and the major concentration quenching mechanism is accomplished by energy transfer between the nearest-neighbour ions. The critical transfer distance (Rc) is estimated to be about 19.01. The Commission International deI’Eclairage (CIE) of NaBaBi1.925(PO4)3:0.075Dy3+ phosphor was calculated to be (x = 0.341 and y = 0.374), which was very close to the “ideal white” (x = 0.33, y = 0.33). Present findings suggest that the phosphor might be a viable option for producing a white-light-emitting phosphor under NUV activation.
... On the other hand, it is important to be mentioned that the variation of the site symmetry of Eu 3+ ions in CaSiO 3 host can be evaluated from the evolution of the integrated emission intensity ratio of 5 D 0 → 7 F 2 and 5 D 0 → 7 F 1 transition also known as the asymmetric ratio R 21 [22]. The High value of this asymmetry ratio indicates lower symmetry of the crystal field around Eu 3+ ions [43,52]. ...
Polycrystalline glass-ceramic CaSiO3 doped with Eu3+ ions was obtained by devitrification. The analysis of the photoluminescent characteristics of the obtained glass-ceramic is carried out. It was found that as a result of the devitrification of CaSiO3, two phases are formed, identified as pseudowollastonite (β-CaSiO3) as the dominant phase together with a small percentage of tridymite (SiO2). The UV–Vis optical absorption of Eu3+-doped CaSiO3 was performed using a UV–Vis spectrophotometer. The main objective of this work was to study the effect of the pulsed corpuscular action of electrons accelerated in a field of 130 keV on energy transitions in the Eu3+ ion. It is found that, upon steady-state excitation of the photoluminescent signal in the PLE spectra of unirradiated samples at wavelengths below 300 nm, two broad excitation peaks are displayed, possibly associated with O − Eu and O − Si CT transitions. Above 300 nm the characteristic excitation band from 7F0 ground state to 5Hj, 5D4, 5Gj, 5L6, 5D3, and 5D2 states of the Eu3+ ions are shown. It was found that, as a result of exposure to an electron beam in the photoluminescence spectra of europium, a redistribution of the relative intensities of the 5D0 → 7F2 and 5D0 → 7F1 transitions occurs. The calculation of the asymmetry ratio of these transitions showed values for an unirradiated sample R21 = 2.06 and irradiated R21 = 2.52, which indicates a decrease in the symmetry of the crystal field around Eu3+ ions after irradiation. Several reasons for the decrease in the relative intensity of the Eu3+ luminescence signal after electron irradiation, caused by the effect of electrization of the material, intrinsic defects of the matrix, and inhomogeneous phase composition, are discussed.
... The bond-structure and planes are explained by Yiyi Ou [1,3,4]. LYBO crystals have been grown for different types of applications so far, such as solid electrolytic material with pure crystal [5], doped with Ce 3þ as single crystal for thermal neutron detection [2,6,7], Nd 3þ and Yb 3þ doped single crystal for laser application [8,9], phosphors doped with Eu 3þ , Dy 3þ etc. for light-emitting diode application [10][11][12] and so on. The wide bandgap is suitable to explain the optical properties of different dopants, which has been performed for Ce 3þ , Er 3þ , Eu 3þ , and Tb 3þ doped crystals and phosphors [3,[13][14][15][16]. 6 Li and 10 B has remarkable thermal neutron absorption cross-section of 947 � 4 b and 9835 � 9 b respectively with the nuclear reactions 6 Li (n, α) 3 H and 10 B (n, α) 7 Li [17]. ...
The orthoborate crystals with a wide optical bandgap allow different rare earth ions as an activator (Ce3þ, Dy3þ,
Eu3þ, etc.) to provide efficient luminescence. In the present study, Li6Y(BO3)3 pure and 4 mol% Dy3þ doped
single crystals have been grown using the Czochralski method. The light emission of the grown crystals has been
characterized by using X-ray luminescence, photoluminescence and thermoluminescence measurements.
Intrinsic luminescence property has been observed for pure crystal at 330 nm and the characteristic emission of
Dy3þ was observed in doped crystal under X-ray excitation. Photoluminescence study of the doped crystal at low
temperature has shown the increased peak intensity with the decrease of temperature from 290 to 10 K. Decay
time has been measured at the temperature ranging from 290 to 10 K which consists of three components in each
stage. Thermally stimulated luminescence of both pure and 4 mol% Dy3þ doped LYBO crystals have been
compared at low temperature from 320 K to 10 K. Scintillation β counts measured from 300 K to 10 K. The
performance of the doped crystal has been tested as a scintillator for thermal neutron imaging.
... 3+ [21] and (1.71) Li 6 Y(BO 3 ) 3 :0.5Eu 3+ [28] phosphors, respectively. It was clearly noticed that the R/O ratio value decreased with the increase of Eu 3+ concentration upto x = 0.5, beyond that it was slightly increased. ...
... Upon excitation at 406 nm, the emission spectrum is composed of several distinct groups of peaks in the range of 475-750 nm (Figure 6b). There are two strong emissions in the orange-red region coming from positions at 605 nm and 650 nm, corresponding to the 4 G5/2→ 6 H7/2 and 4 G5/2→ 6 H9/2 transitions of Sm 3+ , respectively [22]. Besides, there are two weak emissions centered at 566 nm and 714 nm, which can be assigned to the 4 G5/2→ 6 H5/2 and 4 G5/2→ 6 H11/2 transitions of Sm 3+ , respectively. ...
... Upon excitation at 406 nm, the emission spectrum is composed of several distinct groups of peaks in the range of 475-750 nm (Figure 6b). There are two strong emissions in the orange-red region coming from positions at 605 nm and 650 nm, corresponding to the 4 G 5/2 → 6 H 7/2 and 4 G 5/2 → 6 H 9/2 transitions of Sm 3+ , respectively [22]. Besides, there are two weak emissions centered at 566 nm and 714 nm, which can be assigned to the 4 G 5/2 → 6 H 5/2 and 4 G 5/2 → 6 H 11/2 transitions of Sm 3+ , respectively. ...
Sodium samarium borate Na3Sm(BO3)2, was prepared by a flux method and structurally characterized by single-crystal structure analysis for the first time. The results show that it crystallizes in the monoclinic system P21/n, with a = 6.5667(3) Å, b = 8.7675(4) Å, c = 10.1850(5), β = 90.86°, V = 586.32(5) ų and Z = 4. The structure contains NaO7, NaO6, NaO5, SmO8, and BO3 units, which are interconnected via corner- or edge-sharing O atoms into a three-dimensional structure. The excitation spectra, emission spectra, decay time, and Commission International de l’Éclairage (CIE) chromaticity index of Na3Sm(BO3)2 were studied. Under near light excitation (406 nm), the powdered Na3Sm(BO3)2 shows the orange-red emission, which originates from the⁴G5/2→⁶H9/2 and⁴G5/2→⁶H7/2 transformation of Sm³⁺ ion.
... Efforts were directed to study whether solid state reaction, combustion and wet chemical synthesis routes modifies the local crystal environment of the luminescent center and changes the optical characteristics of the material [4]. The synthesis of Li 6 Gd(BO 3 ) 3 :Eu 3þ and Li 6 Y(BO 3 ) 3 :Eu 3þ by solid state reaction method were already reported in our previous publications [21,22]. At present, we have reported the combustion and wet chemical synthesis of the aforesaid phosphors and compared their photoluminescence properties with the same phosphors synthesized by solid state reaction method. ...
... For both the synthesis methods, the optimum PL intensity was recorded for 1 mol% of Eu 3þ ions doped in Li 6 Y(BO 3 ) 3 phosphor. The samples prepared by the combustion and wet chemical methods were compared with the one prepared by solid state method that was reported in our previous publication [21]. On making a combined analysis of the emission spectra of Li 6 Y(BO 3 ) 3 :Eu 3þ phosphor prepared by three distinct methods, it is found that the samples prepared by combustion method showed highest intensity. ...
... The photoluminescence properties analysed in the present work approves that the prepared phosphors are potential red emitting phosphors for LED. These phosphors are already reported to exhibit strong charge transfer band near 275 nm in our previous publications [21,22]. Also, these bands have no contribution in LED phosphors and hence, we have neglected their description in the present case. ...
Abstract In the present paper, we discuss the synthesis route dependence of luminescence in Li6M(BO3)3:Eu3+ (M = Y, Gd) phosphors. The current phosphors were prepared by two distinct methods of synthesis, viz., combustion and wet chemical methods for varying concentration of Eu3+ activator and the prepared phosphors were compared with those prepared by solid state reaction method. The phosphors were effectively synthesized by combustion and wet chemical methods in an open atmosphere. Each phosphor, thus, derived was further characterized for phase purity, morphology, and luminescent properties at room temperature. The emission and excitation spectra were pursued to discover the luminescence traits. The excitation spectra indicate that the prepared phosphors can be efficiently excited at 395nm, 467 and 540nm/550nm light to give emission at 595 and 614nm due to 5D0 →7Fj transition of Eu3+ ions. A strong and dominant red emission is achieved at 614 nm achieved from the 5D0→7F2 transition of Eu3+ ions. Li6M1-x(BO3)3:Eux may be a suitable red-emitting component for solid state lighting.
... Gd 3? and Y 3? possess the same valence and similar ionic radius. Also the compounds Li 6 Gd(BO 3 ) 3 and Li 6 Y(BO 3 ) 3 are isomorphic [19] and hence the XRD pattern resembles that of Li 6 Y(BO 3 ) 3 with JCPDS No.# 80-0843 [20]. Figure 2 displays the SEM images of the present phosphor viewed at different magnifications. ...
... The vibrational frequencies below 450 cm -1 are attributed to lattice vibrations. Our experimental results indicate that B-O bond asymmetric stretching of BO 3 groups is located in the region from 1150 to 1650 cm -1[1,20]. ...
Li6Gd(BO3)3 phosphor doped with varying concentrations of europium was synthesized using a solid-state reaction route. Powder X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy methods were used to characterize the prepared phosphor. Photoluminescence excitation spectra of the Li6Gd(BO3)3:Eu3+ phosphors exhibited bands due to both Eu3+ and Gd3+ ions. Upon excitation of the host at 275 nm, the energy absorbed by Gd3+ ions can be transferred to Eu3+ ions in the Li6Gd(BO3)3 luminescent materials. The optimum concentration of Eu3+ ions for maximum luminescence yield was evaluated for the system. Color coordinates of prepared compound were calculated and plotted on the CIE diagram. The fluorescence lifetime of Eu3+ ions was found to be 2.12 ms. TL properties of the phosphor showed dominant peak at around 231 °C in addition to small shoulders at 131 and 367 °C. Various trap parameters and the kinetics for the glow peak were evaluated using the Chen’s peak shape method.
