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ABSTRACT: This paper reports recent progress in the patterning of non-linear optical crystals on the glass surface by laser irradiation. Two techniques for the writing of crystal lines have been developed, i.e., rare-earth (samarium) atom heat processing and transition metal atom heat processing, in which a continuous wave Nd:YAG laser (wavelength: λ=1064 nm) is irradiated to the glasses containing rare-earth (RE: Sm3+, Dy3+) ions or transition metal (TM: Ni2+, Fe2+, V4+) ions. The writing of crystal lines such as β-BaB2O4, SmxBi1−xBO3, and Ba2TiGe2O8 showing second harmonic generations has been successful. It is clarified from the azimuthal dependence of second harmonic intensity and polarized micro-Raman scattering spectra that crystal lines consist of highly oriented crystals along the crystal line growth direction. It is also possible to write two-dimensional crystal bending or curved lines by just changing the laser scanning direction. The mechanism of the laser-induced crystallization has been proposed.
Journal of the American Ceramic Society 02/2007; 90(3):699 - 705. · 2.27 Impact Factor
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ABSTRACT: Some glasses such as 21.25Sm2O3.63.75MoO3.15B2O3 (mol %) giving the formation of nonlinear optical Sm2(MoO4)3 crystals through conventional crystallization in an electric furnace and through continuous-wave Nd: yttrium aluminum garnet (YAG) laser (wavelength: 1064 nm) irradiation (samarium atom heat processing) have been developed. It is proposed from x-ray diffraction analyses, micro-Raman-scattering spectra, and second-harmonic generation measurements that the crystal structure of Sm2(MoO4)3 formed by the crystallization is the β′-phase structure with an orthorhombic (noncentrosymmetric) symmetry. The lines consisting of nonlinear optical β′-Sm2(MoO4)3 crystals are written at the surface of glasses by YAG laser irradiation (laser power: P = 0.4 W, laser scanning speed: S = 1–10 μm/s), and, in particular, homogeneous crystal lines are formed at the laser scanning speed of 1 μm/s. Refractive index changes (not crystallization) are also induced by YAG laser irradiation of P = 0.4 W and a high laser scanning speed of S = 25 μm/s. The crystallization mechanism in the laser-irradiated region has been proposed. The present study demonstrates that the samarium atom heat processing is a technique for the writing of rare earth containing optical nonlinear/ferroelectric crystal lines in glass.
Journal of Applied Physics 06/2005; 97(12):123516-123516-7. · 2.17 Impact Factor
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ABSTRACT: The electronic polarizability and optical basicity of La2O3 and related glasses have been determined from ultraviolet absorption spectra and calculations based on the Lorentz–Lorenz equation. The optical basicity for La2O3 oxide is found to be 1.07, being much larger compared with typical glass-forming oxides such as B2O3 (0.42) and SiO2 (0.48) but being similar to heavy element oxides such as TeO2 (0.93). The Yamashita and Kurosawa’s interaction parameter of La2O3 is 0.03 Å−3, indicating that La2O3 is classified as a normal ionic (basic) oxide, i.e., an ionic bonding character in the La3+–O bond is proposed. Close correlations are confirmed among optical basicity, interaction parameter, and oxygen 1s binding energy in x-ray photoelectron (XPS) spectra for La2O3–P2O5 and other La2O3-containing glasses. It is found from XPS and Raman spectra that La3+ ions in La2O3–P2O5 glasses act as network modifiers, supporting an ionic bonding character in the La3+–O bond. The parameters related to electronic polarizability in La2O3 determined in the present study would be useful for the design of rare-earth containing optical functional glasses. © 2002 American Institute of Physics.
Journal of Applied Physics 02/2002; 91(5):2942-2950. · 2.17 Impact Factor
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ABSTRACT: The structural relaxation kinetics in the glass transition for xSb2O3⋅(100−x)B2O3 glasses with covalent bonding character has been examined from viscosity and heat capacity measurements. These binary glasses have low glass transition temperatures, Tg = 250–290 °C, but show a high thermal resistance against crystallization. The degree of fragility m estimated from the activation energy for viscous flow (Eη = 290–531 kJ mol−1) is m = 29–51. The activation energy for enthalpy relaxation, ΔH = 297–602 kJ mol−1, is evaluated from the cooling rate dependence of the limiting fictive temperature. The ΔH values are very close to the Eη values, meaning that the decoupling between enthalpy relaxation and viscous flow is small. The values of Kovacs–Aklonis–Huchinson–Ramos (KAHR) parameter θ estimated from ΔH/RTg2 are 0.13–0.25, where R is the gas constant. The glasses with 30–60 mol % Sb2O3 have very similar Eη, m, ΔH, and θ values. It has been demonstrated that the structural relaxation kinetics of the binary antimony borate glasses is affected by the boron coordination numbers (i.e., BO3 and BO4) and the covalent bonding character of Sb–O bonds, and consequently these glasses are regarded as a highly strong glass-forming system in the fragile/strong classification concept. © 2001 American Institute of Physics.
The Journal of Chemical Physics 10/2001; 115(15):7207-7214. · 3.33 Impact Factor
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ABSTRACT: Bi2Sr2CaCu2Ox glass with Cu+/(Cu+ + Cu2+) = 0.76 was prepared by using a conventional melt-quenching method, and crystalline phases and grain orientations at the surface of superconducting glass-ceramics obtained by annealing at various atmospheres were examined. The grain orientation of the Bi2Sr2CaCu2Ox phase (low-T
c phase) at the surface was severely affected by oxygen partial pressure in annealing. The favourable grain orientation, in which the plate-like grains of the low-T
c phase are oriented parallel to the surface plane, was first established in the samples obtained through a newly developed two-step annealing method: first annealing at 780C in oxygen and second annealing at above 750C in nitrogen. It was concluded that the favourable grain orientation of the low-T
c phase at the surface occurred due to the formation of a liquid phase in nitrogen.
Journal of Materials Science Materials in Electronics 01/1994; 5(1):41-46. · 1.08 Impact Factor
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ABSTRACT: High-T
c superconducting ceramics of formula Bi0.8Pb0.2SrCaCu
x
O
y
(x=1.5, 1.8 and 2.0) were prepared by using the melt-quenching method, and the effect of copper content on glass formation and
superconductivity was examined. It was found that the composition withx=1.5 had a tendency to form a glass and Bi2(Sr, Ca)2CuOy crystals tended to precipitate easily during the rapid quenching of melts in the compositions withx=1.8 and 2.0. It was found from the temperature dependence of a.c. complex susceptibility that the intergrain coupling of
superconducting crystals in the samples obtained was weak, but the weak coupling was improved by increasing the annealing
time. The superconducting glass-ceramics Bi0.8Pb0.2SrCaCu1.5Oy exhibited superconductivity with aT
c (zero) of 106 K and aJ
c of 250 Acm−2.
Journal of Materials Science 04/1991; 26(3):683-688. · 2.02 Impact Factor
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Journal of Materials Science Letters 12/1990; 10(6):355-357.
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Journal of Materials Science Letters 12/1990; 10(19):1146-1148.
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Journal of Materials Science Letters 10/1990; 9(11):1359-1361.
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ABSTRACT: The Ag‐coated superconducting Bi 2 Sr 2 CaCu 2 O x glass‐ceramic fibers were successfully prepared. The glass fibers with a length of 50 cm, a width of 100–200 μm, and a thickness of about 20 μm were first drawn from glass plates with a thickness of 1 mm and then silver pastes were coated on the smooth surface of glass fibers. The Ag‐coated glass fibers were converted into superconductors after annealing at temperatures of 820–860 °C. The main crystalline phase in the glass‐ceramic fibers was the superconducting low T c phase. The Ag‐coated glass‐ceramic fibers obtained by annealing at 840 °C for 5 h in air exhibited superconductivity with a T c (zero)=70 K and a critical current density (60 K, zero magnetic field) of more than 40 A/cm<sup>2</sup> .
Applied Physics Letters 08/1990; · 3.84 Impact Factor
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ABSTRACT: Superconducting glass ceramics of Bi 0.8 Pb 0.2 SrCaCu 1.5 O y (sample A) and BiPb 0.2 SrCaCu 1.5 O y (sample B) have been prepared by using the melt quenching method. It was found that the volume fraction of the high T c phases in sample A annealed at 830 or 840 °C for 250 h was much higher than that in sample B. The annealed (840 °C, 250 h) sample A exhibited superconductivity with a T c (zero) of 100 K and a critical current density (77 K, zero magnetic field) of 120 A/cm<sup>2</sup>.
Applied Physics Letters 04/1989; · 3.84 Impact Factor
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ABSTRACT: Various high- T <sub>c</sub> superconducting glass ceramics
based on the Bi-Ca-Sr-Cu-O system were prepared by the melt-quenching
method. The melt-quenched sample of Bi<sub>1.2</sub>CaSrCu<sub>2</sub>O
<sub>x</sub> was found to be a glass that became a high- T <sub>c
</sub> superconductor with T <sub>c</sub> (zero)=85 K by
annealing at 820°C. The Bi<sub>1-x</sub>Pb<sub>x</sub>CaSrCu<sub>2
</sub>O<sub>y</sub> glasses also became high- T <sub>c</sub>
superconductors upon annealing at temperatures above 800°C. The
glass ceramics of Bi<sub>0.9</sub>Pb<sub>0.1</sub>CaSrCu<sub>2</sub>O
<sub>x</sub> exhibited superconductivity with T <sub>c</sub>
(onset)=116 and T <sub>c</sub> (zero)=100 K
IEEE Transactions on Magnetics 04/1989; · 1.36 Impact Factor
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ABSTRACT: New optical nonlinear transparent surface crystallized glasses have been successfully fabricated in the system of Ln2O3–Bi2O3–B2O3 (Ln=La, Sm, Gd). The second harmonic (SH) generation from the crystalline phases at the surface layers has been confirmed from Maker fringe measurements. It is suggested that the optical nonlinear crystals precipitated through the crystallization of Ln2O3–Bi2O3–B2O3 glasses would be new metastable BixLn1−xBO3 phases in which Bi3+ ions in BiBO3 are substituted by Ln3+ ions. The thickness of crystallized surface was approximately 5 μm and SH intensity was 0.02 compared with that of the Z-cut α-quartz with a thickness of 0.6 mm. In 12.5Sm2O3·30Bi2O3·57.5B2O3 glass, the crystalline dots with diameters of 5–65 μm are formed by the irradiation of CW YAG laser with a wavelength of 1064 nm (at 0.6 and 0.7 W, for 1–240 s), and it is found that these crystalline dots generate optical SH waves. This is the first finding on optical nonlinear crystalline dot formation by YAG laser irradiation in bismuth-containing glasses.
Optical Materials.
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ABSTRACT: A continuous-wave Nd:YAG laser operating at a wavelength of 1064 nm is used to irradiate BaO–Sm2O3–TeO2 glasses under various conditions (laser power: 0.5–0.7 W, irradiation time: 1–60 s), and the formation, behavior and morphology of crystal-dots and lines consisting of the Sm2Te6O15 phase are examined. Crystal-dots with a corn-like shape are formed at the surface of the glasses. The diameters of crystal-dots are 3–45 μm and their lengths (depths) toward the interior of glasses are 50–110 μm. The size of crystal-dots depends on laser power, laser irradiation time and Sm2O3 content. The diameter and length of crystal-dots increase almost linearly with the cube root of laser irradiation time t1/3, suggesting that the growth of crystal-dots in the YAG laser-induced crystallization is controlled by diffusion of constituent ions. Crystal-lines with a width of ∼10 μm are also written by scanning the YAG laser at a speed of 20–30 μm s−1. A model of YAG laser-induced crystallization is proposed.
Journal of Non-Crystalline Solids.
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ABSTRACT: Nonlinear optical β-BaB2O4 (β-BBO) crystal straight lines are written in 10Sm2O3·40BaO·50B2O3 glass by irradiation of a continuous wave Nd:YAG laser operating at 1064 nm. The linearly polarized micro-Raman scattering spectra for β-BBO crystal lines are consistent with those for commercially available y-cut β-BBO bulk single-crystals, supporting that β-BBO crystal straight lines with the c-axis orientation along the YAG laser scanning direction might be single-crystals. The photoluminescence spectra with large intensities and Stark splitting are observed for β-BBO crystal lines, and it is concluded that some amounts of Sm3+ ions in the glass are incorporated into β-BBO crystal lines. Two-dimensional β-BBO crystal curved lines with a bending angle of 30° are successfully written in 10Sm2O3·42BaO·48B2O3 glass.
Journal of Physics and Chemistry of Solids 65(10):1705-1710. · 1.63 Impact Factor
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ABSTRACT: The thermal stability and heat capacity changes in the glass transition region of K2O–WO3–TeO2 glasses (glass formation range 20–90 mol% TeO2) have been studied to examine the structural relaxation behavior. The glasses with 60–70 mol% TeO2 and with both K2O and WO3 are thermally stable against crystallization. It is proposed from Raman spectral analyses that TeO4 trigonal bipyramids change to TeO3 trigonal pyramids with the addition of K2O and that Te–O–W bonds are formed in the substitution of WO3 for TeO2. Heat capacity changes of ΔCp=48–58 J mol−1 K−1 (ΔCp=Cpl−Cpg, Cpg and Cpl are the heat capacities of the glasses and supercooled liquids, respectively), and ratios Cpl/Cpg= 1.6–1.8 are obtained for xK2O · xWO3 · (100 − 2x)TeO2 glasses. The ΔCp and Cpl/Cpg increase with decreasing TeO2 content, indicating an increase in thermodynamic fragility with decreasing TeO2 content. But, the kinetic fragility estimated from the activation energy for viscous flow is almost constant irrespective of TeO2 content. These behaviors have been analyzed using the configurational entropy model proposed by Adam and Gibbs. The results indicate that in K2O–WO3–TeO2 glasses, Te–O–Te bonds are weak and bond breakings occur easily in the glass transition region, leading to large configurational entropy changes and thus large ΔCp.
Journal of Non-Crystalline Solids.
