La2O3 Glass Research Articles

Synthesis and optical properties of SiO2–Al2O3–MgO–K2CO3–CaO–MgF2–La2O3 glasses

A series of five glass compositions were prepared by using the conventional melt quenching technique in the system SiO2–Al2O3–MgO–K2CO3–CaO–MgF2–La2O3 with different contents of SiO2, MgO, K2CO3, MgF2 and La2O3. The effects on the optical and physical properties of these glasses due to the addition of La2O3 as well as variation of the various oxides have been investigated. X-ray diffraction analysis is used to confirm the amorphous nature of the prepared glasses. Structures of glasses were studied by using UV–Vis and Fourier transforms infrared spectroscopy. The drilling test was also performed on their glass ceramic samples to confirm the machinability.

Thermo-physical properties of 0.72TeO2–0.24WO3–0.04La2O3 glass

0.72TeO2–0.24WO3–0.04La2O3 glass and melt were studied by differential scanning calorimetry (DSC) method. Heat capacity and transition temperature of the glass were precisely found. The improved comparative technique for DSC-measurement of thermal conductivity coefficient of vitreous state of the sample has been developed. A model-statistical approach was used for processing the experimental data to calculate parameters of elementary excitations, that allowed to find out a complete set of thermal properties along with density and coefficient of thermal expansion.

Chemical compatibility between MgO–SiO2–B2O3–La2O3 glass sealant and low, high temperature electrolytes for solid oxide fuel cell applications

Abstract The chemical interaction study of MgO–SiO2–B2O3–La2O3 (ML) glass with low and high-temperature electrolytes is reported as a function of different heating durations. The as prepared diffusion couples with high-temperature and low temperature electrolytes have been heat-treated at 850 °C and 800 °C, respectively, for 5, 100 and 750 h. The heat-treated diffusion couples have been characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray dot mapping and electron probe microanalysis (EPMA). Microstructural analysis of diffusion couples completely precludes the presence of any unwanted oxides and reaction products at the interface. The glass has shown good bonding characteristics and absence of delamination particularly with yttria stabilized zirconia (YSZ). Efforts have also been made to understand the interfacial reaction by considering different theoretical parameters associated with ML glass.

Optical properties of Nd3+ and Er3+ ions in TeO2–WO3–PbO–La2O3 glasses

Multicomponent telluride-tungstate glasses containing Nd3+ and Er3+ ions were studied experimentally at 77 and 293K using spectroscopic methods. The Judd–Ofelt intensity parameters were derived from the absorption spectra and used to calculate the radiative lifetimes and branching ratios. The quantum efficiency η=0.95 of the 4F3/2 level of Nd3+ ion is higher than the typical value of other tellurite-based glasses. For low concentration of Er3+ ions, the luminescence decay of the 4S3/2 and 4I11/2 levels is governed by radiative transitions and multiphonon relaxation involving the Te-O highest energy vibrations.

Near-infrared broadband luminescence and energy transfer in Bi–Tm–Er co-doped lanthanum aluminosilicate glasses

The Bi–Tm–Er co-doped SiO2–Al2O3–La2O3 (SAL) glasses, which exhibited a broadband near-infrared (NIR) emission, were investigated by the optical absorption and photoluminescence spectra. A super broadband NIR emission extending from 0.95 to 1.6μm with a full-width at half-maximum (FWHM) of 430nm which covered the whole O, E, S, C and L bands, was observed in Bi–Tm–Er co-doped samples under 808nm excitation, as a result of the overlap of the Bi-related emission band (centered at 1270nm) and the emission from Tm3+3H4→3F4 transition (1450nm) as well as Er3+4I13/2→4I15/2 transition (1545nm). In addition, a super broadband emission with amplitude relatively flat from 0.95 to 2.1μm has been observed. The possible energy transfer between Bi-related centers, Tm3+ ions and Er3+ ions was proposed.

Interfacial study between high temperature SiO2–B2O3–AO–La2O3 (A = Sr, Ba) glass seals and Crofer 22APU for solid oxide fuel cell applications

In the present work, the adhesion and chemical compatibility of two glass compositions are investigated with interconnect Crofer 22APU as a function of different heating durations for solid oxide fuel cell applications. Initially, the selected glasses have been characterized using differential thermal analyzer and dilatometer to check their suitability as a sealing material. After that, Crofer 22APU/glass–ceramics are joined to make diffusion couples. Furthermore, these diffusion couples have been heat-treated at 850 °C for different time durations of 5, 100 and 750 h and morphologically characterized. X-ray diffraction (XRD) indicates surface crystallization of various crystalline phases formed in the glass/Crofer 22APU diffusion couple. Coefficient of thermal expansion (CTE) of both the glasses is in good agreement with the CTE of Crofer 22APU. The overall analysis of resulting microstructure by scanning electron microscopy (SEM)/electron probe microanalysis (EPMA) revealed improvement in adhesion with increase in time duration of heat-treatment. Both the sealants have not shown delamination with Crofer 22APU interface even after prolonged duration of heat-treatment. The absence of unwanted oxide products in all the diffusion couples further confirms high gas tightedness and hermeticity of seals with low embrittlement.

Infrared broadband emission of bismuth–thulium co-doped lanthanum–aluminum–silica glasses

The Bi–Tm co-doped SiO2–Al2O3–La2O3 (SAL) glasses, which exhibited a broadband near-infrared (NIR) emission was investigated by the optical absorption and photoluminescence spectra. The super broadband near-infrared emission from 1000 to 2100nm, which covered the whole O, E, S, C and L bands, was observed in the Bi–Tm co-doped samples, as a result of the overlap of the Bi-related emission band (centered at 1270nm) and the emission from Tm3+3H4→3F4 transition (1440nm) as well as Tm3+3F4→3H6 transition (1800nm). Relative luminescence intensity at 1270, 1440 and 1800nm wavelength varied depending on the mixing ratio of Bi and Tm and the full-width at half-maximum (FWHM) extending from 1000 to 1600nm could be 400nm. These results indicated that Bi–Tm co-doped SiO2–Al2O3–La2O3 glasses could provide potential applications in tunable lasers as well as the broadband optical amplifiers in WDM system.

Crystallization Kinematics and Dielectric Behavior of (Ba,Sr)TiO3 Borosilicate Glass Ceramics

Perovskite [(Ba0.6Sr0.4)TiO3]-[2SiO2-B2O3]-[K2O]-La2O3 glass was prepared by conventional melt quench method. The differential thermal analysis (DTA) was performed on glass sample in the temperature range from 100℃ to 1000℃ by different heating rate to study the crystallization kinematics. The kinetic parameters characterizing the crystallization have been determined using an Arrhenius model. Glass samples were subjected to appropriate heat treatment schedules for their suitable crystallization. X-ray diffraction analysis (XRD) of glass and glass ceramic samples were done to check the amorphous state and crystalline nature. XRD of glass ceramic sample shows the major perovskite phase of BaTiO3 (BT) along with the formation of secondary phases Ba2TiSi2O8 (BTS) and Ba2Ti2B2O9 (BTB). Scanning electron microscopy (SEM) is also studied to see the morphology of the grains of major and secondary phase formation in BST glass ceramic samples. La2O3 is played an important role to increase the nucleation of the crystallites in the glassy matrix. The addition of La22O3 results in development of well interconnected crystallites formed as major phase of BST. In this paper, we are reporting the crystallization behavior of BST borosilicate glass system and high temperature dielectric characteristics of their glass ceramics.

Preparation and characteristics of a BaO–Al2O3–B2O3–SiO2–La2O3 glass ceramic via spray pyrolysis

The characteristics of a BaO–Al2O3–B2O3–SiO2–La2O3 glass ceramic prepared by spray pyrolysis were studied. Glass powders with spherical shape and amorphous phase were prepared by complete melting at a preparation temperature of 1 500°C. The mean size and geometric standard deviation of the powders prepared at the temperature of 1 500°C were 0.6 μm and 1.3. The glass powders had similar composition to that of the spray solution. The glass transition temperature (Tg) of the glass powders was 600.3°C. Two crystallization exothermic peaks were observed at 769.3 and 837.8°C. Densification of the specimen started at a sintering temperature of 600°C, in which Ba4La6O(SiO4)6 as main crystal structure was observed. Complete densification of the specimen occurred at a sintering temperature of 800°C. The specimens sintered at temperatures above 800°C had main crystal structure of BaAl2Si2O8.

Structure and bonding in single- and two-phase alumina-based glasses

Pulsed neutron and high energy X-ray diffraction experiments on single- and two-phase Al2O3–Y2O3 and single-phase Al2O3–La2O3 glasses suggest that a polyamorphic phase transition occurs via changes in the Y–O coordination and connectivity. The transformation from a high temperature to a low temperature amorphous phase is mainly associated with the formation of YO8 polyhedra at the expense of YO7 polyhedra. The transition produces a more ordered network structure with increased oxygen connectivity, while maintaining the overall metal∶oxygen stoichiometry. It is estimated that for the two-phase sample studied ∼12% of the Y ions had transformed to the higher coordinate form in the supercooled liquid as the onset of the glass transition was reached.

Electronic polarizability, optical basicity, and interaction parameter of La2O3 and related glasses

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.

Frequency upconversion in Er3+/Yb3+-codoped chalcogenide glass

Frequency upconversion of cw infrared radiation at 1.06 μm into the visible in Er3+/Yb3+-codoped Ga2S3:La2O3 chalcogenide glass samples is presented. Intense green and red emission bands around 530, 555, and 670 nm, respectively, are observed in addition to near-infrared 830 and 925 nm less intense signals. Energy transfer processes and nonradiative phonon-assisted decays account for the population of the H211/2, S43/2, and F49/2 emitting levels. The dependence of the red emission with the Yb3+ concentration is also analyzed. The potential application of the Er/Yb-codoped Ga2S3:La2O3 glass for upconversion based optical devices is discussed.