Emission properties of Eu3+ ions in ZnCl2-BaCl2-KCl glass

In this short communication, we present the results concerning the excitation and emission spectra of I mol% EU3+ -doped 50ZnCl(2) + 20BaCl(2) + 29KCI glass. A bright red color emission was observed under an UV source from this glass. The photoluminescence spectra have shown prominent red emission transition (D-5(0) —> F-7(2)) at 610 nm along with three other weak emission transitions of D-5(0) —> F-7(0), (1 and 3) at 580, 598 and 650 Dm upon excitation with six identified excitation bands. Dependence of the emission intensities and lifetimes based on the excitation wavelengths employed has been investigated. (C) 2002 Elsevier Science B.V. All rights reserved

Infrared spectroscopic method for estimating physical properties of metaphosphates glasses

Calcium metaphosphate glass has been dehydroxylated under vacuum and by calcium fluoride addition. The first overtone band of Vss(OPO) and/or combinational band of Vas(OPO) + vas(POP) at around 2170 cm−1 in the infrared (IR) spectra of the glasses, not originally observed in high hydroxyl (OH) containing glasses, has been found to develop gradually with the progress of dehydroxylation. The absorption coefficient of this band has been statistically correlated with density, refractive index and glass transition temperature of low OH containing glasses in the form of equations. Each of these equations has high correlation coefficient and low residual standard deviation. Thus, they have been employed for the estimation of physical properties of high OH containing glasses. The experimental values of the properties of these glasses present a good fit with the calculated mean values within 95% confidence interval. This fact confirms the validity and utility of this IR spectroscopic approach for the estimation of physical properties of calcium metaphosphate glasses

Temperature dependent luminescence in (Eu3+, Dy3+) doped tellurite glass

This short paper reports both the photoluminescence and the lifetime measurements of a prominent emission transition (D-5(0) —> F-7(2)) of Eu3+ both in the presence and absence of the codopant rare earth ion (Dy3+) in an optical glass of the composition (79-x)TeO2+6AlF(3)+15LiF+xLn(2)O(3) as a function of temperature down to 10K

Energy transfer luminescence in (Eu3+, Nd3+)-doped tellurite glass

Here, we bring out an infrared transmitting new optical glass based on TeO2 added with AlF3 and LiF, containing dual rare earth ions (Eu3+ & Nd3+) as the dopants with a purpose to examine their luminescence and also the decay times pertaining to a prominent transition of Eu3+ (D-5(0) —> F-7(2) at 615 nm) as a function of temperature both in the presence and absence of Nd3+ ions. The energy transfer rates (W-tr), critical distances (R-0) and transfer efficiencies (eta(tr)) have been evaluated based on the measured lifetime data of this glass

Temperature dependent luminescence characteristics of Sm3+-doped silicate glass

We report the optical characterization of Sm3+: SiO2+Al2O3+Li2O+Na2O+MgO glass from the measurements of optical absorption spectra (at 300 K), total luminescence spectra (10 K - 300 K) and fluorescence lifetimes (10 K - 300 K) of the prominent emission transitions of the Sm3+ ions. Besides the analysis of spectral properties, physical and nonlinearity characterizing property parameters have also been computed to understand the optical dispersive power of this glass. By the application of Judd-Ofelt parameters (Omega(lambda)) of the measured absorption spectrum, the radiative transition probability factors (A) and stimulated emission cross-section (sigma(P)(E)) of the observed fluorescent levels have been analyzed. Both emission intensity and measured lifetimes of the prominent luminescent transition ((4)G(5/2) —> H-6(7/2)) concerning Sm3+ - glass are showing a descending trend with a rise in temperature having a N-2-laser (337.1 nm) as the excitation source

Temperature dependent luminescence in (Eu3+, Dy3+) doped tellurite glass

This short paper reports both the photoluminescence and the lifetime measurements of a prominent emission transition (D-5(0)-->F-7(2)) Of Eu3+ both in the presence and absence of the codopant rare earth ion (Dy3+) in an optical glass of the composition (79 - x)TeO2 + 6AlF(3) + 15LiF + xLn(2)O(3) as a function of temperature down to 10 K. (C) 1999 Elsevier Science B.V. All rights reserved

IR spectra and their application for evaluating physical properties of fluorophosphate glasses

Infrared (IR) absorbance spectra in the range 500-4000 cm(-1) of the glasses in the system Ba(PO3)(2)-MgF2-CaF2-AlF3 have been studied with increasing fluoride content. Quantitative justification for assignment of some bands has been attempted. The spectra reveal that the glass structure changes with fluoride addition from metaphosphate, (PO3-)(n) to P-2 (O, F)(7) and P(O, F)(4) along with the formation of Al(O, F)(6), [AlF6](3-) and [AlF4](-). As a result of these structural changes density (a), refractive index n,) and IR band absorption coefficient at similar to 2170 cm(-1)(alpha (IR)) of the glasses vary exhibiting maxima at similar to 36 mol% fluoride. Statistical analyses show that d and n, are correlated with alpha (IR) by linear equations. Each of these equations gives a high correlation coefficient (r) and low residual standard deviation (RSD), and may, thus, be employed for the evaluation of physical properties of fluorophosphate glasses. Physical properties of some fluorophosphate glasses of this work and the published literature have been calculated by using these equations to test their validity. The experimental properties of the glasses present a very good fit of data within 95% confidence interval of the calculated mean values. These facts indicate the suitability of this IR spectroscopic method for the determination of physical properties of fluorophosphate glasse

Infrared spectroscopic method for determination of thermal properties of fluorophosphate glasses

Fluorophosphate glasses of the Ba(PO3)(2)-MgF2-CaF2-AlF3 system exhibit anomalous behavior, in regard to the glass-transition temperature (T-g) and the coefficient of thermal expansion (alpha(CTE)), at a fluoride concentration of similar to 36 mol%. A similar trend in the infrared band absorption coefficient (alpha(IR)) at 2170 cm(-1) of the overtone of 2 nu(ss)(OPO) and/or a combination of nu(as)(OPO)+nu(as)(POP) fundamental vibrations of PO4 tetrahedra also has been observed, relative to changes in the glass composition. Statistical analyses have shown that the T-g and alpha(CTE) values are correlated with alpha(IR) at 2170 cm(-1) by linear equations. The thermal properties of some of the glasses have been calculated using these equations, to test their validity and utility. The experimental property values of the glasses present a very good fit of data within a 95% confidence interval of the calculated mean value

UV transparency and structure of fluorophosphate glasses

Ultraviolet (UV) transparency and local structural environment of fluorophosphate glasses in the Ba(PO3)(2)-MgF2-CaF2-AlF3 system have been studied with increasing fluoride content (covering the whole compositional range) by infrared (IR) reflection spectroscopy (IRRS) in conjunction with P-31 magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. UV cutoff of the glasses shifts towards longer wavelength with increasing fluoride up to similar to 36 mol%. IRRS spectra indicate a gradual increase in nonbridging oxygens (NBOs) in this region. According to P-31 MAS NMR spectra, it is due to the combined effects of gradual increase in Q(1) sites and P-O-Al bridges (increase in optical basicity). Beyond similar to 36 mol% fluoride content, the UV cutoff shifts towards shorter wavelength. It is attributed to decrease in NBOs or Q1 sites (decrease in optical basicity) as revealed in the IRRS and P-31 MAS NMR spectra, respectively. In this region, true partial role of the metal fluorides in controlling UV transparency has been found to contribute significantly as well. (C) 2002 Elsevier Science B.V. All rights reserved

Crystallization kinetics and mechanism of low-expansion lithium aluminosilicate glass-ceramics by dilatometry

The crystallization kinetics and mechanism of a precursor glass of lithium aluminosilicate (LAS)-based commercial low-expansion glass-ceramics were investigated using a dilatometer. The isothermal crystallization behavior of beta-quartz solid solution (ss) was found to obey the Avrami equation. Nonisothermal crystallization data were analyzed by the Ozawa method and modified Kissinger equation. The value of the Avrami exponent (n) was similar to1.5, and the apparent activation energy (E-a) was similar to500 kJ/mol, which was close to that of the diffusion of silicon and aluminum ions as well as metal-oxygen bond strengths, suggesting a three-dimensional (3D) diffusion-controlled reaction mechanism