Elastic properties of binary, ternary and quaternary rare earth tellurite glasses

Abstract

Glasses containing rare earth ions in high concentration are potentially useful for optical data transmission or in laser systems. Tellurite glasses are also of technical interest because of their low melting points and absence of the hygroscopic properties which limit application of phosphate and borate glasses. They have moderately large refractive indices and dielectric constants and are good infrared transmitters for wavelengths up to 5 #m. One aim of the present work has been to attempt to make a number of different glasses, based on tellurite as the principal former, which contain substantial quantities of rare earth ions. Binary, ternary and quaternary glasses have been prepared, most being from glass systems which previously have been examined scantily or not at all. Earlier studies of the effect of incorporating rare earth cations on the structure and physical properties of tellurite glasses include those in the binary TeO2La203 system [1] and also in the [1 - (2x + 0.05)] TeO2" xFe203" (x + 0.05)Ln203 system, where x = 0 and 0.05 and Ln was lanthanum, neodymium, samarium, europium or gadolinium and measurements of the M6ssbauer effect, infrared spectra and electrical conductivity were made [2]. Glass formation in the quarternary Er203-WO3-TeO2-PbO-TeO2 system has been established [3]. Interest in erbiumcontaining tellurite glasses developed because the photochromic properties of erbium-doped tellurite glasses are substantially more pronounced than those of silicate glasses containing an equivalent erbium-ion concentration [4]. To study the elastic properties of the rare earth tellurite glasses prepared here, measurements have been made of the velocity of ultrasonic waves propagated through them. The vibrational anharmonicity associated with these long wavelength acoustic modes has been investigated by measurements of the effects of hydrostatic pressure on the ultrasonic wave velocities. Previous studies of the elastic behaviour of vitreous TeO2 itself [5], binary TeO2-WO3 and TeO2ZnCI2 glasses [6] and the ternary (TeOz)0.5(PbO)0.2(WO3)0.3 and (TeO2)0.75(PbO)0.zl(La203)0.04 glasses [7, 8] have led to the general conclusion that tellurite glasses show normal behaviour in that they stiffen as the pressure is increased or the temperature is decreased. Now we can include in the overall picture the way in which the presence of substantial high concentrations of rare earth ions influences the elastic behaviour of tellurite glasses.