Structural and mechanical features of some lanthanum tellurite glasses

Abstract

Tellurite-based glasses of the chemical formula xLa2O3-(100 – x) TeO2, (2.5 ≤ x ≤ 12.5 mol%) have been prepared and studied by FTIR spectroscopy and the ultrasonic technique. The FTIR analysis indicated that La2O3 transformed the TeO3 into TeO4 structural units in the range 2.5 ≤ x ≤ 5, while in the range 5 ≤ x ≤ 7.5 mol%; there is a coordination transformation of Te atoms in [TeO4] groups into [Formula: see text] groups associated with the formation of non-bridging oxygens. Beyond x = 7.5 mol%, the structural units [Formula: see text] (tp) were destroyed and transformed into TeO4 structural units that acted as a former and tightened the tellurite glass network more. The stretching force constant of the tellurite structural units was affected with the increase of La2O3 content. The structural variations of the structural units of TeO2 and La2O3 affected the increase of density, the behaviour of the ultrasonic velocities, the elastic moduli, and both of the optical and acoustical Debye temperature with increasing La2O3 content. The ratio of optical to acoustic Debye temperature represented the three-dimensional nature of tellurite-based glasses.