Influence of Nd3+ modifying on 80TeO2–xZnO–(20−x)Na2O ternary glass system

Abstract

In this study, the ternary system of TeO2–ZnO–Na2O (TZN) with a fixed TeO2 content of 80 mol. % and with a varied ZnO and Na2O content of totally 20 mol. % was examined for thermal/mechanical properties, Raman and x-ray absorption fine structure (XAFS) spectra, and the evolution of medium distance (correlation length) of order, called blob size here, given from low-frequency Raman spectra and longitudinal/transverse sound velocities as a function of ZnO concentration. The TZN glasses were doped with Nd2O3, and the effects of Nd doping on the above-mentioned properties were reported. High-temperature in situ x-ray diffraction experiments were also conducted to know possible oxygen coordination numbers of these main-constructive cations from crystalline phases precipitated at elevated temperatures. According to the information, the evolution of blob size of Nd-doped and non-doped TZN glasses was attempted to be predicted with a term of theoretical volume of their molar unit constructed with cation–oxygen polyhedra of TeO3, TeO4, ZnO4, ZnO5, NaO4, and NaO5. A transition region due to the structural change owing to the coordination numbers of Te–O and Zn–O was elucidated concerning density, molar volume, and Poisson ratio. XAFS spectroscopy revealed that the ZnO component had different polyhedra of ZnO4 and ZnO5, whose ratio was dependent not only on ZnO concentration but also on whether Nd3+ ions were doped or not. Based on the information taken from a variety of observations, our preliminary analysis suggested that the different mechanical properties between the doped and non-doped glasses were explained by five-coordinated zinc in the glasses. Possible molecular models shall be given for lower and higher ZnO concentrations in TZN glasses.