Modifier role of ZnO on the structural and transport properties of lithium boro tellurite glasses

Abstract

To study the modifier role of ZnO on the structural and transport properties, the quaternary glass system xZnO-(30-x) Li2O-10TeO2–60B2O3 (x = 0, 5, 10, 15 and 20 mol%) was prepared by the conventional melt quenching technique. Amorphous nature of the prepared glasses was confirmed by X-ray diffraction studies. Density (ρ) of the glass samples was measured by Archimedes' principle and it was found to vary non-linearly between 3.06 and 3.44 g/cm3 with the addition of heavy metal oxide (ZnO) mole concentration. Oxygen packing density (OPD) values also varied non-linearly between 66.78 and 74.69 g atm/1. Glass transition temperature (Tg) of the glass system was measured using temperature modulated differential scanning calorimeter and Tg was found to increase from 429 °C-449 °C with the increase of ZnO content. Based on the density and molecular weight of the glass composition, mechanical properties like Young's modulus (E), Shear modulus (S), Bulk modulus (K) etc., have been calculated with the help of Makishima-Mackenzie model in terms of the packing ratio (Vρ) and dissociation energy (Gt). FTIR and Raman spectroscopy studies reveal that the glass network consists of various types of BO3, BO4 units along with TeO3, TeO4 and ZnO4 structural units. To study transport properties, AC conductivity measurements were carried out on the glass system in the frequency range 5 Hz-35 MHz and it was observed that the ionic conductivity plays significant role. At low temperatures (30 °C and 50 °C) the results of conductivity did not give good results. AC conductivity of the studied glass system is increased with increase in frequency and temperature. The highest value of AC conductivity of the glass network is of the order 10−2 Ω−1 cm−1. Impedance plots (Cole-Cole) exhibited semicircle behaviour.