Thermal stability of Sb–V2O5–TeO2 semiconducting oxide glasses using thermal analysis

Abstract

Thermal analysis of the ternary xSb−(60−x) V2O5–40TeO2 oxide glasses (with 0⩽x⩽15 in mole%) has been carried out employing the differential scanning calorimetry (DSC) at heating rates φ=3, 6, 9 and 12K/min. The compositional and heating rate dependence of the glass transition temperature (Tg) is discussed. Using the DSC outputs, the compositional dependence of the activation energy (ΔH∗) of glass transition (the heat absorbed in the endothermic region respecting to Tg) is investigated. The dependence of Tg on φ was used to study the applicability of different empirical formulas describing the glass transition. For these glasses, Moynihan and Kissinger formulas were applied and different values of ΔH∗ were obtained at different heating-rate regions. Also, the fragility parameter (m=ΔH∗/RTg) was obtained and discussed upon the data of thermal stability parameter (S), glass forming tendency (Kgl), CV=[V4+]/Vtot as the ratio of the content of reduced vanadium ions and also oxygen molar volume (VO∗). Results show that glasses with x⩾10 (especially for x=12) have relatively high thermal stability, high glass forming tendency and so lower non-bridging oxygen atoms (NBOs), which introduce them as good candidates for devices with higher resistance against thermal shocks, such as optoelectronic devices. Also, the Seebeck coefficient (Q) of these glasses was measured at different temperatures; for the under studied samples, the thermoelectric power at different temperatures was within the range of ((−392)−(−691))μVK−1, showing the increasing trend with increase of Sb content. The negative sign of Q indicates that these glasses are n-type semiconductors; results show the compositional dependence of Q, indicating that S increases with increasing of Sb content and CV; thus, the important parameter determining Q is the composition and therefore CV.