Physical and thermal characterization and glass stability criteria of amorphous silver-vanadate-tellurate system at different heating rates: Inducing critical Ag2O/V2O5 ratio

Abstract Transition metal oxide containing glasses (TMOGs) have unique thermal properties. This work gives an insight into the thermal stability and the compositional dependence of thermal properties for the understudied glasses. Also, physical, some optical and thermal characterization of 40TeO2-(60 − x)V2O5-xAg2O glasses have been investigated in the compositional range of 0 ≤ x ≤ 50 mol%. DSC experiments were performed on powder samples with a weight of 5 mg, within the temperature range of 30–400 °C at heating rates φ = 2.5, 5, 7.5 and 10 K/min, to obtain the glass transition temperature (Tg) and crystallization temperature (Tcr). The heating rate dependence of Tg has been used to study the applicability Kissinger formula describing the glass transition, in order to determine the glass transition activation energy (Ea). Ea values show that it ranged from 563.22 kJ/mol to 268.36 kJ/mol, indicating that (in relation/justification to other thermal and structural data) less fragility and so higher thermal stability is devoted to in the case of x = 20 mol%. The previously reported optical absorption spectra and optical band gap (Eg) by the same author were used to evaluate the refractive index (n),which both Eg and n have a behavior change at critical content of x = 20 mol%, implying to a drastic structural change with increasing Ag2O. Also, the physical parameters such as density (ρ), molar volume (Vm), oxygen molar volume (VO∗), oxygen packing density (OPD), molar refraction (Rm) and metallization criterion (M) have been evaluated and discussed, showing a behavior change at x = 20 mol%. Different glass stability parameters and different criteria of fragility have been checked, which show that glass with x = 20 has the good stability among the present glasses. In brief, glass with x = 20 has relatively high thermal stability, high glass forming tendency, higher OPD and VO∗, and so lower non-bridging oxygen ions (NBOs), which show that it is suitable option and promising material for optical and optoelectronic devices such as base semiconductor in solar cells and optical fibers because of its resistance against thermal attacks and also its narrower band gap.