Deciphering the thermal, physical, structural, and optical characteristics of sodium-doped vanadophosphate glasses

Abstract

Ionic glasses offer a multitude of prospects for a wide range of electrochemical applications such as solid-state batteries, which eventually require more accessible, secure, and ecologically sound electrolytes and electrode materials. Here, sodium-doped vanadium phosphate (NVP) glasses in the chemical composition, xNa2O.(50-x)V2O5.50P2O5 (where, x = 0, 10, 20, 30, 40, and 50 mol%) were effectively synthesized via the melt-quenching technique, and their amorphous nature was confirmed by the appearance of broad humps in X-ray diffraction technique. Numerous physical parameters, namely, density, molar volume, oxygen packing density (OPD), polaron radius, field strength, etc., were studied as a function of Na2O concentration. Furthermore, the structural alterations of the glass network were examined in relation to the modifications in the FTIR and Raman spectra brought about by varying concentrations of sodium ions, such as the formation of more bridging oxygen sites. The optical characteristics were investigated using UV–vis spectroscopy, and the transmittance in the as-prepared glass series elevated as Na2O content was increased. The presence of three absorption peaks centered at 320, 650, and 864 nm points towards the possibility of V4+ ions in the as-prepared glass samples. They are unequivocally amorphous semiconductors because their Urbach energy values fall between 0.12 and 0.57 eV. Optical band gap energy, refractive index, polarizability, dielectric constant, and additional parameters were also examined.