Effect of Mixed Transition Metal Ions in B₂O₃-V₂O₅-MoO₃ Glass System

Abstract

The effect of having two different transition metal oxides in a glass matrix is an interesting phenomenon to study, as this kind of composition leads to various anomalous effects in terms of electrical and other physical properties. The present series of glasses were explored for density and DC electrical conduction in borate glass systems containing molybdenum and vanadium oxides. The glasses were synthesized using the melt-quench method and their amorphous characteristics were established by XRD techniques. The glasses were explored for density and DC electronic conduction in a temperature range between 318 K and 473 K. The estimated density, molar volume and oxygen packing density (OPD) varied non-linearly with increasing MoO₃ content. The DC conduction and activation energy attained maximum and minimum around 0.15 mole fraction of MoO₃. This was attributed to the fact that with the addition of MoO₃ up to x = 0.15 molar fraction, the V²⁺ transition metal ions and Mo⁵⁺ transition metal ions may create bond defects and non-bridging oxygen (NBO) by altering the bonds of boron-oxygen-boron, boron-oxygen-molybdenum, boron-oxygen-vanadium. As a result, at x = 0.15 mole fraction of MoO₃, the glass linkage among the bonds becomes close or tightly packed. Consequently, the net movement of ions begins effortlessly over the pathways of the tightly packed glass system. The high-temperature conduction data were analysed following Mott’s small polaron hopping theory, and the low-temperature conduction data were analysed in terms of Mott’s and Greave’s variable-range hopping conduction models. Several polaron-related parameters were estimated and are discussed.