Enhancing electrical properties by in-situ controlled nanocrystallization of V2O5 -TeO2 glass

Abstract

Vanadium oxide-containing materials became an interest in the energy industry, therefore, understanding the conductivity enhancement of vanadium oxide glass under annealing became crucial to further developing new, superior materials. V2O5-TeO2 glass-ceramics (VTGC) were prepared by controlled annealing of the V2O5-TeO2 glass (VTG), which serves as an illustration of a parent glass matrix with a single charge carrier. The annealing proceeded at six temperatures selected between the glass transition and the maximum of the first crystallization process to obtain various nanocrystallite sizes. Heat treatment caused an increase in DC conductivity by 2.5–3.5 (250°C-285°C) order of magnitude. Using thermal analysis, the crystal growth process was determined to be 1D. Structural studies show that the obtained materials are partially amorphous and polycrystalline with nanometer-sized crystallites. Subtle thread-like structures were observed using conductive AFM. The activation energy of the conduction process decreased from 0.38 eV in VTG to 0.18 − 0.11 eV (250°C-285°C) in VTGC. The radii of crystallites were calculated based on the theoretical model of electron hopping between connected semiconducting nanocrystallites and vary between 1.7 nm and 2.8 nm (250°C-285°C). Thermoelectric studies indicate constant carrier concentration. Features characteristic of small polaron hopping-governed materials were observed. We suggest V3O7 nano-crystals as conductive media in VTGC.