Electrical conductivity and local structure of iron-containing lithium barium vanadate glass

Abstract

A relationship between the local structure and electrical conductivity of lithium barium iron vanadate glass with a composition of xLi2O·(20-x)BaO·10Fe2O3·70V2O5, abbreviated as xLBFV glass, was investigated by means of 57Fe-Mössbauer spectroscopy, differential thermal analysis (DTA), as well as DC four-probe method. When the Li2O content increased from 0 to 20 mol%, a constant isomer shift (δ) value of 0.35±0.01 mm s−1 and a decreasing quadrupole splitting (Δ) value from 0.71 to 0.67±0.01 mm s−1 were observed in the Mössbauer spectra. From the DTA curves, decrease in both glass transition temperature (Tg) and crystallization temperature (Tg) was confirmed from 317 to 236±5 °C and from 374 to 299±2 °C, respectively. A large slope value of 1560 °C/mm s−1 was estimated from 'Tg − Δ plot', showing that the Fe3+ acts as a network former (NWF). When the xLBFV glass with 'x' of 20 was heated up to 125 °C, a larger increase in the electric conductivity (σ) was observed from 3.2 × 10−5 to 1.3 × 10−3 S cm−1. It was found that replacement of Li+ for Ba2+ reduces the local distortion of FeO4 (Td), and increases the temperature dependence of electrical conductivity.