Characterization of electrically conductive vanadate glass containing tungsten oxide

New conductive glass with a composition of 20BaO·10Fe2O3·xWO3·(70 − x)V2O5 (x = 10–50) was investigated by means of Mössbauer spectroscopy. A marked decrease in quadrupole splitting (Δ) was observed after the isothermal annealing at 500 °C for 1,000 min, due to the structural relaxation of 3D-network composed of FeO4, VO4, and VO5 units. After the isothermal annealing, a marked increase in the electrical conductivity (σ) was observed from 1.7 × 10−5 to 1.0 × 10−1 S cm−1 when “x” was 10, whereas comparable σ values of 1.1 × 10−4 and 2.0 × 10−4 S cm−1 were observed when “x” was 40. These results evidently show that structural relaxation of 3D-network structure involved with a marked increase in σ is intrinsic of “vanadate glass”. XRD pattern indicated several weak peaks due to needle-like BaFe2O4 and α-Fe2O3 when the glass sample with “x” of 20 was annealed at 500 °C for 1,000 min. SEM study proved the formation of needle-like BaFe2O4 just on the surface of the sample, whereas hexagonal BaFe12O19 were observed in the annealed sample with “x” of 40. Chemical durability of WO3-containing vanadate glass was investigated by immersing each glass sample into 20 %-HCl solution for 72 h.