Characterization of electrically conductive vanadate glass containing tungsten oxide
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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.
KeywordsConductive glass Tungsten-substituted vanadate glass Structural relaxation Chemical durability
The authors (SK and TN) would like to express their sincere gratitude to late Prof. Dr. Attila Vértes, L. Eötvös University, for his gentle encouragement and friendship during the last quarter century. This study was partially supported by Grant-in-Aid for Scientific Research (C) (KAKENHI, No. 23550229).
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