engleski

Vanadium phosphate glasses as potential energy materials

Semiconducting glasses based on transition‐metal oxides (TMOs) have great potential as electrode materials for batteries, electronic circuit elements, electrical switching devices, and gas sensors. The necessary condition for electronic conduction in glasses is the presence of the transition metal ion in more than one valence state where electron transfer occurs from the ion in a lower valence state to the ion in a higher valence state. The highest electronic conductivity of the order of 10 × 10–7 (Ω cm)–1 at room temperature was observed for V2O5-P2O5 and WO3– P2O5 glass systems, however, reported results refer to a relatively narrow range of composition (1, 2). The aim of this study is to investigate transport properties of binary xV2O5–(100–x)P2O5 glass system with a widest possible range of composition from x = 30 to x = 90 mol%. The glasses were prepared by the melt quenching method and were investigated by Raman and impedance spectroscopies. The fraction of vanadium ions in different valence states, V4+/Vtot, was determined from the temperature dependence of magnetization, measured with SQUID magnetometer, and analyzed using the Curie constant attributed to the isolated paramagnetic centres V4+. Raman spectra reveal that the glass structure drastically changes with the increase of V2O5 content. When present in low concentrations, V2O5 acts as a network modifier, with the increase of V2O5 content it acts as a network former. Thus, the increase of V2O5 content bands attributed to the stretching vibrations of V–O, and V–O–P bonds is observed as the amount of V2O5 increases. The DC conductivity of glasses increases with the increase of V2O5 due to an increase in the concentration of vanadium ions reaching the highest conductivity of 1.03 × 10-4 (Ω cm)-1 at 30 °C for glass with 90 mol% V2O5. An almost linear DC trend can be observed when V2O5 content is higher than 60 mol%, which can be correlated to the changes in the number density of polarons and gradual changes in the vanadium-rich glass structure.

Electrical properties ; glass structure ; SQUID ; vanadium phosphate glasses

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