Effect of iron substitution on electronic conductivity of bismuth sesquioxide glasses

Several glassy oxide semiconductors exhibit large electron mobilities; however, these oxides may not be considered environmentally friendly because of their toxicity. Herein, we report on the electrical conduction of iron oxide-containing bismuth sesquioxide borate glasses that are not toxic and show ohmic transport in the temperature range of 100–400 °C. The dominant carrier is the electron, which is revealed by the signs of Hall and Seebeck coefficients, without sign anomalies. The Hall mobility is ∼0.1 cm2/(V s), and the carrier density is ∼6 × 1015 cm−3 at 400 °C. The Seebeck coefficient is approximately −500 μV/K at 388 °C. The carriers might be generated by charge transfer between Fe2+ and Fe3+ substituted in the glass, and they exhibit thermally activated hopping-type electronic conduction. The oxide glass can be used as a glass thermistor for a temperature range of 100–400 °C.