Microstructures and electrical properties of Ba _1–x Bi _x Fe _0·9 Sn _0·1 O ₃ thermistor ceramics

The polycrystalline Ba1–xBixFe0·9Sn0·1O3 (x = 0·1, 0·2, 0·3, 0·4 and 0·5) ceramics were prepared using a solid state reaction process, and the effect of Bi substitution on the microstructures and the electrical properties is investigated. The as sintered Ba1–xBixFe0·9Sn0·1O3 ceramics showed the cubic perovskite structure with small amount of spinel BaFe2O4 and some residual Fe2O3. As the Bi concentration increased, the ceramic grain size decreased and the pores or holes were reduced for the ceramics. The values of room temperature resistivity, thermistor constant and activation energy of the Ba1–xBixFe0·9Sn0·1O3 thermistor ceramics, increasing with the rise of Bi content, were in the range of 1–1290 kΩ cm, 4469–7328 K and 0·385–0·632 eV respectively. The electrical properties of Ba1–xBixFe0·9Sn0·1O3 thermistor ceramics are mainly attributed to the contribution of grains, grain shells and grain boundaries by the impedance analysis.