Microstructures and electrical properties of Ba 1–x Bi x Fe 0·9 Sn 0·1 O 3 thermistor ceramics

Abstract

The polycrystalline Ba_1–xBi_xFe_0·9Sn_0·1O₃ (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 Ba_1–xBi_xFe_0·9Sn_0·1O₃ 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 Ba_1–xBi _x Fe_0·9Sn_0·1O₃ 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 Ba_1–xBi_xFe_0·9Sn_0·1O₃ thermistor ceramics are mainly attributed to the contribution of grains, grain shells and grain boundaries by the impedance analysis.