Electrical properties of perovskite YFeO₃ based ceramics modified by Cu/Nb ions as negative temperature coefficient thermistors

Cu/Nb doped YFeO₃ ceramics were synthesized through wet chemical method followed by traditional ceramic sintering technology. The phase component and electrical properties of the ceramics were investigated. The XRD pattern shows that all the prepared ceramics have the orthorhombic perovskite structure with space group of Pnma. The XPS analysis demonstrates the existence of Fe²⁺ and Fe³⁺ in the ceramics. The temperature dependence of resistivity indicates that YFeO₃-based materials have a characteristics of negative temperature coefficient (NTC) of resistivity. The room temperature resistivities (306–1.52 × 10⁵ Ω cm) and temperature sensitivity B values (2693–5395 K) can be effectively adjusted by changing the contents of Cu- and Nb- ions. According to the analysis of complex impedance spectra at various temperatures, the NTC characteristic could be attributed to grain effect and grain boundary effect. The possible conduction mechanisms are propose to hopping conduction and band conduction in grain, and thermal activation transport of charge carries in grain boundary.