Electrical properties of hexagonal BaTi1-x Fe x O3-δ (x=0.1, 0.2, 0.3) ceramics with NTC effect

BaTi1-x Fe (x) O3-delta (x = 0.1, 0.2, 0.3) powders were prepared by a wet chemical process polymerized with polyvinyl alcohol, and the related ceramics were obtained by conventional sintering process. The phase component and electrical properties of the ceramics were investigated. The analysis of X-ray diffraction indicates that the BaTi1-x Fe (x) O3-delta ceramics have a hexagonal crystalline structure. The temperature dependence of resistivity of the ceramics show a characteristic of negative temperature coefficient (NTC) of resistivity with the material constants of around 5,000 K. The impedance analysis reveals that both the grain effect and grain-boundary effect contribute simultaneously to the NTC effect. The conduction mechanisms for the NTC characteristic are proposed to be the electron-hopping model between Fe3+/Fe2+ ions inside grains and the charge carrier transports overcoming the energy barrier of the grain boundary by thermal activation.