Electrical property and temperature sensitivity of NiFe 2− x Sb x O 4 ( x ≤ 0.02) ceramics for negative temperature coefficient thermistors

The NiFe 2− x Sb x O 4 ( x = 0.0, 0.008, 0.01, 0.015, 0.02) ceramics were prepared by a wet chemical process. The related ceramics were obtained by powders compacting and sintering by conventional ceramic processing. The phase component, cationic valence and electrical properties of the prepared ceramics were investigated. The investigation results indicate that NiFe 2− x Sb x O 4 ceramics have a cubic spinel structure and display a typical characteristic of negative temperature coefficient (NTC) of resistivity. The room temperature resistivity of NiFe 2− x Sb x O 4 ceramics can be adjusted from 75597 to 2714 Ω cm by changing the contents of Sb, and the ceramics hold high thermal sensitivity with NTC material constants between 3612 and 5408 K. The investigation of impedance spectra measured at different temperatures revealed that the grain effect and grain-boundary effect contribute simultaneously to the electrical conductivity and NTC effect. Conduction mechanism of NiFe 2− x Sb x O 4 NTC thermistors are proposed to follow the polaron hopping model.