Electrical conductivity & temperature sensitivity of ceramics based on NiO simple oxides for NTC applications

LiF-doped NiO ceramics with various contents of B2O3/SiO2 additives were prepared by a wet-chemical synthesis method. The phase component and micro-structures of the ceramics were detected by using X-ray diffraction, scanning electron microscope and X-ray photoelectron spectroscopy. The related electrical conductivity and thermal sensitivity were investigated by analyzing the resistance–temperature characteristic and complex impedance spectra. The results show that the NiO-based ceramics have the cubic crystalline structure, and show the typical characteristic of negative temperature coefficient (NTC) of resistivity. The NiO-based ceramics, with various contents of B2O3/SiO2, have the NTC materials constant B values ranging from 3500 to 3800 K. The substitution of B2O3/SiO2 affects obviously the room-temperature resistivity of the ceramics, but has insignificant effect in the B values. The band conduction and electron hopping models are proposed for the conduction mechanisms for the NiO-based ceramics.