Li/Fe modified Zn0.3Ni0.7O NTC thermistors with adjustable resistivities and temperature sensitivity

Li/Fe modified Zn0.3Ni0.7O, (Zn0.3Ni0.7)1−x−yLixFeyO (x = 0–0.06, y = 0–0.04), were synthesized by a wet chemical synthesis methods and sintered by the traditional ceramic sintering technology. The phase component and related electrical properties of the ceramics were investigated. The analysis of X-ray diffraction indicates that all the prepared ceramics have a cubic crystalline structure. The resistance-temperature feature exhibits a typical effect of negative temperature coefficient (NTC) of resistivity in a temperature range from 25 to 250 °C. The ceramics have room-temperature resistivities ranging from 26.6 Ω cm to 102.8 MΩ cm and thermal-sensitivity constants from 2444 to 8378 K by changing the concentrations of Li and Fe. The complex impedance analysis reveals that both grain effect and grain boundary effect contribute collectively to the NTC feature of the ceramics. The possible conduction models were proposed to combine with electron-hopping conduction and band conduction.