Electrical properties of Y/Mg modified NiO simple oxides for negative temperature coefficient thermistors

Abstract The semiconductors based on simple oxide have unique features with controllable electrical property by element doping. Y ³⁺ doped NiO (Ni _{1− x} Y _x O, x ≤ 0.01) and Mg ²⁺ substituted Ni _0.995 Y _0.005 O (Ni _{0.995− y} Y _0.005 Mg _y O, y ≤ 0.5) powders were synthesized by a wet chemical method. The related ceramics were obtained by conventional ceramic processing. Phase component, microstructure, electrical property and temperature sensitivity of the prepared ceramics were investigated. All ceramics have a rock‐salt type crystalline structure. The room‐temperature resistivity of the ceramics can be widely adjusted from 254 to 12 322 Ω·cm by changing the concentrations of Y ³⁺ and Mg ²⁺ ions. The samples show typical characteristics of negative temperature coefficient of resistivity and have high temperature sensitivity with material constants higher than 4745 K. The analysis of impedance spectra indicates that the electrical properties resulted from both grain effect and grain boundary effect. Both band conduction and small polaron hopping were proposed as possible conduction mechanisms in the studied ceramics.