Effects of Ta2O5 on the microstructure and electrical properties of ZnO linear resistance ceramics

ZnO linear resistance ceramics were synthesized from ZnO–Al2O3–MgO–TiO2–SiO2–Ta2O5 by a conventional ceramics method. Effects of Ta2O5 on the phase composition, microstructures, and electrical properties of ZnO linear resistive ceramics were investigated. The results show that doping with appropriate amount of Ta2O5 can refine the grains of the main crystalline phase ZnO and the secondary crystalline phase ZnAl2O4 in terms of microstructure, and also can reduce the grain boundary barrier and optimize the I–V characteristics in terms of electrical properties. In addition, the doping of Ta2O5 can improve the stability of the resistivity , and the impedance frequency indicates that the doping of Ta2O5 makes the sample suitable for high-frequency electric fields. The resistivity of the sample doped with 0.2 mol% Ta2O5 is 56.2 Ω·cm, and this sample has the best grain boundary barrier height, nonlinear coefficient and temperature coefficient of resistance of 0.054 eV, 1.04 and −3.48 × 10−3 °C−1, respectively.