Mechanical, microstructure and electrical properties of ternary ZnO–V2O5–Mn3O4 varistor with sintering temperature

Abstract

The mechanical, microstructure and electrical properties of the ZnO–V2O5–Mn3O4 (ZVM)-based varistors were investigated at different sintering temperatures of 825–950∘C. The microstructure of the samples consists mainly of ZnO grains with Zn3(VO4)2, ZnV2O4 and VO2 as minor secondary phases. These minor phases disappeared for samples sintered at 950∘C. Energy-dispersive X-ray spectroscopic (EDS) analysis confirmed the above microstructure results. The sintered density is decreased linearly from 5.45 to 5.30 g cm −3 with an increase in the sintering temperature. The E B- and α-values of ZnO-based varistor can be controlled in a straightforward manner through the control of grain size. The breakdown field exhibited the highest value (2110 V cm −1) at 825∘C in the sintering temperature and the lowest value (1427 V cm −1) at 950∘C in the sintering temperature. The non-linear coefficient exhibited the highest value, reaching 19.81 at 875∘C and the lowest value, reaching 6.71 at 850∘C. As the average grain size increases both the longitudinal wave velocity and the longitudinal elastic modulus decrease while the ultrasonic attenuation increases and vice versa.