Mechanical, microstructure and electrical properties of ternary ZnOa€“V2O5a€“Mn3O4 varistor with sintering temperature

摘要

The mechanical,microstructure and electrical properties of the ZnOa€“V₂O₅a€“Mn₃O₄ (ZVM)-based varistors were investigated at different sintering temperatures of 825a€“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 cma?’3 with an increase in the sintering temperature. The e???_B- and e???-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 cma?’1) at 825?° C in the sintering temperature and the lowest value (1427 V cma?’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.