Microstructure and electrical properties of Y(NO3)3·6H2O-doped ZnO–Bi2O3-based varistor ceramics

Y(NO3)3·6H2O-doped ZnO–Bi2O3-based varistor ceramics were prepared using a solid reaction route. The microstructure, electrical properties, degradation coefficient (DV), and dielectric characteristics of varistor ceramics were studied in this paper. With increasing amounts of Y(NO3)3·6H2O in the starting composition, Y-containing Bi-rich, Y2O3, and Sb2O4 phases were formed, and the average grain size decreased. Results also showed that with the addition of 0.16 mol% Y(NO3)3·6H2O, Y(NO3)3·6H2O -doped ZnO-based varistor ceramics exhibit comparatively better comprehensive electrical properties, such as a threshold voltage of 425 V/mm, a nonlinear coefficient of 73.9, a leakage current of 1.78 μA, and a degradation coefficient of 1.7. The dielectric characteristics and lightning surge test also received the same additional content of Y(NO3)3·6H2O. The results confirmed that doping with rare earth nitrates instead of rare earth oxides is very promising route in preparing high-performance ZnO–Bi2O3-based varistor ceramics.

► Y(NO3)3·6H2O as rare earth dopant. ► Dopant for improve electrical characteristics of varistor ceramics. ► Higher nonlinear coefficient is important for high performance varistor ceramics. ► Doping with rare earth nitrates is a very promising route.