Microstructure and electrical properties of rare earth doped ZnO-based varistor ceramics

Abstract ZnO-based varistor ceramics doped with Nd 2 O 3 and Y 2 O 3 have been prepared by the conventional ceramics method. The phase composition, microstructure and electrical properties of the ceramics have been investigated by XRD, SEM and a V – I source/measure unit. The XRD and EDS analyses show the presence of ZnO, Bi 2 O 3 , Zn 7 Sb 2 O 12 , Y 2 O 3 , Nd-rich phase and Y-containing Bi-rich phase. The electrical properties analyzed show that the nonlinear coefficient of the varistor ceramics is in the range of 4.4–70.2, the threshold voltage is in the range of 247.1–1288.8 V/mm, and the leakage current is in the range of 1.51–214.6 μA/cm 2 . The 0.25 mol% Nd 2 O 3 added varistor ceramics with 0.10 mol%Y 2 O 3 sintered at 1050 °C exhibits excellent electrical properties with the high threshold voltage of 556.4 V/mm, the nonlinear coefficient of 61 and the leakage current of 1.55 μA/cm 2 . The results illustrate that doping Nd 2 O 3 and Y 2 O 3 in ZnO-based varistor ceramics may be a very promising route for the production of the higher threshold voltage and the nonlinear coefficient of ZnO-based varistor ceramics.