Attaining a homogeneous microstructure of a ZnO-based multilayer varistor by constrained sintering

The performance of a ZnO-based multilayer varistor (MLV) is affected strongly by the homogeneity of its microstructure. In this study, a homogeneous microstructure of ZnO-based MLV was attained by using constrained sintering when nonreactive borosilicate glass +90 wt% alumina (Al₂O₃) was used as a constraining layer laminated on both sides of the multilayer ZnO-based MLV. The mean grain size and the distribution of grain size of ZnO-based MLVs are both reduced because by constrained sintering, an in-plane tensile stress results from constrained sintering in the x-y plane of a multilayer device, which could modify the densification rate of the dielectric materials.