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.