ZnO single crystals with an intermediate layer of metal oxides—A macroscopic varistor model

Abstract

Crystalline ZnO plates with an intermediate layer consisting of a mixture of Bi₂O₃, MnO₂, and Co₃O₄ were prepared and sintered for 1 h at 1223 K in air. The sandwiches were used as a macroscopic model system substituting the grain boundary contacts in ceramic varistor materials. Measurements of the current‐voltage characteristics confirm a breakthrough voltage of 3.5 V. Microscopic investigation supports the concept of a heterojunction with depletion layers being responsible for the nonlinear varistor properties.