Nonlinear Electrical Behaviour of Composite SnO2-Zn2SnO4 System

We have found a new composite SnO2-Zn2SnO4 varistor material and the effect of different content ratios of SnO2 to Zn2SnO4 on this system is investigated. The lowest breakdown voltage (EB = 6.4 V/mm) and the highest relative dielectric constant (er = 1.54 × 10^4) with higher nonlinear coefficient (α = 4.5) is obtained when the ratio of SnO2 to ZnO equals 100/35. The disappear of the Zn2SnO4 peak in x-ray diffraction (XRD) spectra of the SnO2+2.S mol%ZnO sample and the electric insulation behaviour of the samples with 2.5mol% ZnO and 200 mol％ ZnO indicate that 2.5mol% ZnO can be dissolved into SnO2 lattices and some reaction contributing to nonlinear electrical behaviour should occur between SnO2 and Zn2SnO4. The role of oxygen on the grain boundary is confirmed by the degradation of nonlinear electrical properties and the increase of relative dielectric constant of the samples annealed in nitrogen-rich atmosphere.