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 (E_B=6.4V/mm) and the highest relative dielectric constant (ε_r=1.54× 10⁴) 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+2.5mol%ZnO sample and the electric insulation behaviour of the samples with 2.5mol% ZnO and 200mol% 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.