were fabricated via the conventional solid state reaction method. The addition of Cr2O3 caused a transformation of secondary phases from CrBi18O30/Co2Cr0.5Sb0.5O4 to MnCr2O4 at x=0.5. It was also found that the average grain size decreased with increasing the Cr2O3 content, resulting in an increase of the breakdown voltage. On the other hand, the donor density (Nd) was decreased from 2.91 x 1024 m-3 to 1.05 x 1024 m-3 and the interface state (Ns) arrived at a peak value of 3.88 eV at x=0.5. Conclusively ,Cr2O3 controls ZnO grain growth and leads to the transformation of secondary phases, which results in a large potential barriers and better nonlinear properties due to the formation of the inter face state.