Structural and Nonlinear I–V Characteristics of Co-Substituted Sn1−x−yZnxMyOz Varistors with Various x, y and M.

We report the structural and nonlinear behavior of Sn_1−x−yZn_xM_yO_z varistors with x = 0.00, 0.50, y = 0.00, 0.25 and M = Fe, Co, Ni and Mn. The crystallite and grain sizes and porosity of SnO₂ are decreased by Zn doping, followed by a further decrease by (Zn + M) co-substitution. The breakdown field (E_B), nonlinear coefficient (α), leakage current (I_K) and residual voltage (K_r) of SnO₂ are respectively 333.35 V/cm, 5.6, 900 μA/cm² and 5.32. When SnO₂ was substituted by Zn, I_K and K_r are decreased to 816 μA/cm² and 3.62, whereas E_B and α are increased to 666.67 and 11.48. The E_B and α values are increased by co-substitution in the SnZnMn sample, whereas I_K and K_r are decreased. Rather than containing many elements and compounds, the current varistors are based on only two well-known ions co-substituted into SnO₂. These findings are discussed in terms of the oxygen vacancies. [ABSTRACT FROM AUTHOR]