Influence mechanism of Ni₂O₃ doping on leakage current of SnO₂ varistor ceramics

The doping of Ni 2 O 3 has significantly enhanced the electrical properties and density of SnO 2 –Co 3 O 4 –Cr 2 O 3 –Nb 2 O 5 varistor ceramics. The leakage current density is reduced to 4.73 µA/cm 2 , the nonlinear coefficient is 37, and the voltage gradient is 549 V/mm. The undoped varistor ceramics exhibited a considerably higher leakage current of 48.04 µA/cm 2 . The performance improvement comes from alterations in grain boundary parameters. The doping of an appropriate amount of Ni improves the grain boundary barrier of SnO 2 varistor ceramics and makes samples obtain higher grain boundary resistance, which hinders the leakage current path and results in excellent nonohmic characteristics. The stable grain boundary barrier structure dominated by Ni enables the sample to obtain stable power loss performance under long‐term direct current (DC) bias.