Synthesis of varistor powders by accelerated combustion and properties of ceramics based on them

Resumo

Varistor powders were synthesized by accelerated combustion of an aqueous solution of hydrated zinc, bismuth, aluminum, cobalt, and nickel nitrates, antimony tartrate, and sugar at 500°С with isothermal heating for 10 min, followed by grinding and calcination at 700°С for 1 h. The varistor powders obtained have high specific surface area and allow preparation of a ceramic with high values of the breakdown voltage and nonlinearity coefficients and with low leakage current density. The ceramic of the optimum composition (wt %), ZnO 75, Bi₂O₃ 7.36, Sb₂O₃ 5.1, Al₂O₃ 7.19, Co₂O₃ 4.8, and NiO 0.61, sintered at 975°С for 4 h, has U_b = 4.2 kB mm^–1, α = 54, and I_leak = 0.2 μA cm^–2.