ZnO VARISTOR POWDER

A varistor powder that is dispersed in a polymer matrix to obtain a composite used for electric field relaxation,

• wherein the main ingredient is zinc oxide (ZnO);
• at least bismuth (Bi), cobalt (Co), manganese (Mn), antimony (Sb), nickel (Ni), and aluminum (Al), calculated as Bi2O3, Co2O3, MnO, Sb2O3, NiO, and Al3+, are contained as accessory ingredients in amounts of 0.3 to 1.5 mol % Bi2O3, 0.3 to 2.0 mol % Co2O3, 0.3 to 3 mol % MnO, 0.5 to 4 mol % Sb2O3, 0.5 to 4 mol % NiO, and 0.0005 to 0.02 mol % Al3+;
• and
• the zinc oxide (ZnO) content is greater than or equal to 90 mol %;
• the bulk density is greater than or equal to 2.5 g/cc;
• the powder is a spherical powder in which the 50% particle diameter in the particle size distribution is 20 μm to 120 μm;
• the particle size deviation in the particle size distribution ((86% particle diameter−16% particle diameter)/2) is greater than or equal to 15 μm;
• and
• the ZnO primary crystal mean particle diameter is less than or equal to 10 μm.