Patent ID: 8216544

Claim:
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 Bi 2 O 3 , CO 2 O 3 , MnO, Sb 2 O 3 , NiO, and Al 3+ , are contained as accessory ingredients in amounts of 0.3 to 1.5 mol % Bi 2 O 3 , 0.3 to 2.0 mol % CO 2 O 3 , 0.3 to 3 mol % MnO, 0.5 to 4 mol % Sb 2 O 3 , 0.5 to 4 mol % NiO, and 0.0005 to 0.02 mol % Al 3+ ; 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.