METHOD OF PRODUCING ZINC OXIDE VARISTORS Russian patent published in 2025 - IPC H01L21/447 H01C7/112 H01C17/00 

FIELD: electric power industry.

SUBSTANCE: method of making zinc oxide varistors involves preparation of an initial composition, production of moulding powder, moulding a varistor workpiece from the press powder by pressing, drying the varistor workpiece and its subsequent annealing. Initial composition based on zinc oxide containing oxide components in the following quantitative ratio, wt.%: ZnO 90.0÷95.0; Bi₂O₃ 1.247÷2.37; Co₂O₄ 0.89÷1.69; Sb₂O₃ 1.12÷2.14; Al₂O₃ 0.37÷1.61, with addition of nickel oxide NiO 0.37÷0.71 and manganese oxide MnO₂ 0.25÷0.48, wherein oxides of bismuth, cobalt, antimony, aluminium, nickel and manganese are determined in ratio: 1:0.9:0.678:0.71:0.3:0.2, is prepared by mixing said components in a solution consisting of 55 % distilled water, 0.05-0.1% aluminium sulphate solution and 1.75-2.0% aqueous solution of polyvinyl alcohol PVA, wherein the proportions of water, aluminium sulphate and alcohol are determined from the total weight of the above components. After mixing the components in the solution, a drying process is performed for 60-90 minutes at temperature of 200 °C to obtain press powder, then, by pressing the moulding powder, billets of a cylindrical shape are produced, which are dried for 10-12 hours at temperature of 600 °C, then workpieces are placed in corundum boxes and primary annealing is performed in tunnel furnace, where on moving conveyor for 5-8 hours they pass temperature range from 650 °C to 950 °C, after which the boxes are placed in a chamber furnace and for 2-3 hours additional annealing of workpieces is carried out at temperature of 960 °C to 1300 °C, then cooled workpieces are ground and metal electrode is applied on end surface, and insulation is applied on side surface.

EFFECT: invention enables to obtain zinc oxide varistors for alternating and direct current OVL of non-aging type, with charge density of throughput of not less than 0.045 C/cm² and specific conductivity current of not more than 10 mcA/cm².

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