Abstract: Sinterless zinc oxide varistor devices are prepared in one embodiment by flame spraying premixed zinc oxide and additive metal oxide powders onto a refractory substrate. The coated substrate is then treated by an abrasive removal process to form a trimmable resistor. A further embodiment comprises the use of a plasma spray process wherein carbonates and nitrates of the varistor constituents are oxidized in situ by entrainment within an oxygen gas stream and directing the plasma upon a rotating substrate. Ultra pure zinc oxide varistor devices having excellent electrical properties can be prepared in this manner.

Abstract: a zinc oxide compound nonlinear resistance overvoltage surge arrester disc is provided with a low temperature-curing ceramic antiflashover collar having relatively low coefficient of thermal expansion of about 4.5 .times. 10.sup.-6. The cured ceramic comprises the reaction product of a dry mixture of 80% by weight of mullite refractory filler and 20% kaolin suspending clay, together with 5% to 15% of the weight of the dry mixture of a binder consisting of equal weights of monoaluminum phosphate and concentrated phosphoric acid.Also disclosed is a method of application comprising the steps of applying the slurry to the perimeter of the disc and baking at a temperature below about 600.degree. Celsius.