Ceramic semiconductor resistor, esp. thermistor and varistor prodn. - by contacting one side of moulded base powder with metal oxide and heating

摘要

In the prodn. of ceramic semiconductor resistors by moulding a powdered base, contacting this with a metal (mixed) oxide additive and subjecting to heat treatment to effect reactive diffusion of the additive into the grain structure of the moulding, the temp. and period of heat treatment and the mass of the additive are selected so that the additive diffuses only into one vol. region of the moulding. The process is used esp. for the prodn. of thermistors and (ZnO) varistors. The process is suitable for use on the industrial scale and the prods. can be used even below 20V, as well as at medium and high voltages. The base pref. is (un)doped ZnO and the additive Bi2O3, Sb2O3, Mn2O3, TiO2 and/or CdO.