IMPROVEMENTS IN OR RELATING TO CERMET RESISTIVE LAYERS

1278728 Resistor compositions ZAKLADY WYTWORCZE PODZESPOLOW TELEKOMUNIKACY JNYCH "TELPOD" 23 April 1970 [24 April 1969] 19503/70 Heading C1M [Also in Division H1] A resistive layer is prepared by applying to a substrate, such as a ceramic, a glass or glass ceramic, a layer of paste comprising (i) a crystallizable glass powder fusible at 550- 800‹ C., (ii) a powdered electrically conductive material which is a metal, alloy or metal oxide, and (iii) an inert organic vehicle; heating the coated substrate to 550-800‹ C.; and further heat-treating the coated substrate at a temperature not above the glass softening point to effect crystallization of the glass around the conductive particles. The further heat-treatment may follow directly the treatment at 550-800‹ C., or may be cooled between the treatments. Preferably the glass is of maximum particle size 60 Á, and the conductive material of maximum size 40 Á. The metal may be Ag or Pd. Preferably the metal is a mixture of metals formed by co-precipitation of the metals from solutions of salts thereof, preferably by treatment with a reducing agent, e.g. hydrazine, substituted hydrazine, or alkali metal or alkaline earth metal borohydride.