OXIDE-COATED CATHODE AND MANUFACTURE THEREOF

PURPOSE:To obtain an oxide-coated cathode having good emission characteristic under long operation in large current density, and high reliability, by coprecipitating scandium carbonate to alkaline earth metal carbonate to form a layer of electron emission substance. CONSTITUTION:An oxide-coated cathode has a layer of electron emission substance deposited on the surface of a cathode substrate by coprecipitating small quantity of scandium carbonate to alkaline earth metal carbonate. Small quantity of scandium carbonate (preferably 0.05-1.0 weight percent) is coprecipitated to crystals of alkaline earth metal carbonate as impurities, preferably to be based, for example, at 400-650 deg.C and the suspension thereof is applied to the oxide cathode substrate. By this method, an oxide cathode accompanying little deterioration of emission characteristic can be formed even if it is to be operated for many hours in particularly large current density.