Metallising of ceramics which conduct oxygen ions - thorium oxide-yttrium oxide ceramic coated with tungsten, molybdenum or niobium

摘要

Metallising process comprises applying a powder contg. tungsten-, molybdenum-, or niobium- oxide to the surface of the ceramic followed by sintering in a reducing at atmos. in which the powder penetrates the ceramic and is simultaneously reduced to the metal on the surface. The substrate is pref. annealed in a reducing atmos. prior to the metallising treatment in which a powder with a particle size below 1 mu is used. The ceramic e.g. ThO2-Y2O3, is used as a solid electrolyte in appts. for determn. of the oxygen content of gases and liq. metals. Metallising facilitates soldering of the ceramic to metal parts of the appts. to form joints which can withstand the thermal stress arising when the appts. is used at 300-800 degrees C. Process allows a much lower temp. to be used during sintering, thus preventing the tungsten from attacking the ThO2 in a ThO2-Y2O3 ceramic.