Processing and performance of Cr 2 O 3 –Fe 2 O 3 reference electrode powders prepared by oxide coprecipitation

Abstract

Cr₂O₃–Fe₂O₃ based oxide mixtures for reference electrode powders of oxygen sensors were processed using oxide coprecipitation route. A special method for preparing reference electrode powders has been developed by mixing coarse Cr particles with the oxide mixture in the form of Cr–Fe hydroxide. Morphology and size of the mixed oxide powders were characterised by means of scanning electron microscopy and laser diffraction method. With the coprecipitation process, chemically homogeneous and very fine powders with a mean particle size of 1.53 μm were prepared. This powder mixture adhered and loosely coated to Cr particles. The processed reference electrode powders were tested in low level oxygen concentration measurements of steelmaking process under industrial scale. The reference electrode powders showed excellent results in terms of electromotive force reproducibility, response time and accuracy in soluble aluminium predictions at the oxygen concentration measurements. Most of the particles of the reference electrode powder remained separated after dipping to molten steel.