Protective Alumina Coatings Prepared by Aerosol Deposition on Magnetocaloric Gadolinium Elements

In this work the preparation of a protective insulating alumina coating on magnetocaloric gadolinium elements was investigated. In order to prepare a dense ceramic coating at room temperature the aerosol deposition technique was used. The study reveals that the powder morphology and particle size are important parameters that influence the deposition efficiency, powder packing and consequently also the density and functional properties of the alumina coating. The optimal powder pre-deposition treatment includes heating the powder to 1150 degrees C, followed by milling. The deposition of this powder resulted in the preparation of dense alumina coatings with a low specific electrical conductivity of 6.4.10(-14) Omega(-1)m(-1).