Suspension Plasma Spraying for the Preparation of Perovskite Powders and Coatings

LaMnO₃ powders and coatings have been prepared by reactive suspension plasma spraying (SPS) of MnO₂ powders and LaCl₃ solutions. A 40 kW inductively coupled plasma with an oxygen plasma sheath gas has been used. Water and ethanol have been tested as the liquid phase in the SPS process. High perovskite content (70-90%) has been achieved for both powders and coatings when spraying a suspension of fine MnO₂ powder in a saturated ethanol solution of LaCl3 with a 1:1 molar ratio of La and Mn. Materials obtained by a 1100 °C oven treatment have been used as reference during the study. The reactor pressure was varied from 30 to 80 kPa. Low pressure was found to be necessary to suppress the formation of undesired phases in the powders and coatings obtained. A plasma post treatment of the coatings results in an increase of the perovskite content.