Preparation of barium hexaferrite coatings using atmospheric plasma spraying

Thick coatings of barium hexaferrite with the compositions BaFe12O19 and BaCoTiFe10O19 were prepared using atmospheric plasma spraying (APS) technology. The coatings were prepared from pre-reacted powders of the desired composition. The as-deposited coatings were poorly crystallized, but their crystallinity was improved with a subsequent annealing. The crystallization mechanism of the sprayed hexaferrites was studied during annealing up to 1300 ◦C, using X-ray powder diffraction combined with thermal analysis and with electron microscopy including microanalysis. Single-phase coatings were obtained after annealing treatments at 1100–1300 ◦C. Their magnetic properties showed that they would be suitable for absorbers at microwave and mm-wave frequencies, depending on the coating phase’s composition, the crystallinity and the thicknesses.