Thermal Spraying of Co,Ti-Substituted Ba-Hexaferrite Coatings for Electromagnetic Wave Absorption Applications

The increasing exploitation of millimeter-waves and microwaves in electronics and telecommunications has aroused the need to protect electronic parts from interferences with electromagnetic wave-absorbers, which can be based on the Ba-hexaferrites. These absorbers can be ceramics or composites and have some limitations. Pure Ba-hexaferrites-based coatings could instead be produced by thermal spraying. In this research, Co,Ti-substituted Ba-hexaferrite (BaCoTiFe₁₀O₁₉) coatings were prepared by APS and HVOF, using BaCoTiFe₁₀O₁₉ powders manufactured with solid-state reaction at 1100°C followed by spray-drying.

The SEM+EDX, XRD and micro-Raman analyses indicated that the melting and quenching of the agglomerates during spraying hindered the crystallisation of the hexaferrite structure and consequently delivers poor magnetic properties of the coatings. Adjusted processing conditions enabled the deposition of a coating retaining enough hexaferrite phase. Its magnetic properties, close to bulk BaCoTiFe₁₀O₁₉, show that thermally-sprayed hexaferrites hold promise as high-quality electromagnetic wave-absorbing layers.