Yttrium Aluminum Garnet (YAG) Films through a Precursor Plasma Spraying Technique

Coatings of yttrium aluminum garnet (Y₃Al₅O₁₂, YAG), which is a promising high-temperature ceramic, were developed for the first time using a novel precursor plasma spraying (PPS) technique. The precursor sol was sprayed using a radio-frequency induction plasma technique. X-ray diffraction analysis of the as-sprayed coatings confirmed that a metastable hexagonal yttrium aluminate (H-YAlO₃) was the major phase. The above-described specimen, on further treatment with plasma, was converted to cubic garnet (YAG) as the major phase, with a minor amount of orthorhombic YAlO₃ (O-YAP) phase. ²⁷Al magic-angle spinning nuclear magnetic resonance of the YAG coating corroborated the X-ray results and confirmed the presence of YAG and O-YAP phases. Formation of the garnet phase through the PPS technique is proof that the chemistry can be controlled in the plasma. This finding opens up new avenues for developing complex functional oxide deposits.