ZrSiO₄/ZrO₂ thermal barrier coatings produced by suspension plasma spraying

Zircon has excellent thermal properties that make it a good candidate for thermal barrier coatings. Although it suffers decomposition at high temperature, significant amounts of zircon phase can be retained in the coatings obtained by suspension plasma spraying. The aim of the present work is to evaluate the partial substitution of zirconia, commonly used for TBCs, by zircon, cheaper and more available. Zircon/zirconia aqueous suspensions with different ratios were prepared and sprayed by suspension plasma spraying. The obtained coatings has lamellar and columnar microstructures depending on the zircon/zirconia ratio. Up to 20 wt% of the starting ZrSiO4 content is retained for high zircon content feedstocks. A tetragonal zirconia matrix resulting from the decomposition of zircon is obtained as a result of the small crystallite size obtained for this phase (<30 nm). This opens the possibility of partially replacing zirconia by zircon to obtain new TBCs at lower cost.