Vapor deposited samarium zirconate thermal barrier coatings

The rare earth zirconates (M2Zr2O7, M = La→Gd) have a low intrinsic thermal conductivity and high temperature phase stability making them attractive candidates for thermal barrier coating applications. An electron-beam evaporation, directed-vapor deposition (EB-DVD) technique has been used to investigate the synthesis of Sm2Zr2O7 (SZO) coatings and to explore the relationships between the deposition conditions and the coating composition, structure, texture, pore morphology, and thermal conductivity. The coatings exhibited significant fluctuations in composition because of differences in the vapor pressures of the constituent oxides and had a metastable fluorite structure because kinetic limitations hindered the cation ordering needed to form the equilibrium pyrochlore structure. The growth morphology of the EB-DVD SZO was similar to that of EB-DVD 7YSZ and EB-PVD Gd2Zr2O7. The SZO coatings had as-deposited conductivities of 0.5 ± 0.1 W m− 1 K− 1, about one-half of their DVD 7YSZ counterparts. The majority of the conductivity difference appears to be associated with the lower intrinsic conductivity of this zirconate.