Microstructure and Thermophysical Properties of SrZrO3 Thermal Barrier Coating Prepared by Solution Precursor Plasma Spray

Strontium zirconate (SrZrO3) thermal barrier coatings were deposited by solution precursor plasma spray (SPPS) using an aqueous precursor solution. The phase transition of the SrZrO3 coating and the influence of the aging time at 1400 °C on the microstructure, phase stability, thermal expansion coefficient, and thermal conductivity of the coating were investigated. The unique features of SPPS coatings, such as interpass boundary (IPB) structures, nano- and micrometer porosity, and through-thickness vertical cracks, were clearly observed evidently in the coatings. The vertical cracks of the coatings remained substantially unchanged while the IPB structures gradually diminished with prolonged heat treatment time. t-ZrO2 developed in the coatings transformed completely to m-ZrO2 phase after heat treatment for 100 h. Meanwhile, the SrZrO3 phase in the coatings exhibited good phase stability upon heat treatment. Three phase transitions in the SrZrO3 coatings were revealed by thermal expansion measurements. The thermal conductivity of the as-sprayed SrZrO3 coating was ~1.25 W m−1 K−1 at 1000 °C and remained stable after heat treatment at 1400 °C for 360 h, revealing good sintering resistance.