Hydrothermal synthesis and thermophysical properties of (Sm1-Gd )2Zr2O7 (0≤x≤1) thermal barrier coating materials

Abstract

(Sm1-xGdx)2Zr2O7 (0≤x≤1) ceramics, a new thermal barrier coating material, are commonly synthesised by chemical coprecipitation and calcination methods. However, when using the chemical coprecipitation method to synthesise ceramic powder, a large amount of strong acids and ammonium hydrate are consumed, leading to environmental pollution and restricting the production of new ceramics. Thus, a cleaner one-step hydrothermal synthesis method is proposed to synthesise (Sm1-xGdx)2Zr2O7 (0≤x≤1) thermal barrier coating ceramic powders, which avoids the use of strong acids and reduces the use of ammonium hydrate. Using this cleaner method, pure (Sm1-xGdx)2Zr2O7 ceramic powders were synthesised with particle sizes smaller than 1 μm. Subsequently, bulk ceramics were prepared, and the thermophysical properties of the bulk ceramics were determined. The results show that the thermal expansion coefficients of the ceramics changed slightly after 1300 K, and the coefficient values of the ceramics were approximately 11 × 10−6 K−1 at 1300 K. The thermal conductivities were in the range of 0.95–1.4 W m−1 K−1 from 700 K to 1500 K, which is slightly smaller than that of the ceramic synthesised by the chemical coprecipitation method. These results show that the thermophysical properties of the (Sm1-xGdx)2Zr2O7 bulk ceramics synthesised using ceramic powders are satisfactory, further demonstrating that the hydrothermal synthesis process designed in the present study is feasible.