Phase variation and thermophysical properties of La₂Hf₂O₇ with alumina addition

La₂O₃-Al₂O₃-HfO₂ ceramics were prepared by solid reaction of La₂Hf₂O₇ ceramic powders which were synthesized by solution combustion and commercial alumina powders at 1600 °C in air for 10 h. Phase variation and thermophysical properties of La₂O₃-Al₂O₃-HfO₂ ceramics were investigated. With the increase of alumina content, LaAlO₃, HfO₂ and LaAl₁₁O₁₈ phase structures appeared. The thermal expansion coefficients gradually increased with the increase of alumina content from 1000 °C to 1300 °C. The thermal conductivities of La₂O₃-Al₂O₃-HfO₂ ceramics had nonlinear variation with the increase of alumina content and reached the lowest value around 1.1 W·m⁻¹·K⁻¹ when the ratio of La₂Hf₂O₇ to Al₂O₃ was 1:0.25. Therefore, the La₂O₃-Al₂O₃-HfO₂ ceramics with a proper content of alumina can be considered as a new thermal barrier materials. Meanwhile, as potential application as interface layer in TBC, La₂O₃-Al₂O₃-HfO₂ ceramics are beneficial to improve the effectiveness of the thermal barrier coating.