Effect of in situ LaAlO3 phase addition on the thermal shock resistance of Y2O3/LaAlO3 composite materials

Yttrium oxide is extensively utilized in high-temperature industries due to its excellent vacuum and high-temperature chemical stability. However, its applications are limited by poor thermal shock resistance, which arises from its intrinsic brittleness. The ferroelastic toughening phase LaAlO 3 offers significant fracture toughness, which is attributed to the ferroelastic domain-switching toughening effect. This study focuses on enhancing the properties of yttrium oxide using Y 2 O 3 , La 2 O 3 , and Al 2 O 3 fine powders as primary raw materials. Y 2 O 3 /LaAlO 3 composite materials are developed, and the LaAlO 3 phase is formed in situ within the Y 2 O 3 matrix. The effects of varying in situ-synthesized LaAlO 3 content on the phase composition, microstructure, mechanical properties, and thermal shock resistance of Y 2 O 3 /LaAlO 3 composite materials are investigated. The key findings are as follows: 1) The use of a Y 2-x La x O 3 solid solution, instead of pure yttrium oxide, as the matrix allows for the synthesis of the LaAlO 3 phase in situ within the matrix. This approach enables the coexistence of LaAlO 3 and yttrium oxide, resolving the issue of chemical compatibility between Y 2 O 3 and LaAlO 3 . 2) The solid solution effect of the Y 2-x La x O 3 matrix and the ferroelastic toughening effect of the LaAlO 3 phase collectively enhance the material performance. The addition of an appropriate amount of LaAlO 3 improves the sintering performance, strength, hardness, and toughness of yttrium oxide. These enhancements significantly improve the thermal shock stability of yttrium oxide materials. 3) The excessive formation of the in situ LaAlO 3 phase, driven by the LaAlO 3 reaction expansion effect, negatively impacts the sintering performance and toughness of yttrium oxide materials, thereby compromising their thermal shock stability. To address this issue, an optimal amount of in situ LaAlO 3 phase should be incorporated to achieve a balance between toughness and thermal shock stability in Y 2 O 3 /LaAlO 3 composite materials while preserving their hardness and strength.