Elinvar-Like Effect Induced by High Lattice Distortion in Zr₆Ta₂O₁₇ Ceramics

Super strength and toughness, excellent deformation resistance, and high-temperature service performance are the key factors to determine the practical application of new thermal barrier coatings (TBCs). The limited mobility of dislocations and the internal inherent defects in ceramics will inevitably lead to the decline of strength-plasticity and the reduction of service performance. Introducing preexisting twin boundaries and stacking faults (SFs) or preparing ceramic materials with high configuration entropy has demonstrated to be an effective strategy for enhancing the mechanical properties of ceramics. However, due to the positive thermal expansion coefficient of most ceramics and the remarkable increase of structural disorder at elevated temperature, the problem of elastic softening has become a bottleneck restricting the high-temperature service life of new TBCs. In this paper, the deformation behavior of high configuration entropy Zr₆Ta₂O₁₇ ceramics at 25 to 1,200 °C was in situ monitored via digital image correlation technique and three-point bending test platform in high-temperature environment. A remarkable Elinvar-like effect appears in the Zr₆Ta₂O₁₇ ceramic. More interestingly, mechanical deformation dominates the severe lattice distortion (deformation twins, SFs) and the disorder-order transition of chemical order at the atomic scale, while temperature can further enhance the degree of lattice distortion and ordering of Zr₆Ta₂O₁₇ ceramics. Furthermore, the atomic fluctuations at high temperature promotes the comprehensive improvement of mechanical properties in the Zr₆Ta₂O₁₇ ceramics.