@article{Zhang2025, 
author = {Shuang Zhang and Yize Yao and Xiaohui Wang and Huimin Xiang and Cheng Fang and Hailong Wang and Yanchun Zhou},
title = {CrTa0.5Nb0.5O4: A solid solution strategy to enhance the mechanical and thermal properties of rutile structured ternaries},
year = {2025},
journal = {Extreme Materials},
volume = {1},
number = {3},
pages = {61-73},
keywords = {Mechanical properties, Thermal properties, STEM, CrTaO4, Solid solution strengthening, CrNbO4, Cr(Ta0.5Nb0.5)O4, Thermal barrier materials},
url = {https://www.sciopen.com/article/10.1016/j.exm.2025.08.002},
doi = {10.1016/j.exm.2025.08.002},
abstract = {CrTaO4 and CrNbO4, rutile structured ternary scales formed on refractory high-entropy alloys (RHEAs), protect the RHEAs from oxidation and thermal attack. However, the Vickers hardness (12.20/10.20 GPa for CrTaO4 and CrNbO4, respectively) is lower than that of YSZ (14 GPa), making them prone to erosion. In addition, further reduction of thermal conductivity (1.31/1.09 W·m−1·K−1 for CrTaO4 and CrNbO4, respectively) benefits to protect the substrate materials from thermal attack. As such, optimizing their properties is urgently needed. To enhance the mechanical properties and further reduce the thermal conductivity of rutile-type ternary oxides CrTaO4 and CrNbO4, herein we designed a CrTa0.5Nb0.5O4 solid solution based on the mechanism of solid solution strengthening, and systematically investigated its phase composition, microstructure, mechanical and thermal properties. The HAADF and ABF-STEM analyses confirmed the rutile-structure of CrTa0.5Nb0.5O4, while minor impurities of rutile-structured CrNbO4 and CrO2 were also identified. The elastic modulus, bulk modulus, and shear modulus of CrTa0.5Nb0.5O4 are 201, 119, and 175 GPa, respectively. Notably, the mechanical properties of CrTa0.5Nb0.5O4 have been significantly improved via solid solution strengthening, with the Vickers hardness of 13.01 ± 0.2 GPa, fracture toughness of 2.07 ± 0.017 MPa·m1/2, and flexural strength of 201 ± 12 MPa. The measured melting point of CrTa0.5Nb0.5O4 is 2073 ± 20 K, with an average thermal expansion coefficient of (5.91 ± 0.52) × 10⁻6 K⁻1. The room-temperature thermal conductivity of CrTa0.5Nb0.5O4 is 1.07 W·m⁻1·K⁻1, which decreases to 0.57 W·m⁻1·K⁻1 at 1473 K, being lower than most of the well-known thermal barrier coating materials. In terms of thermal expansion coefficient matching, CrTa0.5Nb0.5O4 is a qualified thermal barrier material for refractory metals and their alloys and ultra-high temperature ceramics. Therefore, this study has not only successfully developed a thermal barrier coating material with excellent mechanical properties and low thermal conductivity, but also provided new ideas for the research and development of materials in high-temperature fields from the perspective of material design.}
}