@article{Wu2026, 
author = {Bingyan Wu and Guangrong Li and Lin Chen and Jiankun Wang and Wei Pan and Jing Feng},
title = {Non-equimolar compositional design engineered thermal expansion coefficients and conductivities of m´-RETaO4 (RE = Sc, Y, Tm, Ho, Dy, Gd) high-entropy ceramics},
year = {2026},
journal = {Journal of Advanced Ceramics},
keywords = {high-entropy ceramics, lattice distortion, disorders, non-equimolar design, EBCs},
url = {https://www.sciopen.com/article/10.26599/JAC.2026.9221351},
doi = {10.26599/JAC.2026.9221351},
abstract = {Rare-earth tantalates RETaO4 have been extensively investigated as thermal protective materials, but their applications as environmental barrier coatings (EBCs) for ceramic matrix composites (CMCs) are limited by their high thermal expansion coefficients (TECs≥9.0×10-6 K-1). The high-entropy design provides a feasible route to tailor the thermal properties of RETaO4; however, most reports focus on equimolar RETaO4 HECs. In this study, a series of non-equimolar monoclinic-prime (m´) RETaO4 HECs are designed and synthesized to clarify the composition-structure-property relationships. The non-equimolar design is used to regulate configurational complexity, polyhedral distortion, and lattice strain in m´-RETaO4 within the same m´ phase. Atomic-scale TEM and GPA characterizations reveal the associated local distortion and lattice strain. These observations link non-equimolar composition with local structural distortion and macroscopic thermal transport behavior. The lowest thermal conductivity reaches 1.52-2.68 W·m-1·K-1 at 25-900 °C, and is mainly associated with RE-site disorder, lattice strain, and polyhedral distortion. Polyhedral distortion also suppresses thermal expansion by restricting atomic anharmonic vibrations. Among the designed compositions, the optimized non-equimolar m´-RETaO4 HECs (Sc0.2Y0.2Tm0.2Ho0.2Dy0.1Gd0.1)TaO4 exhibits the lowest TECs of 6.2×10-6 K-1 at 1500 °C, closer to SiC-based CMCs than the other compositions, indicating its potential as candidate EBCs.  This work proposes that polyhedral distortion and lattice strain are important structural factors for tailoring the thermal properties of non-equimolar RETaO4 HECs, providing guidance for the design of complex oxides.}
}