Synthesis and thermophysical properties of ATa2O6 (A = Co, Ni, Mg, Ca) tantalates with robust CMAS resistance.

A new family of ceramic environmental/thermal barrier coating (E/TBC) materials, that is, ATa2O6 (A = Co, Ni, Mg, Ca), for high‐temperature applications, are investigated and reported in this study. We focus on the synthesis and features of crystal structures, and on the mechanical and high‐temperature properties. ATa2O6 oxides have an extraordinary phase stability (up to 1300°C), and their thermal expansion coefficients (6.2–7.3 × 10−6 K−1) match those of SiC fiber‐enhanced SiC ceramic matrix composites (3–7 × 10−6 K−1). Their low thermal conductivities (min: 1.15 W·m−1·K−1) root in the slow phonon spreading speed and fierce phonon‐phonon scattering process, and they will provide exceptional thermal insulation. Moreover, their hardness (5.6–8.8 GPa), toughness (1.4–1.9 MPa·m1/2), and moduli (100–210 GPa) have good comparability with current E/TBCs. We propose the 33CaO‐9MgO‐13AlO1.5‐45SiO2 (CMAS) corrosion mechanisms of ATa2O6 ceramics, and their robust CMAS resistance relies on the phase stability of CaTa2O6 oxides. The excellent high‐temperature properties ensure that ATa2O6 can be used as E/TBCs to provide thermal insulation and CMAS corrosion protection. [ABSTRACT FROM AUTHOR]