Synthesis and thermophysical properties of <i>A</i> Ta <sub>2</sub> O <sub>6</sub> ( <i>A </i> = Co, Ni, Mg, Ca) tantalates with robust CMAS resistance
Baihui Li, Lin Chen, Keren Luo, Guo Jun, Jiankun Wang, Luyang Zhang, Jing Feng
Abstract
Abstract A new family of ceramic environmental/thermal barrier coating (E/TBC) materials, that is, A Ta 2 O 6 ( 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. A Ta 2 O 6 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·m 1/2 ), and moduli (100–210 GPa) have good comparability with current E/TBCs. We propose the 33CaO‐9MgO‐13AlO 1.5 ‐45SiO 2 (CMAS) corrosion mechanisms of A Ta 2 O 6 ceramics, and their robust CMAS resistance relies on the phase stability of CaTa 2 O 6 oxides. The excellent high‐temperature properties ensure that A Ta 2 O 6 can be used as E/TBCs to provide thermal insulation and CMAS corrosion protection.