Sintering, thermal expansion, and thermal transport properties of A4Ta2O9 (A= Ca, Mg) tantalates.

Searching for new oxides with low thermal conductivity and high thermal expansion coefficients (TECs) as thermal barrier coatings (TBCs) is vital for the development of highly efficient gas turbines and aeroengines. We report the densification sintering, high TECs, and low thermal conductivity of A 4 Ta 2 O 9 (A = Ca, Mg) tantalates. The best sintering temperature of dense A 4 Ta 2 O 9 ceramics was determined via an optical contact angle tester, and samples with a relative density of 99.8% were synthesized via spark plasma sintering (SPS). The hardness (9–10 GPa), Young's modulus (172.7–211.8 GPa) and fracture toughness (1.5–1.6 MPa m1/2) of the A 4 Ta 2 O 9 ceramics are primarily affected by the bonding strength. Furthermore, we studied the thermal transport properties of A 4 Ta 2 O 9. The low thermal conductivity (1.78–1.93 W m−1 K−1 at 900 °C), extraordinary phase stability, and high TECs (11.4–11.8 × 10−6 K−1 at 1200 °C) of A 4 Ta 2 O 9 ceramics make them candidate TBCs with high operating temperatures. [ABSTRACT FROM AUTHOR]