Thermo-Physical Properties of Hexavalent Tungsten W6+-Doped Ta-Based Ceramics for Thermal/Environmental Barrier Coating Materials

The CaTa0.8WO6 ceramic was fabricated by a solid-state reaction for thermal/environmental barrier coating (Thermal and Environmental Barrier Coating) applications, and the microstructures, mechanical and thermal properties were investigated. The result showed CaTa0.8WO6 has a lower thermal conductivity (1.05 W·m−1·K−1 at 900 °C) than 8 wt.% yttria-stabilized zirconia and the doped Ta-based ceramics with Mg2+, Yb3+, Zr4+ and Nb5+, indicating that hexavalent tungsten element W6+ doping effectively reduces thermal conductivity and improves thermal insulation performance of Ta-based ceramics. The thermal expansion rates curve without inflection points resulting from phase transition indicates that CaTa0.8WO6 has excellent high-temperature phase stability. Since the Young’s modulus and Pugh’s ratio of CaTa0.8WO6 ceramics were lower than those of various valence states doping Ta-based ceramics, which means that CaTa0.8WO6 has better damage tolerance.