Rare-earth tantalates for next-generation thermal barrier coatings

Ceramic thermal barrier coatings (TBCs) have attracted significant research attention owing to their utility in the thermally insulating alloy components of gas turbines and aircraft engines that operate at high temperatures. Most TBCs comprise yttria-stabilized zirconia (YSZ); however, YSZ no longer meets the demands of modern TBC applications due to its low working temperature and high thermal conductivity. It is therefore imperative to develop a ferroelastic ceramic to replace YSZ in TBC applications. Ferroelastic rare-earth tantalates (RETaO4) possess many desirable properties, such as ferroelastic toughening, low thermal conductivity, high thermal expansion coefficients, and excellent comprehensive mechanical properties, and thus, they are promising next-generation TBCs, which are expected to operate at ultra-high temperatures (≥1600 °C). This review summarizes the thermophysical properties, CaO-MgO-AlO1.5-SiO2 (CMAS) corrosion resistance, coatings, and shortcomings of three types of tantalate ceramics (RETaO4, RE3TaO7, and RETa3O9) and outlines the direction of future work in this field.