Improvement strategy on thermophysical properties of A₂B₂O₇-type rare earth zirconates for thermal barrier coatings applications: A review

The A₂B₂O₇-type rare earth zirconate compounds have been considered as promising candidates for thermal barrier coating (TBC) materials because of their low sintering rate, improved phase stability, and reduced thermal conductivity in contrast with the currently used yttria-partially stabilized zirconia (YSZ) in high operating temperature environments. This review summarizes the recent progress on rare earth zirconates for TBCs that insulate high-temperature gas from hot-section components in gas turbines. Based on the first principles, molecular dynamics, and new data-driven calculation approaches, doping and high-entropy strategies have now been adopted in advanced TBC materials design. In this paper, the solid-state heat transfer mechanism of TBCs is explained from two aspects, including heat conduction over the full operating temperature range and thermal radiation at medium and high temperature. This paper also provides new insights into design considerations of adaptive TBC materials, and the challenges and potential breakthroughs are further highlighted for extreme environmental applications. Strategies for improving thermophysical performance are proposed in two approaches: defect engineering and material compositing.