Designing high-entropy rare-earth zirconates with tunable thermophysical properties for thermal barrier coatings

Abstract

The development of rare-earth zirconates with tunable thermal expansion coefficient (TEC) and thermal conductivity is of great importance in the area of thermal barrier coatings. In general, TEC can be tailored by the average electronegativity difference, and the thermal conductivity can be customized by the atomic mass difference and/or ionic radius. Based on this thermophysical properties design principle, a series of high-entropy rare-earth zirconate ceramics were synthesized and characterized, and the obtained results indicate that: (1) the TEC is negatively correlated with the average electronegativity difference of cation and anion concerning its corresponding compound; (2) the thermal conductivity is negatively correlated with the atomic mass difference and ionic radius difference concerning its corresponding compound; (3) the synthesized ceramics have excellent high-temperature long-term thermal phase stability, larger TEC (RT-1500 °C, 10.20 ~ 10.39 × 10-6 K-1), lower thermal conductivity (1500 °C, 1.17 ~ 1.37 W·m-1·K-1), and higher fracture toughness (1.61 ~ 1.69 MPa·m1/2) compared with lanthanum zirconate. The tailorable design principle involved in this work sheds new insights for designing alternative ceramics with pre-assigned thermophysical properties for the next-generation thermal barrier coatings.