Dual-phase zirconate/tantalate high-entropy ceramics boost thermal properties and fracture toughness for thermal barrier coating materials

Working temperatures, thermal insulation performance, and life span of thermal barrier coatings (TBCs) are primarily influenced by their high-temperature stability, thermal expansion coefficients (TECs), thermal conductivity, and fracture toughness. To address the limitations of current zirconate- and tantalate-based oxides, dual-phase zirconate/tantalate high-entropy ceramics (HECs) are designed and synthesized to improve their thermal and mechanical properties. The combined effects of high entropy, high concentrations of oxygen vacancies, and relatively low phonon velocity result in glass-like thermal conductivity, with a minimum value of 1.55 W m−1 K−1 at 1200 °C. The high TECs (10.6–10.9 × 10−6 K−1 at 1400 °C) and exceptional high-temperature stability demonstrate that these materials can withstand 1300 °C for more than 300 h, significantly surpassing the performance of traditional yttria-stabilized zirconia (YSZ). Compared with YSZ (3.6 MPa m1/2) and YTaO4 (2.5 MPa m1/2), the increments in fracture toughness (4.4 MPa m1/2) of dual-phase zirconate/tantalate HECs are as high as 22.2% and 76.0%, respectively. It is evident that the designed dual-phase zirconate/tantalate HECs can effectively promote thermal properties and fracture toughness, positioning them as the next-generation TBCs with high operating temperatures and outstanding thermal insulation performance.