Elevating the comprehensive thermal properties of rare-earth cerates through high-entropy design

In the rapidly evolving aerospace sector, the quest for sophisticated thermal barrier coating (TBC) materials has intensified. These materials are primarily sought for their superior comprehensive thermal characteristics, which include a low thermal conductivity coupled with a high coefficient of thermal expansion (CTE) that synergizes with the substrate. In our study, we adopt a solid-state method to synthesize a series of high-entropy rare-earth cerates: La2Ce2O7 (1RC), (La1/2Nd1/2)2Ce2O7 (2RC), (La1/3Nd1/3Sm1/3)2Ce2O7 (3RC), (La1/4Nd1/4Sm1/4Eu1/4)2Ce2O7 (4RC), and (La1/5Nd1/5Sm1/5Eu1/5Gd1/5)2Ce2O7 (5RC), all sintered at 1600 °C for 10 h. We thoroughly examine their phase structure, morphology, elemental distribution, and thermal properties. Our in-depth analysis of the phonon scattering mechanisms reveals that 4RC and 5RC exhibit exceptional thermal properties: high CTEs of 13.00 × 10−6 K−1 and 12.77 × 10−6 K−1 at 1400 °C, and low thermal conductivities of 1.55 W/(m·K) and 1.68 W/(m·K) at 1000 °C, respectively. Compared to other TBC systems, 4RC and 5RC stand out for their excellent thermal characteristics. This study significantly contributes to the development of high-entropy oxides for TBC applications.