Recently, in order to develop novel materials with optimized properties, "high entropy" has attracted significant attention in the field of materials research relate to structural entropy within a material. [1][2] Multi-principal high-entropy alloys and ceramics can be synthesized, which exhibit several excellent properties, such as high strength and toughness, corrosion resistance, wear resistance, thermal performance, and electrical performance, on the basis of four high-entropy effects [3][4][5][6] : (1) high-entropy effect of thermodynamics; (2) lattice distortion effect of structure; (3) hysteretic diffusion effect; and (4) cocktail effect on performance.The high-entropy can significantly improve the comprehensive performance of the materials. For example, Gild et al. 7 reported high-entropy fluorite rare-earth oxides, that is, REO 2-δ , with thermal conductivities of 1.1-2.02 W•m -1 •K -1 , therefore, REO 2-δ has shown potential as low-thermal-conductivity materials. Ren et al. 8 synthesized a (Y 1/4 Ho 1/4 Er 1/4 Yb 1/4 ) 2 SiO 5 ceramic with excellent phase stability and low thermal conductivity (1.1 W•m -1 •K -1 at 1300°C), which is considered to be applied as a thermal and environmental barrier coating (TEBC) material. Yan et al. 9 reported a high-entropy ceramic (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )C, which exhibited a much lower thermal conductivity (5.42-6.45 W•m -1 •K -1 at room temperature) than the binary carbides, such as HfC, ZrC, TaC, and TiC(6.3-29.3 W•m -1 •K -1 at room temperature). Zhao et al. 10 reported a new type of rare-earth zirconate (La 0.2 Ce 0.2 Nd 0.2 Sm 0.2 Eu 0.2 ) 2 Zr 2 O 7 high-entropy ceramic with low thermal conductivity (0.76 W -1 •m -1 •k -1 ) and low grain growth speed, which consolidated its potential value in the field of TBCs. Zhao et al. 11 reported (Nd 0.2 Sm 0.2 Eu 0.2 Y 0.2 Yb 0.2 ) 4 Al 2 O 9 exhibits a close thermal expansion coefficient (6.96 × 10 −6 K −1 at 300-1473 K) to that of mullite, good phase stability from 300 to 1473 K, and low thermal conductivity (1.50 W -1 •m -1 •k -1 at room temperature).