(Sm_0.2Eu_0.2Tb_0.2Dy_0.2Lu_0.2)₂Si₂O₇: A novel high-entropy rare earth disilicate porous ceramics with high porosity and low thermal conductivity

Herein, a novel quinary high-entropy rare earth disilicate (Sm_0.2Eu_0.2Tb_0.2Dy_0.2Lu_0.2)₂Si₂O₇ ((5RE_1/5)₂Si₂O₇) porous ceramics were synthesized through a sol-gel/vacuum freeze-drying method with high-temperature calcination process. The microstructure, phase composition, thermal conductivity, compressive strength, and thermal stability of the as-prepared (5RE_1/5)₂Si₂O₇ porous ceramics were systematically investigated. The results indicated that the samples possess high porosity of 76.83%, pore size of 0.3–1.2 μm, homogeneous microstructure with small grain size of 400–800 nm, which results in low thermal conductivity of 0.94 W/(m·K) at 1273 K and high compressive strength of 6.55 MPa. These excellent properties indicated that as-prepared (5RE_1/5)₂Si₂O₇ porous ceramics has a great potential application value in the field of high-temperature thermal insulation materials.