Porous high-entropy rare-earth phosphate (REPO₄, RE = La, Sm, Eu, Ce, Pr and Gd) ceramics with excellent thermal insulation performance via pore structure tailoring

Thermal insulation materials play an increasingly important role in protecting mechanical parts functioning at high temperatures. In this study, a new porous high-entropy (La_1/6Ce_1/6Pr_1/6Sm_1/6Eu_1/6Gd_1/6)PO₄ (HE (6RE_1/6)PO₄) ceramics was prepared by combining the high-entropy method with the pore-forming agent method and the effect of different starch contents (0–60vol%) on this ceramic properties was systematically investigated. The results show that the porous HE (6RE_1/6)PO₄ ceramics with 60vol% starch exhibit the lowest thermal conductivity of 0.061 W·m⁻¹·K⁻¹ at room temperature and good pore structure stability with a linear shrinkage of approximately 1.67%. Moreover, the effect of large regular spherical pores (>10 µm) on its thermal insulation performance was discussed, and an optimal thermal conductivity prediction model was screened. The superior properties of the prepared porous HE (6RE_1/6)PO₄ ceramics allow them to be promising insulation materials in the future.