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

Thermal insulation materials are playing an increasingly important role in protecting mechanical parts served at high temperature. In this work, novel porous high-entropy (La_1/6Ce_1/6Pr_1/6Sm_1/6Eu_1/6Gd_1/6)PO₄ (HE (6RE_1/6)PO₄) ceramics have been prepared firstly with the aid of the HE strategy in combination with the pore-forming agent method. The effect of different starch contents (0-60vol%) on the comprehensive properties of porous HE (6RE_1/6)PO₄ ceramics is systematically investigated. The results show that porous HE (6RE_1/6)PO₄ ceramics containing 60vol% starch exhibit the lowest thermal conductivity of 0.061 W·m⁻¹·K⁻¹ at room temperature and good pore structure stability with the linear shrinkage of approximate 1.67%. Furthermore, the influence of larger regular spherical pores on thermal insulation performance is discussed and the optimal thermal conductivity prediction model is also screened. The superior comprehensive properties allow porous HE (6RE_1/6)PO₄ ceramics to be promising insulation materials in the future.