Highly porous Y ₂ SiO ₅ ceramic with extremely low thermal conductivity prepared by foam‐gelcasting‐freeze drying method

Foam‐gelcasting‐freeze drying method is developed to fabricate porous Y 2 SiO 5 ceramic with ultrahigh porosity of 92.2%‐95.8% and isotropous multiple pore structures. As prepared porous samples have quite low shrinkages of 0.8%‐1.9% during demolding and drying processes, lightweights of 0.19‐0.35 g/cm 3 , and extremely low thermal conductivities of 0.054‐0.089 W·(m·K) −1 . Our approach combines the merits of foam‐gelcasting method and freeze drying method. It is a simple and effective method to fabricate porous ceramics with very high porosity and extremely low thermal conductivity through low shrinkage of green body and near net complex shape forming.