Silicic Acid–Ammonia Water‐Assisted Cold Sintering for High‐Performance Thermal Insulating S‐1 Zeolite Ceramics

ABSTRACT It is a formidable challenge to achieve superior mechanical properties combined with excellent thermal insulation performance and high thermal stability in porous ceramics for safeguarding sensitive microelectronic devices in extreme environments. Here, high‐purity silicalite‐1 (S‐1) zeolite ceramics are prepared by cold sintering and post annealing to overcome this intrinsic trade‐off, yielding an ultralow thermal conductivity of 0.25 W m −1 K −1 at room temperature combined with a high compressive strength of 74.0 MPa. This outstanding thermal insulating and load‐bearing capacity originates from the silanol‐condensation‐driven processes involving submicron welding and defect healing, which engineer an optimized hierarchical pore structure. This structure comprises well‐preserved ordered micropores that restrict the phonon‐free paths while maintaining structural integrity and fine macropores/mesopores that suppress gaseous heat conduction through Knudsen effects. Furthermore, the cold‐sintered zeolite ceramics exhibit excellent thermal stability up to 950°C. The present work demonstrates a zeolite defect‐healing mechanism for designing advanced thermal insulation materials via the microstructure‐engineered strategy.