Microporous Collapse Engineering Enables Concurrent Optical Transparency and Mechanical Robustness in Mullite Glass‐Ceramics via Low‐Temperature Spark Plasma Sintering

The intrinsic trade‐off between optical transparency and mechanical robustness represents a fundamental challenge in glass‐ceramic materials design. Herein, we demonstrate that engineering microporous collapse pathways in FAU zeolite precursors enables the fabrication of mullite glass‐ceramics with exceptional concurrent optical and mechanical performance through low‐temperature spark plasma sintering (SPS). By implementing two orthogonal controls—precursor collapse pathway (pre‐collapse versus in situ evolution) and framework chemistry (FAU‐Y versus FAU‐X)—we systematically elucidate how these parameters govern defect evolution, crystallization kinetics, and microstructure development. The optimized samples achieve an in‐line transmittance of ∼85% at 550 nm, coupled with a Vickers hardness of ∼8.6 GPa and indentation fracture toughness of ∼1.6 MPa·m 1/2 . Our findings reveal that pre‐collapse shifts degassing and structural reorganization upstream, enabling more controllable pore evolution and significantly enhanced transparency. Furthermore, composition‐regulated nucleation‐growth behavior and aluminum partitioning dictate grain coarsening and mechanical differentiation. This work establishes a comprehensive process‐structure framework for designing transparent, mechanically robust glass‐ceramics through rational engineering of microporous collapse mechanisms under rapid, low‐temperature densification conditions.