Ultra‐low temperature preparation of mullite glass‐ceramics with high transparency sintered from EMT‐type zeolite

Abstract Nanocrystalline mullite glass‐ceramics have been regarded as an ideal optical window material due to its excellent thermal shock resistance, low dielectric constant, and perfect high‐temperature strength. However, the fabrication of high‐purity mullite glass‐ceramics at a low temperature still faces great challenges. Herein, highly transparent mullite glass‐ceramics have been prepared at an ultra‐low temperature (~800°C) via the spark plasma sintering (SPS) of EMT‐type zeolite. Unlike the mullite glass‐ceramics made by the conventional sintering process, the one obtained in this study present high transparency both in the visible and infrared regions. The sintering activity and linear thermal shrinkage behavior of sample during the SPS process has been thoroughly investigated. Benefitted from the existence of ultra‐small mullite nanocrystals, the derived glass‐ceramics g‐950 possess a high Vickers hardness (7.0 GPa), Young's modulus (86.6 GPa), and MSP strength (123.2 MPa), which show more excellent mechanical properties than conventional aluminasilicate or silica glass.