Microstructural Characterization and Fracture Toughness of Cordierite-ZrO2 Glass-Ceramics

Crystallization of an MgO‐Al2O3‐SiO2‐ZrO2 sintered glass frit was studied. Heat treatment at 850° or 900°C caused initial crystallization of μ‐cordierite and tetragonal (t) ZrO2. The t‐ZrO2 crystallized with an irregular dendritic morphology and could be transformed to monoclinic (m) symmetry under certain conditions; the cordierite underwent the μ→α a transformation with extended annealing. Heat treatments at 1000°C caused crystallization of t‐ZrO2 rods and spheroids in an α‐cordierite matrix; these ZrO2 crystals, however, are resistant to transformation to m‐ZrO2. The beneficial effects of ZrO2 on the fracture toughness of cordierite‐based glass‐ceramics are described.