Pressureless sintering and mechanical properties of SiO2–Al2O3–MgO–K2O–TiO2–F (CaO–Na2O) machinable glass–ceramics

To develop a high strength machinable glass–ceramic through pressureless sintering, the glassy compositions were obtained by mixing a mica-based frit and a frit in the SiO2–CaO–Na2O system. According to XRD results, the glass compositions mainly crystallized into phlogopite and diopside after sintering. The optimum sintered glass–ceramic with desirable mechanical properties, machinability and sinterability was achieved by addition of 30 wt.% SiO2–CaO–Na2O glass powder to 70 wt.% mica glass composition. SEM results confirmed presence of needle-like diopside crystals which played a reinforcement role to the platelet phlogopite and glassy matrix combination. The measurements showed bending strength and fracture toughness enhanced up to 144.6 ± 17.6 MPa and 1.7 ± 0.2 MPa m1/2, respectively.