Fluorophlogopite porcelain based on talc–feldspar mixture

Talc–feldspar mixture was utilized for the processing of dense mica containing porcelain through controlled crystallization for dental use. Uniform microstructure with fine equigranular fluorophlogopite grains was developed at 950°C. Fluorophlogopite grains, 0.2 μm in size, are well distributed in the glassy phase. The thermal expansion coefficient was measured to be 107×10−7/°C (20–780°C). The first crystallization was found to be at 645°C,while the crystallization of fluorophlogopite existed at 910°C. On firing at 1050°C, a small amount of forsterite was detected associated with mica grain growth. The formation of forsterite was related to the decomposition of fluorophlogopite. Two fluorophlogopite crystal habits were detected via SEM. EDAX showed that the two crystal forms have the same composition at 950 and 1000°C. The amount of Al2O3 increases with the amount of MgO and SiO2 at 1050°C.