Crystallization process and some properties of calcium mica–apatite glass-ceramics

A feature of calcium–mica is the great glass stability of the melt. However, the calcium–mica glass-ceramic disintegrates naturally in air. If the disintegration is hindered by the separation of other materials, glass-ceramics containing calcium–mica become usable. In this study, mica–apatite glass-ceramics with the different ratio of fluoroapatite (Ca10(PO4)6F2) to calcium–mica (Ca0.5Mg3(AlSi3O10)F2), were prepared and the crystallization process, microstructure development and some properties were investigated. Mica crystals first appeared and then apatite crystals in all specimens. This crystallization process was different from that of Bioverit®I and the other mica–apatite glass-ceramics. Specimens, in which the mica crystals formed interlocking microstructure and fine apatite crystals were dispersed on the surface of the mica crystals, showed good machinability but disintegrated naturally in air or distilled water. On the other hand, specimens consisting of fine mica and fine apatite crystals, showed higher bending strength and hardness than Macor® and high chemical resistance in distilled water. But they showed inferior machinability because the mica crystals formed incomplete interlocking microstructure.