Machinable calcium pyrophosphate glass-ceramics

Glass-ceramics containing a large amount of calcium pyrophosphate (beta -Ca 2P2O7) crystal were prepared via crystallization and sintering; compacts of a calcium phosphate glass powders with a composition of 60CaO . 30P(2)O(5) . 5TiO(2) . 5Na(2)O (in mol%) were heated for 3-6 h at 850 degreesC in air . The compacts were densified by the viscous flow of the glassy phases duri ng heating. The calcium phosphate glass-ceramics were found to show a bendi ng strength of approximately 100 MPa, and they were easy to machine, as con firmed by a drilling test using a conventional carbide tool. The machinabil ity is thought to arise from the microstructure consisting predominantly of the interlocking and platelike beta -Ca2P2O7 precipitated in the glass.