MACHINABLE Dy-CONTAINING β-Ca3(PO4)2 CERAMICS PREPARED BY HEATING THE MIXTURES OF HYDROXY-APATITE AND DyPO4

The Dy-containing β-Ca3(PO4)2 ceramics obtained by heating the mixtures of hydroxy-apatite (Ca10(PO4)6(OH)2) and tetragonal DyPO4 with mixing mole ratio ((Ca+Dy)/P)=1.52-1.49 at 1300°C, and with mole ratio=1.57-1.49 at 1350-1400°C for 3h in air, were found to be machinable; they can be drilled and cut easily using a conventional inexpensive metallic Fe-Co-W (mostly Fe) drills or gravers. The relative density was larger than 95% at 1350-1400°C for the (Ca+Dy)/P mole ratio=1.57-1.49. The bending strength, Vickers' hardness and thermal expansion coefficient of the machinable Dy-containing β-TCP ((Ca+Dy)/P ratio=1.57-1.49) ceramics sintered at 1350°C for 3h were in the range 20-50 MPa, 2.8-3.9 GPa and 11~12x10-6/°C (~1000°C), respectively.