Microstructure of apatite glass ceramic

Phase separation could be observed in a base glass from the system SiO2-Al2 O3-Na2O-K2O-CaO-P2O5-F-. Both surface and volume crystallisation of leucite and apatite, respectively, were found after heat treatment of the powdered and sintered material at temperatures between 850 degreesC and 1150 degree sC. After removing the leucite crystals from monolithic blocks, which were cast and heat treated at temperatures between 580 degreesC and 800 degreesC for 8 h only apatite crystallisation in the volume could be found. Optical microscopy (Zeiss: Jenaplan), X-ray diffraction (Siemens: D5000), scanning electron microscopy (Zeiss: DSM 940A), AFM (Ultraobjektiv: SIS), and trans mission electron microscopy/electron diffraction (Hitachi: H8100) were used to characterise the phase content of the glass ceramic material.