THERMAL-EXPANSION OF HOT ISOSTATICALLY PRESSED HYDROXYAPATITE

A dense and transparent hydroxyapatite produced by hot isostatic press ing was investigated with respect to its stability and thermal expansi on behaviour in the range 20-1150-degrees-C. The evaluation was made b y high-temperature X-ray diffraction in a reconstructed test chamber w ith a BN sample holder and Pt as an internal (in situ) reference. No d egradation of the hydroxyapatite was detected in the range investigate d. The lattice parameters, a and c, were determined as a function of t emperature. The linear thermal expansion coefficient, determined by di latometry, was 17.1 x 10(-6)-degrees-C-1, which agreed well with the v alue 17.3 x 10(-6)-degrees-C-1 obtained by X-ray diffraction.