In situ observation of defects in hydroxyapatite up to 1200 degrees C by ultraviolet Raman spectroscopy

Raman spectra of hydroxyapatite have been successfully obtained at temperat ures up to 1200 degrees C for the first time by using a new system of ultra violet (UV) Raman spectroscopy. With increasing temperature, the intensity of a band ascribed to the stretching vibration of the OH ion continuously d ecreased. The total intensity of bands in the wavenumber range of 3300-3800 cm(-1) did not change significantly up to about 800 degrees C, whereas the y decreased at temperatures higher than about 800 degrees C. This result is interpreted as producing oxy-hydroxyapatite due to dehydration of hydroxya patite over 800 degrees C. The withdrawal of water is accompanied by the cr eation of defects. This consideration is strongly supported by results of t hermodynamic calculations and the line width of the Raman band. (C) 2000 Pu blished by Elsevier Science B.V.