HYDROXIDE AND OXIDE IMPURITIES IN CALCIUM HALOPHOSPHATES

A number of defects giving rise to specific optical absorption and fluorescence, and to the formation of color and paramagnetic centers upon X-ray irradiation, can be produced in polycrystalline Ca10(PO4)6F2 (calcium fluorapatite). Heating in vacuum results in the formation of F ion vacancies. Heating in water vapor introduces OH ions which substitute for F ions and heating in water vapor followed by heating in vacuum results in the formation of oxide ion impurities at F ion sites and F ion vacancies which can associate. Models for several color and paramagnetic centers proposed on the basis of the results of earlier EPR studies on single crystals are supported. A new paramagnetic defect consisting of a hole trapped at an O-OH ion pair is reported for the first time. Some ideas on the defects responsible for extrinsic u.v. absorption bands seen previously in fluorapatite are presented. Finally, chlorapatite is shown to behave in an analogous manner. © 1969.