Influence of defects on dipolar reorientations of bioelectrets: hydroxyapatites

The natural filler of calcified tissues is nonstoichiometric apatites. These apatites are characterized by a Ca/P ratio larger or lower than 1.66 (stoichiometric ratio). Defects responsible for modification of the crystalline structure can be eliminated by annealing apatites at various temperatures. Hence, pretreated samples of nonstoichiometric apatites have been studied by thermally stimulated current (TSC) spectroscopy. Analysis of polarization phenomena shows the existence of either monophasic or biphasic structure. Information on localization and interaction of defects with structural ions is also provided.<
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