Influence of chemical composition on polarization phenomena in bioelectrets: apatites

Apatites, filler of calcified tissues, are bioelectrets characterized by tunnels in which hydroxyl ions can move. The dipolar reorientations, at the origin of the monoclinic-hexagonal structural transition, have been studied by the thermally stimulated current (TSC) method. The various TSC spectra have been resolved by the technique of fractional polarizations. The analysis of the dielectric relaxation times shows that a single compensation phenomenon characterizes stoichiometric apatites. The compensation temperature, analogous to the hexagonal-monoclinic transition temperature, is indicative of the width of the tunnel and of the interaction between hydroxyl ions and substituted ions inside the tunnels