Crystallinity and fluorine substitution effects on the proton conductivity of porous hydroxyapatites

Porous calcium hydroxyapatite (p-HAp) was prepared by wet chemical methods. The poorly crystalline structure and the high surface specific area (235m ²/g) of this hydroxyapatite have effects on the variation of the electrical properties. Good linearity of logarithm of conductivity versus the relative humidity in the range from 19% to 88% (RH) was observed using the complex impedance spectroscopy. The proton conduction was affected by the relative humidity related to H₂O adsorption on the material surfaces. The fluorine substitution in p-HAp also modifies the crystalline and the proton conduction properties.