Structural and electrical study of calcium phosphate obtained by a microwave radiation assisted procedure

The hydroxyapatite (Ca10(PO4)6 (OH)2-HAP) is the main mineral constituent of teeth and bones with excellent biocompatibility with hard and muscle tissues. This material exhibits several problems of handling and preparation, which can be minimized by mixing the HAP with a suitable binder. In order to improve the phase structure, morphology and the dielectric properties, nanocrystalline hydroxyapatite was prepared by a microwave assisted solid-state reaction technique from Ca(OH)2 and CaHPO4 powders. After milling the mixture was submitted to microwave radiation in a domestic microwave oven (f=2.45 GHz-1 kW) during 15 and 30 min at 1000, 1100 and 1200 deg. C. The samples were analyzed by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), EDS (energy dispersive spectroscopy), FT-IR spectroscopy. The dielectric properties were measured in the frequency range 1 Hz-30 MHz at several temperatures (250-350 K). The dielectric study in function of frequency, at 300 K, was made using the Modulus formalism (M*=1/ε*) and a distribution of relaxation times was observed.