STRUCTURAL TRANSITION AND DIELECTRIC CHARACTERISTICS OF HIGH-PURITY HYDROXYAPATITE

The temperature and frequency dependences of the dielectric permittivi ty epsilon and dielectric loss tangent tan delta of high-purity hydrox yapatite, Ca-10(PO4)(6)(OH)(2), were investigated in the range 20-500 degrees C. It was established that in the range 20-300 degrees C the t emperature dependences of epsilon and tan delta are determined by dipo le polarization brought about by polar hydroxy groups. Space-charge po larization prevails above 300 degrees C owing to the generation of cha rge carriers. The results were compared with earlier data on heat capa city and thermally stimulated exoelectron emission of hydroxyapatite.