Direct and ultrasonic measurements of macroscopic piezoelectricity in sintered hydroxyapatite

Macroscopic piezoelectricity in hydroxyapatite (HA) ceramic was measured by a direct quasistatic method and an ultrasonic interference technique. The effective symmetry of polycrystalline aggregate was established and a detailed theoretical analysis was carried out to determine by these two methods the shear piezoelectric coefficient, d(14), of HA. Piezoelectric nature of HA was proved qualitatively although a specific quantitative value for the d(14) coefficient could not be established. Ultrasound method was also employed to anisotropic elastic constants, which agreed well with those measured from the first principles.