Effect of step-by-step depolarization on electret performance of OH defect-controlled ceramic hydroxyapatite.

Ceramics electrets of hydroxyapatite (HAp) have been developed for both power generators and artificial bones. However, the formation mechanisms of the HAp electrets have not yet been completely understood. In particular, it is unclear how the OH− ion-dipoles in HAp lattices contribute to electret performance. Herein, we show that HAp with controlled OH− ion content exhibits excellent performance as an electret. We prepare OH−-defect-controlled HAp samples either by restricted dehydration during thermal process or by valence control through the substitution of Ca2+ with Nd3+. The experimental results prove that the electrets prepared by partially dehydrated HAp and Nd-substituted HAp with a small number of OH− ions showed better performance. Our results suggest that the OH− ion-dipole polarization contributes negatively to the electret performance. [ABSTRACT FROM AUTHOR]