Preparation and Structure of Zinc–Calcium Hydroxyapatite Solid Solution Particles and Their Ultraviolet Absorptive Ability

The calcium ions (Ca2+) of calcium hydroxyapatite (CaHap) were substituted with zinc ions (Zn2+), and zinc–calcium hydroxyapatite solid solution (ZnCaHap) particles were prepared via a precipitation method. The structure of the various obtained particles was investigated via powder X-ray diffraction, field emission scanning electron microscopy and energy dispersive X-ray spectrometry. The ultraviolet (UV) absorption ability of the particles was also investigated using UV–Vis spectroscopy. The morphology of the CaHap comprised fine ellipsoidal particles, and long rod-like particles and large plate-like particles were mixed with the fine particles at higher Zn2+ contents in the particles. Pure ZnCaHap particles were obtained from the starting solution at less than Zn/(Zn + Ca) ([XZn]) of 0.25. Another crystal phase was mixed with the ZnCaHap phase at [XZn] ≥ 0.25. The crystallinity and lattice parameters a and c of the particles decreased with an increase in [XZn] from 0 to 0.10. The UV absorptive ability of the particles first increased and then decreased with increasing Zn2+ content and showed a maximum at [XZn] = 0.30.