Transparent nanocrystalline hydroxyapatite by pressure-assisted sintering

Transparent nanocrystalline hydroxyapatite (HA) bodies with a relative density of 99.8% and a mean grain size of 81 nm exhibit an optical transmittance of 66% at a wavelength of 645 nm. Light scattering analysis reveals that grain boundary reflection is significant for nanograined crystals, and nanopores in HA substantially reduce the transmittance of visible light even though the wavelength of visible light is about 32–64 times the pore size.