Optical and structural properties of undoped and Mn2+ doped Ca-Li hydroxyapatite nanopowders using mechanochemical synthesis

Undoped and Mn2+ doped calcium-lithium hydroxyapatite (CLHA) nanopowders were prepared by mechanochemical synthesis. The prepared samples were characterized by powder X-ray diffraction, scanning electron microscope, transmission electron microscope, optical absorption, photoluminescence, electron paramagnetic resonance and FT-IR spectroscopy techniques. From powder XRD pattern, lattice cell parameters and average crystallite sizes were evaluated. The morphologies of prepared samples were analyzed by using SEM and TEM studies. Optical and EPR data confirmed that the doped Mn2+ enter into the host material as distorted octahedral site. Photoluminescence spectra of undoped and Mn2+ doped CLHA nanopowders exhibited blue, blue-green emission bands at 425, 443, 468 nm and green, strong orange emission bands at 534, 577 nm respectively under the excitation wavelength of 365 nm. The CIE chromaticity coordinates were also calculated from emission spectra for undoped and Mn2+ doped CLHA nanopowders. Vibrational bands related to phosphate molecules, P-O-H and hydroxyl ions are observed in FT-IR spectra.