Effect of sodium and cerium co-doping on microstructure and luminescent properties of hydroxyapatite ceramics

The hydroxyapatite powders with co-doping of Ca²⁺ with Na⁺ and Ce³⁺ were obtained by aqueous precipitation. Co-doping was considered as a method of charge compensation in the cationic sublattice of the HA structure by means of the ${2\mathit{Ca}}^{2+}\to {\mathit{Ce}}^{3+}+{\mathit{Me}}^{+}$${2\mathit{Ca}}^{2+}\to {\mathit{Ce}}^{3+}+{\mathit{Me}}^{+}$ in order to maintain the stability of phase composition, improve the optical and microstructural properties of the HA ceramics. The content of dopants ranged from 0.25 to 1.0 mol. % relative to calcium atoms in HA. The ceramics were obtained by traditional sintering in an air atmosphere and by hot pressing under soft reducing conditions in order to trace Ce oxidizing in HA matrix. Phase and chemical composition of the obtained ceramics were investigated using powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and atomic emission spectrometry with inductively coupled plasma (AES-ICP). Microstructure and microhardness were estimated in order to trace the dopant effect on the ceramic formation. Luminescence spectra were recorded to evaluate the content of cerium ions in the ${\mathit{Ce}}^{3+}$${\mathit{Ce}}^{3+}$ state and to reveal the dopant effect on structure features of the HA.