Crystal Chemistry and Luminescence Properties of Eu-Doped Polycrystalline Hydroxyapatite Synthesized by Chemical Precipitation at Room Temperature

Abstract

Europium-doped hydroxyapatite Ca10(PO4)6(OH)2 (3% mol) powders were synthesized by an optimized chemical precipitation method at 25 °C, followed by drying at 120 °C and calcination at 450 °C and 900 °C. The obtained nanosized crystallite samples were investigated by means of a combination of inductively coupled plasma (ICP) spectroscopy, powder X-ray diffraction (PXRD), Fourier Transform Infrared (FTIR), Raman and photoluminescence (PL) spectroscopies. The Rietveld refinement in the hexagonal P63/m space group showed europium ordered at the Ca2 site at high temperature (900 °C), and at the Ca1 site for lower temperatures (120 °C and 450 °C). FTIR and Raman spectra showed slight band shifts and minor modifications of the (PO4) bands with increasing annealing temperature. PL spectra and decay curves revealed significant luminescence emission for the phase obtained at 900 °C and highlighted the migration of Eu from the Ca1 to Ca2 site as a result of increasing calcinating temperature.

Neutron and XRD Single-Crystal Diffraction Study and Vibrational Properties of Whitlockite, the Natural Counterpart of Synthetic Tricalcium Phosphate

“…TPCs are biomaterial particularly wanted for their biocompatibility in human biosystem [1], and for the possibility of different cation replacements at the sites typically occupied by Ca [11], giving rise to different products, employed as commercial cement and paste for bone replacement [13,14]. In this regard, they are preferred to the more common synthetic Ca 10 (PO 4 ) 6 (OH) 2 hydroxyapatite because of their brittle nature [15,16]. Recently, additional interest has been also devoted to a series of rare-earth-doped TCP that are largely investigated as possible optical materials for biosciences application [10,11,17].…”

Lanthanides-Substituted Hydroxyapatite for Biomedical Applications

“…On the contrary, samples prepared by hydrothermal treatment exhibit a nanorod-like morphology that enhances luminescence due to the high packing density and reduction of light scattering [ 61 ]. Working at low temperatures, such as 120 °C, led to the ordering of Eu 3+ ions at the Ca 1 site [ 62 ]. Silva et al observed that the thermal treatment of the doped NPs from 500 °C to 800 °C induces the diffusion of the rare element from Ca 1 to Ca 2 sites that seem to be more energetically stable to Eu 3+ [ 63 ].…”

Synthesis of Hydroxyapatite/Iron Oxide Composite and Comparison of Selected Structural, Surface, and Electrochemical Properties

“…Its chemical formula is Ca 10 (PO 4 ) 6 (OH) 2 . The Ca/P ratio in stoichiometric hydroxyapatite is equal to 1.67, but in nonstoichiometric hydroxyapatite it is between 1.5–2.0 [ 2 ]. The compound is a part of human bones and teeth, which makes them properly durable.…”