The influence of sintering temperature on the photoluminescence properties of oxyapatite Eu3+:Ca2Gd8Si6O26 nanophosphors

Eu3+ activated oxyapatite Ca2Gd8Si6O26 (CGS) nanophosphors were synthesized using a solvothermal reaction method. The structural and luminescent properties of these nanophosphors were investigated as a function of sintering temperature and Eu3+ ion concentration. The SEM images of the prepared phosphors reveal spherically shaped particles in the nanometer range and the XRD patterns confirm their hexagonal structure. The photoluminescence excitation (PLE) spectra of Eu3+:CGS showed the charge transfer band (CTB) and intense f–f transitions of Eu3+ and Gd3+. The intensity of the f–f transitions of Gd3+ increases with increasing the sintering temperature and decreases with increasing the Eu3+ concentration. It was observed that the CTB of Eu3+ shifted to a shorter wavelength region with an increase the crystallite size due to the variation of coordination environments. The photoluminescence (PL) spectra of Eu3+:CGS exhibit two emission lines corresponding to the 5D0 → 7F0 transition which results from occupation of Eu3+ ions in two different low symmetry local sites in CGS host lattice. The optimized sintering temperature and concentration of Eu3+ were observed for Eu3+:CGS nanophosphors based on the dominant red (5D0 → 7F2) emission intensity under NUV (395 nm) excitation. The decay curves of 5D0 level show that the lifetime decreases with increasing the crystallite size. These luminescent powders are expected to find potential applications such as WLEDs and optical display systems.