The influence of sintering temperature on the photoluminescence properties of oxyapatite Eu 3+:Ca 2Gd 8Si 6O 26 nanophosphors

Abstract

Eu 3+ activated oxyapatite Ca 2Gd 8Si 6O 26 (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 Eu 3+ 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 Eu 3+:CGS showed the charge transfer band (CTB) and intense f–f transitions of Eu 3+ and Gd 3+. The intensity of the f–f transitions of Gd 3+ increases with increasing the sintering temperature and decreases with increasing the Eu 3+ concentration. It was observed that the CTB of Eu 3+ shifted to a shorter wavelength region with an increase the crystallite size due to the variation of coordination environments. The photoluminescence (PL) spectra of Eu 3+:CGS exhibit two emission lines corresponding to the 5D 0 → 7F 0 transition which results from occupation of Eu 3+ ions in two different low symmetry local sites in CGS host lattice. The optimized sintering temperature and concentration of Eu 3+ were observed for Eu 3+:CGS nanophosphors based on the dominant red ( 5D 0 → 7F 2) emission intensity under NUV (395 nm) excitation. The decay curves of 5D 0 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.