Spectroscopy properties of Eu3+ doped Ca9R(VO4)7 (R=Bi, La, Gd and Y) phosphors by sol-gel method

An attempt has been made to synthesize the Eu3+-activated Ca9R(VO4)(7) (R=Bi, La, Gd, and Y) red emitting phosphors by a modified sol-gel process. The phase formation processes of these samples have been characterized by thermogravimetric analysis (TGA) and x-ray diffraction (XRD). The optical excitation spectra of Ca9R(VO4)(7) samples showed an intense charge transfer band (CTB) along with a group of typical sharp lines from Eu3+, and the emission spectra have been dominated by the electric dipole D-5(0)-F-7(2) transition peaked at 614 nm. The parameters for the synthesis of these phosphors including their annealing temperature and concentration of Eu3+ ions have also been optimized. No concentration quenching is found in this class of samples, and the Ca9Eu(VO4)(7) phosphor shows the strong red light. In addition, the thermal stability of phosphor Ca9Eu(VO4)(7) was also investigated, and the results indicate that this class of phosphors can be served as a potential red emitting phosphor candidate for LEDs. (C) 2012 Elsevier Ltd. All rights reserved.