Photoluminescence properties of Na+-free and Na+ co-doped Ca9Gd(VO4)7:Eu3+, Dy3+

The Na+-free and Na+ co-doped Ca9Gd(VO4)7:Eu3+, Dy3+ phosphors have been synthesized by the conventional solid-state reaction. For the Na+-free Ca9Gd(VO4)7:Eu3+, Dy3+ phosphors, the emission spectra at λex = 300 nm exhibit red, yellow and blue emission due to f–f transitions of Dy3+ and Eu3+, and the emission intensity can be tuned by the concentration of Dy3+ and Eu3+. For the Na+ co-doped Ca9Gd(VO4)7:Eu3+, Dy3+ phosphors, all the emission intensity of red, yellow and blue increases with the Na+ concentration, and the origin for the enhanced emission can be assigned to the variation of crystal field surrounding the Eu3+ and Dy3+ activator which results from the oxygen vacancy created by substituting Na+ for Ca2+.