Synthesis, luminescence and photometric characteristics of Ca0.5La(MoO4)2:Ln3+ (Ln = Eu, Tb, Dy) phosphors

Ca0.5La(MoO4)(2):Ln(3+) phosphors, where Ln = 4, 8, 12, 16, and 20 mol% of Eu, Tb, or Dy, were successfully synthesized by a conventional solid-state reaction method at 900 degrees C for 3 h. The Ca0.5La(MoO4)(2):Ln(3+) phosphors exhibit a scheelite tetragonal crystal structure belonging to the I4(1)/a space group. The strong absorption bands seen in Fourier transform infrared (FIR) spectra confirm that F-2(v(3)) modes of vibration are IR active. The photoluminescence(PL) spectra reveal that, under optical excitation, the as-synthesized phosphors show high intensity narrow emission bands in the red (615 nm), and green (545 nm), and yellow (570 nm) regions for samples doped with Eu3+, Tb3+, and Dy3+ ions, respectively. The critical concentrations of Eu3+, T3+, and Dy3+ as dopants in Ca0.3La(MoO4)(2) were found to be 16,12 and 12 mol %, respectively. Thereafter, concentration quenching effect occurred in the solid solutions. The fluorescence decay times for the major transitions of D-5(0) -> F-7(2), D-5(4) -> F-7(3), and F-4(912) -> H-6(13/2) were estimated for different doping concentrations of Eu3+, Tb3+, and Dy3+ in Ca0.3La(MoO4)(2), respectively. To determine the color purity and emission quality of the phosphor, photometric parameters such as color chromaticity coordinates, color correlated temperature (CCT), color rendering index (CRI), and luminous efficacy of radiation (LER) were estimated using the spectral energy distribution functions of the Ca0.5La(MoO4)(2):Ln(3) phosphors. (C) 2015 Elsevier B.V. All rights reserved.