Single-phase and warm white-light-emitting phosphors CaLa2−x−y(MoO4)4: xDy3+, yEu3+: Synthesis, luminescence and energy transfer

A series of single-phase warm white light emitting CaLa2−x−y(MoO4)4: xDy3+, yEu3+ phosphors were synthesized by a typical sol-gel method. X-ray diffraction (XRD) analysis reveals that the crystal structures of the samples are matched well with the tetragonal CaMoO4. Upon ultraviolet (UV) light radiation, the Dy3+ or Eu3+ ions singly activated CaLa2(MoO4)4 phosphors exhibit corresponding emissions originated from the f-f transitions of Dy3+ or Eu3+ ions. Under near ultraviolet (n-UV) light excitation, in the Dy3+ and Eu3+ ions co-doped samples, the energy transfer (ET) phenomenon from Dy3+ to Eu3+ ions can be observed and has been demonstrated to be a quadrupole-quadrupole interaction mechanism. The emission color of CaLa1.98−y(MoO4)4: 0.02Dy3+, yEu3+ samples can be tuned from cool to warm white light by adjusting the concentration of Eu3+ ions. In addition, it can be found that CaLa1.974(MoO4)4: 0.02Dy3+, 0.006Eu3+ samples emit bright white light with the CIE coordinate of (0.348, 0.313) and the color temperature of 5087 K, which is very close to the standard white light. All the results demonstrate that the as-synthesized phosphors have great potential applications in the field of n-UV white light emitting diodes (WLEDs).