CaMoO4:Dy3+,Eu3+ phosphors: microwave synthesis, characterization, tunable luminescence properties and energy transfer mechanism

A series of Dy3+/Eu3+ co-doped CaMoO4 phosphors were synthesized by a rapid microwave synthesis method. The samples were investigated using X-ray powder diffraction (XRD), scanning electron microscope (SEM), fourier transform infrared (FT-IR) spectra, diffused reflectance spectra, fluorescence spectrometer, and photoluminescence decay curves, respectively. The XRD results indicated that all the samples were pure tetragonal CaMoO4 structure. The as-synthesized samples exhibited cubic particles and some irregular polyhedron particles. The big cubic particles were assembled by many closely packed quasi-spherical grains. Under 301 nm excitation, the increase of Eu3+ content in CaMoO4:Dy3+,Eu3+ led to the enhancement of red emission (613 nm) of Eu3+ and the decrease of blue and yellow emissions of Dy3+, which was possibly due to the efficient energy transfer (ET) from level of Dy3+ to 5D0 level of Eu3+ through the phonon-aided non-radiative relaxation. The phosphors could generate different color light from yellow-green through yellow and orange-reddish and eventually to red by properly tuning the content of Eu3+ based on the ET process, which suggested that they might be potentially applied in the fields of lighting and display. Besides, the possible energy transfer mechanism and schematic energy level diagram were discussed in detail.