Ca(1-x-y)Dy(x)K(y)WO4: a novel near UV converting phosphor for white light emitting diode

A series of Dy(3+)/K(+) doped calcium tungstate phosphors were synthesized by solid state reaction method. The crystal structure, surface morphology, chemical composition and photoluminescence properties of the prepared phosphors were investigated. The luminescence decay curves of doped/codoped phosphors were recorded. The X-ray diffraction analysis shows that the phosphors are of tetragonal structure. SEM studies confirm the particle size in the micro-meter (μm) range. The photoluminescence results indicate that these phosphors could be efficiently excited by the near-ultraviolet radiation which causes the emission in the blue and yellow regions. The white light was achieved by tailoring this yellow to blue ratio varying the Dy(3+)/K(+) dopant concentration. The quality of emitted white light was checked by calculating different CIE parameters of these phosphors. Decay kinetics studies confirms the life time of activator ions in micro-second (μs) range.