Photoluminescence Properties of Dy 3+ Activated CaWO 4 Nanophosphors: a Potential Single Phase near White Light Emitter.

A multicolor tunable CaWO4 :xDy3+ nanophosphors have been synthesized via hydrothermal route. X-Ray Diffraction and Fourier transform infrared confirm the formation of CaWO4 :Dy3+ nanophosphors. Transmission electron microscopy image and selected area electron diffraction (SAED) reveal the formation of nanosize and crystalline CaWO4 :Dy3+ . Dependence of energy transfer rate from WO4 2- to the activator (Dy3+ ) is observed from the photoluminescence studies. An enhancement of energy transfer efficiency from 36% to 90% is observed after annealing the as-prepared samples at 800 °C. The exchange type energy transfer mechanism is observed to be dominant in as-prepared samples while the electric dipole-dipole interaction is dominant in annealed samples. Variation in energy transfer rate from the host to Dy3+ activator ions leads to the tuning of color emission from this nanophosphor. A near white light emission could be achieved with 6 at.% Dy3+ doped CaWO4 annealed at 800 °C with x = 0.310 and y = 0.327.