Cool white light emission from Dy³⁺ activated alkaline alumino silicate phosphors

A series of single phase white light emitting CaSrAl₂SiO₇:Dy³⁺ phosphors were prepared by traditional high temperature solid state reaction method. Structural characterization was done by X-ray diffraction, field emission scanning electron microscopy and energy dispersive spectroscopy analyses. Optical characterization was performed from photoluminescence and thermoluminescence studies. When excited at 350 nm, CaSrAl₂SiO₇:Dy³⁺ phosphors showed two intense emission bands in the blue region (480 nm and 493 nm) corresponding to ⁴F_9/2 → ⁶H_15/2 transition and one in yellow region (576 nm) corresponding to ⁴F_9/2 → ⁶H_13/2 transition. The Commission Internationale de I'Eclairage diagram was drawn for entire series. It confirmed that by manipulating Dy³⁺ content the luminescence color of CaSrAl₂SiO₇:Dy³⁺ phosphors were tuned from blue to white region. Computation of correlated color temperature suggested that present phosphor was cool in appearance hence CaSrAl₂SiO₇:Dy³⁺ phosphor can serve as a white light emitting phosphor and may be useful in outdoor illumination. A detailed study on thermoluminescence of ultraviolet exposed samples was done and possible mechanism of thermoluminescence was discussed. TL emission spectrum was also measured.