Chromaticity of inhomogeneous broadening effect on CaxSr1-xAl2O4:Eu2+ phosphors

In this study, calcium strontium aluminate phosphors CaxSr1-xAl2O4 doped 1 mol% Eu2+ was prepared as the fluorescent material for UV-LED performed as a light source. The crystal structure, peak wavelength (lambda(p)), and chromaticity were investigated by XRD patterns and photoluminescence (PL), respectively. The inhomogeneous broadening effects of emission spectra were also discussed by electron paramagnetic resonance (EPR). In the CaxSr1-xAl2O4:Eu2+ system, the dominant structure transforms from monoclinic to hexagonal at 0.2 <= x <= 0.5, and lambda(p) ranges from 440 to 529 nm. The shift in lambda(p) could be explained by the crystal field effect, which is affected by different coulomb attracting forces due to the various fractions of Ca2+/Sr2+ in the host lattice. The near-white chromaticity of Ca0.5Sr0.5Al2O4:Eu2+ (1 mol%) phosphor was explained by the reasons of inhomogeneous broadening and re-absorption effects. The EPR spectra indicated that the inhomogeneous broadening effect could be attributed to the substitutional disorder (compositional disordering) of Ca2+ and Sr2+ in the host lattice. (c) 2006 Elsevier B.V. All rights reserved.