Chromaticity of inhomogeneous broadening effect on Ca_xSr_1-xAl₂O₄:Eu²⁺ phosphors

In this study, calcium strontium aluminate phosphors Ca_xSr_1-xAl₂O₄ doped 1 mol% Eu²⁺ was prepared as the fluorescent material for UV-LED performed as a light source. The crystal structure, peak wavelength (λ_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 Ca_xSr_1-xAl₂O₄:Eu²⁺ system, the dominant structure transforms from monoclinic to hexagonal at 0.2 ≤ x ≤ 0.5, and λ_p ranges from 440 to 529 nm. The shift in λ_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 Ca_0.5Sr_0.5Al₂O₄: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.