Cr doping optimization in CaAl2O4:Eu blue phosphor

A new composition of phosphor material CaAl₂O₄:Eu²⁺ co-doped with Cr³⁺ was investigated. Various compositions with Eu²⁺ (1 and 2 mol%) and Cr³⁺ (0.05–0.1 mol%) were prepared by solid-state reaction method. These compositions show high brightness and longer persistent luminescence. Phase and crystallinity were investigated by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Excitation and emission spectra were taken to investigate the luminescence characteristics. Broad band UV excited luminescence of the CaAl₂O₄:Eu²⁺, Cr³⁺ was observed in the blue region (λ_max = 440 nm) due to transitions from 4f⁶5d¹ to the 4f⁷ configuration of the Eu²⁺ ion. Cr³⁺ ion co-doping generates deep traps which results in longer afterglow phosphorescence compared to parent phosphor.