Achieving tunable luminescence in Eu2+ and Eu3+ codoped MAl2B2O7:Eu (M = Ca2+, Sr2+, and Ba2+) phosphor by structure defect designing and site symmetry controlling

Eu2+ and Eu3+ codoped alkaline-earth aluminum borates MAl2B2O7:Eu (M = Ca2+, Sr2+, and Ba2+) phosphors were prepared by a conventional high-temperature solid-state method. The phosphor exhibits strong absorption in the spectral range of ∼200–450 nm and bright tunable emission in the blue region, white region, and red region. The effect of composition, excitation wavelength, and doping concentration of europium ion on luminescence behavior of the phosphors were investigated systematically. Upon 254 nm excitation, SrAl2B2O7:Eu exhibits blue and bluish-green emission of Eu2+ and red emission of Eu3+. Ca2+ substitution for Sr2+ promoted the optimization of luminescence quality, and even the emergence of white light with chromatic coordination (0.382, 0.234), and Ba2+ substitution for Sr2+ increased the total luminescence intensity by ∼12.5 times. The changes in luminescence behavior were explained according to the structural defect of the phosphor and the site symmetry of the europium ions. The tunable luminescence and white-light emission upon 254 nm excitation imply that the phosphors have potential application prospects in cold cathode fluorescent lamps.