The luminescence and mechanism of a novel ultraviolet Li7M1-AlB12O24: xEu2+ (M=Ca, Sr, Ba) phosphors synthesized by high-temperature solid-state method

The Li7M1-xAlB12O24: xEu2+ (M = Ca、Sr、Ba) phosphors were prepared by the conventional high temperature solid-state reaction. The as-prepared phosphors had novel and attractive ultraviolet emissions at 386 nm (M = Ca), 388 nm (M = Sr), 391 nm (M = Ba) under the excitation of 289 nm, 293 nm, and 304 nm, respectively. The concentration quenching process between Eu2+ ions is determined and the critical quenching concentration of Eu2+ in Li7Ca1-xAlB12O24: xEu2+ phosphor is x = 0.11. The corresponding concentration quenching mechanism is verified as dipole-quadrupole (d-q) interaction. The critical transfer distance of Li7Ca0.89AlB12O24:0.11Eu2+ was determined to be 1.88 nm, Further evaluation on the absorbance spectra indicated that the energy transfer between Eu2+ was little affected by the matrix crystal field. The fluorescence lifetime of Li7Ca0.89AlB12O24: 0.11Eu2+ was 768.5 ns and the quantum efficiency was 55.91%. Therefore, the as prepared Li7M1-xAlB12O24: xEu2+ (M = Ca、Sr、Ba) phosphors exhibited a rare near ultraviolet emission with a potential applications on UV LED and anti-counterfeiting ink.