Site occupation and fluorescence properties of MgAl2O4: Eu3+ phosphors

Abstract A series of Mg1-xEuxAl2O4 and MgAl2-xEuxO4 (x = 0.01, 0.02, 0.03, 0.04, 0.05) phosphors were synthesized by using a low-temperature hydrothermal method combined with a calcination process. The crystal structure, morphology and fluorescence performance of the samples was investigated. Eu3+ substitutes into the majority of Mg2+ sites in the Mg1-xEuxAl2O4 and MgAl2-xEuxO4 system host lattices and does not alter the phase prototype. However, the charge balance for the two systems is maintained by vacancy generation and cation inversion. The sample morphologies are composed of platelet-like and rod-like structures with good dispersion achieved by using urea as a precipitant. The main emission peaks for all samples are located at 592 nm and 616 nm and change regularly with increasing Eu3+ concentration. Compared with the Mg1-xEuxAl2O4 series and other reported MgAl2O4: Eu3+ phosphors, the MgAl2-xEuxO4 series is prone to avoid concentration quenching in the Eu3+ doping range of x ≤ 0.05. This is attributed to the special charge balance mechanism and larger transition probability at the 5D0→7F2 level for these series of samples. The energy transfer rate among Eu3+ in the two systems is influenced differently by vacancy generation and cation inversion. The MgAl2-xEuxO4 series, as promising phosphors, shows better emission colour quality. The CIE coordinate (x, y), CCT, and colour purity for the MgAl1.95Eu0.05O4 phosphor were determined to be (0.6296, 0.3699), 2014 K, and 85.36%, respectively.