Luminescence characteristics and site-occupancy of Eu2+- and Eu3+-doped MgZn2(PO4)2 phosphors

Abstract

Eu2+- and Eu3+-doped MgZn2(PO4)2 were prepared using the high temperature solid-state reaction method. The excitation spectra in the UV and VUV region, the emission spectra, and the luminescence decay curves of the Eu2+ and Eu3+ ions were investigated. The crystallographic distributions of the Eu2+ and Eu3+ sites in MgZn2(PO4)2 lattices are different. MgZn2(PO4)2:Eu2+ presents a bluish green luminescence with two distinct emission centers at 450 and 525 nm. MgZn2(PO4)2:Eu3+ presents an reddish orange color with luminescence transitions from the 5D0 level of the Eu3+ ions. There exist two Eu2+-crystallographic sites in MgZn2(PO4)2:Eu2+, which occupy both Mg2+ and Zn2+ sites. However, there is only one Eu3+-site in the MgZn2(PO4)2:Eu3+ lattices, which was confirmed by site-selective excitation and emission spectroscopy, and the luminescence decay in the 5D0 → 7F0 region of the Eu3+ ions under a pulsed, tunable, narrowband dye laser. The Eu3+ ion was suggested to occupy the octahedral Mg2+-site in the MgZn2(PO4)2 lattices. The spectral characteristics, the temperature-dependent luminescence intensity and activation energies of thermal stabilities and the microstructures were discussed on the basis of the crystal structure and the luminescence results.