(INVITED) A review on the Eu2+ doped β-Ca3(PO4)2-type phosphors and the sites occupancy for photoluminescence tuning

β-Ca3(PO4)2-type phosphors have received much attention due to their ability for heterovalent substitution of Ca2+ by different cations to form the new phases, and their abundant crystallographic sites for the doped activator, such as Eu2+, to tune the photoluminescence. Thus, these phosphors have great potential on the applications in white light-emitting diodes (WLEDs) for their tunable emission. Accordingly, there is increasing interest in the discovery of new β-Ca3(PO4)2-type phosphors for WLEDs and the deep understanding on the mechanisms responsible for occupation by Eu2+ ions of particular sites in the host lattice, so that the modulation of emission color and intensity can be controlled. In this review, we summarized the structural construction of β-Ca3(PO4)2-type compounds based on such a mineral-inspired prototype evolution perspective. Then we reviewed the recent research on the luminescence properties and sites occupancy of Eu2+ ions in different β-Ca3(PO4)2-type phosphors. Finally, combining with the current advances, we proposed the research prospects and future work of β-Ca3(PO4)2-type phosphors.