Structural and luminescence properties of Sr2VO4Cl and Sr5(VO4)3Cl: self-activated luminescence and unusual Eu3+ emission

Novel self-activated vanadate phosphors, blue-emitting Sr2VO4Cl and green-emitting Sr5(VO4)3Cl, were synthesized via the solid-state reaction route, and the relationship between the structure and luminescence properties was comparatively investigated. Self-activated luminescence originating from the VO43− charge transfer (VCT) transition in relation to different V–O distances was verified in two vanadate phases with different crystal structures. Sr2VO4Cl showed a blue emission band from 375 to 600 nm with a peak at 424 nm, while Sr5(VO4)3Cl exhibited a green emission band from 375 to 700 nm with a peak at 517 nm. With the introduction of Eu3+ to Sr2VO4Cl, both the VCT and Eu3+ emissions were found; however, the VCT emission was quenched in Sr5(VO4)3Cl after Eu3+ doping. Sr5(VO4)3Cl:Eu3+ only shows the characteristic red emission lines originating from Eu3+, while Sr5(VO4)3Cl:Eu3+,Na+ shows typical emissions coming from the VCT transition and the Eu3+ ions. As a comparison, the emission intensity of Sr2VO4Cl:Eu3+,Na+ decreased compared to that of Sr2VO4Cl:Eu3+. The intrinsic luminescence mechanism is discussed based on the differences in the crystal structures and the measured lifetimes.