A novel Eu3+- and self-activated vanadate phosphor of Ca4La(VO4)3O with oxyvanadate apatite structure

Pure and Eu3+-activated Ca4La(VO4)(3)O phosphors were prepared via three-step solid-phase synthesis. The phase formation and structure were investigated by X-ray diffraction (XRD) with Rietveld refinements. All the samples crystallized in an apatite-type structure. The morphological properties were measured via by SEM and EDS measurements. Ca4La(VO4)(3)O is a new vanadate optical material with a direct band feature and a band energy of 3.1 eV. The undoped Ca4La(VO4)(3)O phosphor presents self-activated yellow luminescence from 400 nm to 750 nm with a maximum wavelength of 525 nm originating from VO4 groups. Luminescence characteristics of Ca4La(VO4)(3)O indicate that the phosphor is not sufficient for practical applications. In Eu3+-activated Ca4La(VO4)(3)O, there is an efficient energy transfer from VO4 to Eu3+ ions. The luminescence spectra, concentration quenching, decay curves, color chromaticity, and quantum efficiencies (QE) of Ca4La(VO4)(3)O:Eu3+ were investigated. The phosphor presents optimal Eu3+ doping concentration of about 20 mol%. The dominant red emission in Ca4La(VO4)(3)O:Eu3+ is 615 nm from electronic D-5(0) -> F-7(2) dipole transitions. The quantum efficiency and the luminescence stability of the pure and Eu-activated Ca4La(VO4)(3)O were reported. The luminescence was discussed on the structural characteristics.