Lattices selective occupation, optical spectra regulation, and photoluminescence properties of Eu2+ activated Ca9La(PO4)7 phosphor

Abstract

Rare earth ions doping multiple activation lattice sites is an important strategy to control luminescent properties of luminescent materials. In the work, Eu2+ doped Ca9La(PO4)7 phosphor was fabricated to study with the dependence of lattice structure, site occupation on the luminescence properties. Rietveld refinement results of XRD shows that the phosphors are pure phases with the same crystal structure of whitlockite β-Ca3(PO4)2. Further, Eu2+ ions at four lattice sites are distinguished by comparing the change of bond energy, preferentially occupies the smaller energy variation sites of Eu(3)[CN = 8], Eu(4)[CN = 6](Eu luminescent center at La site), Eu(1)[CN = 7], Eu(2)[CN = 8]. The activation energy of the emission band at 418 nm is calculated at about 0.2872eV, and the activation energy of the emission band at 512 nm about 0.2022eV.