Electronic structure and luminescent properties of Ca5(PO4)2(SiO4):Eu2+ green-emitting phosphor for white light emitting diodes

A green-emitting phosphor, Eu2+-activated Ca5(PO4)2(SiO4) phosphor was synthesized by conventional solid-state reaction. X-ray powder diffraction (XRD) and FT-IR spectra analysis confirmed the phase formation. The calculated band structure shows that Ca5(PO4)2(SiO4) is an insulator with a band gap ≈4.98 eV, which is close to the experimental value ≈5.16 eV from the diffuse reflection spectrum. The photoluminescence excitation and emission spectra, the concentration dependence of the emission intensity and decay curves of the phosphor were investigated. The results showed that Ca5(PO4)2(SiO4):Eu2+ could be efficiently excited by UV chips (360–400 nm) and Eu2+ has three emission centers in Ca5(PO4)2(SiO4). The nature of the Eu2+ emission in Ca5(PO4)2(SiO4), e.g. the major mechanism for concentration quenching were discussed in order to further investigate the potential application for white light-emitting diodes (LED).