Electronic structure and photoluminescence properties of Eu2+-activated Ca4Si2O7F2

The blue-emitting phosphors Ca(4−x)EuxSi2O7F2 (0 < x ⩽ 0.05) have been prepared by solid-state reaction and the photoluminescence properties have been studied systematically. The electronic structure of calcium fluoride silicate Ca4Si2O7F2 was calculated using the CASTEP code. The calculation results of electronic structure show that Ca4Si2O7F2 has an indirect band gap with 5 eV. The top of the valence band is dominated by O 2p and Si 3p states, while the bottom of the conduction band is mainly composed of Ca 3d states. Under the 350 nm excitation, the obtained sample shows a broad emission band in the wavelength range of 400–500 nm with peaks of 413 nm and 460 nm from two different luminescence centers, respectively. The relative intensity of the two peaks changes with the alteration of the Eu2+ concentration. The strong excitation bands of the powder in the wavelength range of 200–420 nm are favorable properties for the application as lighting-emitting-diode conversion phosphor.

► Eu2+ doped Ca4Si2O7F2 phosphor was synthesized by the solid state reaction.
► Electronic structure of host lattice was researched using the CASTEP module of MS 4.0.
► Under 350 nm excitation, the sample shows a broad emission band peaking at 413 nm and 460 nm.
► The relative intensity of the two peaks changes with the alteration of Eu2+ concentration.