Crystal Structure and Luminescence Properties of Ca₈Mg₃Al₂Si₇O₂₈:Eu²⁺ for WLEDs

Abstract

In this paper, a novel green phosphor Ca 8 Mg 3 Al 2 Si 7 O 28 :Eu 2+ is synthesized via a conventional high‐temperature solid‐state reaction. The crystal structure of the phosphor is confirmed from the Rietveld method. The obtained phosphor has a wide absorption band from the UV to the visible spectral region, ranging from 230 to 450 nm, which fits well with the characteristic emission of UV light‐emitting diode (LED) chips. Upon excitation at 420 nm, the phosphor shows a bright and broad green color emission band with a maximum centered at 535 nm, which is attributed to the parity and spin allowed 5d–4f transition. The longer emission wavelength is caused by both the d orbital preferential orientation and the lowered symmetry of the Eu 2+ ions caused by the discrepancy of the tetrahedrons composed of MgO 4 , SiO 4 , and AlO 4 . Additionally, the energy transfer mechanism among Eu 2+ ions is demonstrated via a dipole–dipole interaction by the luminescence spectra and the fluorescence decay analysis calculations on the basis of the Inokuti–Hirayama model. Furthermore, the thermal stability of the phosphor is investigated in detail. These results suggest that the Ca 8 Mg 3 Al 2 Si 7 O 28 :Eu 2+ phosphor has great potential to be a green phosphor for white light emitting diodes (WLEDs).