Luminescent and thermal properties of a new green emitting Ca 6Sr 4(Si 2O 7) 3Cl 2:Eu 2+ phosphor for near-UV light-emitting diodes

Abstract

A novel green emitting phosphor, Eu 2+-activated Ca 6Sr 4(Si 2O 7) 3Cl 2, was synthesized using the solid-state reaction and its temperature-dependent luminescence characteristic was reported for the first time. Crystallographic site-occupations of Eu 2+ ions in this host were assigned and two distinguishable Sr 2+ sites were confirmed. As the temperature increases, the emission lines of Ca 6Sr 3.99(Si 2O 7) 3Cl 2:0.01Eu 2+ show an anomalous blue-shift along with the broadening bandwidth and decreasing emission intensity, which is ascribed in terms of the phonon-assisted back tunneling from the excited state of low-energy emission band to the high-energy emission band in the configuration coordinate diagram. Further, the luminescence quenching temperature, the activation energy for thermal quenching (Δ E), and the chromaticity coordinates were also investigated. In view of its preferable excitation spectrum profile, intense green emission peaking at 511 nm, and high thermal luminescence stability, the as-prepared phosphor is expected to find applications as a new green emitting phosphor for near-UV light emitting diodes.