Luminescent and thermal properties of a new green emitting Ca6Sr4(Si2O7)3Cl2:Eu2+ phosphor for near-UV light-emitting diodes

A novel green emitting phosphor, Eu2+-activated Ca6Sr4(Si2O7)3Cl2, was synthesized using the solid-state reaction and its temperature-dependent luminescence characteristic was reported for the first time. Crystallographic site-occupations of Eu2+ ions in this host were assigned and two distinguishable Sr2+ sites were confirmed. As the temperature increases, the emission lines of Ca6Sr3.99(Si2O7)3Cl2:0.01Eu2+ 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 (ΔE), 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.

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► Ca6Sr4(Si2O7)3Cl2:Eu2+ has been synthesized by the solid-state reaction.
► Two distinguishable Eu2+ sites are confirmed on the basis of the PL spectra.
► The temperature quenching and anomalous blue-shift are observed.
► With increasing temperature, the CIE coordinates vary from green to cyan.