Cation substitution induced novel gehlenite Ca2GaAlSiO7:Eu2+/Ce3+ phosphor with green/blue emission for UV-WLEDs

Abstract

By partially substituting Ga³⁺ ions at Al1(2a) and Al2/Si1(4e) sites in gehlenite Ca₂Al₂SiO₇, novel Ca₂GaAlSiO₇:Eu²⁺/Ce³⁺ phosphors with efficient green and blue emissions have been prepared for the first time. Structure and luminescence properties of these newly obtained samples have been investigated in detail together with the effect of Ga³⁺ substitution which has caused a decrement of Eu–O bond length and covalency. The excitation spectra suggested that both the Eu²⁺ and Ce³⁺ doped Ca₂GaAlSiO₇ samples had broad excitation bands in the UV range, which are favourable properties for application as UV-WLED phosphors. Under 350 nm irradiation, the Ca₂GaAlSiO₇:Eu²⁺ had intense emission peaking at 510 nm, while Ca₂GaAlSiO₇:Ce³⁺ emitted bright blue light. The energy migration mechanism of the Eu²⁺ ions was confirmed to be electric dipole–dipole interaction in terms of the experimental results and analysis. The thermal quenching mechanism, and quantum efficiency of the composition-optimized samples have been investigated. Moreover, a white LED device has been obtained by coating our prepared phosphors with CaAlSiN₃ red phosphor on a UV chip. The experimental results suggested that the Ca₂GaAlSiO₇:Eu²⁺ and Ca₂GaAlSiO₇:Ce³⁺ samples might have potential value in serving as green and blue phosphors for UV-WLEDs, respectively.