The structures and luminescence properties of Sr₄Gd₃Na₃(PO₄)₆F₂:Ce³⁺,Tb³⁺ green phosphors with zero-thermal quenching of Tb³⁺ for WLEDs

Abstract

In this paper, novel green-emitting Sr4Gd3Na3(PO4)6F2:Ce3+,Tb3+ phosphors with zero-thermal quenching of Tb3+ have been prepared and investigated. X-ray diffraction together with Rietveld structure refinement was employed to give an insight into the structures of the samples. The luminescence spectra at 300 K and 80 K confirmed that the Ce3+ ions in Sr4Gd3Na3(PO4)6F2:Ce3+ were distributed randomly on the cation sites and gave intense emission. Utilizing the Ce3+ → Tb3+ energy transfer, intense green emitting Sr4Gd3Na3(PO4)6F2:Ce3+,Tb3+ had been obtained. The energy migration mechanism of Ce3+ in Sr4Gd3Na3(PO4)6F2:Ce3+ and the energy transfer mechanism of Ce3+ → Tb3+ in Sr4Gd3Na3(PO4)6F2:Ce3+,Tb3+ were determined by the analysis of photoluminescence spectra and decay curves. Sr4Gd3Na3(PO4)6F2:Ce3+,Tb3+ exhibited a thermal-induced enhancement of Tb3+ emission at 25-300 °C, indicating an excellent thermal stability. Moreover, utilizing our prepared Sr4Gd3Na3(PO4)6F2:0.06Ce3+,0.15Tb3+ phosphor, green and white emitting LED devices have been fabricated. Our investigation indicated the potential application of prepared green phosphors in UV WLEDs and a feasible method to explore highly thermally stable phosphors utilizing the high thermal stability of donors together with energy transfer from donors to acceptors.