Improvement of quantum efficiency through Gd3+ to Eu3+ energy transfer in YF3 phosphor

This paper reports the energy transfer from Gd3+ to Eu3+ in YF3 and the consequent downconversion luminescence for the YF3:Gd3+, Eu3+ fluoride phosphor. The phosphor was synthesized using a soft chemical route, followed by a reactive atmosphere process. Because of the wide band gap in YF3 and the correct energy site for 8S7/2–6GJ transitions of Gd3+ ions, fluoride YF3 doped with Gd3+−Eu3+ were studied in their vacuum–ultraviolet (VUV) spectral regions. Powder X‐ray diffraction (XRD) analysis showed the structural purity of YF3. VUV excitation and emission properties were explored using a VUV synchrotron radiation beam line. Downconversion of energy from VUV (157 nm) to visible light with quantum efficiency c. 189% was seen. This YF3:Gd3+, Eu3+ phosphor would be an option for mercury‐free fluorescence lamps. The combination of Gd3+ and Eu3+ ions in YF3 plays a vital role in bringing the luminescence quantum efficiency of the phosphor beyond 100%. The process of absorption of VUV photons through 8S7/2→6GJ transition of the Gd3+ ion, and transfer of energy to two Eu3+ ions leading to 7FJ→5D0 transitions and emission of two visible photons through 5DJ→7FJ transitions of Eu3+ ions is described in an energy level diagram (Figure 6).