VUV excited luminescence of MGdF4:Eu3+ (M=Na, K, NH4)

Eu3+-doped NaGdF4, KGdF4 and NH4GdF4 phosphors with little oxygen contamination have been synthesized by hydrothermal technique. The emission spectra show that the doped Eu3+ ions are located in noncentrosymmetric sites in the three compounds. The two-photon emission has been observed in NaGdF4:Eu3+ and KGdF4:Eu3+ compounds under VUV excitation from the ground states to higher 6GJ excited states of Gd3+ ions, while in Eu3+-doped NH4GdF4, emissions from 5D1,2,3 excited states of Eu3+ cannot be detected in the luminescence spectra.