Effects of crystal structure on the luminescence properties and energy transfer between Gd3+ and Ce3+ ions in MGd(PO3)4:Ce3+ (M = Li, Na, K, Cs)

Abstract

Cerium-activated polyphosphates MGd(PO3)4 (M = Li, Na, K, Cs), were synthesized by a solid-state reaction technique at high temperature. The ultraviolet (UV) and vacuum ultraviolet (VUV) luminescence spectra of this series of samples were determined at room temperature (RT). On the basis of the VUV excitation spectra of MGd(PO3)4:1.0 at% Ce3+, the centroid shift ec, total crystal field splitting ecfs, and total redshift D(A) were calculated. According to the ligand polarization model, the values of the spectroscopic polarizability αsp were also calculated from the observed centroid shifts. It was found that the ec, ecfs, D(A) and αsp were influenced by the crystal structure. Based on the luminescence spectra of these polyphosphate samples, the energy level diagram of Gd3+–Ce3+ in MGd(PO3)4:Ce3+ systems was also proposed. Through the energy level diagram and the decay curves of Ce3+ emission, the energy transfer between Gd3+ and Ce3+ ions was investigated. It was found that there existed efficient energy transfer between Gd3+ and Ce3+ ions in MGd(PO3)4:Ce3+ systems. Considered the efficient energy transfer from Gd3+ to Ce3+ ions and short lifetime of Ce3+ emission, this series of compounds doped with Ce3+ ions could be used as promising scintillator materials.