Exploring crystal-field splittings of Eu3+ ions in γ- and β-SrGa2O4

Eu3+-doped SrGa2O4 from gamma- to beta-phases is successfully manipulated by controlling sintered temperature from 1273 K to 1673 K. The related structural changes are characterized by the thermal analysis, Rietveld refinement and Raman investigation. And on that basis, the photoluminescence (PL) survey is used to study the corresponding crystal-field splittings of Eu3+ ions in gamma- and beta-SrGa2O4, which shows the obvious difference in the 4f-4f energy transitions of Eu3+ ions between two SrGa2O4 phases, especially in the non-degenerate D-5(0) -> F-7(0) transition region. Both gamma- and beta-SrGa2O4 show two D-5(0) -> F-7(0) transition peaks, being in agreement with the two nonequivalent Sr sites in each SrGa2O4 phase. For gamma-SrGa2O4, it is 580.8 nm (SrO7) and 579 nm (SrO8), respectively, and for beta-SrGa2O4, it is 579.6 nm (SrO7) and 578.7 nm (SrO8), respectively. The difference of Eu3+ crystal field splitting between SrO7 sites and SrO8 sites in gamma-SrGa2O4 is larger than that in beta-SrGa2O4, which is mainly derived from the larger polyhedral difference between two Sr sites (SrO7 and SrO8). What discussed in this work manifests the sensitive response of Eu3+ ions for the change of local structural surroundings, and further indicates the potential application of rare-earth fluorescent probes in the field of phase identification.