COMPARATIVE-STUDY OF THE CRYSTAL-FIELD EFFECTS IN RARE-EARTH OXYNITRATES

The photoluminescence spectra of the lanthanum and gadolinium oxynitra tes doped with Eu3+, REONO3:Eu3+ (RE = La and Gd) were measured at 77 and 300 K. The F-7(J) (J = 0-5) energy level schemes for the 4f6 elect ron configuration were simulated by a C2nu phenomenological crystal fi eld (CF). The nine non-zero CF parameters for the C2nu site symmetry r eproduce the experimental energy level schemes with rms deviations of 7 and 5 cm-1 for the LaONO3 and GdONO3 hosts, respectively. The CF eff ect is stronger in the lanthanum host although otherwise the CF parame ters for the two oxynitrate hosts differ only slightly. The B2k (k=2, 4 and 6) values are low indicating only a slight deviation from a high er C4nu symmetry. The B-0(2), B-0(4) and B-4(4) parameters assume high values which are similar to those obtained previously for the other R E oxy compounds, i.e. oxyhalides, oxysulfates, oxymolybdates, and oxyt ungstates. The sixth rank parameters deviate considerably from those o btained for the other RE oxy compounds.