On the Eu3+ Fluorescence in Mixed Metal Oxides. V. The Eu3+ Fluorescence in the Rocksalt Lattice

The fluorescence of phosphors ABO2:Eu(A=Li, Na; B=Sc, Y, In, La, Gd, and Lu) is reported and discussed. The Eu3+ emission is strongly influenced by the crystal surroundings: in the α-NaFeO2 structure the 5D0—7F1 transition dominates; in the α-LiFeO2 structure the 5D0—7F2 transition, although both structures can be derived from the rocksalt structure. The greater part of the phosphors is excited directly into the Eu3+ center by shortwave uv radiation. The strong excitation band in this region is ascribed to a charge-transfer process. It is shown that the position of this band is dependent on the cations in the lattice. A relation exists between the efficiency of the phosphors and the position of the charge-transfer band. A possible explanation is put forward. The concentration quenching of the fluorescence of NaGd1−xEuxO2 was studied. Quenching occurs at x=0.1, which agrees with Van Uitert's theory on this phenomenon.