On the Eu3+ Fluorescence of Mixed Metal Oxides. IV. The Photoluminescent Efficiency of Eu3+-Activated Oxides

Four rules are proposed to explain the photoluminescent efficiency of Eu3+-activated oxides: (a) uv absorbing groups in the host lattice should be nearest neighbors in the crystal structure to have sufficient wavefunction overlap; (b) the emission spectrum of the absorbing group should overlap the absorption spectrum of the group; (c) the configuration consisting of the center of the absorbing group, the intermediary O2− ion, and the Eu3+ ion should be as collinear as possible; (d) O2− ions surrounding the Eu3+ ion must feel a high potential field. If all these rules are satisfied, highly efficient Eu3+ phosphors can be expected; if one or more of the rules are violated, phosphors with low efficiency must be expected. These ideas are applied to a large number of Eu3+-activated oxides. There is a very good agreement between experimental results and predictions from the rules. As far as possible the physical background of the rules is discussed.