Determination of the Eu3+ ion local structure in oxide and fluoride crystals

In this work a procedure to determine the local structure of the optically active site was developed. The local structure of the Eu3+ ion in high symmetry sites of the SnO2(D2h) and BaLiF3(D4d) crystals was carried out using the simple overlap model (SOM) and the method of equivalent nearest neighbours (MENN). From equations of the crystal field parameters (CFP), of the maximum splitting of F17 multiplet and of the electrostatic equilibrium of luminescent site it was possible to predict the Eu-NN distances. The overlap between the 4f and 2p orbitals has been 0.05 and the charge factor between 0.45≤gj≤8.0. The Batista-Longo Improved Model (BLIM) was used to show that the Eu3+ ion charge can be greater than its own valence. The F17 level splitting (316 cm−1 for the SnO2; and 83 cm−1 for the BaLiF3) and the predicted Stark levels are in very good agreement with the experimental data. In all cases the magnitude of the charge factors are quite close to each other. This strongly indicates that the Eu3+ ion treats any chemical species in its immediate neighbourhood as negative charges.