EPR INVESTIGATIONS ON EUROPIUM(II)-DOPED ALUMINATES

The europium(II)-doped aluminates, SrAl2O4 and CaAl2O4 with beta-tridy mite structure and BaMgAl10O17 with beta-Al2O4 structure, have been in vestigated by means of EPR spectroscopy. From the complicated X-band E PR spectra observed for SrAl2O4 : Eu,Dy and CaAl2O4 : Eu,Nd it is dedu ced that they have large zero-field splittings in contrast to BaMgAl10 O17 : Eu. High frequency EPR spectroscopy at 180 GHz shows symmetrical weak satellites on both sides of the strongest resonance centred arou nd at 6.45 T. Spectral simulation with second order perturbation has m ade it clear that for SrAl2O4 : Eu,Dy the europium(II) ions occupy thr ee different sites, while for the CaAl2O4 they occupy a single site wi th trigonal anti-prism symmetry, despite the fact that there are two o ther sites associated with octahedral symmetry.