EPR investigations on europium(II)-doped aluminates

Abstract

The europium(II)-doped aluminates, SrAl₂O₄ and CaAl₂O₄with β-tridymite structure and BaMgAl₁₀O₁₇ with β-Al₂O₄ structure, have been investigated by means of EPR spectroscopy. From the complicated X-band EPR spectra observed for SrAl₂O₄:Eu,Dy and CaAl₂O₄:Eu,Nd it is deduced that they have large zero-field splittings in contrast to BaMgAl₁₀O₁₇:Eu. High frequency EPR spectroscopy at 180 GHz shows symmetrical weak satellites on both sides of the strongest resonance centred around at 6.45 T. Spectral simulation with second order perturbation has made it clear that for SrAl₂O₄:Eu,Dy the europium(II) ions occupy three different sites, while for the CaAl₂O₄ they occupy a single site with trigonal anti-prism symmetry, despite the fact that there are two other sites associated with octahedral symmetry.