Abstract

Emerald and alexandrite, the chromiferous varieties of beryl, Be3Al2[Si6O18], and chrysoberyl, BeAl2O4, respectively, are, as gems, of high economical and technological interest. The Cr3+ properties in natural beryl and chrysoberyl samples have been studied by mainly photoluminescence technique and electron paramagnetic resonance (EPR) as a function of Cr content (50–11370 ppm) as well as impurities, such as Fe and V. In emeralds, the Cr3+ crystal field value is linked to the Cr content and decreases when Cr increases. In chrysoberyl with low Cr content, the vanishing of Cr3+ emission from Cr3+ ions located on the inversion-symmetry site suggests a competition between Cr and V regarding chemical substitution. The Fe3+ ion substitutes efficiently on the mirror-symmetry site, with a strong impact on the Cr3+ lifetime on this site.

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