Luminescence study of transition metal ions in natural magmatic and metamorphic yellow sapphires

Optical absorption and luminescence spectra of yellow corundum have been analyzed, both in magmatic and metamorphic materials, looking at the role of localized electronic transitions of transition metal ions at substituted Al sites. By the aid of energy dispersed x-ray fluorescence (EDXRF) elemental analysis and electron paramagnetic resonance (EPR) measurements, the results confirm that Fe 3+ is the dominant impurity ion. However, the results also evidence that Cr