Luminescence Properties of Al₂O₃:Ti in the Blue and Red Regions: A Combined Theoretical and Experimental Study

Using jointly experimental results and first-principles calculations, we unambiguously assign the underlying mechanisms behind two commonly observed luminescence bands for the Al₂O₃ material. Indeed, we show that the red band is associated with a Ti³⁺ d-d transition as expected, while the blue band is the combination of the Ti³⁺ + O^- → Ti⁴⁺ + O^2- and V_O^•+e^- → V_O^× de-excitation processes. Thanks to our recent developments, which take into account the vibrational contributions to the electronic transitions in solids, we were able to simulate the luminescence spectra for the different signatures. The excellent agreement with the experiment demonstrates that it should be possible to predict the color of the material with a CIE chromaticity diagram. We also anticipated the luminescence signature of Al₂O₃:Ti,Ca and Al₂O₃:Ti,Be that were confirmed by experiment.