Specific absorption in Y3Al5O12:Eu ceramics and the role of stable Eu2+ in the energy transfer processes
Several sets of Eu-doped Y3Al5O (YAG) ceramic samples were synthesized by vacuum sintering technique. Their structural, optical and magnetic properties were investigated by means of X-ray diffraction, X-ray fluorescence, optical absorption, time-resolved luminescence spectroscopy and electron paramagnetic resonance. Multiple annealing in different atmospheres was employed to understand the nature of strong specific absorption bands found in these ceramics peaking at about 250, 370 and 550 nm. The influence of sintering aids used during the ceramics preparation (such as tetraethyl orthosilicate and/or magnesium oxide) on the optical properties is thoroughly studied. The charge transfer transition in the EuY2+ + F+ pair center is suggested to explain the nature of these absorption bands which is also supported by the peculiarities of the Eu2+ 5d-4f and F/F+ luminescence occurrence. Application potential of the studied ceramics in industrial implementations is discussed as well.