Specific absorption in Y3Al5O12:Eu ceramics and the role of stable Eu2+ in energy transfer processes

Several sets of Eu-doped Y3Al5O12 (YAG) ceramic samples were synthesized by the 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 peaking at about 250, 370 and 550 nm in the case of these ceramics. The influence of sintering aids used during the preparation of ceramics (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 the industrial implementation is discussed as well.