engleski

XANES/EXAFS studies of barium aluminate (BaAl2O4) doped with Cr

Barium aluminate (BaAl2O4) is widely used in the field of optical communication and electronics. In particular, BaAl2O4 exhibits good luminescence properties when it is doped/co-doped with rare earth or transition metal cations. Chromium is a low cost activator and Cr3+ -doped systems are already used in modern technologies, for example for the production of solid-state lasers. However, the literature data on optical properties of Cr-doped BaAl2O4 are very rare, while structural data are completely missing. In this context, we have conducted X-ray absorption measurements at the absorption edges of the dopant and the host elements in order to elucidate for the first time the mechanism of incorporation of Cr in the BaAl2O4 structure, as well as to understand the origin of the optical/ luminescence properties of Cr-doped barium aluminate. Powder sample of undoped BaAl2O4 and ones of BaAl2O4 doped with 4, 6 and 8 at.% Cr (in relation to Al) were prepared by a hydrothermal method, additionally annealed at 1100 ºC for 4h and characterized by X-ray diffraction at room temperature. The X-ray absorption experiments on doped samples were performed at DELTA beamline BL10, making use of the Si(111) channel cut monochromator, ionization chambers for the incident and transmitted intensities, and a silicon drift diode with a multichannel analyzer for the detection of the fluorescence from the samples. As can be already deduced from the raw data, Cr incorporated in the doped samples seems to be in both 6+ and 3+ states, and the coordination is mainly tetrahedral.

Barium aluminate; Cr doping; X-ray absorption spectroscopy; XANES; EXAFS

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