Naslov
XAFS investigations of nanocrystalline Eu-doped BaAl2O4

Autori
Lützenkirchen-Hecht, Dirk ; Gržeta, Biserka ; Vrankić, Martina ; Bosnar, Sanja ; Šarić, Ankica ; Takahashi, Masashi ; Petrov, Dimitar ; Bišćan, Marijan

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Abstracts of the 17th International Conference on X-Ray Absorption Fine Structure ; u: Synchrotron Radiation in Natural Science 17, Issue 1-2 / Kwiatek, Wojciech M. - Varšava : Polish Synchrotron Radiation Society, 2018, 21-21

Skup
17th International Conference on X-Ray Absorption Fine Structure

Mjesto i datum
Kraków, Poljska, 22.07.2018. - 27.07.2018

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
Barium aluminate ; Europium doping ; X-ray diffraction ; X-ray absorption spectroscopy ; XANES ; EXAFS ; Crystal structure

Sažetak
Alkaline earth aluminates are promising starting compounds for the preparation of fluorescent and phosphorescent doped materials. The room- temperature (RT) phase of BaAl2O4 becomes a luminescent material with emission in the red or blue-green spectral range when doped with Eu3+ or Eu2+ ions, respectively. The quite complicated crystal structure of the host material (hexagonal system, space group P63) with several possible lattice sites for the Eu dopant makes XAFS an ideal tool to determine the Eu position and its coordination in Eu-doped BaAl2O4. Here we investigate the influence of Eu doping on the structure of BaAl2O4 by means of XAFS at RT. Nanosized powder samples of pure BaAl2O4 and one doped with 4.9 at.% Eu in relation to Ba were prepared from Ba(NO3)2, Al(NO3)3·9H2O, and Eu(NO3)3·6H2O using a hydrothermal route followed by a thermal treatment at 1100 °C for 4h. For the XAFS studies, the powder samples were diluted with BN and dispersed on self-adhesive kapton tapes. Several tapes were stacked in order to obtain an absorption suited for XAFS measurements, which were carried out at both the Ba and the Eu L3-edges on beamline BL10 at the Dortmund Electron Accelerator DELTA using a channel-cut Si(111) monochromator and gas-filled ionization chambers as detectors. EXAFS studies at the Ba L3-edge for both samples, pure and Eu- doped BaAl2O4, gave evidence that the structure of the doped sample was very similar to that of pure BaAl2O4. The determined Ba-O and Ba-Al distances in these samples agree well with those obtained by the Rietveld structure refinement using the X-ray diffraction patterns for both samples. XANES measurements at the L3-edge of the Eu-doped sample clearly revealed the presence of solely Eu3+ ions, but the radial distribution function resulting from the EXAFS data was completely different from those for Eu2O3 and AlEuO3 reference phases. Impurity phases containing Eu were not detected in the doped sample, so the incorporation of the Eu3+ dopant on a regular lattice site of the BaAl2O4 host is very likely. We tested several possible lattice sites in the course of the Eu-EXAFS data fitting. Replacement of Ba2+ ions on the regular Ba2 site by Eu3+ ions, and including an additional oxygen into the lattice for charge compensation, gave the best results. EXAFS investigations have shown that Eu-doping in BaAl2O4 leads to substitution of Eu3+ ions for Ba2+ on the Ba2 site in the host structure, with charge compensation by interstitial oxygen in the vicinity of the related Ba2 site. The presence of any impurity phase could be excluded.

Izvorni jezik
Engleski

Znanstvena područja
Fizika, Kemija

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