Tin-doped LuCrO3: A new type of material allowing the location of a 119Sn Mössbauer spectroscopic probe on the gas–solid interface
✍ Scribed by M.I. Afanasov; A. Wattiaux; C. Labrugère; P.B. Fabritchnyi; C. Delmas
- Publisher
- Elsevier Science
- Year
- 2009
- Tongue
- English
- Weight
- 917 KB
- Volume
- 149
- Category
- Article
- ISSN
- 0038-1098
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✦ Synopsis
In situ 119 Sn Mössbauer measurements show that annealing in hydrogen atmosphere of co-precipitated chromium and lutetium hydroxides, doped with 0.2 at.% Sn 4+ , results in the formation of Sn 2+ cations on the surface sites of LuCrO 3 microcrystals. Such a distribution of dopant cations is consistent with the anomalously high concentration of tin revealed by X-ray photoelectron spectroscopy (XPS). The 119 Sn spectrum recorded above the Néel point of LuCrO 3 attests to the distribution of Sn 2+ ions over two kinds of site. For both of them, the isomer shift and quadrupole splitting values agree with those previously reported for 119 Sn 2+ on surface sites of several oxides other than the perovskite-type one. The instantaneous oxidation of tin upon contact with ambient air did not allow us to characterize the cationic surrounding of Sn 2+ by measurements involving sample transfer into a liquid-helium cryostat. Relevant information is obtained for the Sn 2+→4+ oxidized species located on the sites with unchanged cationic surroundings. The spectrum recorded at 4.2 K shows that nearly two-thirds of the Sn 2+→4+ species are spin-polarized to different extents. Comparison with Mössbauer parameters reported for 119 Sn 4+ ions sitting in the regular Cr-substitution site in the bulk of LuCrO 3 allows us to ascribe the diffuse magnetic contribution to a distribution of Sn 2+→4+ species over Cr-substitution sites with lower (than in the bulk) number of neighboring Cr 3+ ions. The presence of an additional non-magnetic component in the spectrum of Sn 2+→4+ ions points to the location of the remaining Sn 4+ ions and, very likely, the predecessor Sn 2+ ones, on Lu-substitution sites with magnetically compensated (2Cr ↑ +2Cr ↓) surroundings.