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Sr2GaScO5, Sr10Ga6Sc4O25, and SrGa0.75Sc0.25O2.5: a Play in the Octahedra to Tetrahedra Ratio in Oxygen-Deficient Perovskites
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2012 (English)In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 51, no 2, 1094-1103 p.Article in journal (Refereed) Published
Abstract [en]

Three different perovskite-related phases were isolated in the SrGa1-xScxO2.5 system: Sr2GaScO5, Sr10Ga6Sc4O25, and SrGa0.75Sc0.25O2.5, Sr2GaScO5 (x = 0.5) crystallizes in a brownrnillerite-type structure [space group (S.G.) Icmm, a = 5.91048(5) angstrom, b = 15.1594(1) angstrom, and c = 5.70926(4) angstrom] with complete ordering of Sc3+ and Ga3+ over octahedral and tetrahedral positions, respectively. The crystal structure of Sr10Ga6Sc4O25 (x = 0.4) was determined by the Monte Carlo method and refined using a combination of X-ray, neutron, and electron diffraction data [S.G. I4(1)/a, a = 17.517(1) angstrom, c = 32.830(3) angstrom]. It represents a novel type of ordering of the B cations and oxygen vacancies in perovskites. The crystal structure of Sr10Ga6Sc4O25 can be described as a stacking of eight perovskite layers along the c axis ...[-(Sc/Ga)O-1.6-SrO0.8-(Sc/Ga)O-1.8-SrO0.8-](2 center dot center dot center dot) Similar to Sr2GaScO5, this structure features a complete ordering of the Sc3+ and Ga3+ cations over octahedral and tetrahedral positions, respectively, within each layer. A specific feature of the crystal structure of Sr10Ga6Sc4O25 is that one-third of the tetrahedra have one vertex not connected with other Sc/Ga cations. Further partial replacement of Sc3+ by Ga3+ leads to the formation of the cubic perovskite phase SrGa0.75Sc0.25O2.5 (x = 0.25) with a = 3.9817(4) angstrom. This compound incorporates water molecules in the structure forming SrGa0.75Sc0.25O2.5 center dot xH(2)O hydrate, which exhibits a proton conductivity of similar to 2.0 x 10(-6) S/cm at 673 K.

Place, publisher, year, edition, pages
2012. Vol. 51, no 2, 1094-1103 p.
National Category
Chemical Sciences
URN: urn:nbn:se:su:diva-72097DOI: 10.1021/ic202236hISI: 000299028800042OAI: diva2:489119
Available from: 2012-12-20 Created: 2012-02-02 Last updated: 2012-12-20Bibliographically approved

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Grins, JekabsSvensson, Gunnar
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Department of Materials and Environmental Chemistry (MMK)
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