Crystal Growth and Properties of New Ruthenium Oxides

Samata, H.; Mishiro, A.; Sawada, S.; Nagata, Y.; Uchida, Takayuki; Kai, Masahiro; Ohtsuka, Masao; Lan, M. D.

doi:10.1016/s0022-3697(98)00228-5

Cited by 4 publications

(3 citation statements)

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“…This fact becomes more important as we discuss the low-temperature structure (vide infra). Ba 3 MRu 2 O 9 (M = Li, Na) represent the first examples of ordered ruthenium triple perovskites containing an alkali metal and, furthermore, two of only a few oxide compounds reported to contain ruthenium in as high of an oxidation state as +6 . Quadruple perovskites containing alkali metals and Ru(V) such as Ba 4 NaRu 3 O 12 as well as one disordered triple perovskite containing an alkali metal and Ru(V) Ba 4 LiRu 3 O 12 (equivalent to Ba 3 Li 3/4 Ru 9/4 O 9 ) have been reported by Battle et al The materials reported in this paper represent an extension on the work by Battle and co-workers by expanding the known ruthenium oxidation states in triple perovskites to mixed +5 and +6.…”

Section: Resultsmentioning

confidence: 99%

“…Among the perovskites, the ruthenates in particular have attracted much attention due to the structural variety exhibited (simple, double, triple, and quadruple perovskite structure) − and the existence of several accessible oxidation states (+4, +5, +6, +7) ,, and the resulting interesting magnetic behaviors that have been observed. ,, The formal oxidation state(s) of the ruthenium are determined by a combination of the overall elemental composition, that is, the specific M cation, and the particular structural variant, that is, double perovskite Ba 2 M(II)Ru(VI)O 6 , triple perovskite Ba 3 M(II)Ru(V) 2 O 9 , quadruple perovskite Ba 4 M(I)Ru(V) 3 O 12 , etc. The combination of a fixed valent M element, such as alkali metals, alkaline earths and rare earths, and a specific structural variant, can give rise to mixed valency.…”

Section: Introductionmentioning

confidence: 99%

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Novel Mixed-Valent (V/VI) Triple Perovskite Ruthenates: Observation of a Complex Low-Temperature Structural and Magnetic Transition

et al. 2002

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Two new mixed-valent triple perovskites, Ba(3)MRu(2)O(9) (M = Li, Na), were grown from reactive hydroxide fluxes. They crystallize in the hexagonal space group P6(3)/mmc, where Ru(V) and Ru(VI) are disordered on only one crystallographic site. Upon cooling, single crystals of Ba(3)NaRu(2)O(9) undergo a complex symmetry-breaking structural transition at ca. 225 K from room-temperature hexagonal symmetry to a low-temperature orthorhombic symmetry, space group Cmcm. Accompanying this structural transition is a rather abrupt decrease in the magnetic susceptibility at 210 K followed by a steady decrease in the susceptibility with decreasing temperature. Interestingly, the lithium analogue does not display any structural transition down to 100 K. The structural transition in Ba(3)NaRu(2)O(9) generates three crystallographically unique Ru sites in the low-temperature structure as compared to only one distinct site in the room-temperature structure. On the basis of an analysis of the Ru-Ru distances in the face-sharing bi-octahedra, the structural transition also appears to involve charge ordering of Ru(V) and Ru(VI), causing all Ru(V) to occupy one set of bi-octahedra and all Ru(VI) to occupy another set.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Novel Mixed-Valent (V/VI) Triple Perovskite Ruthenates: Observation of a Complex Low-Temperature Structural and Magnetic Transition

et al. 2002

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“…The inclusion of a small amount of Ru in the Li sites preserves charge neutrality without oxidising Ru beyond Ru(V), which until recently was the highest oxidation state of Ru reported in oxides. However, it has now been suggested that Ru adopts a higher oxidation state in the systems ABa 3 Ru 2 O 10 (A ~Na, Na/Sm, Na/Dy), Sr 2 Ru 3 O 10 and Sr 4 Ru 3.05 O 12 [7][8][9] and an average valence of 5.5 in Ba 3 MRu 2 O 9 (M ~Li, Na). 10 Trial refinements in which no Ru was allowed to occupy vacant Li sites, and which thus relied on oxidation from Ru 51 to Ru 5.21 to provide charge compensation, gave a fit which was equal in quality to that described above.…”

Section: Discussionmentioning

confidence: 99%