Crystal structure and phase transitions in Sr3WO6

Graham King, Artem M. Abakumov, J. Hadermann, Anastasiya M. Alekseeva, Marina G. Rozova, Tyche Perkisas, Patrick M. Woodward, Gustaaf Van Tendeloo, Evgeny V. Antipov

Research output: Contribution to journalArticlepeer-review

30 Citations (Scopus)

Abstract

The crystal structures of the β and γ polymorphs of Sr 3WO6 and the γ?β phase transition have been investigated using electron diffraction, synchrotron X-ray powder diffraction, and neutron powder diffraction. The γ-Sr3WO6 polymorph is stable above Tc ≈ 470 K and adopts a monoclinically distorted double perovskite A2BB′O6 = Sr 2SrWO6 structure (space group Cc, a = 10.2363(1)Å, b = 17.9007(1)Å, c = 11.9717(1)Å, β = 125.585(1)o at T = 1373 K, Z = 12, corresponding to a = ap + 1/2bp ? 1/2cp, b = 3/2bp + 3/2cp, c = ?bp + cp, ap,bp, cp, lattice vectors of the parent Fm3̄m double perovskite structure). Upon cooling it undergoes a continuous phase transition into the triclinically distorted β-Sr 3WO6 phase (space group C1, a = 10.09497(3)Å, b = 17.64748(5)Å, c = 11.81400(3)Å, α = 89.5470(2)o, β = 125.4529(2)o, γ = 90.2889(2)o at T = 300 K). Both crystal structures of Sr3WO6 belong to a family of double perovskites with broken corner sharing connectivity of the octahedral framework. A remarkable feature of the γ-Sr3WO6 structure is a non-cooperative rotation of the WO6 octahedra. One third of the WO6 octahedra are rotated by ∼45° about either the bp or the cp axis of the parent double perovskite structure. As a result, the WO6 octahedra do not share corners but instead share edges with the coordination polyhedra of the Sr cations at the B positions increasing their coordination number from 6 to 7 or 8. The crystal structure of the β-phase is very close to the structure of the γ-phase; decreasing symmetry upon the γ→β transformation occurs because of unequal octahedral rotation angles about the bp and cp axes and increasing distortions of the WO6 octahedra.

Original languageEnglish
Pages (from-to)6058-6065
Number of pages8
JournalInorganic Chemistry
Volume49
Issue number13
DOIs
Publication statusPublished - 5 Jul 2010
Externally publishedYes

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