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Room temperature structure and transport properties of the incommensurate modulated LaNb0.88W0.12O4.06

Lookup NU author(s): Dr Stevin Pramana

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This is the authors' accepted manuscript of an article that has been published in its final definitive form by Royal Society of Chemistry, 2019.

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Abstract

The crystal structure of a (3 + 2)D incommensurate modulated LaNb0.88W0.12O4.06 phase, a novel oxygen ionic conductor, is refined using a combination of synchrotron X-ray diffraction and electron diffraction data. The superspace group I2/c(α10γ1)00(α20γ2)00 (a = 5.4131(1) Å, b = 11.6432(2) Å, c = 5.2963(1) Å, β = 91.540(1)°, q1 = 0.2847(5)a* + 0.1098(9)c* and q2 = −0.1266(9)a* + 0.2953(1)c*) was chosen for the refinement. Similar to other scheelite type modulated structures, the modulation of LaNb0.88W0.12O4.06 stems from the cation occupancy ordering in the xz plane. To facilitate the modulated cation sub-lattice, and to compensate for the difference in their size and charge, the B site polyhedra are distorted by stretching the B-O bond lengths. Consequently, an extension in the B site coordination number from 6 to 8 is observed in the modulated phase. An interconnected 3D network of BOx polyhedra, similar to that of modulated CeNbO4.25, is obtained as a result of the structure modulation, which is not present in the unmodulated parent structure. Oxygen tracer diffusivity measurements indicate that the composition is an oxygen ion conductor, which relies on an interstitialcy conduction mechanism with a diffusion coefficient of 2.46 × 10-9 cm2 s-1, at 750 °C reported.


Publication metadata

Author(s): Cheng L, Pramana SS, Skinner SJ

Publication type: Article

Publication status: Published

Journal: Dalton Transactions

Year: 2019

Volume: 48

Issue: 5

Pages: 1633-1646

Print publication date: 07/02/2019

Online publication date: 03/12/2018

Acceptance date: 02/12/2018

Date deposited: 07/12/2018

ISSN (print): 1477-9226

ISSN (electronic): 1477-9234

Publisher: Royal Society of Chemistry

URL: https://doi.org/10.1039/C8DT03958E

DOI: 10.1039/C8DT03958E


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