Five-dimensional incommensurate structure of the melilite electrolyte [CaNd]2[Ga]2[Ga2O7]2

Fengxia Wei; Tom Baikie; Tao An; Martin Schreyer; Christian Kloc; Tim J. White

doi:10.1021/ja206441x

Five-dimensional incommensurate structure of the melilite electrolyte [CaNd]₂[Ga]₂[Ga₂O₇]₂

Fengxia Wei, Tom Baikie^*, Tao An, Martin Schreyer, Christian Kloc, Tim J. White

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

33 Citations (Scopus)

Abstract

Melilite-type gallium oxides are potential intermediate temperature electrolytes for solid oxide fuel cells. Single crystals of [CaNd] ₂[Ga]₂[Ga₂O₇]₂ grown using an optical floating zone furnace have been investigated using transmission electron microscopy and powder and single-crystal X-ray diffraction. The anion array topologically conforms to a [(3.5.4.5)², 3.5.3.5] network that contains distorted pentagonal tunnels. The distortion is necessary to achieve space filling and accommodate structural misfit between the layers. Satisfactory bond lengths and angles are obtained through two-dimensional modulation in the tetragonal based plane, leading to five-dimensional symmetry in the superspace group P4̄2₁m(α,α,0)00s(ᾱā,a,0)000, α = 0.2319(2), with modulation vectors q₁ = α(a* + b*) and q₂ = α(-a* + b*). Both displacive and occupational modulations are found. Through this mechanism, melilites are primed to accommodate mobile oxygen interstitials, suggesting a rational approach to crystallochemical tailoring that will enhance ionic diffusion and optimize electrolyte performance.

Original language	English
Pages (from-to)	15200-15211
Number of pages	12
Journal	Journal of the American Chemical Society
Volume	133
Issue number	38
DOIs	https://doi.org/10.1021/ja206441x
Publication status	Published - Sept 28 2011
Externally published	Yes

ASJC Scopus Subject Areas

Catalysis
General Chemistry
Biochemistry
Colloid and Surface Chemistry

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title = "Five-dimensional incommensurate structure of the melilite electrolyte [CaNd]2[Ga]2[Ga2O7]2",

abstract = "Melilite-type gallium oxides are potential intermediate temperature electrolytes for solid oxide fuel cells. Single crystals of [CaNd] 2[Ga]2[Ga2O7]2 grown using an optical floating zone furnace have been investigated using transmission electron microscopy and powder and single-crystal X-ray diffraction. The anion array topologically conforms to a [(3.5.4.5)2, 3.5.3.5] network that contains distorted pentagonal tunnels. The distortion is necessary to achieve space filling and accommodate structural misfit between the layers. Satisfactory bond lengths and angles are obtained through two-dimensional modulation in the tetragonal based plane, leading to five-dimensional symmetry in the superspace group P{\=4}21m(α,α,0)00s(ᾱā,a,0)000, α = 0.2319(2), with modulation vectors q1 = α(a* + b*) and q2 = α(-a* + b*). Both displacive and occupational modulations are found. Through this mechanism, melilites are primed to accommodate mobile oxygen interstitials, suggesting a rational approach to crystallochemical tailoring that will enhance ionic diffusion and optimize electrolyte performance.",

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AU - Schreyer, Martin

AU - Kloc, Christian

AU - White, Tim J.

PY - 2011/9/28

Y1 - 2011/9/28

N2 - Melilite-type gallium oxides are potential intermediate temperature electrolytes for solid oxide fuel cells. Single crystals of [CaNd] 2[Ga]2[Ga2O7]2 grown using an optical floating zone furnace have been investigated using transmission electron microscopy and powder and single-crystal X-ray diffraction. The anion array topologically conforms to a [(3.5.4.5)2, 3.5.3.5] network that contains distorted pentagonal tunnels. The distortion is necessary to achieve space filling and accommodate structural misfit between the layers. Satisfactory bond lengths and angles are obtained through two-dimensional modulation in the tetragonal based plane, leading to five-dimensional symmetry in the superspace group P4̄21m(α,α,0)00s(ᾱā,a,0)000, α = 0.2319(2), with modulation vectors q1 = α(a* + b*) and q2 = α(-a* + b*). Both displacive and occupational modulations are found. Through this mechanism, melilites are primed to accommodate mobile oxygen interstitials, suggesting a rational approach to crystallochemical tailoring that will enhance ionic diffusion and optimize electrolyte performance.

AB - Melilite-type gallium oxides are potential intermediate temperature electrolytes for solid oxide fuel cells. Single crystals of [CaNd] 2[Ga]2[Ga2O7]2 grown using an optical floating zone furnace have been investigated using transmission electron microscopy and powder and single-crystal X-ray diffraction. The anion array topologically conforms to a [(3.5.4.5)2, 3.5.3.5] network that contains distorted pentagonal tunnels. The distortion is necessary to achieve space filling and accommodate structural misfit between the layers. Satisfactory bond lengths and angles are obtained through two-dimensional modulation in the tetragonal based plane, leading to five-dimensional symmetry in the superspace group P4̄21m(α,α,0)00s(ᾱā,a,0)000, α = 0.2319(2), with modulation vectors q1 = α(a* + b*) and q2 = α(-a* + b*). Both displacive and occupational modulations are found. Through this mechanism, melilites are primed to accommodate mobile oxygen interstitials, suggesting a rational approach to crystallochemical tailoring that will enhance ionic diffusion and optimize electrolyte performance.

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Five-dimensional incommensurate structure of the melilite electrolyte [CaNd]₂[Ga]₂[Ga₂O₇]₂

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