TY - JOUR
T1 - Five-dimensional incommensurate structure of the melilite electrolyte [CaNd]2[Ga]2[Ga2O7]2
AU - Wei, Fengxia
AU - Baikie, Tom
AU - An, Tao
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.
UR - http://www.scopus.com/inward/record.url?scp=80053061612&partnerID=8YFLogxK
U2 - 10.1021/ja206441x
DO - 10.1021/ja206441x
M3 - Article
SN - 0002-7863
VL - 133
SP - 15200
EP - 15211
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 38
ER -