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Solid-State 29Si NMR and Neutron-Diffraction Studies of Sr0.07K0.3SiO2.85 Oxide Ion Conductors



Jungu Xu, Xiaoming Wang, Hui Fu, Craig Brown, Xiping Jing, Fuhui Liao, Fengqi Lu, Xiaohui Li, Xiaojun Kuang, Mingmei Wu


The new oxide ion conductors Sr1-xKxSiO3-05x, recently reported as promising candidate electrolytes for solid oxide fuel cells, were characterized using solid-state 29Si nuclear magnetic resonance (NMR)spectroscopy, neutron powder diffraction (NPD) and variable temperature X-ray diffraction (VT-XRD). Differing with the average structure containing the vacancies stabilized within the isolated Si3O9 tetrahedral rings derived from the NPD study, the 29Si NMR data provide new insight into the local defect structure in Sr1-xKxSiO3-05.x. The Q1-linked tetrahedral Si signal in the 29Si NMR data suggest that the Si3O9 tetrahedral rings in the K-doped SrSiO3 materials were broken by removing the bridging oxygen atoms, forming Sid3^O8 chains, consistent with the oxide vacancy preferences on bridging sites over the terminal sites from NPD data refinement. The Si3O8 chains can be stabilized by either bonding with the oxygen atoms of absorbed water molecules, leading to the Q1-linked tetrahedral Si, or sharing oxygen atoms with neighbouring Si3O9 units, which is consistent with the Q3-linked tetrahedral Si signal in the 29Si NMR spectra. In addition to the linkage of Si3O8 chains with Si3O9 rings, condensation of Si3O9 rings via local rotating and distorting the rings for corner-sharing are also discussed. VT-XRD measurement showed an instability gap between 700 °C and 1000 °C for Sr1-xKxSiO3-0.5x. Both the VT-XRD and conductivity data revealed that a firing temperature above 1100 Degree}C is favourable for stabilizing the K-doped SrSiO3 materials as single phase on cooling and that the defect structure in the K-doped SrSiO3 materials is temperature dependent.
Inorganic Chemistry


Neutron diffraction, NMR, X-ray diffraction, oxide conductor


Xu, J. , Wang, X. , Fu, H. , Brown, C. , Jing, X. , Liao, F. , Lu, F. , Li, X. , Kuang, X. and Wu, M. (2014), Solid-State <sup>29</sup>Si NMR and Neutron-Diffraction Studies of Sr<sub>0.07</sub>K<sub>0.3</sub>SiO<sub>2.85</sub> Oxide Ion Conductors, Inorganic Chemistry, [online], (Accessed June 19, 2024)


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Created July 6, 2014, Updated October 12, 2021