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Issue 42, 2014
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Understanding the defect chemistry of alkali metal strontium silicate solid solutions: insights from experiment and theory

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Abstract

Recent reports of remarkably high oxide ion conduction in a new family of strontium silicates have been challenged. It has recently been demonstrated that, in the nominally potassium substituted strontium germanium silicate material, the dominant charge carrier was not the oxygen ion, and furthermore that the material was not single phase (R. D. Bayliss et. al., Energy Environ. Sci., 2014, DOI: 10.1039/c4ee00734d). In this work we re-investigate the sodium-doped strontium silicate material that was reported to exhibit the highest oxide ion conductivity in the solid solution, nominally Sr0.55Na0.45SiO2.775. The results show lower levels of total conductivity than previously reported and sub-micron elemental mapping demonstrates, in a similar manner to that reported for the Sr0.8K0.2Si0.5Ge0.5O2.9 composition, an inhomogeneous chemical distribution correlating with a multiphase material. It is also shown that the conductivity is not related to protonic mobility. A density functional theory computational approach provides a theoretical justification for these new results, related to the high energetic costs associated with oxygen vacancy formation.

Graphical abstract: Understanding the defect chemistry of alkali metal strontium silicate solid solutions: insights from experiment and theory

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Publication details

The article was received on 19 Aug 2014, accepted on 05 Sep 2014 and first published on 24 Sep 2014


Article type: Paper
DOI: 10.1039/C4TA04299A
Citation: J. Mater. Chem. A, 2014,2, 17919-17924
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    Understanding the defect chemistry of alkali metal strontium silicate solid solutions: insights from experiment and theory

    R. D. Bayliss, S. N. Cook, D. O. Scanlon, S. Fearn, J. Cabana, C. Greaves, J. A. Kilner and S. J. Skinner, J. Mater. Chem. A, 2014, 2, 17919
    DOI: 10.1039/C4TA04299A

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