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

DOI: 10.1039/C4TA04299A DOI Help

Authors: Ryan D. Bayliss (University of Illinois at Chicago) , Stuart N. Cook (Massachusetts Institute of Technology) , David O. Scanlon (University College London; Diamond Light Source) , Sarah Fearn (Imperial College London) , Jordi Cabana (University of Illinois at Chicago) , Colin Greaves (University of Birmingham) , John A. Kilner (Imperial College London) , Stephen Skinner (Imperial College London, U.K.)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Materials Chemistry A , VOL 2 (42) , PAGES 17919 - 17924

State: Published (Approved)
Published: September 2014

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.

Subject Areas: Materials, Chemistry

Technical Areas: