Understanding the defect.pdf (692.64 kB)
Download fileUnderstanding the defect chemistry of alkali metal strontium silicate solid solutions: insights from experiment and theory
journal contribution
posted on 08.01.2017, 00:00 authored by R.D. Bayliss, S.N. Cook, D.O. Scanlon, S. Fearn, J. Cabana, C. Greaves, J.A. Kilner, S.J. SkinnerRecent 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.