A new structural model for the solid state electrolyte yttria stabilised zirconia
The use of fuel cells to convert chemical to electrical energy is promising as a technology to facilitate a fossil fuel free energy system. Solid oxide fuel cells have many advantages but have to be operated at elevated temperatures for efficient operation due to the need to diffuse ions through a solid state electrolyte. There is therefore an imperative to understand the structure and transport properties within the electroloyte. A data driven approach has been used to survey the many possible structures of the technologically important electrolyte yttria stabilized zirconia (YSZ). A periodic model at 6.7 mol% Y2O3 concentration has 2857 symmetry inequivalent structures. Calculating the energy of all of these structures within DFT suggests that current force field models of the structural energetics do not predict the low energy structures reliably and that the lowest energy structures have Y-Ovac-Y species oriented along the crystallographic <210> direction rather than <111> as suggested in previous studies.