Effect of ionic radius on local structure in lanthanide doped cerias

Doped cerias are currently being used as oxide ion conducting electrolytes in intermediate temperature solid oxide fuel cells (SOFCs). Differences have been found in the local structures of neodymium doped ceria and gadolinium doped ceria, which we suspect are due to a small difference in the proximity of the ionic radii of Nd3+ and Gd3+ to the so called “critical radius” of 1.038 Å. Through reverse Monte Carlo analysis of total neutron scattering data, it is proposed to carefully study the local structures of lanthanum doped ceria and ytterbium doped ceria, where the dopant cations are respectively much larger than and much smaller than Nd3+ and Gd3+. In particular the effect of these dopants on dopant-vacancy association and vacancy pair ordering will be evaluated along with how such features change with temperature. The results of the study will help in the understanding the influences of small changes in local structure on ionic conductivity in such fluorite-based electrolytes.