Influence of the precursor pyrolysis temperature on the microstructure and conductivity of Gd-doped ceria materials

Gd-doped ceria nanopowders have been synthesized via a modified sol–gel technique using different pyrolysis temperatures to produce a range of particle sizes. Such nanocrystalline oxides have been sintered at 1400 °C for 24 h to produce fully dense disks. The microstructural characterization reveals that the pyrolysis temperature notably affects the grain size distribution in the sintered ceramics, e.g. powders treated at 700 °C render the narrowest grain size distribution. The electrochemical characterisation performed by electrochemical impedance spectroscopy shows that the distribution of grain sizes in the dense electrolytes rules the electrical conductivity of CGOs rather than the average grain size. Narrower grain size distributions render electrolytes exhibiting higher overall conductivity, independent of the average grain size.