Synthesis, sintering and electrical properties of yttria–calcia-doped ceria

Crystalline yttria and calcia doped ceria powder, with a composition of Ce0.8Y0.18Ca0.02O2−δ has been prepared by a coprecipitation procedure from the corresponding nitrates of component cations. Nanopowder was obtained after thermal treatment at 700 °C 2 h of the coprecipitated mixtures. Specific surface area was 45 m2/g. Isostatically and uniaxially pressed pellets were prepared from the powder. Sintering behaviour was followed by CHR dilatometer. Isothermal sintering was carried out between 1100 and 1300 °C. Apparent density as high as 98% Dth was attained by firing isostatically pressed pellets at 1150 °C 4 h. Uniaxially pressed pellets attained the same apparent density at 1275 °C 2 h, being in both cases very low the densification temperatures. Microstructure was observed by scanning electron microscopy (SEM). Ionic conductivity was determined by complex impedance spectroscopy. Bulk and grain boundary conductivities have similar values, and the total conductivity attains good value compatible with the use as electrolyte in solid oxide fuel cell (SOFC).