Sintering behaviour of ceria-based nanopowders

One of the most important component of a SOFC is the electrolyte, which consists in a thin and dense ceramic ionic conductor layer. Ceria-based ceramics, doped with trivalent rare earths (Gd3+, Sm3+…), have been identified as optimal choice for such application, due to their high ionic conductivity in the intermediate temperature range (500-800°C). Despite these advantages, ceria-based materials present some drawbacks like the high temperature required for sintering. This limits the use of many anode materials with low melting point. So, the sintering temperature reduction of these materials represents a fundamental issue. Many works have been focused on the addition of different sintering aids to ceria although in most cases the ionic conductivity is reduced. Alternatively, attempts have been made to reduce the size of the powder. In the present work we studied the sintering behavior of nanograined ceria-based materials produced by co-precipitation method. In particular, the effect of different precipitating agents used during the synthesis on the densification process was pointed out. The produced powders were shaped by uniaxial pressing and subjected to “conventional” sintering cycles, analyzed by dilatometric tests. Also fast firing treatments were carried out for comparison. The results show that the densification properties are strongly related to the chemicals used during the precipitation step and to the sintering schedule.