Sintering behavior of Ln-doped ceria compounds containing gallia

The sintering behavior of Ln-doped ceria (Ln=Y, Gd, Sm, Nd, La) containing gallia (Ga2O3) was investigated. Ln-doped ceria samples containing gallia were well sintered at 1500 °C by a common solid-state reaction method. On the other hand, Ln-doped ceria samples without gallia did not become well sintered until the sintering temperature was raised to 1600 °C. We investigated the crystal structures, microstructures, density, and electrical conductivity of Ln-doped ceria sintered with gallia. The grain sizes of Ln-doped ceria sintered with gallia were much larger than those of Ln-doped ceria sintered without gallia. All samples except Y-doped ceria showed improvement in conductivity by the addition of gallia. The variation in acceleration of grain growth with Ln3+ radius was consistent with the tendency of the melting points of solid solutions of Ln2O3 and gallia, indicating that the acceleration of sintering was due to the effect of the liquid phase partly formed from Ln2O3 and gallia during sintering.