The effect of grain boundaries on electrical conductivity and on oxygen exchange behaviour of lanthanum-doped ceria has been studied as a function of increasing concentrations of lanthanum. Highly sinterable lanthanum-doped ceria powders (CeO_2)_(1-n)(LaO_(1.5))_n (n=0.1, 0.2, 0.3, 0.4) were fabricated by a coprecipitation route using ammonia. The bulk and grain boundary ionic conductivities have been examined by d.c. and a.c. measurements at high oxygen pressures between 0.21-1 atm. It was found that the grain boundary conductivity is markedly increased by the increasing grain boundary area. The nonstoichiometry of Ce_(1-n)La_nO_(2-0.5 n-x) was coulometrically measured at temperatures of 700-900°C and oxygen partial pressures between 10~(-21) -1 atm. The effect of grain boundaries on oxygen exchange behaviour of lanthanum-doped ceria is discussed.
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