Grain growth in CeO2: Dopant effects, defect mechanism, and solute drag

The effects of the dopants, Mg2+, Ca2+, Sr2+, SC3+, Yb3+, Y3+, Gd3+, La3+, Ti4+, Zr4+ and Nb5+, On the grain boundary mobility of dense CeO2 have been investigated from 1270 degrees to 1420 degrees C. Parabolic grain growth has been observed in all instances, Together with atmospheric effects, the results support the mechanism of cation interstitial transport being the rate-limiting step, A strong solute drag effect has been demonstrated for diffusion-enhancing dopants such as Mg2+ and Ca2+, which, at high concentrations, can nevertheless suppress grain boundary mobility. Severely undersized dopants (Mg, Sc, Ti, and Nb) have a tendency to markedly enhance grain boundary mobility, probably due to the large distortion of the surrounding lattice that apparently facilitates defect migration, Overall, the most effective grain growth inhibitor at 1.0% doping is Y3+, while the most potent grain growth promoter is either Mg2+ (e.g., 0.1%) or Sc3+ at high concentration (greater than 1.0%).