Grain Boundary Mobility in Y 2 O 3 : Defect Mechanism and Dopant Effects

The effects of the dopants, Mg 2+ , Sr 2+ , Sc 3+ , Yb 3+ , Gd 3+ , La 3+ , Ti 4+ , Zr 4+ , Ce 4+ , and Nb 5+ , on the grain boundary mobility of dense Y 2 O 3 have been investigated from 1500° to 1650°C. Parabolic grain growth has been observed in all cases over a grain size from 0.31 to 12.5 μm. Together with atmospheric effects, the results suggest that interstitial transport is the rate‐limiting step for diffusive processes in Y 2 O 3 , which is also the case in CeO 2 . The effect of solute drag cannot be ascertained but the anomalous effect of undersized dopants (Ti and Nb) on diffusion enhancement, previously reported in CeO 2 , is again confirmed. Indications of very large binding energies between aliovalent dopants and oxygen defects are also observed. Overall, the most effective grain growth inhibitor is Zr 4+ , while the most potent grain growth promoter is Sr 2+ , both at 1.0% concentration.