Effect of Superplastic Deformation on Ion Conductivity of Sc_2O_3 doped ZrO_2 to be used as Electrolyte inSOFC(Synergy by Microstructuring)

The 4mol%Sc_2O_3 doped ZrO_2 (4ScSZ) shows superplasticity in a range of strain-rate at 1773K. The large elongation is caused by both of high strain-rate sensitivity and high strain hardening during the deformation. Ion concuctivity of the 4ScSZ, deformed superplastically in a relatively high strain-rate region, is higher than that of non-deformed one, indicating that the superplastic deformation can improve its conductivity. Roughly, two kinds of cavities can appear during superplastic deformation depending on its condition; they are (1) fine and equi-axial shaped cavities formed at grain boundary triple points and (2) flat ones formed along grain boundaries. We have found that the existence of the former ones in a specimen can improve its ion conductivity, whereas the latter ones can lower it. Superplastic deformation (SPD) under a proper condition may, therefore, improve ion conductivity of the 4ScSZ, i.e., SPD can show a synergistic effect.