Neutron diffraction experiments were carried out  in situ  on cubic single crystals at high temperatures and, simultaneously, under an applied direct-current electric field (that is, a persistent ionic current). Disorder diffuse scattering of material which was stabilized with 15mol%CaO, and 9.5 or 21mol%Y2O3, was measured at temperatures of up to 1200K. The applied direct-current field ranged up to 20V/cm, with the E-field vector directed parallel to [100]. At 1000K, the CaO-stabilized material exhibited a sharpening of the diffuse maxima with increasing E-field strength. However, the integrated intensities remained constant. No such differences were found at 800 or 1200K. On the basis of an interpretation of the diffuse maxima in terms of micro-domains, an ordering process between the micro-domains (the correlation length increased from 2.5nm at room temperature to 6nm at 1000K) was supported by enhanced ionic motion at high temperatures. On the other hand, the higher mobility of the O vacancies at 1200K acted so as to destroy the micro-clusters and led to a subsequent loss of correlation between them. Equivalent measurements which were performed on Y2O3-stabilized material revealed no significant changes in diffuse intensity distribution; thus indicating a different order/disorder behavior.

H.Kahlert, F.Frey, H.Boysen, K.Lassak: Journal of Applied Crystallography, 1995, 28, 812-9