Defect Structure and Diffuse Scattering of Zirconia Single Crystals at Elevated Temperatures and Simultaneously Applied Electric Field

In situ neutron diffraction experiments on cubic zirconia single crystals were carried out at elevated temperatures and, simultaneously, under an applied DC electric field, i.e. lasting ionic current. Disorder diffuse scattering of CaO (15 mol%) stabilized ZrO₂ (CSZ15) and Y₂O₃ (9.5 mol%, 21 mol%) stabilized ZrO₂ (YSZ9.5 and YSZ21, respectively) was measured up to 1200 K as function of an applied DC field E ≤ 20 V cm⁻¹ with the E field vector parallel to [100]. At 1000 K, CSZ15 showed a sharpening of the diffuse maxima with increasing E field strength; the integrated intensities remained, however, constant. No such differences were found at 800 and 1200 K. Based on an interpretation of the diffuse maxima by microdomains, an ordering process between the microdomains (the correlation length increases from 25 Å at RT to 60 Å at 1000 K) is supported by an enhanced ionic motion at high temperatures. On the other hand, the higher mobility of the oxygen vacancies at 1200 K acts to destroy the microclusters and leads to a subsequent loss of correlation between them. The equivalent measurements with YSZ showed no significant changes of diffuse intensity distributions indicating a different order/disorder behaviour.