Origin of diffuse electron scattering in yttria-cubicstabilized zirconia single crystals with 24–32 mol% yttria

Abstract

Transmission electron microscopy (TEM) of yttria (Y₂O₃)-cubic-stabilized zirconia with an yttria content between 24 and 32 mol% reveals diffuse electron scattering. Analysis of the diffuse intensity maxima in electron diffraction patterns recorded with the incident electron beam along (112)_c or (110)_c zone axes suggests that they originate from incipient microdomains of the δ phase', a superstructure with the composition Zr₃Y₄O₁₂. A compound with this composition has been observed before, however, for Y₂O₃ concentrations substantially higher (40 mol% or greater) than in our case. The microdomains are probably platelets and must have a diameter of less than 10 nm, rendering them hard to detect in TEM images. Apart from the δ phase, we have considered two other superstructures to explain the experimental observations, the pyrochlore type phase Zr₂Y₂O₇ and the structure of the C-type rare-earth oxide Y₂O₃. However, our data allow us to rule out these superstructures as the main source of diffuse electron scattering.