Abstract
High-angle annular dark-field (HAADF) and annular bright-field (ABF) images recorded from the Pb(ZrxTi1−x)O3morphotropic phase boundary (PZTmpb) showB-site displacements along the 〈110〉 directions and prominent distortions in the oxygen cages surrounding both theBsites and the Pb environments. The measured range ofB-site displacements is about 0.25–0.4 Å. Oxygen cage distortions appear to be variable in shape and dimensions at the unit-cell level. Comparison of the observed displacements with the structural projections based on the established monoclinic space groupCm(Cs3) shows a good overall agreement. A qualitative match betweenCm(Cs3) and the reported observations is inconclusive because of inaccuracy in the measurements, originating from imprecise identification of atomic column centres inherent in the HAADF and ABF images. In most of the observed cases,B-site displacements in HAADF images, and oxygen cage distortions in ABF images, appear pronounced compared with the structural projections inCm(Cs3). Columnar chemical inhomogeneity has been commonly observed in bothB-site and Pb columns in PZTmpb. Weak 〈110〉 diffuse streaking along the [001], [110] and [111] zone axes has been imaged, suggestive of correlation with the systematic ion disorder along 〈110〉.
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