ADPD - A NEW APPROACH TO SHARED-SITE PROBLEMS IN CRYSTALLOGRAPHY

From the anomalous dispersion of X-rays close to the Zr and Y absorption edges it has been found that individual cation B factors can be determined independently in a refinement of the structure of an yttria-stabilized zirconia ceramic material with composition Zr0.81Y0.19O1.90. With X-ray powder data collected at a single wavelength this is not possible because of the high correlations. Simultaneous refinement of data collected at three different X-ray wavelengths [0.7726(1), 0.7283(1) and 0.6892(1) Å] has allowed the determination of separate mean-square displacements for each atom, the respective values are 0.045(2) for Zr4+, 0.024(6) for Y3+ and 0.098(2) Å2 for O2−. The results indicate that the structural configuration of Zr4+ is significantly different from that of Y3+. This anomalous-dispersion powder diffraction (ADPD) technique should be of general application to similar shared-site problems of this kind. © 1988, Wiley-Blackwell. All rights reserved.