SHORT-RANGE STRUCTURE OF ZIRCONIA XEROGEL AND AEROGEL, DETERMINED BY WIDE-ANGLE X-RAY-SCATTERING

The short-range structure of amorphous zirconia, investigated by X-ray diffraction, has been found to bear more resemblance to the monoclini c ZrO2 structure than it does to the tetragonal structure. This result was achieved in two zirconia samples (xerogel and aerogel) by analyzi ng both the positions of the maxima of the experimental (Fourier-trans formed) 'reduced' radial correlation function, G(r), and the experimen tal radial atom (number) density distribution, rho(r). This latter fun ction was simulated as a weighted sum of three partial atom density di stributions, rho(Zr-O)', rho(Zr-Zr)', and rho(O-O)', based on the mono clinic or the tetragonal coordination frame and limited inside a spher e of 9 angstrom in radius. The coordination statistics are described i n terms of sums of Gaussian functions into which distortion effects (f irst-type and second-type disorder) were introduced.