Rietveld refinement of two-phase Zr-doped Y2O3

High resolution X-ray and neutron scattering studies on powder samples of pule and Zr-doped Y2O3 (10% molar) show that mesoscopic compositional inhomogeneities may exist in the doped compound which are unlikely to be revealed by conventional diffraction methods. The Rietveld refinement of X-ray and neutron data on the pure compound collected at room temperature and at 8 K gives very satisfactory results in the cubic space group Ia (3) over bar. Even if the results of the structural refinement of the doped compound show quite good reliability factors, the careful analysis of the individual peaks suggests the existence of two phases. A structural model for both phases is proposed. The main phase (90%) has a composition and a structure very close to the one of pure Y2O3. The Zr richer phase (10%) segregates and Zr atoms show site selectivity.