X-ray diffraction study of polycrystalline Y2BaO4: a test of the new EXPO program

In order to test the new EXPO program, an ab initio structure determination from conventional X-ray powder diffraction data has been performed on Y2Ba O4. a stable compound that can form during the synthesis of mixed oxides be longing to the Y-Ba-Cu-O and Y-Ba-Ni-O systems. An orthorhombic cell (Pnma space group) with a = 10.3955(1) Angstrom, b=3A5 03(1) Angstrom, c=12.1157(1) Angstrom. Z =1 and D-c = 5.795 g/cm(3) has bee n obtained, in agreement with the hypothesis that Y2BaO4 is isotypic with Y 2SrO4, as reported by Costa Ferretti. Fornasini, Franceschi, Olcese, 1989. The: Pnca space group (60) related to the Pnab proposed by Kwestroo, van Ha l, Langereis, 1974 can be rejected. On the basis of accurate atomic fractional coordinates determined by direct methods application and Rietveld refinement, bond lengths and angles have been estimated and discussed with respect to the data of the isotypic Y2SrO 4 structure.