A COMPARISON OF 3 SETS OF DIFFRACTION DATA FOR AL2Y4O9 - X-RAY SYNCHROTRON POWDER DATA, X-RAY SINGLE-CRYSTAL DATA FROM AG K-ALPHA-RADIATION, AND NEUTRON SINGLE-CRYSTAL DATA FROM 1.01-A NEUTRONS

Al2Y4O9 is monoclinic, space group P2(1)/c (No. 14) with a = 7.375(1), b = 10.507(2), c = 11.113(1) angstrom, beta = 108.58(2)-degrees, Z = 4 and d(x) = 4.52 g cm-3. Two yttrium atoms are coordinated with six, and two with seven, oxygen atoms. The two aluminium atoms are coordinated with four oxygen atoms. Single crystals of the compound were made from a melt of Al2Y4O9. Three sets of diffraction data are compared: (i) X-ray synchrotron powder data where the pattern had contributions from 574 reflections, (ii) single crystal X-ray data from Ag K(a) radiation with 1540 independent reflections and (iii) single crystal neutron diffraction data with 1.01 angstrom neutrons and 984 independent reflections. The precision of the atomic coordinates from the synchrotron X-ray powder diffraction data is comparable with or slightly lower than that for the coordinates from the two single crystal data sets.