NICKEL DISTRIBUTION ON ALUMINUM SITES IN LANIAL11O19

The crystal structure and the distribution of nickel atoms over the fi ve aluminum sites in LaNiAl11O19 have been determined on the basis of high resolution, synchrotron, powder diffraction data. Nickel occupies predominantly the tetrahedral Al2-site, whereas lanthanum achieves tw elve coordination in the magnetoplumbite-related structure. Nickel beh aves hence correspondingly as manganese, iron and cobalt. This contras ts results from earlier single crystal studies. The discrepancies are discussed on the basis of differences in sample preparation, i.e. grow th from the melt versus solid state diffusion.