MODULATED STRUCTURE OF LA2NIO4+DELTA AS A MECHANISM OF OXYGEN EXCESS ACCOMMODATION

A microstructural characterization by means of high resolution transmi ssion electron microscopy has been performed in La2NiO4+delta in order to confirm the distribution of the oxygen excess. A structure commens urately modulated along [010] with modulation period a(s) = 3a, and an other with b(s) = 4b along [100] were found. The origin of such modula tions is discussed in terms of the irregular distribution of interstit ial oxygen atoms within the crystal lattice. Although the structural c hanges may be electron beam induced and these new phases are minoritie s and possibly metastable, the results contribute new information abou t how the interstitial oxygen can be accommodated. (C) 1996 Academic P ress, Inc.