MICROSTRUCTURAL CHARACTERIZATION OF THE LANIO3-Y SYSTEM

An electron diffraction and high-resolution electron microscopy study of the LaNiO3-y perovskite-related system shows that compositional var iations lead to the formation of new superstructures corresponding to a homologous series of the general formula LanNinO3n-1 when y = 0.5 an d 0.25, i.e., for n = 2 and 4, respectively. These members can be desc ribed as being formed by ordered intergrowths of (n - 1) octahedral la yers alternating with one layer in which Ni2+ adopts square planar coo rdination. For different y values, the nonstoichiometry is accommodate d by means of disordered intergrowths of octahedral and square-planar layers. (C) 1994 Academic Press, Inc.