Magnetic properties of quasi-two-dimensional La2NiO4

Magnetic susceptibility studies on single crystals of nearly stoichiometric La2NiO4 with the applied field both parallel and perpendicular to the c axis show a transition at 204 K below which two-dimensional canted antiferromagnetic order seems to exist. This oxide also undergoes a transition from isotropic to anisotropic susceptibility near 100 and 250 K

ADF-STEM imaging of nascent phases and extended disorder within the Mo–V–Nb–Te–O catalyst system

Materials investigated for their potential use as heterogeneous selective oxidation catalysts may sometimes show highly ordered regions at the nanoscale which are embedded within highly disordered matrices from which they nucleate. These are often referred to as X-ray amorphous due to the lack of higher-order Bragg reflections; however, here we use annular dark-field scanning transmission electron microscopy (ADF-STEM) real space imaging to characterize the local structure of nanometer size domains of compositionally and structurally complex nascent oxide phases present in multi-phase disordered solids. These images have been obtained using aberration-corrected scanning transmission electron microscopy and point to its potential for local structural characterization where the synthesis conditions for a particular phase are not optimized or where self-assembly to extended structures has been locally hindered. Such studies may lead to identification of new catalysts, provided their targeted synthesis can be scaled up

ADF-STEM imaging of nascent phases and extended disorder within the Mo–V–Nb–Te–O catalyst system

Materials investigated for their potential use as heterogeneous selective oxidation catalysts may sometimes show highly ordered regions at the nanoscale which are embedded within highly disordered matrices from which they nucleate. These are often referred to as X-ray amorphous due to the lack of higher-order Bragg reflections; however, here we use annular dark-field scanning transmission electron microscopy (ADF-STEM) real space imaging to characterize the local structure of nanometer size domains of compositionally and structurally complex nascent oxide phases present in multi-phase disordered solids. These images have been obtained using aberration-corrected scanning transmission electron microscopy and point to its potential for local structural characterization where the synthesis conditions for a particular phase are not optimized or where self-assembly to extended structures has been locally hindered. Such studies may lead to identification of new catalysts, provided their targeted synthesis can be scaled up

Oxygen excess in layered lanthanide nickelates

Density measurements on large single-crystal specimens of La2NiO4+δ and Pr2NiO4+δ show that oxygen nonstoichiometry arises from the presence of excess lattice oxygen. X-ray photoelectron spectra as well as X-ray absorption edge studies provide no evidence for the existence of Ni3+ in these oxygen-excess nickelates under the conditions of the measurements. Transmission electron microscopy has revealed a novel type of exsolution process of the stoichiometric phase out of nonstoichiometric La2NiO4 during heating in CO2 at 870 K for 3 h. An interpretation of the results in terms of the existence of peroxide species within the conducting layers is proposed

Crystal structure and semiconductor-metal transition of the quasi-two-dimensional transition metal oxide, La2NiO4

Abstract is not available