University of Belgrade, Institute for Multidisciplinary Research
Abstract
Lanthanum nickelate (LaNiO3, LNO) belongs to the group of materials with
perovskite-type structure and it crystallizes in rhombohedrally distorted perovskite
lattice. This material exhibits interesting electrical, magnetic, optical and catalytic
properties and it is suitable for various applications. Still, the preparation of single
phase LNO is difficult, because at temperatures above 850 °C it decomposes into the
lower oxides with formula Lan+1NinO3n+1 (n = 3, 2, 1) and NiO.
In this work we present the synthesis of pure and Nb doped LNO powders,
LaNi1-xNbxO3 (x = 0.000, 0.005, 0.010) prepared from mechanochemically activated
oxide precursors – La2O3, NiO and Nb2O5. For this experiment, precursor powders
homogenized in isopropyl alcohol were dried and mechanochemically activated in
the planetary ball mill for 3 h. As-prepared powders were calcined at 700 °C for 3 h
in air and further analyzed by X-ray diffraction analysis (XRD), Transmission
electron microscopy (TEM), Scanning electron microscopy (SEM) and UV-Vis
spectroscopy. Photocatalytic activity in visible light was investigated.
The XRD analysis of undoped LNO revealed the existence of rhombohedral
LaNiO3 and small amount of NiO phase. The doped samples, apart from LNO,
contained products of thermal decomposition – layered oxides and NiO. TEM and
HRTEM analyses of undoped LNO revealed the presence of agglomerated particles
with single particle size being in the range of 20–40 nm. Doping with Nb led to
decrease of agglomeration process and allowed better dispersion between particles
of LNO based powders. Calculated band gaps were 1.12 eV, 0.89 eV and 0.87 eV
for x = 0.00, 0.005, 0.010. The absorption spectra indicated photocatalytic
degradation of Reactive Orange 16, textile dye used as a model in these
experiments
