Preparation of Nanosized LaCoO₃through Calcination of a Hydrothermally Synthesized Precursor

Abstract

A method for obtaining nanosized LaCoO3crystals from calcination of a precursor powder synthesized by a hydrothermal route is reported. Details concerning the evolution of the microstructure and formation mechanism of the perovskite phase were studied by powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, Raman spectroscopy, and thermal analysis. It was found that the morphology of the sample progressively turns from a mix of fibers and rods to interconnected nanocrystals. It is determined that LaCoO3phase is produced by a reaction of cobalt and lanthanum oxides, the latter produced by a two-step dehydration process of La(OH)3. Finally, it was found that nearly stoichiometric LaCoO3nanocrystals can be obtained at temperatures as low as 850°C. Nevertheless, whether higher calcination temperatures are used, appropriate reaction times and a controlled atmosphere are required in order to avoid formation of lanthanum carbonates and high density of lattice defects.

Preparation of Supported Perovskite Catalyst to Purify Membrane Concentrate of Coal Chemical Wastewater in UV-Catalytic Wet Hydrogen Peroxide Oxidation System

“…The prepared catalyst had a pure perovskite structure and orthogonal crystal. The XRD spectra of the supported catalyst LaCoO 3 /CeO 2 prepared by impregnation showed not only obvious characteristic diffraction peaks of LaCoO 3 perovskite structure but also characteristic peaks of CeO 2 at 29.08°, 33.04°, and 56.51°, corresponding to the standard card of CeO 2 (PDF#1-800) [ 24 ]. This result confirmed that an LaCoO 3 perovskite-type structure was formed on the surface of the CeO 2 support, and the crystal forms of the support and active component were not destroyed.…”

Opportunities, Challenges and Prospects for Electrodeposition of Thin-Film Functional Layers in Solid Oxide Fuel Cell Technology

“…The precursor in this case was identified to be [Co 2 O 3 ·2La(NO 3 ) 3 ·3H 2 O], which, after heat treatment at 500 °C, yielded the LaCoO 3 coating. This temperature is significantly lower than that used for the calcination of LaCoO 3 powders obtained by solid-state reaction (1000 °C [ 38 ]) hydrothermal synthesis (850 °C [ 39 ]) methods.…”

Influence of Cobalt Substitution in LaNiO₃ Nanoperovskite on Catalytic Propylene Oxidation

“…In other conditions, preferred distortions orthorhombic, rhombohedral, and to a lesser extent tetragonal, mono, or triclinic perovskites will appear [8]. Although, it is difficult to synthesize these materials in their pure bulk form, due to the stabilization of Ni(III) and either oxygen pressure and/or high temperatures of ~950 ºC are necessary [1,2,8,9], it is possible to prepare these perovskite materials comparatively in the pure form either by modified conventional ceramic, co-precipitation, sol-gel, hydrothermal, auto-combustion and also by other modern techniques like pulse laser, spray pyrolysis techniques for thin films. LaNiO 3 and LaCoO 3 have rhombohedrally distorted perovskite structures at room temperature [3,4,[9][10][11].…”