Preparation of Nanosized LaCoO3through Calcination of a Hydrothermally Synthesized Precursor

L Tepech-Carrillo,A Escobedo-Morales,J F Sánchez-Ramírez,E Chigo-Anota,A Pérez-Centeno,E López-Apreza,J Gutiérrez-Gutiérrez

doi:10.1155/2016/6917950

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.

Highlights

Perovskite-type oxides (ABO3; A: rare earth; B: transition metal) constitute an important class of strategic materials because of their electrical, mechanical, optical, magnetic, and catalytic properties [1,2,3,4,5]
It is determined that LaCoO3 phase is produced by a reaction of cobalt and lanthanum oxides, the latter produced by a two-step dehydration process of La(OH)3
The microstructure and formation mechanism of LaCoO3 crystals prepared from calcination of a powder precursor (Co3O4 + La(OH)3) synthesized by a hydrothermal route were studied

Summary

Introduction

Perovskite-type oxides (ABO3; A: rare earth; B: transition metal) constitute an important class of strategic materials because of their electrical, mechanical, optical, magnetic, and catalytic properties [1,2,3,4,5]. This class of oxides has been used to fabricate efficient electrodes for solid oxide fuel cells [6,7,8,9,10], chemical sensors [11,12,13,14], oxygen-permeating membranes [15], and thermoelectric devices [16] and as catalysts for combustion of CO, hydrocarbons, and NOx decomposition [17,18,19,20,21]. Developing of reliable methods for obtaining nanosized LaCoO3 powders with large specific surface area to be used as electrocatalysts is an active research field nowadays [23]

Objectives

Methods

Results

Conclusion