Synthesis, characterization and kinetic study of the Sr_2FeMoO_(6-δ) double perovskite: New findings on the calcination of one of its precursors

摘要

Sr2FeMoO6-delta double perovskites are widely-recognized due to several important factors: high electronic conductivity and electrocatalytic activity, structural stability under reducing atmospheres, high transition temperature, enormous magnetoresistance, reasonable tolerance to carbon formation, and their desirable capacity to avoid sulfur poisoning. One of the methods most commonly-used to synthetize these perovskites is solid-state reaction. The precursor phases usually associated with this method are the oxides SrMoO4 and SrFeO3-delta when Fe2O3, SrCO3, and MoO3 are the initial reagents used. Morphological, XRD (Rietveld), and thermogravimetry (calcination and reduction) analyses are steps or routes towards achieving the final result. While recent studies suggest that the temperature of calcination is always 900 degrees C and that reduction occurs at 1200 degrees C, they fail to explain why this occurs. This article demonstrates, according to the results of thermog-ravimetric analysis (TGA), that as calcination advances weight loss increases until a temperature of 850 degrees C is reached. In addition, it stresses the importance of the ball milling technique at ambient temperature to prevent sublimation of the MoO3 compound at 700 degrees C in the later steps of synthesis, such as calcination and reduction. According to the kinetic study, the values of activation energy (Ea) and reaction order (n) were 130.47 kJ/mol and 1 respectively. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.