Sol-Gel Synthesis of the Double Perovskite Sr2FeMoO6 by Microwave Technique.

Jesús Valdés,Rufino Nava,Bertha Aguilar,Carlos M Cortés-Romero,Daniel Reséndiz,Ángeles Cuán,Oracio Navarro

doi:10.3390/ma14143876

Abstract

The effect of microwave radiation on the hydrothermal synthesis of the double perovskite Sr2FeMoO6 has been studied based on a comparison of the particle size and structural characteristics of products from both methods. A temperature, pressure, and pH condition screening was performed, and the most representative results of these are herein presented and discussed. Radiation of microwaves in the hydrothermal synthesis method led to a decrease in crystallite size, which is an effect from the reaction temperature. The particle size ranged from 378 to 318 nm when pH was 4.5 and pressure was kept under 40 bars. According to X-ray diffraction (XRD) results coupled with the size-strain plot method, the product obtained by both synthesis methods (with and without microwave radiation) have similar crystal purity. The Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) techniques showed that the morphology and the distribution of metal ions are uniform. The Curie temperature obtained by thermogravimetric analysis indicates that, in the presence of microwaves, the value was higher with respect to traditional synthesis from 335 K to 342.5 K. Consequently, microwave radiation enhances the diffusion and nucleation process of ionic precursors during the synthesis, which promotes a uniform heating in the reaction mixture leading to a reduction in the particle size, but keeping good crystallinity of the double perovskite. Precursor phases and the final purity of the Sr2FeMoO6 powder can be controlled via hydrothermal microwave heating on the first stages of the Sol-Gel method.

Highlights

Introduction iationsThe general formula of an ideal double perovskite is A2 B’B”O6, where A denotes an alkaline-earth or rare-earth ion, B’ and B” are transition-metal sites, and there are oxygen bridges every B’ and B”, which gives an alternating B’O6 and B”O6 octahedral form
As the temperature reached 220 ◦ C in A and B, it seems that high temperature reached (>170 ◦ C), by using microwave radiation, enhanced the generation of the phases SrMoO4 and Fe2 O3, the former being the most abundant
In agreement with the decrease crease in crystallite size, experiment F generates an intense response in the phase transition in crystallite size, experiment F generates an intense response in the phase transition comcompared to experiment E (Figure 10), in which its crystallite size is comparable to those pared to experiment E (Figure 10), in which its crystallite size is comparable to those obobtained in traditional Sol-Gel experiments

Summary

Introduction

The general formula of an ideal double perovskite is A2 B’B”O6 , where A denotes an alkaline-earth or rare-earth ion, B’ and B” are transition-metal sites, and there are oxygen bridges every B’ and B”, which gives an alternating B’O6 and B”O6 octahedral form. The double perovskite Sr2 FeMoO6 , known as SFMO, consist of a body centered cubic lattice with alternating FeO6 and MoO6 octahedral at the corners and the strontium atom in its center [1]. SFMO compound is a half-metallic ferromagnetic oxide with colossal magnetoresistance and a Curie temperature of 400 K [2]. This transition metal oxide has been widely investigated in view of their attractive applications for spintronics and digital storage [3]. One of the best opportunities in energy storage and Licensee MDPI, Basel, Switzerland

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Results

Discussion

Conclusion