College of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China. §. College of Chemistry and Chemical ...
J. Am. Ceram. Soc., 96 [5] 1345–1348 (2013) DOI: 10.1111/jace.12296 © 2013 The American Ceramic Society
Journal
Rapid Communication
Ethanol-Assisted Hydrothermal Synthesis and Characterization of BiFeO3 Nanopowders Zhiwu Chen,‡,† Yongpeng Wu,‡ and Jianqiang Hu§ ‡ §
College of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China
College of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, China calcined process at >400°C, which is high-energy consumption and also results in irregular morphology and broad particle size distribution. Hence, it will be a challenge to prepare pure BiFeO3 powder at a mild condition. Compared with other synthetic methods, hydrothermal method possesses many advantages such as high crystallinity degree, well-controlled morphology, and high purity, narrow particle size distribution.14–16 However, in the previous works, 180°C was usually requisite in hydrothermal synthesis of pure BiFeO3.14–16 In this study, we have successfully synthesized well-crystallized single-phase BiFeO3 nanopowders under 120°C hydrothermal temperature, and which is so far the lowest synthetic temperature of pure BiFeO3 powders. In our system, the composition of the solvent played important roles in the low-temperature synthesis of pure BiFeO3. The hydrothermal temperature of pure BiFeO3 could be lowered to 120°C only using the ethanol–water mixed solvents. The process has advantages of simplicity and energy saving.
Well-crystallized pure BiFeO3 nanopowders were successfully synthesized at the temperature as low as 120°C by an ethanolassisted hydrothermal process. In this synthesis, the composition of the solvent played important roles in the formation of pure BiFeO3. The BiFeO3 nanopowders synthesized with 4:3 ethanol/water ratio mainly consists of cubic structures with size from 50 to 150 nm. Zero-field-cooled (ZFC) and field-cooled (FC) magnetization measurements indicated that pure BiFeO3 nanopowders showed a spin-glass transition below the freezing temperature. Moreover, the BiFeO3 nanopowders exhibited ferromagnetic order at room temperature.
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Introduction
materials, which exhibit simultaneous effects of ferroelectricity, ferromagnetism or ferroelasticity in the same material, have been intensively studied due to their potential applications in information storage, spintronics, and sensors.1,2 As one of very few existing singlephase multiferroics materials, perovskite BiFeO3 has recently received considerable attention because it displays high ferroelectric Curie temperature (830°C) and high antiferromagnetic Neel temperature (370°C).2,3 However, a superimposed spiral spin structure with an incommensurate long-wavelength period of 62 nm cancels macroscopic magnetization and also inhibits linear magnetoelectric effect in bulk BiFeO3.4 Another obstacle for BiFeO3 applications has large leakage current because of the existence of the second phase. Due to kinetic and thermodynamic properties of Bi2O3–Fe2O3 system, pure phase BiFeO3 possesses very narrow range of temperature stability, which greatly increases difficulty of synthesizing single-phase BiFeO3.5 In solid-state route, nitric acid leaching was usually applied to eliminate the impurity phases after calcinations, which resulted in coarser powders with poor reproducibility.6 To overcome above-mentioned disadvantages, many attempts have been done recently, which include synthesizing BiFeO3 nanoparticle with the size of
