Soft Chemical Synthesis And Modification Of BiFeO₃

Multiferroic materials, which are a class of materials that yield simultaneous effects of ferroelectricity, ferromagnetism or ferroelasticity in the same material, offer a wide opportunity for potential applications in information storage, such as spintronic devices and sensors, especially in new four-state memory device.Among single-phase multiferroic materials, BiFeO3has attracted much attention recently due to its relatively high Curie temperature (TC～830℃) and Neel temperature (TN～370℃) and high polarization value (～100μC·cm-2), which is advantageous for research and various applications. BiFeO3is well known to be an antiferromagnetic and ferroelectric material, which exhibits most possibility of practical applications at room temperature.In this paper, the main contents are as follows:Use hydrothermal and sol-gel method to prepare structural stability BiFeO3and analysis of phase structure, ferroelectric and dielectric properties; Optimize the synthesis process and discuss the influence factors, at the same time, modification BiFeO3by doping La (A-site), Dy (A-site), Sc (B-site). Results are as follows:1. When the temperature is200℃, KOH (0.3mol/L) as mineralizer, under different hydrothermal time to prepare BiFeO3pure powders, the best reaction time is9h.2. By sintering BiFeO3ceramics at different temperatures to determine the best sintering temperatures (750℃and800℃, through X-ray diffraction patterns and density changes of BiFeO3). At that temperature, BiFeO3has the best phase structure and micro-morphology.3. Prepare Bi(1-x)LaxFeO3powders and ceramics by hydrothermal method. With increasing the doping amount of La, dielectric properties of BiFeO3are improved. When doping amount of10mol%La, BiFeO3ceramics achieve the best dielectric properties.4. With sol-gel method, the synthesis temperature of BiFeO3drops to500℃and the synthesis process of BiFeO3has been optimized. Besides, BiFeO3is modified by doping Dy(A-site), La(A-site), Sc(B-site) and the optimal doping content of each element is determined to be Dy(x=0.1), La(x=0.125), Sc(x=0.025).