Acta Phys. -Chim. Sin. ›› 2011, Vol. 27 ›› Issue (05): 1254-1260.doi: 10.3866/PKU.WHXB20110423

• PHYSICAL CHEMISTRY OF MATERIALS • Previous Articles     Next Articles

Preparation of BaTiO3-BaFe12O19 Core-Shell Structure Particles by Homogeneous Coprecipitation

LIU Jian-Hua, YOU Dun, YU Mei, LI Song-Mei   

  1. School of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100191, P. R. China
  • Received:2010-09-09 Revised:2011-01-14 Published:2011-04-28
  • Contact: LIU Jian-Hua E-mail:liujh@buaa.edu.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (51001007).

Abstract:

BaTiO3-BaFe12O19 core-shell structure particles were obtained using the homogeneous coprecipitation method. The effects of temperature, molar ratio of urea to metal ions (R), and BaTiO3 concentration on the morphology and structure of the core-shell particles were investigated. The mechanism of formation for the BaTiO3-BaFe12O19 core-shell structure particles and their magnetic property were also discussed. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to characterize the morphology and structure of the BaTiO3-BaFe12O19 precursor core-shell structure particles and the BaTiO3-BaFe12O19 core-shell structure particles. A vibrating sample magnetometer (VSM) was used to characterize the magnetic property. The results indicated that the obtained sample possessed an integrated and smooth shell of about 10 nm in size and the metal ions precipitated completely after homogeneous coprecipitation when the sample was synthesized under the following conditions: 100 °C, R=180, and a BaTiO3 concentration of 2.5 g·L-1. A large amount of free particle impurities appeared if the temperature and R value were too high. The shell thickness of the BaTiO3-BaFe12O19 precursor core-shell structure particles tended to decrease as the BaTiO3 concentration increased. The BaFe12O19 phase in the shell began to form when the calcination temperature reached 900 °C. The mechanism of formation included the formation of BaFe2O4 by the reaction of crystalline α-Fe2O3 and BaCO3 initially, and this was followed by the reaction of BaFe2O4 and α-Fe2O3 to form the final BaFe12O19. As the temperature increased to 1000 °C, a complete BaFe12O19 shell was obtained. The saturation magnetization and coercivity of the BaTiO3-BaFe12O19 core-shell structure particles increased and decreased from 16.5 to 39.5 A·m2·kg-1 and from 340 to 316 kA·m-1, respectively, as the calcination temperature increased from 900 to 1000 °C.

Key words: Homogeneous coprecipitation, Core-shell particles, BaTiO3, BaFe12O19

MSC2000: 

  • O645