The Research Of Multiferroic Composite Material

Multiferroic material is one that possesses two—or more—of the so-called"ferroic"properties: (anti)ferroelectricity, (anti)ferromagnetism and ferroelasticity. In this thesis, we investigated the preparation, structural, ferroelectrical and ferromagnetic properties of the prepared single-phase BiFeO₃ ceramics, BiFeO₃/BaTiO₃ diphase ceramics, BiFeO₃/PZT diphase ceramics.First, we synthesized the primary powder of BiFeO₃ by sol-gel method, then calcined the primary powder of BiFeO₃ to prepare single-phase BiFeO₃ ceramics under high-pressure. The phases other than BiFeO₃ are restrained and the density of BiFeO₃ ceramics is increased during high-temperature high-pressure sintering. The ferroelectricity and ferromagnetism of single-phase BiFeO₃ ceramics have been studied.The BiFeO₃/BaTiO₃ and BiFeO₃/PZT diphase ceramics are synthesized by the method of high-temperature high-pressure sintering. It was found that high-pressure can effectively shorten the time of sintering, depress the temperature of sintering, restrain the chemical reaction between the composite materials themselves and restrain the grain size under high-temperature. Then, we studied the structure and morphology using XRD and SEM, analyzed the ferroelectricity and ferromagnetism of BiFeO₃/BaTiO₃ and BiFeO₃/PZT diphase ceramics.BiFeO₃/BaTiO₃ and BiFeO₃/PZT diphase ceramics were synthesized for different proportion (1 : 1, 1 : 2, 1 : 3) and studied the influence of content of BaTiO₃ and PZT in composite materials to ferroelectricity and ferromagnetism. For BiFeO₃/PZT diphase ceramics, polarization hysteresis loops and magnetic hysteresis loops were measured, and the ferroelectricity and ferromagnetism of BiFeO₃/PZT diphase ceramics increase with increasing content of PZT. For BiFeO₃/BaTiO₃ diphase ceramics, standard polarization hysteresis loops were not measured successfully because of large leakage current of the samples, but for its ferromagnetism, the ferromagnetic property of the composite material is enhanced with increasing the content of BaTiO₃.