| As a kind of multifunctional materials, multiferroics materials, which exhibits ferroelectric in combination with ferromagnetism have received great attention due to their potential applications in information storage, spintronics, and sensors fields. BiFeO3 materials with a distorted perovskite (ABO3) structure, is one of the most promising due to its coupling between the ferroelectricitu and magnetic ordering at room temperature, which have received extensive attentions in recent years. Nowadays, it is a main mean for BiFeO3 ceramics to dope with rare ions or transition elements, but it need high cost. Glass as a additive which has simple preparation and easy accessibility not only is a sintering aids but also can optimize the creamic performance. In this work, BiFeO3 powders were successfully synthesized by solid state method. The effect of different calcination temperatures on the BiFeO3 powders purity were investigated and ultimately the optimum parameter were confirmed. On this basis, the BiFeO3 ceramic samples with different contents of the (Ba0.5Sr0.5)Nb206-G (abbreviate as BSN-G), the SrO-Fe2O3-SiO2-B2O3 glass-ceramics (abbreviate as SFSB) and Bi2O3-B2O3-ZnO (abbreviate as SFSB) addition were prepared by conventional process and the effects of different glass contents on the sintering property, microstructure, the crystal structure, the leakage current density, ferroelectric and ferromagnetic properties of the BiFeO3 ceramic were investigated systematically.(1) A series of BiFeO3-x[BSN-G] (x=0.0-5.0 wt%) ceramic samples were prepared by a solid-state reaction method. The influences of BSN-G contents on the microstructure, electrical and magnetic property of BiFeO3 ceramics were investigated. The results indicated that with BSN-G addiction the sintering temperatures and the porosity of the ceramic samples were decerased and the density was enhanced. It was beacuse the portion glass phase existed BSN-G made the liquid phase form in the sintering process of the ceramic, which could easily infiltrate the solid particle. The liquid phase participated in the sintering process and promoted the mass transfer, which made the densification of the ceramic enhance. The dielectric constant and losses of the samples were reduced with BSN-G addiction. The dielectric constant was 72 and the dielectric loss was 0.003 for x=5.0% sample at 1 kHz. The leakage current could be effectively suppressed with BSN-G addiction, which the x=5.0% sample showed a saturation ferroelectric hysteresis loop with Ps=1.5 ?C/cm2 and J=0.39?A/cm2. Additionally, it was confirmed that the magnetic behaviors of the samples were slightly improved with x increasing.(2) The SrO-Fe2O3-SiO2-B2O3 based glass was successfully prepared by conventional melt casting, and subsequently Sr2FeSi2O7-crystallized glass-ceramics was prepared by heat treatment. The magnetization hysteresis (M-H) loop of the glass-ceramics exhibits typical ferromagnetic behavior with saturation magnetization values Ms=10.527 emu/g and coercive field Hc=210.462 Oe. The investigations of BiFeO3-xSFSB (x=1.0?9.0 wt%) ceramics showed that:The relative density of the x=5.0% sample attained the maximum value, which suggested that excessive glass phase made the viscosity of the ceramic system increase in the sintering process. This was harmful to the elimination of the pore and made the densification of the ceramic enhance. Besides, the dielectric constant decerased while the dielectric loss showed decreased firstly and then increased. The dielectric constant of the x=5.0% sample was 85 and the dielectric loss decreased below 0.02 at 1 kHz. The M-H plots showed linear relation for x=1.0% sample, which suggested a typical antiferromagnetic material. While the maximum magnetization (Ms) and the coercive field (Hc) were greatly enhanced with x increasing. The Ms was 0.230 emu/g and Hc was 3122 Oe for x=9.0% sample, which showed the magnetic property of BiFeO3 ceramics could be sharply improved by SFSB addition.(3)The investigations of BiFeO3-xBBZ (x=0.0?5.0 wt%) ceramics showed that:With BBZ addition, the sintering temperatures could be clearly reduced, the relative density could be enhanced and the grain size could be refined. The Raman analysis showed that the Bi-O bond and Fe-O bond in the BiFeO3 ceramics could be enhanced with BBZ addition, which further could make the ferroelectric and ferromagnetic properties improve. It could be ascribed that the Bi3+ existed BBZ system could supplement the volatilization of Bi3+ in the BiFeO3 ceramics. The dielectric constant reached 168 and the dielectric loss was 0.05 at 100 Hz. Additionally, in the frequency range of 100 Hz?1 MHz, the dielectric constant and dielectric loss as a function of temperatures showed dispersion phenomenon, which provided a clear rationalization of the Maxwell-Wagner type of relaxation. The leakage current of the x=5.0% sample was reduced by three orders of magnitudes when compared with the x=1.0% sample. Besides, both the maximum magnetization (Ms) and the coercive field (Hc) were greatly enhanced with x increasing, which the Ms was 0.170 emu/g emu/g and Hc was 2796 Oe for x=5.0% sample. It could be ascribed that the position of the FeO6 octahedron was changed by the BBZ addition, which made the rhombus perovskite structure of the BiFeO3 ceramics distort and the bond angle between Fe-O-Fe was diminished. This is good for the increase of the magnetization. |
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