Dy,Co共掺杂对BiFeO3陶瓷磁特性和磁相变温度Tc的影响

采用快速液相烧结法制备BiFeO₃和Bi_0.95Dy_0.05Fe_1-xCo_xO₃ (x=0, 0.05, 0.1, 0.15)陶瓷样品. 实验结果表明: 所有样品的主衍射峰与纯相BiFeO₃相符合且具有良好的晶体结构, 随着Co³⁺掺杂量的增大, Bi_0.95Dy_0.05Fe_1-xCo_xO₃样品的主 衍射峰由双峰(104)与(110)逐渐重叠为单峰(110), 当掺杂量x>0.05时, 样品呈现正方晶系结构; SEM形貌分析可知: Dy³⁺, Co³⁺共掺杂使BiFeO₃晶粒尺度由原来的3—5 μ减小到约1 μ. 室温下, BiFeO₃样品表现出较弱的铁磁性, 随着Dy³⁺和Co³⁺掺杂, BiFeO₃样品的铁磁性显著提高. 在外加磁场为30 kOe的作用下, Bi_0.95Dy_0.05Fe_1-xCo_xO₃ (x=0.05, 0.1, 0.15)的M_r分别为0.43, 0.489, 0.973 emu/g; M_S分别为0.77, 1.65, 3.08 emu/g. BiFeO₃和Bi_0.95Dy_0.05Fe_1-xCo_xO₃样品磁矩M随着温度T的升高而逐渐减小, Dy掺杂使BiFeO₃样品的T_N由644 K升高到648 K, 而T_C基本没有变化. Dy和Co共掺杂导致BiFeO₃样品磁相变温度T_C由870 K降低到780 K, 其T_C变化主要取决于Fe-O-Fe反铁磁超交换作用的强弱和磁结构的相对稳定性. 关键词： 铁磁电材料 磁滞回线 磁相变温度

Effects of Dy and Co co-substitution on the magnetic properties and TC of BiFeO3 ceramics

Multiferroic Bi_0.95Dy_0.05Fe_1-xCo_xO₃ (x=0, 0.05, 0.1, 0.15) ceramics were prepared by rapid liquid phase sintering method. We studied the effect of (Dy+Co) doping on the structure, electrical and ferromagnetism properties of BiFeO₃ ceramics. The structure and morphology of BiFeO₃ ceramics were characterized by X-ray diffraction (XRD) and scanning electron microscopey (SEM). The results showed that all the peaks for Bi_0.95Dy_0.05Fe_1-xCo_xO₃ samples can be indexed based on the crystal structure of pure BiFeO₃. And XRD analysis revealed a phase transition in (Dy+Co) co-doped BiFeO₃ when x was larger than 0.1 and grain sizes changed from 1 to 5 μm. Magnetic hysteresis loops were clearly observed in co-substituted specimens and magnetization was greatly improved. Magnetic measurements showed that all samples possess strong ferromagnetism at room temperature expect BiFeO₃ and Bi_0.95Dy_0.05FeO₃, which are weakly ferromagnetic. The M'_rs, of Bi_0.95Dy_0.05Fe_1-xCo_xO₃ with x=0.05, 0.01 and 0.15 are 0.43, 0.489, 0.973 emu/g and the M'_rs of them are 0.77, 1.65, 3.08 emu/g, respectively. The magnetic moment of BiFeO₃ and B_0.95Dy_0.05Fe_1-xCo_xO₃ ceramics varies with temperature from 300 to 900 K at an applied field of 5 kOe. It shows that the T_N of BiFeO₃ from 644 to 648 K with different content of Dy³⁺ can be changed by crystal structures and exchanges between Dy³⁺-Fe³⁺. The phase transition temperature of Bi_0.95Dy_0.05Fe_1-xCo_xO₃ shifted to lower temperatures from 870 K to 780 K demonstrate that Co³⁺ doping causes a drop of T_C as compared with BiFeO₃. The change of T_C of Bi_0.95Dy_0.05Fe_1-xCo_xO₃ depends mainly on the Fe-O-Fe super-exchange strength and the relative stability of magnetic structure.
Keywords： multiferroic magnetic hysteresis loops leakage current