Effect of La³⁺ substitution on the phase transitions, microstructure and electrical properties of Bi_1?xLa_xFeO₃ ceramics

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• 作者：Qiang Zhang ; Xiaohong Zhu ; ^{xhzhu@scu.edu.cn} ; Yunhui Xu ; Haobin Gao ; Yunjun Xiao ; Dayun Liang ; Jiliang Zhu ; Jianguo Zhu ; Dingquan Xiao
• 关键词：La3+ doping ; Bi1&minus ; xLaxFeO3 ceramics ; Multiferroics ; Phase transition ; Microstructure ; Electrical properties
• 刊名：Journal of Alloys and Compounds
• 出版年：2013
• 出版时间：5 January, 2013
• 年：2013
• 卷：546
• 期：Complete
• 页码：57-62
• 全文大小：1285 K

文摘

Multiferroic Bi_1?xLa_xFeO₃ (x = 0.00, 0.05, 0.10, 0.15, 0.20) (represented as B_1?xL_xFO) ceramics were prepared using the conventional solid state reaction route. The effects of La³⁺ doping on the density, phase structure, morphology, dielectric and ferroelectric properties were investigated. Judging from X-ray diffraction patterns, all the B_1?xL_xFO ceramic samples were well crystallized in a pure perovskite phase while the crystal structure changed from rhombohedral to orthorhombic with increasing the La³⁺ substitution. SEM observations clearly revealed that the grain size was remarkably decreased by La³⁺ doping. As a result, the ferroelectric Curie temperature was lowered in the La-doped ceramics. However, the abnormal dielectric responses near the antiferromagnetic N¨¦el temperature (T_N) demonstrated the existence of remarkable magnetoelectric coupling in the Bi_1?xLa_xFeO₃ ceramics, and the T_N was shown to increase substantially with the increase in La³⁺ doping content. It was found that the dielectric permittivity of the ceramics was significantly increased and the dielectric loss was slightly increased with the increase in La³⁺ content. The dielectric constant ¦Å_r of the Bi_0.85La_0.15FeO₃ ceramic at 10 kHz reached as high as 1008, 20 times larger than that for pure BiFeO₃. In addition, the ferroelectric properties of the B_1?xL_xFO ceramics were improved and the remanent polarization was increased by La³⁺ doping. This is probably because the A-site doping with more stable La³⁺ could reduce the volatilization of Bi³⁺ and, thus, reduce the concentration of charged defects or defect dipole complexes, such as , or in the ceramics.