Mn4+掺杂对BiFeO3陶瓷微观结构和电学性能的影响研究

利用传统的固相反应法制备了BiFe_1-xMn_xO₃ (x= 0-0.20)陶瓷样品, 研究了不同Mn⁴⁺掺杂量对BiFeO₃陶瓷密度、物相结构、显微形貌、 介电性能和铁电性能的影响.实验结果表明:所制备的BiFe_1-xMn_xO₃ 陶瓷样品的钙钛矿主相均已形成,具有良好的晶体结构, 且在掺杂量x=0.05附近开始出现结构相变.随着Mn⁴⁺添加量的增加, 体系的相结构有从菱方钙钛矿向斜方转变的趋势,且样品电容率大幅度增大, 而介电损耗也略有增加;在测试频率为10⁴ Hz条件下, BiFe_0.85Mn_0.15O₃ (ε_r=1065)的 ε_r是纯BiFeO₃ (ε_r=50.6)的22倍; 掺杂后样品的铁电极化性能均有不同程度的提高,可能是由于Mn⁴⁺稳定性优于 Fe³⁺,高价位Mn⁴⁺进行B位替代改性BiFeO₃陶瓷, 能减少Bi³⁺挥发,抑制Fe³⁺价态波动,从而降低氧空位浓度,减小样品的电导和漏电流.

Effect of Mn4+ doping on the microstructure and electrical property of BiFeO3 ceramic

Multiferroic BiFe_1-xMn_xO₃（x = 0,0.05,0.10,0.15,0.20）(represented as BF_1-xM_xO) ceramics are prepared by the conventional solid state reaction technique.The effects of Mn⁴⁺ doping on density,phase structure,morphology,dielectric and ferroelectric properties are investigated.The X-ray diffraction patterns of the samples indicate that the typical perovskite phase structure of BiFeO₃ is formed,and a phase transition starts near x=0.05,i.e.,the phase structure is distorted from rhombohedral to orthorhombic by Mn⁴⁺ doping.The dielectric susceptibility of the sample is significantly increased and the dielectric loss is slightly increased with the increase of Mn⁴⁺ content.The dielectric constantε_r of the BiFe_0.15Mn_0.15O₃ ceramic at 10 kHz is as high as 1065,22 times larger than that for pure BiFeO₃ It is suggested by hysteresis loop measurements that the ferroelectric property of the BF_1-xM_xO ceramics is improved and the remanent polarization is increased by Mn⁴⁺ doping.This is probably because Mn⁴⁺ is more stable than Fe³⁺, and the B-site doping with higher valent Mn⁴⁺ could reduce the volatilization of Bi³⁺ and suppress the valence fluctuation of Fe³⁺, thereby reducing the concentration of oxygen vacancies and the leakage current in the ceramic.