钆掺杂对0.7BiFe0.95Ga0.05O3-0.3BaTiO3陶瓷的结构、介电性能和多铁性能的影响

Effect of Gd doping on the structure, dielectric and multiferroic properties of 0.7BiFe0.95Ga0.05O3-0.3BaTiO3 ceramics

采用固相烧结法制备了不同Gd掺杂含量的0.7Bi1-xGdxFe0.95Ga0.05O3-0.3BaTiO3(BGxFG-BT,x=0,0.05,0.1,0.15,0.2)陶瓷,系统研究了Gd掺杂对BGxFG-BT陶瓷的晶体结构、微观形貌、介电性能以及多铁性能的影响.通过X射线衍射图谱分析、扫描电镜形貌分析、X射线光电子能谱分析等工具表明,Gd掺杂会使BGxFG-BT陶瓷由菱面体(R3c)结构转变为赝立方(P4mm)结构,晶粒尺寸会明显减小,从未掺入Gd时的6.2μm降低到约3.2μm左右,同时发现少量的Gd掺杂能够抑制BFG-BT陶瓷中Fe^2+离子的产生,减少氧空位的存在.最终导致,在适量的Gd掺杂下,陶瓷的介电性能和铁电性能均得到明显改善.适量的Gd掺杂可使介电常数增加、介电损耗减少、电滞回线形状改善、剩余电极化强度增加(最高达9.06μC/cm^2).同时,在磁性能方面,Gd掺杂陶瓷均表现铁磁性,剩余磁极化强度与饱和磁化强度均有显著提高.

The 0.7 Bi1-xGdxYe0.95Ga0.05O3-0.3 BaTiO3(BGxFG-BT,x=0,0.05,0.1,0.15,0.2) ceramics were successfully synthesized via the conventional solid-state reaction method.The effects of Gd doping on crystal structure,microstructure,dielectric,ferroelectric and magnetic properties were systematically investigated.X-ray diffraction analysis indicates that Gd doping induce a structural transition from rhombohedral(R3 c) to pseudocubic(P4 mm) in BGxFG-BT ceramics.Scanning electron microscopy results show a decrease of grain size with doping Gd in BFG-BT.The average grain sizes of the ceramics range from 3.2μm to 6.2μm.The dielectric constant and loss tangent are drastically increased and reduced respectively with introducing Gd into the ceramics.Temperature dependent dielectric constant presents a broad peak in the vicinity of Neel temperature(TN) for all the samples,signifying strong magnetoelectric coupling.An increment in TN is also observed as a result of Gd-doping in the temperature regions of 230 to 340℃.The leakage current density is reduced by about two orders of magnitude under the electric field of 20 kV/cm.This can be ascribed to the reduction of the oxygen vacancy concentration,which is confirmed by the X-ray photoelectron spectroscopy result.The ferroelectricity and ferromagnetism are also improved after the addition of Gd seen from the polarization hysteresis(P-E) loops and the magnetization hysteresis(M-H)loops.The greatly enhanced magnetism with Mr=0.0186 emu/g and Ms=1.084 emu/g is obtained in the ceramic with x= 0.2,almost three point six times larger than that of the undoped ceramic.