Nd含量对Bi_(6-x)Nd_xFe_(1.4)Ni_(0.6)Ti_3O_(18)多晶材料多铁性的影响

Effects of Nd-doping on multiferroic properties of Bi_(6-x)Nd_xFe_(1.4)Ni_(0.6)Ti_3O_(18) polycrystalline

采用柠檬酸-硝酸盐法制备了Bi_(6-x)Nd_xFe_(1.4)Ni_(0.6)Ti_3O_(18)(BNFNT-x,x=0.00,0.10,0.20,0.25和0.30)前驱液,再经过干燥、烧结过程制备了单相多晶材料.研究发现,少量Nd掺杂有助于提高样品的铁电性能,BNFNT-0.25样品的铁电性能(2Pr)最大,约达到19.7μC/cm^2.室温下BNFNT-0.20样品磁性能(2Ms)最大约达到4.132 emu/g(1 emu/g=10–3 A·m^2/g).变温介电损耗结果表明Nd掺杂降低了Fe^(3+)和Fe^(2+)间的电子转移或跃迁的激活能.X射线光电子能谱结果表明小量Nd掺杂有助于增强Bi离子稳定性,对改善样品的铁电性能有积极意义.

Single phase polycrystalline Nd-modified BNFNT-x series samples are obtained from the precursors of the same chemical formula,and prepared by using the citric acid-nitrate method.The X-ray photoelectron spectroscopy measurement indicates that a slight Nd modification does not exert significant influence on the stability of the octahedral FeO6,nor NiO6 nor TiO6.When the molar concentration of Nd exceeds 0.25,the stability of BiO layer is cemented and conducive to the insulating role of BiO layer.It is seen that a small quantity of Nd substitution for bismuth can improve the ferroelectric polarization(2 Pr)of^19.7μC/cm2.The room-temperature magnetization(2 Ms)can reach a maximal value of^4.132 emu/g(1 emu/g=10-3 A·m2/g)in the BNFNT-0.20 sample.Two anomalies are observed in the temperature-dependent dielectric loss spectrum:one is situated in the temperature range from 200 K to 400 K and the other is located in the vicinity of 900 K.It is considered that the loss anomaly found near 900 K might be associated with the viscous motion of ferroelectric domain walls.In addition,the loss peak shown in a temperature range from 200 K to 400 K shifts toward the higher temperature with measuring frequency increasing,indicating the characteristics of dielectric relaxor behavior.The activation energy is evaluated to be 0.287-0.366 eV,which suggests that the relaxor is associated with the electrons transfer and hop between Fe3+and Fe2+.The room-temperature magnetization(2 Ms)has reached a maximal value of^4.132 emu/g in the BNFNT-0.20 sample.The lattice distortion due to the introduction of Nd changes the angle of such antiferromagnetic coupling bonds as Fe8+—O—Fe8+,Fe8+—O—Ni8+and Ni8+—O—Ni8+,which leads the AFM spin states to break,and thus increases the magnetic properties.While with further modification of Nd,the drastic lattice distortion reduces the occupation of the Bsites of the magnetic ions,which might be responsible for further deteriorating the magnetic properties.