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

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.

Effects of Nd-doping on multiferroic properties of Bi6-xNdxFe1.4Ni0.6Ti3O18 polycrystalline

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 (2P_r) of~19.7 μC/cm. The room-temperature magnetization (2M_s) 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 (2M_s) 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 Fe³⁺-O-Fe³⁺, Fe³⁺-O-Ni³⁺ and Ni³⁺-O-Ni³⁺, 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 B-sites of the magnetic ions, which might be responsible for further deteriorating the magnetic properties.