Khomchenko V A, Paixão J A
CFisUC, Department of Physics, University of Coimbra, P-3004-516 Coimbra, Portugal.
J Phys Condens Matter. 2016 Apr 27;28(16):166004. doi: 10.1088/0953-8984/28/16/166004. Epub 2016 Mar 24.
The investigation focuses on the crystal structure, microstructure, local ferroelectric and magnetic properties of the Bi0.9Sr0.1Fe1-x Ti(x)O(3-δ) (x = 0.05, 0.1, 0.15; δ = (0.1 - x)/2) multiferroics prepared by a solid-state reaction method. All the samples have been found to be isostructural with the pure BiFeO3 (the material crystallizes in a polar rhombohedral structure belonging to the space group R3c). It has been shown that the pattern of changes in the lattice parameters of the Bi0.9Sr0.1Fe(1-x)Ti(x)O(3-δ) samples can be interpreted as consistent with the doping-driven elimination of anion vacancies at x ⩽ 0.1 and the formation of cation vacancies at x > 0.1. The readjustment of the defect structure associated with the mechanism of charge compensation in the aliovalent-substituted BiFeO3 is accompanied by correlated changes in the morphology, ferroelectric/ferroelastic domain structure and magnetic properties of the materials. In particular, it has been found that the deviation from the ideal (δ = 0) cation-anion stoichiometry in the Bi0.9Sr0.1Fe(1-x)Ti (x)O(3-δ) system leads to a significant decrease in the average size of crystal grain and ferroelectric domains and gives rise to an antiferromagnetic-weak ferromagnetic transformation. Results of this study have been compared with those obtained for equally substituted samples of the Bi0.9Ca0.1Fe(1-x)Ti(x)O(3-δ) series (Khomchenko and Paixão 2015 J. Phys.: Condens. Matter 27 436002) to demonstrate how the variation in the chemical pressure introduced by the partial replacement of Bi(3+) with bigger (Sr(2+)) and smaller (Ca(2+)) ions can affect the multiferroic behavior of Ti-doped bismuth ferrites.
该研究聚焦于通过固态反应法制备的Bi0.9Sr0.1Fe1-xTi(x)O(3-δ)（x = 0.05、0.1、0.15；δ = (0.1 - x)/2）多铁性材料的晶体结构、微观结构、局部铁电和磁性。已发现所有样品与纯BiFeO3同构（该材料结晶为属于空间群R3c的极性菱面体结构）。结果表明，Bi0.9Sr0.1Fe(1-x)Ti(x)O(3-δ)样品晶格参数的变化模式可解释为：在x ≤ 0.1时，掺杂驱动阴离子空位消除；在x > 0.1时，形成阳离子空位。与异价取代BiFeO3中电荷补偿机制相关的缺陷结构调整，伴随着材料形态、铁电/铁弹性畴结构和磁性的相关变化。特别地，已发现Bi0.9Sr0.1Fe(1-x)Ti (x)O(3-δ)体系中偏离理想（δ = 0）的阳离子-阴离子化学计量比会导致晶粒和铁电畴平均尺寸显著减小，并引发反铁磁-弱铁磁转变。本研究结果已与Bi0.9Ca0.1Fe(1-x)Ti(x)O(3-δ)系列等取代样品的结果进行比较（Khomchenko和Paixão，2015年，《物理学报：凝聚态物质》27卷，436002），以证明用较大（Sr(2+)）和较小（Ca(2+)）离子部分替代Bi(3+)所引入的化学压力变化如何影响Ti掺杂铋铁氧体的多铁性行为。
