This study focuses on the effects of substitution of Bi³⁺ ions in bismuth ferrite (BiFeO₃) nanocrystals by dysprosium (Dy³⁺) ions with special emphasis on the role of defects on its physical properties. X-ray diffraction studies showed a structural transformation from the distorted rhombohedra (R3c) to stable orthorhombic (Pnma) phase at Dy³⁺ concentration x = 0.15–0.20, although no strain was involved as the ionic radii of Dy³⁺ (0.92 Å) is smaller than that of Bi³⁺ (1.17 Å). The crystallite sizes, unit cell volume and the band gap energies reduced with increase in x whereas the dielectric constant drastically increased at x = 0.2. A strong magneto electric coupling is also observed. Positron lifetime and coincidence Doppler broadening studies gave clear indications of the transformation at x = 0.2 and further indicated that vacancy type defects can be used as tools to identify the structural property changes during cationic substitution.

这项研究的重点是（Dy ³⁺）离子取代铋铁氧体（BiFeO ₃）纳米晶体中Bi ³⁺离子的影响，特别着重于缺陷对其物理性质的作用。X射线衍射研究显示从失真菱面体（结构变换R3C），以稳定的斜方晶（晶Pnma）相在的Dy ³⁺浓度X  = 0.15-0.20，虽然没有应变参与的Dy的离子半径³⁺（0.92埃）比Bi ³⁺（1.17Å）小。随着x的增加，微晶尺寸，晶胞体积和带隙能量减小而介电常数在x  = 0.2时急剧增加。还观察到强磁电耦合。正电子寿命和巧合多普勒展宽研究清楚地表明了x  = 0.2时的转变，并且进一步表明空位类型缺陷可以用作识别阳离子取代过程中结构性质变化的工具。