Abstract Different rare-earth (Ho, Gd, Sm, Pr, and La)-doped nickel ferrites were prepared through the sol-gel citrate auto-combustion method. Rietveld refinement of the X-ray diffraction patterns confirmed the formation of an orthorhombic impurity phase for each doped sample. Structural parameters, including lattice parameter, crystallite size, microstrain, and different bond lengths, were calculated. Field emission scanning electron micrographs showed spherical grains and the existence of secondary phases for the doped samples. Elemental analysis of each component were performed using energy dispersive X-ray spectra. The shifting of the absorption bands of the Fourier transform infrared spectra depicted the rare earth-to-Fe substitution in octahedral sites of nickel ferrites. The optical band gap decreased with the smaller ionic radii of dopants. The study of ac and dc conductivity provided information about the conduction and dielectric relaxation mechanism and the effect of impurity phases. The electrical conductivity and dielectric study suggested that La- and Sm-doped samples showed the highest resistivity with high losses, whereas Ho- and Gd-doped samples showed moderate resistivity with minimum losses.

中文翻译：

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一些稀土掺杂的镍铁氧体的结构、光学和电传输特性：掺杂剂离子半径影响的研究

摘要 采用溶胶-凝胶柠檬酸盐自燃法制备了不同稀土（Ho、Gd、Sm、Pr、La）掺杂的镍铁氧体。X 射线衍射图的 Rietveld 细化证实了每个掺杂样品的正交杂质相的形成。计算了结构参数，包括晶格参数、微晶尺寸、微应变和不同的键长。场发射扫描电子显微照片显示了掺杂样品的球形晶粒和二次相的存在。使用能量色散 X 射线光谱对每个组分进行元素分析。傅里叶变换红外光谱吸收带的移动描述了镍铁氧体八面体位点中稀土对铁的取代。光学带隙随着掺杂剂离子半径的减小而减小。交流和直流电导率的研究提供了有关导电和介电弛豫机制以及杂质相影响的信息。电导率和介电研究表明，La 和 Sm 掺杂的样品显示出最高的电阻率和高损耗，而 Ho 和 Gd 掺杂的样品显示出中等电阻率和最小的损耗。