Issaoui H, Benali A, Issaoui F, Dhahri E, Costa B F O, Graca M P F, Valente M A, Bouazizi Mohamed Lamjed
University of Coimbra, CFisUC, Physics Department P-3004-516 Coimbra Portugal.
Laboratoire de Physique Appliquée, Faculté des Sciences, Université de Sfax B.P. 1171 3000 Sfax Tunisia.
RSC Adv. 2021 Oct 7;11(52):33070-33080. doi: 10.1039/d1ra04041c. eCollection 2021 Oct 4.
This work involves the synthesis and study of physical properties of the LaCaPbFeMgO compound, which has been characterized by various experimental techniques, such as X-ray diffraction, SEM and complex impedance spectroscopy. The structural study showed that the LaCaPbFeMgO compound crystallized in the orthorhombic structure with the space group. The particle size and the surface morphology of this compound have been analysed using SEM. The particle size was found to be around 120 nm and we confirmed that one particle contains more than one crystallite. Importantly, the studied compound presented a giant dielectric permittivity (' of around 9 × 10 at high temperature and low frequencies). An equivalent electric circuit has been deduced from the Nyquist plots of the complex impedance parts ('' ') to correctly describe the electrical behavior of the LaCaPbFeMgO compound. The chosen circuit consists of two cells mounted in series corresponding to the grain and grain boundary contributions. The electrode contribution has been detected from the frequency dependence of the imaginary part of modulus where the activation energy of each constitution has been calculated. The relaxation process and the electrical conductivity are attributed to the same type of charge carriers characterized by similar values of the activation energy determined from loss factor tangent (tg()), the imaginary part of the permittivity and the modulus spectrum.
这项工作涉及LaCaPbFeMgO化合物的合成及其物理性质的研究，该化合物已通过多种实验技术进行了表征，如X射线衍射、扫描电子显微镜（SEM）和复阻抗谱。结构研究表明，LaCaPbFeMgO化合物结晶为具有特定空间群的正交结构。使用扫描电子显微镜分析了该化合物的粒径和表面形态。发现粒径约为120纳米，并且我们证实一个颗粒包含不止一个微晶。重要的是，所研究的化合物在高温和低频下呈现出约9×10的巨介电常数。从复阻抗部分（'' '）的奈奎斯特图推导出一个等效电路，以正确描述LaCaPbFeMgO化合物的电学行为。所选择的电路由两个串联的单元组成，分别对应于晶粒和晶界的贡献。从模量虚部的频率依赖性检测到电极贡献，其中计算了每种结构的活化能。弛豫过程和电导率归因于同一类型的电荷载流子，其特征在于由损耗因子正切（tg()）、介电常数虚部和模量谱确定的相似活化能值。
