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Abstract
| In recent years, the synthesis of all-inorganic halide perovskite Cs(Pb, Sn)X$_{3}$ (X = Cl, Br, and I) quantum dots (QDs) and the study of their physical properties have been of great interest due to their high potential as photoactive materials in optoelectronic technologies. Indeed, this family of semiconductors exhibits an ultralow thermal conductivity and a larger Seebeck coefficient with high carrier mobility. Furthermore, perovskite lead zirconate PbZrO$_{3}$ is of great attention due to the ferroelectric state transition and exhibits high charge storage for future large-energy storage capacitors. An interesting fact about halide perovskite systems is that they exhibit structural phase transitions as a function of temperature (orthorhombic - tetragonal – cubic), which notably affect their optical, thermal, and electrical properties. Furthermore, similar dynamical order-disorder structural transitions have been proposed to occur for both of the halide perovskites, Cs(Pb/Sn)X$_{3}$ and the lead zirconate PbZrO$_{3}$ system. However, such structural phase transitions and their crystalline structure are widely debated in the literature. In this project, we will focus on studying the microscopic structural properties of these two families of Pb-based perovskites, namely for the PbZrO$_{3}$ and Cs(Pb, Sn)X$_{3}$ materials via perturbed angular correlation (PAC) spectroscopy technique. Here, hyperfine interactions between probe nuclei at specific sites in the crystalline structure of the compound and their local environment provide information at the sub-nano (atomic) scale on charge distributions in the probe neighborhood through measurements of the electric field gradient. To analyze the time scale of the possible dynamical hyperfine interactions, a suitable model will be implemented on the $\textit{PACme}$ software, that allows the fitting of experimental data considering stochastic hyperfine interactions. In this perspective, the evolution of the experimental perturbation functions will be analyzed in terms of the increase in the rates of reorientation of the EFG tensor at the probe site, as according to the proposed dynamic order-disorder structural transition model, the tilt and rotation modes of the octahedra units can rapidly fluctuate between distinct orientations. |