“…143 The - transition was observed between 50 -59 o C, while the -α transition was observed between 108 -117 o C. These ranges represent phase transition temperature depressions of at least 29 and 13 o C, respectively, compared to those observed in bulk crystals. In the analogous organic-inorganic hybrid system of MAPbBr 3 , Liu and coworkers used temperaturedependent photoluminescence measurements to identify the -α transition for PQDs with an average diameter of 3.7 0.6 nm at 150 K, 144 compared to ~236 K in the bulk. 40 Close agreement was found between the experimental data and the predicted phase transition temperature between the paraelectric α phase and ferroelectric β-phase following Ginzburg-Landau-Devonshire theory.…”
Metal halide perovskites (MHPs) are frontrunners among solution-processable materials for lightweight, large-area and flexible optoelectronics. These materials, with the general chemical formula AMX3, are structurally complex, undergoing multiple polymorph transitions...
“…143 The - transition was observed between 50 -59 o C, while the -α transition was observed between 108 -117 o C. These ranges represent phase transition temperature depressions of at least 29 and 13 o C, respectively, compared to those observed in bulk crystals. In the analogous organic-inorganic hybrid system of MAPbBr 3 , Liu and coworkers used temperaturedependent photoluminescence measurements to identify the -α transition for PQDs with an average diameter of 3.7 0.6 nm at 150 K, 144 compared to ~236 K in the bulk. 40 Close agreement was found between the experimental data and the predicted phase transition temperature between the paraelectric α phase and ferroelectric β-phase following Ginzburg-Landau-Devonshire theory.…”
Metal halide perovskites (MHPs) are frontrunners among solution-processable materials for lightweight, large-area and flexible optoelectronics. These materials, with the general chemical formula AMX3, are structurally complex, undergoing multiple polymorph transitions...
“…10–0319 of jacobsite ferrite with a face-centered cubic structure (space group ). Although bulk samples crystallize in a tetragonal structure, a similar XRD patterns indicating the formation of a cubic structure was observed for FeMn 2 O 4 nanoparticles [ 17 , 18 ], which may be associated with the existence of a size-dependent phase transition in FeMn 2 O 4 nanoparticles [ 30 ]. Fig.…”
Mixed-metal oxide nanoparticles have attracted great scientific interest since they find applications in many fields. However, the synthesis of size-controlled and composition-tuned mixed-metal oxide nanoparticles is a great challenge that complicates their study for practical application. In this study, Co-doped FeMn2O4 nanoparticles were synthesized by the solvothermal method in which the crystallization was carried out under autogenous pressure at temperatures of 190 °C for 24 h. The influence of Co doping on the evolution of the structural and magnetic properties was investigated by various methods. It was found from XRD data that crystallite size decreases from 9.1 to 4.4 nm with the increase in Co content, which is in good agreement with the results of TEM. Based on the results of magnetic measurements, it was found that the saturation magnetization first increases with an increase in the cobalt content and reaches its maximum value at x = 0.4, and a further increase in x leads to a decrease in the saturation magnetization. The influence of cation redistribution on the observed changes has been discussed.
“…It is additionally revealed that the overtones keep stable outline even at room temperature, implying the polaron states have a very robust lifetime, which will benefit not only the experimental observation but also the potential exploitation of polaron properties in perovskite materials. Finally, we must emphasize that these perovskite materials undergo two structure phase transitions with temperature, which has an influence on the strength of the electron-phonon coupling and phonon energy [51][52][53]. These effects are not taken into account in the present paper.…”
The formation of Fröhlich polaron in metal halide perovskites, arising from the charge carrierlongitudinal optical (LO) phonon coupling, has been proposed to explain their exceptional properties, but the effective identification of polaron in these materials is still a challenge task. Herein, we theoretically present the infrared optical absorption of Fröhlich polaron based on Huang-Rhys model. We find that multiphonon overtones are appeared as the energy of incident photon matches the multiple LO phonons, wherein the average phonon numbers of a polaron can be directly evaluated by the order of the strongest overtone. These multiphonon structures sensitively depend on the scale of electronic distribution in the ground state and the dimensionality of the perovskite materials, which gives the enlightenment for the effective modulation of competing processes between the polaron formation and carrier cooling. Moreover, the order of the strongest overtone shifts to the higher ones with temperature, providing a potential proof of the carriers mobility affected by LO phonons scattering. The present model not only suggests a direct way to verify Fröhlich polaron, but also enriches the understanding of the polaron properties in metal halide perovskites.
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