China
Africa
Explore chapters and articles related to this topic
A Theoretical Description of Piezoelectricity
Published in Kenji Uchino, Micro Mechatronics, 2019
Let us take as an example a barium titanate (BaTiO3) single crystal, which has a tetragonal symmetry at room temperature. X-ray diffraction of the crystal reveals a slight elongation along the [001] direction of the perovskite unit cell with c/a = 1.01. Therefore, if an electric field is applied on an a plane single crystal (electrode on the top and bottom of the BT plane), a 90° domain reorientation from an a to a c domain is induced, resulting in a strain of 1% in the field direction. However, the situation is much more complicated in the case of a polycrystalline specimen. Uchida and Ikeda treated this problem statistically, assuming the grains (or small crystallites) are randomly oriented.23,24
Iodine doping of CsPbBr3: toward highly stable and clean perovskite single crystals for optoelectronic applications
Published in Philosophical Magazine, 2023
P. Sujith, Saidi Reddy Parne, Padmanabhan Predeep
DSC thermograms of CsPbBr2.4I0.6 single crystals show excellent phase stability than CsPbBr3 single crystals (Figure 10). When CsPbBr3 is heated from room temperature to higher temperatures, two-phase transitions are common- the transition from orthorhombic to tetragonal crystal phase happens at 88°C, while the transition from tetragonal to cubic crystal phase that occurs near 131°C [36]. Generally, phase transition temperature increases with increasing iodine concentration in bromine-rich lead halide perovskites [37]. Here a strong increase in phase transition temperature is visible for both phase transitions- from orthorhombic to tetragonal and tetragonal to cubic. In this study, the phase transformation of CsPbBr2.4I0.6 single crystals takes place nearly at 127 and 250°C, which means that the incorporation of iodine into the CsPbBr3 perovskite material improves its characteristics properties with phase stability at ambient conditions. The orthorhombic phase CsPbBr2.4I0.6 single crystal can withstand high temperatures than the orthorhombic CsPbBr3 perovskite. Thus the incorporation of iodine in the orthorhombic CsPbBr3 perovskite crystal structure leads to extended sustainability of the perovskite material against high-temperature conditions and stabilises the orthorhombic phase of the compound up to higher temperatures.