Structures, phase transitions, thermodynamic properties, and structural dynamics of eco-friendly hybrid perovskite NH3(CH2)3NH3CoCl4 and NH3(CH2)5NH3CoCl4 crystals

Abstract

The present study investigates the structures, phase transition temperatures, thermodynamic properties, and structural dynamics of the organic–inorganic perovskite NH3(CH2)nNH3CoCl4 (n = 3 and 5) crystals according to the number of carbon atoms. The structure and lattice constants were confirmed by single-crystal X-ray diffraction (XRD) at 298 K. From differential scanning calorimetry and XRD powder patterns, the phase transition temperature TC obtained at 483 K for n = 3 was isostructural without changing the crystal structure, whereas the TC for n = 5 was obtained at 494 K with change in the crystal structure. The thermodynamic properties of the two crystals studied by thermogravimetric analysis exhibited relatively high thermal stability at 600 K. From the spin-lattice relaxation times (T1ρ) according to the temperature change for n = 3 and 5, it was determined that the energy transfer, demonstrating a small thermal displacement around the 1H and 13C atoms of the cation, was minuscule. The effects of T1ρ for 1H and 13C were insignificant, indicating a minor change in the N–H⋯Cl hydrogen bond related to the coordination geometry of the CoCl4 anion. Thus, the obtained results for NH3(CH2)nNH3CoCl4 (n = 3 and 5) can be helpful for future research on the application of eco-friendly organic–inorganic hybrid perovskite materials.