Study on structural geometry and dynamic property of [NH 3 (CH 2 ) 5 NH 3 ]CdCl 4 crystal at phases I, II, and III.

Organic-inorganic hybrid perovskites can potentially be used in electrochemical devices, such as batteries and fuel cells. In this study, the structure and phase transition temperatures of the organic-inorganic material [NH ₃ (CH ₂ ) ₅ NH ₃ ]CdCl ₄ crystal were confirmed by X-ray diffraction and differential scanning calorimetry. From the nuclear magnetic resonance results, the crystallographic configurations of ¹ H, ¹³ C, and ¹⁴ N in the cation changed at temperatures close to T _C1 (336 K), whereas that of ¹¹³ Cd in the anion shows significant changes at temperatures close to T _C1 and T _C2 (417 K). The activation energy, E _a , values for ¹ H and ¹³ C obtained from the spin-lattice relaxation time, T _1ρ , below and above T _C1 were evaluated, where the E _a value for ¹³ C was more flexible at low temperatures than at high temperatures. In addition, the effect on molecular motion was effective at high temperatures. The phase transition at 336 K was associated with the change in the N-H···Cl bond due to the change in the coordination geometry of Cl around Cd in the CdCl ₆ anion. On the other hand, the phase transition at 417 K was related to the ferroelastic phase transition attributed to the twin domains.
(© 2022. The Author(s).)