Structural phase transitions and ferroelastic properties of perovskite-type layered (CH3NH3)2CdCl4

Herein, we perform a structural characterization of (CH3NH3)(2)CdCl4 by H-1 and C-13 magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectrometry, discussing the geometry around CH3NH3 cations. H-1 MAS NMR determined two sets of protons in hydrogen-bonded CH3NH3 groups, exhibiting large T-1 rho (L) and small T-1 rho (S) values corresponding to long and short C-H/N-H bonds, respectively. The spin-lattice relaxation time of Cd-113 in CdCl6 octahedra is shown to exhibit an anomaly near 283K (T-C2) due to the occurrence of a phase transition that is not governed by changes in the motion of CH3NH3 groups but is accompanied by the corresponding changes for Cd in CdCl6 units. The observed domain pattern corresponds to an exchange of a- and c-axes of the orthorhombic structure, with the resulting domain orientations viewed as the main reason for the occurrence of phase transitions, and changes in CdCl6 group motion observed by Cd-113 NMR. Published by AIP Publishing.