Molecular motions and phase changes in the perovskite-type compound (C10h21nh3)2zncl4

Authors:

• J. Fenrych,
• E.C. Reynhardt,
• Stefan Jurga,
• Kazimierz Jurga

Abstract

A virgin sample of polycrystalline (C₁₀H₂₁NH₃)₂ZNCl₄ shows two phase transitions, at 284 K and 363 K. In the low-temperature phase threefold reorientations of methyl and NH₃ groups dominate the nuclear magnetic resonance relaxation results. The motion of the NH₃ groups can be described as a threefold jump among three potential minima of which one is shallower than the other two. In the intermediate temperature phase a defect motion of chain ends has been identified. In the high-temperature phase the spacing between adjacent layers of ZnCl₄ tetrahedra is increased by ~ 16% due to the non-intercalation of the chains. In this phase the chains experience a high degree of mobility, which is partly due to the diffusion of chain defects along the chain. On cooling the sample from the high-temperature phase, it transforms to the intermediate phase, but the transition to the low-temperature phase is absent. © 1993 Taylor & Francis Group, LLC.