|JKMRS Volume 21, No 2, pp 63; Paraelectric-Ferroelectric Phase...|
|2017년 06월 20일 / 조회수: 220|
Paraelectric-Ferroelectric Phase Transition of (NH4)2SO4 Single Crystals by 14N NMR
Ae Ran Lim1,2,*
1Analytical Laboratory of Advanced Ferroelectric Crystals, Jeonju University, Jeonju 55069, Korea
2Department of Science Education, Jeonju University, Jeonju 55069, Korea
Abstract The 14N NMR spectra for (NH4)2SO4 crystals were obtained near the phase transition temperature TC=223 K, and were found to precisely reflect the symmetry change in the crystal at this first-order phase transition. Changes in the resonance frequencies near TC were attributed to the structural phase transition. In the ferroelectric and paraelectric phases, two inequivalent NH4 groups were distinguished in the 14N NMR spectra. The two types, NH4(1) and NH4(2), have slightly different local environments. Consequently, we conclude that the phase transition is caused by the change in the environment of the 14N nuclei in the NH4 groups, rather than by the SO4 groups.