科研之友
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摘要
We study the dynamics of inorganic antiferroelectric nanoclusters formed during an order-disorder transition and demonstrate the coexistence of the two phases in a region of 2-3 K around the transition temperature T-N similar to 215 K. Single crystals of NH4H2AsO4, a model hydrogen-bonded compound, show an antiferroelectric-paraelectric transition studied by means of highly sensitive magic angle spinning N-15 NMR at 21.1 T. The phase coexistence is demonstrated by a double-peak structure of the chemical shift. Two-dimensional chemical exchange spectroscopy and spin-lattice relaxation time (T-1) measurements show that the clusters are dynamic with sizes similar to 50 nm and lifetimes approaching seconds as T -> T-N. Their occupancy increases rapidly to fill the crystal volume below T-N. This study provides evidence for the commonality of the phase transitions in systems with electric properties and provides an improved spectroscopic method for such studies.
- 出版日期2015-4-17
