1H Nuclear Magnetic Resonance study of Ferroelectric (NH4)3H(SO4)2
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초록
1H nuclear magnetic resonance (NMR) experiments have been performed at 30 - 300 K and 7 T to investigate dynamics of hydrogen bond network in the single crystal (NH4)3H(SO4)2. The two proton sites, ammonium proton and hydrogen-bond proton, are identified from the 1H NMR MAS spectrum at 340 K. As temperature decreases, the 1H NMR spectrum shifts to the higher frequency side with a larger linewidth. The spectrum at 65 K shows a distinctive change in line shape toward the ferroelectric transition at 63 K. The measured values of T1 for ammonium and hydrogen-bond protons are similar in the whole range of temperature. T1 of 1H NMR shows a gradual decrease down to 120 K and starts to steeply increase below 100 K. Then T1 shows abrupt decrease below 70 K with a sharp minimum at 63 K, where the ferroelectric transition occurs. This temperature dependence of spectrum and T1 clearly prove that the large change in the dynamics of hydrogen bond network is associated with the ferroelectric phase transition at 63 K.
Abstract
1H nuclear magnetic resonance (NMR) experiments have been performed at 30 - 300 K and 7 T to investigate dynamics of hydrogen bond network in the single crystal (NH4)3H(SO4)2. The two proton sites, ammonium proton and hydrogen-bond proton, are identified from the 1H NMR MAS spectrum at 340 K. As temperature decreases, the 1H NMR spectrum shifts to the higher frequency side with a larger linewidth. The spectrum at 65 K shows a distinctive change in line shape toward the ferroelectric transition at 63 K. The measured values of T1 for ammonium and hydrogen-bond protons are similar in the whole range of temperature. T1 of 1H NMR shows a gradual decrease down to 120 K and starts to steeply increase below 100 K. Then T1 shows abrupt decrease below 70 K with a sharp minimum at 63 K, where the ferroelectric transition occurs. This temperature dependence of spectrum and T1 clearly prove that the large change in the dynamics of hydrogen bond network is associated with the ferroelectric phase transition at 63 K.
참고문헌 (18)
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