CATIONIC SELF-DIFFUSION IN THE HIGHEST-TEMPERATURE SOLID-PHASES OF AMMONIUM-CHLORIDE AND BROMIDE STUDIED BY H-1-NMR

被引:22
作者
TANSHO, M [1 ]
FURUKAWA, Y [1 ]
NAKAMURA, D [1 ]
IKEDA, R [1 ]
机构
[1] UNIV TSUKUBA,DEPT CHEM,TSUKUBA 305,JAPAN
来源
BERICHTE DER BUNSEN-GESELLSCHAFT-PHYSICAL CHEMISTRY CHEMICAL PHYSICS | 1992年 / 96卷 / 04期
关键词
CRYSTALS; DIFFUSION; PHASE TRANSITIONS; SPECTROSCOPY; NUCLEAR MAGNETIC RESONANCE;
D O I
10.1002/bbpc.19920960407
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Ionic motions in the highest-temperature solid phases (Phase I) of NH4Cl and NH4Br having the NaCl-type cubic structure were investigated by measuring H-1 NMR spin-lattice and spin-spin relaxation times (T1, T1-rho and T2). A long T2 of ca. 1 ms observed at 750 K in Phase I of both salts was attributed to the excitation of the rapid cationic self-diffusion and isotropic rotation suggesting the plastic nature of this phase. The observed relaxation times could be explained well using the monovacancy-diffusion model proposed by Sholl. The activation energy of self-diffusion was determined as 120 kJ mol-1 for both salts, which value is much larger than those observed in ionic-plastic phases with the CsCl-type cubic structure. The diffusion mechanisms of the NH4+ ions in Phase I, and Phase II having the CsCl-type structure, were compared.
引用
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页码:550 / 553
页数:4
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