Proton, Deuterium, and Sodium-23 Magnetic Resonance of Ferroelectric Lecontite NaNH4SO4·2H2O
- 1 April 1969
- journal article
- research article
- Published by AIP Publishing in The Journal of Chemical Physics
- Vol. 50 (7), 2842-2850
- https://doi.org/10.1063/1.1671474
Abstract
Proton, deuterium, and sodium‐23 nuclear magnetic resonances of deuterated and ordinary lecontite have been studied from 77° to 300°K and particularly in the vicinity of the ferroelectric phase transitions at 92° and 101°K. Proton–proton vector directions were determined for the two kinds of water molecules in the unit cell and are observed not to alter as the phase transitions are traversed. Above 230°K the deuterium magnetic resonance of one type of water molecule is observed in the 180° flip state of motion. Below 101°K axial and equatorial deuterons of ND4+ groups rotating about the threefold axis are observed with no detectable change at the transition temperatures. At 300°K one kind of 23Na site is observed; below 101°K, 23Na satellite line splitting occurs indicating that there are two kinds of 23Na site in the unit cell. This splitting is attributed to an abrupt lattice distortion which occurs as the crystal is cooled below 101°K. Proton spin–lattice relaxation time data show two minima, one at 170°K and one at 120°K, which are, respectively, assigned to rotation about the twofold and threefold axes of the NH4+ tetrahedron. Rotating frame relaxation times show minima at 80°, 110°, and 210°K, respectively, due to the threefold and twofold axis rotations of the NH4+ ion and a 180°, flip motion of one kind of H2O molecule. Near 101°K the activation energy for the threefold axis rotation of the NH4+ ion changes from 2.0 to 3.1 kcal mole−1. It is proposed on the basis of the magnetic resonance data that the transition at 101°K in lecontite is of the displacive type with a relatively large lattice distortion.Keywords
This publication has 12 references indexed in Scilit:
- Nuclear Magnetic Resonance and Nonexponential Spin-Lattice Relaxation in Ferroelectric Ammonium FluoroberyllatePhysical Review B, 1967
- Magnetic Resonance Studies of Ferroelectric Methylammonium AlumPhysical Review B, 1967
- The crystal structure of lecontite, NaNH4SO4.2H2OActa Crystallographica, 1967
- NMR Study of Ferroelectric NaNH4SO4·2H2OJournal of the Physics Society Japan, 1967
- Deuteron Magnetic Resonance and Proton Relaxation Times in Ferroelectric Ammonium SulfateThe Journal of Chemical Physics, 1967
- Thermal-Energy Ion—Neutral Reaction Rates. VI. Some Ar+ Charge-Transfer ReactionsThe Journal of Chemical Physics, 1966
- Nuclear Magnetic Resonance Study of the Structure of Ferroelectric NaNH4SO4·2H2OThe Journal of Chemical Physics, 1966
- Deuteron Magnetic Resonance of Ferroelectric Potassium Ferrocyanide TrihydrateThe Journal of Chemical Physics, 1965
- Dielectric Properties of a New Ferroelectric, NaNH4SO4·2H2O, near Its Curie TemperatureJournal of the Physics Society Japan, 1965
- Electric Quadrupole Interactions of Deuterons and Molecular Motion in Li2SO4·D2OThe Journal of Chemical Physics, 1957