Studies of layered uranium(VI) compounds. IV. Proton conductivity in single-crystal hydrogen uranyl phosphate tetrahydrate (HUP) and in polycrystalline hydrogen uranyl arsenate tetrahydrate (HUAs)
Single-crystal measurements on hydrogen uranyl phosphate tetrahydrate, HUO/sub 2/PO/sub 4/.4H/sub 2/O (HUP), have confirmed that the high proton conductivity is a bulk characteristic. The conductivity values were in substantial agreement with those previously reported for polycrystalline disks. A conductivity of 0.6 ohm/sup -1/ m/sup -1/ at 290/sup 0/K and an activation energy of 30 +- 1 kJ mole/sup -1/ were measured parallel to the structural layers of the crystal. The conductivity was at least 100 times lower when measured in the perpendicular direction. A reasonable attempt frequency ..omega../sub 0/ of approximately 10/sup 15/ Hz could be derived from the parallel conductivity on the assumption that the charge carrier concentration was equal to that of the H/sub 3/O/sup +/ ions. This implies a low proton mobility, of the order of 10/sup -9/ m/sup 2/ V/sup -1/ sec/sup -1/ at 290/sup 0/K, in support of previous estimates. We have also shown that polycrystalline hydrogen uranyl arsenate tetrahydrate, HUO/sub 2/AsO/sub 4/.4H/sub 2/O (HUAs), has a high conductivity of 0.6 ohm/sup -1/ cm/sup -1/ at 310/sup 0/K, with an activation energy of 31 +- 2 kJ mole/sup -1/. Below the respective dielectric ordering transition temperatures of HUP and HUAs of 274 and 301/sup 0/K, the lower conductivity values show a marked frequency dependence, which may be due to dispersion effects caused by water reorientations.
- Research Organization:
- Univ. of Leeds, England
- OSTI ID:
- 6873023
- Journal Information:
- J. Solid State Chem.; (United States), Vol. 34:2
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ARSENATES
ELECTRIC CONDUCTIVITY
URANYL COMPOUNDS
URANYL PHOSPHATES
ACTIVATION ENERGY
CATIONS
DISPERSIONS
HYDRATES
HYDROGEN
HYDROGEN COMPOUNDS
LAYERS
MEDIUM TEMPERATURE
OXONIUM IONS
POLYCRYSTALS
TRANSITION TEMPERATURE
WATER
ACTINIDE COMPOUNDS
ARSENIC COMPOUNDS
CHARGED PARTICLES
CRYSTALS
ELECTRICAL PROPERTIES
ELEMENTS
ENERGY
IONS
MOLECULAR IONS
NONMETALS
OXYGEN COMPOUNDS
PHOSPHATES
PHOSPHORUS COMPOUNDS
PHYSICAL PROPERTIES
THERMODYNAMIC PROPERTIES
URANIUM COMPOUNDS
400702* - Radiochemistry & Nuclear Chemistry- Properties of Radioactive Materials