Microscopic view of disorder in the ordered phase of superionic RbAg/sub 4/I/sub 5/
Moessbauer spectroscopy in /sup 129/I was employed to verify the existence and investigate the properties of local disorder in the ''ordered'' state of the superionic conductor RbAg/sub 4/I/sub 5/. Studies were conducted in the temperature range of 4--180 K covering the low-temperature ..gamma.. phase (T<122 K) and part of the high-conductivity, disordered ..beta.. phase. The absorption spectra at all temperatures were analyzed with two iodine sites, characterized by their quadrupole splitting and isomer-shift values and a third site with a nonsplit single line. It was found that the electric field gradient (efg) at the /sup 129/I nucleus, produced by the neighboring Ag ions, has a continuous linear temperature dependence down to 4.2 K. The hyperfine constants and the Debye-Waller factor showed no discontinuity at T/sub c/. The anomalous existence of the single line has been attributed to a fast fluctuating efg due to local hopping of the Ag ions. This dynamic disorder is present even at low temperatures where (8--10)% of Ag ions are locally hopping, and its occurrence increases drastically at T>T/sub c/. A nonharmonic Debye-Waller factor was observed from which a linear temperature-dependent Debye temperature could be derived.
- Research Organization:
- Department of Physics and Astronomy, Tel Aviv University, Ramat Aviv, 69978 Tel Aviv, Israel
- OSTI ID:
- 5696565
- Journal Information:
- Phys. Rev. B: Condens. Matter; (United States), Vol. 28:1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
IODINE 129
MOESSBAUER EFFECT
RUBIDIUM IODIDES
ORDER-DISORDER TRANSFORMATIONS
SILVER IODIDES
DEBYE TEMPERATURE
DEBYE-WALLER FACTOR
IONIC CONDUCTIVITY
IONIC CRYSTALS
ORDER PARAMETERS
SPECTROSCOPY
VERY LOW TEMPERATURE
ALKALI METAL COMPOUNDS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CRYSTALS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
HALIDES
HALOGEN COMPOUNDS
INTERMEDIATE MASS NUCLEI
INTERNAL CONVERSION RADIOISOTOPES
IODIDES
IODINE COMPOUNDS
IODINE ISOTOPES
ISOTOPES
NUCLEI
ODD-EVEN NUCLEI
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
RADIOISOTOPES
RUBIDIUM COMPOUNDS
SILVER COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
YEARS LIVING RADIOISOTOPES
360104* - Metals & Alloys- Physical Properties