Bulk-wave characterization of high-Tc superconductors. Annual summary report, 1 August-1 November 1988
The objective of this research is to characterize high-Tc superconductors with longitudinal and transverse ultrasonic waves. Both attenuation and velocity measurements were performed on sinter forged samples of YBa/sub 2/Cu/sub 3/O/sub 7/, which has two CuO planes perpendicular to the c-axis per unit cell. Three elastic constants, C11, C33 and C44, out of five , for this axially symmetric sample, with 80% of the c-axis of platelet-like crystallites aligned along the forging axis, have been determined. Three maxima in attenuation are observed at 70, 180, and 250 K when longitudinal waves are propagated perpendicular to the forging axis. Only the middle maximum is observed when either longitudinal or transverse waves propagate parallel to the forging axis or perpendicular to CuO planes. Thus, the middle maximum may be due to an isotropic interaction while the other maxima may be produced by interactions associated with distortions of the CuO planes. Frequency-dependent measurements on sintered samples of YBa/sub 2/Cu/sub 3/O/sub 7/ show that the low temperature maximum is produced by a relaxation mechanism. The activation energy of the relaxation time for this maximum is about 400 k which is near the Debye temperature of this compound. Sound measurements in a sample of Ba0.625K0.375BiO3, which has a Tc=28 k and which is postulated to be a BCS superconductor, show a maximum in attenuation around 50 K.
- Research Organization:
- Wisconsin Univ., Milwaukee (USA). Dept. of Physics
- OSTI ID:
- 6506513
- Report Number(s):
- AD-A-200795/3/XAB
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
ACOUSTIC TESTING
ACTIVATION ENERGY
ALKALINE EARTH METAL COMPOUNDS
ATTENUATION
BARIUM COMPOUNDS
CHALCOGENIDES
COPPER COMPOUNDS
CUPRATES
DOCUMENT TYPES
ENERGY
FABRICATION
FORGING
LOW TEMPERATURE
MATERIALS TESTING
MATERIALS WORKING
NONDESTRUCTIVE TESTING
OXIDES
OXYGEN COMPOUNDS
PROGRESS REPORT
RELAXATION
RELAXATION TIME
SAMPLING
SINTERING
SUPERCONDUCTORS
TESTING
TRANSITION ELEMENT COMPOUNDS
ULTRASONIC TESTING
VELOCITY
WAVE PROPAGATION
YTTRIUM COMPOUNDS