The effects of rapid heating and cooling on the composition, structure, and superconducting properties of Bi-Sr-Ca-Cu-O compounds

Miscellaneous · Fri Jan 01 00:00:00 EST 1993

OSTI ID:6916371

Duan, Q

Bulk and thin film samples of Bi[sub 2[minus]x]Pb[sub x]Sr[sub 2]Ca[sub 2]O[sub y] compounds were prepared and exposed to argon gas at temperatures of about 2000[degrees]C and pressures of about 300 atm. in a ballistic compressor (BC) and then cooled at a rate of about 10[sup 5][degrees]C/sec. The samples before and after this treatment were examined and compared using a transmission electron microscope (TEM), a scanning electron microscope (SEM), an energy dispersive spectrometer (EDS), and an x-ray diffractometer (XRD). Resistance and magnetic susceptibility measurements were made to determine changes in superconducting temperature T[sub c]. Resistance and AC susceptibility measurements of bulk and thin film samples demonstrated that the T[sub c] increased after the BC treatment, and step-shaped curves were often observed in the resistance versus temperature graphs. The x-ray diffraction study revealed that the relative intensities of lines of the two high T[sub c] phases clearly increased, and the relative intensities of lines of the low T[sub c] phase decreased after the BC treatment. Scanning electron micrographs of the exposed samples showed that surface melting had occurred, and the BC treatment affected the surface of samples to a depth of about 10 [mu]m. Energy dispersive spectral analysis showed that oxygen loss occurred in the exposure process. Transmission electron diffraction patterns showed that the crystal structure of the Bi-based compounds have an incommensurate modulation along the b-axis with different periods of 25.4 [angstrom], 38.7 [angstrom], and 72.6 [angstrom]. After the BC treatment, the lattice parameters of superconductors did not change, but the relative intensities of spots changed, the modulation of 72.6 [angstrom] disappeared, and the density of twist boundaries increased. These studies tentatively indicate that the increase in structural defects was caused by oxygen loss.

• Research Organization: Portland State Univ., OR (United States)
• OSTI ID: 6916371
• Resource Relation: Other Information: Thesis (Ph.D.)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CUPRATES
HEAT TREATMENTS
PHASE STUDIES
SUPERCONDUCTIVITY
HIGH-TC SUPERCONDUCTORS
BISMUTH OXIDES
CALCIUM OXIDES
COOLING
CRYSTAL DEFECTS
ELECTRIC CONDUCTIVITY
HEATING
INTERMETALLIC COMPOUNDS
STRONTIUM OXIDES
SUPERCONDUCTING FILMS
TRANSITION TEMPERATURE
ALKALINE EARTH METAL COMPOUNDS
ALLOYS
BISMUTH COMPOUNDS
CALCIUM COMPOUNDS
CHALCOGENIDES
COPPER COMPOUNDS
CRYSTAL STRUCTURE
ELECTRICAL PROPERTIES
FILMS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
STRONTIUM COMPOUNDS
SUPERCONDUCTORS
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
360207* - Ceramics
Cermets
& Refractories- Superconducting Properties- (1992-)
665411 - Basic Superconductivity Studies- (1992-)
360202 - Ceramics
Cermets
& Refractories- Structure & Phase Studies