Thermal desorption studies of isotopically-labeled oxygen-induced superconductivity in La sub 2 CuO sub 4+. delta

Conference · Mon Jan 01 00:00:00 EST 1990

OSTI ID:6335387

Shinn, N D; Bartram, M E; Schirber, J E; Overmyer, D L; Rogers, Jr, J W ^[1]; Fisk, Z; Cheong, S W ^[2]

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1. Sandia National Labs., Albuquerque, NM (USA)
2. Los Alamos National Lab., NM (USA)

Isotopically-labeled oxygen enrichment and thermal desorption mass spectroscopy (TDMS) have been combined to study interstitial oxygen desorption from superconducting La{sub 2}CuO{sub 4+{delta}} ({delta} {le} 0.032). Single crystal samples of magnetic insulating La{sub 2}CuO{sub 4.00} were annealed at 860K under 1--3 kbar oxygen pressure for 12--100 hours to yield hole-doped, superconducting La{sub 2}CuO{sub 4+{delta}} samples with 35K < {Tc} < 40K. Whereas no TDMS signals were observed for the insulator, rapid bursts (FWHM < 0.5 sec) of molecular oxygen were observed above 350K while heating the superconductor at less than 1 K sec{sup {minus}1} in high vacuum. A kinetic model is proposed in which the interstitial oxygen diffuses to internal grain boundaries and defects during heating, thereby inducing stress in the lattice as it attempts to revert to the LaCuO{sub 4.00} crystal structure. This stress is relieved by lattice fracture at grain boundaries during the TDMS experiment, releasing the trapped oxygen from the sample as micro-cracks are formed. In addition, the facile oxygen exchange between interstitial and lattice oxygen sites has been discovered by TDMS and weight gain measurements from isotopically-enriched crystals, supporting the structural model of Chaillout, et al. in which the interstitial oxygen atom dimerizes with a lattice oxygen ion.

• Research Organization: Sandia National Labs., Albuquerque, NM (USA)
• Sponsoring Organization: DOE/DP
• DOE Contract Number: AC04-76DP00789
• OSTI ID: 6335387
• Report Number(s): SAND-90-1875C; CONF-901105-36; ON: DE91004898
• Resource Relation: Conference: Fall meeting of the Materials Research Society, Boston, MA (USA), 24 Nov - 1 Dec 1990
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
HIGH-TC SUPERCONDUCTORS
DESORPTION
COPPER OXIDES
CRYSTAL STRUCTURE
LANTHANUM COMPOUNDS
MASS SPECTROSCOPY
OXYGEN
CHALCOGENIDES
COPPER COMPOUNDS
ELEMENTS
NONMETALS
OXIDES
OXYGEN COMPOUNDS
RARE EARTH COMPOUNDS
SPECTROSCOPY
SUPERCONDUCTORS
TRANSITION ELEMENT COMPOUNDS
360204* - Ceramics
Cermets
&amp; Refractories- Physical Properties
400201 - Chemical &amp; Physicochemical Properties