The effects of oxygen and strontium vacancies on the superconductivity of single crystals of Bi sub 2 Sr sub 2-x CuO sub 6-y

Conference · Sun Jan 01 04:00:00 EST 1989

OSTI ID:5178144

Sales, B C; Sonder, E; Chakoumakos, B C

Single crystals of Bi{sub 2}Sr{sub 2-x}CuO{sub 6-y} were grown from CuO-rich melts. The Sr content in the crystals was varied from x=0.1 to x=0.5 by varying the starting composition of the melt and the oxygen content was adjusted using an appropriate heat treatment of the crystals in a thermogravimetric system. With decreasing Sr content the superconducting transition temperature, {Tc}, of the crystals decreased rapidly from 10 K to below 4.2 K and the resistivity in the a-b plane changed from metallic (linear in T from 30 to 300 K) to semiconducting. Reducing the oxygen content in the crystals had a similar effect on the resistivity. Only crystals with close to the maximum oxygen content (y=0) were superconducting, and removal of oxygen from previously superconducting crystals resulted in a rapid decrease of {Tc}, and the eventual loss of superconductivity ({Tc} < 4.2 K). Although crystals of Bi{sub 2}Sr{sub 2-x}CuO{sub 6-y} could be made sequentially superconducting-semiconducting-superconducting by the addition-removal-addition of oxygen, the process was not totally reversible. After only one such cyclic heat treatment x-ray diffraction indicated that for some compositions such cycling resulted in the appearance of CuO and another layered structure that has been identified previously and is slightly deficient in CuO. The new layers structure is semiconducting and has a layer-stacking repeat distance that is 1 {angstrom} smaller than the superconducting 221'' phase. 9 refs., 3 figs.

• Research Organization: Oak Ridge National Lab., TN (USA)
• Sponsoring Organization: DOE/ER
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 5178144
• Report Number(s): CONF-891119-43; ON: DE90004242
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204* -- Ceramics
Cermets
&amp; Refractories-- Physical Properties
426001 -- Engineering-- Superconducting Devices &amp; Circuits-- (1990-)
656100 -- Condensed Matter Physics-- Superconductivity
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALKALINE EARTH METALS
ALLOYS
BISMUTH ALLOYS
CRYSTALS
DATA
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELEMENTS
EXPERIMENTAL DATA
INFORMATION
LAYERS
MECHANICAL STRUCTURES
METALS
NONMETALS
NUMERICAL DATA
OXYGEN
PERFORMANCE TESTING
PHYSICAL PROPERTIES
RESEARCH PROGRAMS
STRONTIUM
SUPERCONDUCTIVITY
TEMPERATURE EFFECTS
TESTING