Oxygen disorder effects in high temperature Y-Ba-Cu-O superconductor

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:6916564

Yang, S

A study of the oxygen vacancy disordering effects on the properties of high temperature superconducting YBaCu[sub 3]O[sub 7[minus][delta]] system is carried out. The degree of atomic order in the crystals is altered by quenching and annealing the sample at selected temperature for a certain amount of time. Superconducting transition temperature T[sub c] depends on atomic ordering, it decreases after quenching, then increases with low temperature aging. The maximum observed variation of T[sub c] (at fixed stoichiometry) is increased to about 27 K. The kinetics of atomic short-range ordering is systematically studied. It is found that the activation energies for oxygen diffusion in the basal plane are oxygen contents dependent. The different kinetics for samples with and without Au impurities is also studied. In addition to this, a change in the nature of the equilibrium state is observed at temperatures above a concentration dependent threshold temperature T*. The author associated T* with the phase boundary between the low temperature phase and the high temperature Ortho I phase. When samples are quenched from temperature above T* and subsequently annealed at temperatures around 51[degrees]C, two relaxation processes with relaxation time constants differing by about two orders of magnitude are observed. The faster and slower relaxation processes are associated with changes in vacancy short-range disorder and the restoration of long-range chain vacancy order respectively. T* is determined for different oxygen concentrations and compared to theoretical phase diagram calculations.

• Research Organization: Illinois Univ., Chicago, IL (United States)
• OSTI ID: 6916564
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202 -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
360207* -- Ceramics
Cermets
& Refractories-- Superconducting Properties-- (1992-)
ACTIVATION ENERGY
ALKALINE EARTH METAL COMPOUNDS
ALLOYS
BARIUM COMPOUNDS
BARIUM OXIDES
CHALCOGENIDES
COPPER COMPOUNDS
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
CUPRATES
ENERGY
HIGH-TC SUPERCONDUCTORS
INTERMETALLIC COMPOUNDS
ORDER-DISORDER TRANSFORMATIONS
OXIDES
OXYGEN COMPOUNDS
PHASE STUDIES
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
POINT DEFECTS
RELAXATION
SUPERCONDUCTORS
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE
VACANCIES
YTTRIUM COMPOUNDS
YTTRIUM OXIDES