Phase transformations in YBa/sub 2/Cu/sub 3/O/sub 7-//sub delta/

Journal Article · Wed Mar 01 04:00:00 EST 1989 · Phys. Rev. B: Condens. Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.39.4299· OSTI ID:6229515

Shi, D

Isothermal annealing experiments have been carried out over a wide temperature range (200--700 /sup 0/C) to study the mechanisms of the tetragonal-to-orthorhombic phase transformation. The annealed samples were analyzed by means of x-ray diffraction, electrical resistivity and magnetization measurements, and polarized light microscopy. The x-ray diffraction and magnetization results show that the tetragonal-to-orthorhombic phase transformation proceeds isothermally, indicating an oxygen diffusion-controlled process. Data from the polarized light microscopy show that a phase boundary exists between the tetragonal-to-orthorhombic phases, which moves gradually as a result of oxygen diffusion, from the sample surface towards the center, as annealing time is extended. Twinning occurs as oxygen is increased to just above 6.5, and twin boundaries are found to extend through all the grains even near the moving phase boundary. This twinning clearly indicates a martensite-related shear transformation. Transport properties, diffusion mechanisms, and the tetragonal-to-orthorhombic phase transformation process are discussed.

• Research Organization: Materials Science Division, Building 223, Argonne National Laboratory, Argonne, Illinois 60439
• OSTI ID: 6229515
• Journal Information: Phys. Rev. B: Condens. Matter; (United States), Journal Name: Phys. Rev. B: Condens. Matter; (United States) Vol. 39:7; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
656100 -- Condensed Matter Physics-- Superconductivity
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALKALINE EARTH METAL COMPOUNDS
ANNEALING
BARIUM COMPOUNDS
BARIUM OXIDES
CHALCOGENIDES
COHERENT SCATTERING
COPPER COMPOUNDS
COPPER OXIDES
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTAL-PHASE TRANSFORMATIONS
DIFFRACTION
DIFFUSION
ELEMENTS
HEAT TREATMENTS
HIGH TEMPERATURE
MAGNETIZATION
NONMETALS
ORTHORHOMBIC LATTICES
OXIDES
OXYGEN
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
SCATTERING
SUPERCONDUCTORS
TETRAGONAL LATTICES
TRANSITION ELEMENT COMPOUNDS
TWINNING
X-RAY DIFFRACTION
YTTRIUM COMPOUNDS
YTTRIUM OXIDES