Hysteretic phase transition in Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-//sub x/ superconductors

Journal Article · Thu Dec 01 04:00:00 EST 1988 · Phys. Rev. B: Condens. Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.38.11857· OSTI ID:6616921

Ledbetter, H M; Kim, S A

We studied ultrasonic-wave velocities, both longitudinal and shear, in Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-//sub x/, between 5 and 295 K, during both cooling and warming. Both waves, expecially the longitudinal, show thermal hysteresis. The results suggest a hysteretic phase change that occurs between 160 and 70 K during cooling and between 170 and 260 K during warming. This phase-change hypothesis explains anomalies in several physical properties. The phase change agrees with thermodynamic-instability predictions. We confirmed the hysteresis in Ho-Ba-Cu-O, where it is smaller than in Y-Ba-Cu-O, and in Eu-Ba-Cu-O, where it is larger. In a companion perovskite, BaTiO/sub 3/, we observed zero hysteresis. At T/sub c/, 91 K, sound velocities show no measurable change in either magntiude or slope. This continuity disputes the current popular view that, contrary to thermodynamics, elastic stiffness increases upon cooling through T/sub c/ into the superconducting state. We believe that stiffening results from the usual thermal effects after a phase transformation from a stiffer phase.

• Research Organization: Center for Materials Science and Engineering, National Bureau of Standards, Boulder, Colorado 80303
• OSTI ID: 6616921
• Journal Information: Phys. Rev. B: Condens. Matter; (United States), Journal Name: Phys. Rev. B: Condens. Matter; (United States) Vol. 38:16; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
CHALCOGENIDES
COOLING
COPPER COMPOUNDS
COPPER OXIDES
ELASTICITY
HEATING
HYSTERESIS
MECHANICAL PROPERTIES
MEDIUM TEMPERATURE
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SOUND WAVES
TENSILE PROPERTIES
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
ULTRALOW TEMPERATURE
ULTRASONIC WAVES
VELOCITY
VERY LOW TEMPERATURE
YTTRIUM COMPOUNDS