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Anomalies of ultrasonic velocity in high-Tc ceramics YBa2Cu3Oy and BiSrCaCu2Oy |
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| Authors: | P. -K. Choi H. Koizumi K. Takagi T. Suzuki |
| Affiliation: | Institute of Industrial Science, University of Tokyo, Roppongi, Minato-ku, Tokyo 106, Japan |
| Abstract: | Ultrasonic longitudinal velocity and adsorption have been measured in ceramic superconductors YBa2Cu3Oy with various porosity and also in BiSrCaCu2Oy. A velocity drop of about 400 ppm was found at Tc only in the measurements on cooling. The magnitude of the velocity drop is anomalously large compared with the value expected from the thermodynamics. A hysteresis of velocity with respect to temperature was observed in all the samples studied. It is suggested that some structural change at pore size level is responsible for this phenomenon. |
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