PROPAGATION OF ULTRASONIC-WAVES AND ANOMALIES NEAR TC IN SINGLE CRYSTALLINE YBA2CU3O7-X HIGH-TC SUPERCONDUCTORS

The attenuation and the velocity of ultrasonic waves in single crystalline high-Tc YBa2Cu3O7-x have been measured in the temperature range from 3 to 280 K for the C11-, C33-, C44- and C66-mode. At the superconducting transition a pronounced peak in the absorption is observed for the longitudinal C11-mode. The longitudinal C11- and C33-modes and the transverse C44-mode exhibit a plateau in the temperature dependence of the velocity. The temperature dependence of the absorption of the transverse C44-mode reveals a change in the slope at Tc. The data are compared with the predictions derived from a thermodynamic treatment and with the results of measurements on coarse grain and fine grain sintered and sinter-forged materials. © 1990 Springer-Verlag.