ULTRASONIC STUDIES OF SOME BI-BASED HIGH-T(C) SUPERCONDUCTORS

A series of Bi2-xPbxSr2Ca2Cu3O10 (0 < x < 0.5) high-T(c) superconducto rs has been prepared by the solid state reaction method. After charact erization, ultrasonic longitudinal velocity and attenuation studies we re undertaken over the temperature range 80-300 K using the pulse tran smission technique. In contrast to normal solids, the ultrasonic veloc ities of all the samples in the temperature range 250-150 K are found to decrease with decreasing temperature (softening). It has also been observed that most of the samples are found to exhibit longitudinal at tenuation peaks at temperatures almost-equal-to 250 K, almost-equal-to 170 K and almost-equal-to 100 K. A qualitative explanation for the so ftening of velocity and the attenuation peaks is given on the basis of microstructure and relaxation.