ANOMALIES IN ULTRASONIC ATTENUATION OF Pb-DOPED Bi₂Sr₂CaCu₂O_8+x SUPERCONDUCTORS AT T_c

At the transition from normal to superconducting states there were anomalies of ultrasonic attenuation in single-phased specimens Bi_2-xPb_x Sr₂ CaCu₂ O_y ( T_cmid=80K); and as the temperature was lowered below T_cmid, the attenuation decreased rapidly. At the temperature about 135K there was a relatively high peak, which may be due to a certain relaxation process.