SUPERCONDUCTING PROPERTIES OF GLASS-CERAMICS IN THE BI-R-SR-CA-CU-O (WITH R = PB OR AG) SYSTEM

The influence of partial substitution of Pb and Ag in the Bi1-xRxSrCaC u1.5Oy (R = Pb or Ag; x = 0.2) glass ceramics has been investigated. I t was found that the Ag-containing compound exhibited superconductivit y with a T(c) of 78 K while the Pb-containing compound exhibited a T(c ) of 87 K. The ultrasonic attenuation was measured at frequencies of 5 , 10, 20 and 30 MHz in the temperature range 77 to 300 K. Five relaxat ion peaks were observed in Bi0.8Pb0.2SrCaCu1.5Oy and Bi0.8Ag0.2SrCaCu1 .5Oy compounds. As the frequency of the measurement is increased, the temperature of the peaks shifts to higher values while the height of t he peaks decreases. The first three peaks (P1, P2 and P3) may be attri buted to the electronic defects (hopping of holes) and the other two c ould be ascribed to the thermally activated movement of boundaries by interaction with the defects.