ELASTIC ANOMALIES IN BI-PB-2223 AG SUPERCONDUCTING COMPOSITE-MATERIALS/

A series of high-T-c superconducting samples having the compositional formula Bi1.7Pb0.3Sr2Ca2Cu3O10 + x% Ag2O [x varies between 0-6 in the interval of 1] have been prepared by the solid-state reaction method, After usual characterisation by XRD, resistivity and scanning electron microscopy, bulk density porosity studies etc., the ultrasonic measur ements were carried out by the pulse transmission technique in the tem perature range of 80-300 K. It has been observed that two samples viz, , Bi-2223-0 and Bi-2223-1 are found to exhibit an elastic softening in the temperature region 300 to 210 K, while all the seven samples exhi bited a velocity maximum between 125 to 190 K. Qualitative explanation s for both the phenomena of elastic softening and the velocity maxima are given on the basis of the microstructure and ordering readjustment of the oxygen atoms among the Cu-O planes of the samples.