Anomalous Behaviour of Bi-System Superconductors in the Normal State and their Correlation with Superconductivity

Abstract

Our experiments show that Bi-system samples exhibit two parameter anomalies and two heat and weight anomalies in normal state. For the samples of (Bi,Pb)2Sr2CaCu2Oy, as the superconducting volume is over 65%, two anomalies of heat and weight at about 400 °C and 750 °C, respectively, are significantly observed; as the superconducting volume of the samples is under 50%, or the samples are non-superconducting, the anomaly at about 400 °C is hardly observed. For the samples of (Bi,Pb)2Sr2Ca2Cu3Oy, as the superconducting volume is over 65%, they exhibit two anomalies at about 300 °C and 750 °C, respectively; as the superconducting volume is under 50%, the anomaly at about 300 °C disappears, and as the samples are non-superconducting, it shows a quite opposite behavior to the superconducting samples at about 300 °C. We develop a computer program based on calculation of lattice energy to simulate the experimental results, it is found that the change of the lattice energy can well explain the anomalous phenomena in the samples.