Influence of oxygen deficiency on electrical properties in the superconductor (Bi, Pb)2Sr2Ca2Cu3Oy phase

Abstract

The samples annealed in lower and higher oxygen partial pressure than P(O2)=10(-2) atm show T(c) shift to the lower temperatures compared with the sample annealed in P(O2)=10(-2) atm which shows the highest T(c) (T(c(end)) =107 K). The resistivity curve also shows a minimum value from room to superconducting transition temperatures in sample annealed in P(O2)=10(-2) atm. From the sign of the measured thermopower, the major carrier of (Bi, Pb)2Sr2Ca2Cu3Oy is identified as hole. As the oxygen partial pressure decreases, or as the oxygen deficiency increases, the thermopower increases by more than a factor of 7. According to this, we knew the oxygen deficiency in (Bi, Pb)2Sr2Ca2Cu3Oy reduces the hole concentration in the conduction band. And the T(c) maximum and the minimum resistivity from room temperature to superconducting transition temperature occurs at an optimal value of carrier concentration. Similar to low temperature data, the resistivity curve of the sample cooled in P(O2)=10(-2) atm from 700-degrees-C to room temperature is minimum.