Correlation between Carrier Concentration and Superconductivity in the 123-phase System

Besides the structure and oxygen content, the resistance-temperature relationship, Hall carrier concentration (nH) and midpoint temperature of superconducting transition (Tc) were measured for more than six 123-phase systems with elemental substitution. No correlation is found between the oxygen content and Tc, nor is between the orthorhombic structure and Tc. Instead, an unmonotonic relationship is found between nH and Tc. The optimum nH for the highest Tc is about 3.8 × 1021 cm-3. All this draws a conclusion that nH is a parameter to describe the high Tc superconductivity.