Oxygen nonstoichiometry and high-temperature conductivity of YBa 2Cu 4O y

Abstract

The oxygen nonstoichiometry and the high-temperature conductivity of YBa 2Cu 4O y have been studied as functions of temperature and oxygen partial pressure. It was found that the variable range of oxygen content y in YBa 2Cu 4O y is about 1 20 of that in YBa 2Cu 3O 7−δ. As a result, the critical temperature does not depend on the oxygen content. It is shown that the conductivity is proportional to the excess copper valence ΔZ (= Z−2) calculated from the oxygen nonstoichiometry, and the extrapolated straight lines pass a point where both Δ Z and σ are zero. The carrier concentration in YBa 2Cu 4O y calculated from Δ Z was very close to that in 90 K class superconductors. The mobility of YBa 2Cu 4O y was 4 times higher than that of 90 K class superconductors.