Structural and superconducting properties of RE<inf>1-2x</inf>Pr<inf>x</inf>Ca<inf>x</inf>Sr<inf>0.8</inf>Ba<inf>1.2</inf>Cu<inf>3</inf>o<inf>7-δ</inf>(RE = Er and Gd) high T<inf>c</inf>superconductors

Abstract

We report here on the structural and superconducting properties of RE1-2xPrxCaxSr0.8Ba1.2Cu3O7-δ(RE = Er and Gd, 0 ≤ x ≤ 0.2) high temperature superconductors. The transition temperature (Tc) of these compounds decreases when the Pr and Ca concentrations are increased. At constant Pr and Ca concentrations, the Te of Er1-2xPrxCaxSr0.8Ba1.2Cu3O7-δsuperconductor system is higher than that observed for the Gd1-2xPrxCaxSr0.8Ba1.2Cu3O7-δsystem. For the Gd0.8Pr0.1Ca0.1Sr0.8Ba1.2Cu3O7-δsample, after heating in argon followed by oxygen annealing, the orthorhombicity increases accompanied by 10 K increase in Tc. These results show that though our data indicate an ion-size effect, the Tcsuppression rate dTc/dx depends very much on the heat treatment adopted to prepare the samples.