Effect of co-substitution on superconductivity in (Y, Ca)(Ba, Sr)2Cu4O8 prepared by the molten KOH method

Abstract

Abstract Effect of co-substitution of Ca and Sr in the Y-124 phase of Y1-x CaxBa2-y Sr y Cu4O8 has been investigated. Polycrystalline samples of Y1-x CaxBa2-y Sr y Cu4O8 with 0 ≤ x(Ca) ≤ 0.2 and 0 ≤ y(Sr) ≤ 0.2 have been prepared by the molten KOH method. The lattice parameters decrease with increasing y(Sr), indicating that the smaller Sr ions are systematically substituted for the larger Ba ions. The value of Tc increases from 83 K to ∼ 90 K through the Sr-substitution for x(Ca) = 0, while Tc ∼ 90 K are almost independent of y(Sr) for x(Ca) = 0.1 and 0.2.