The effect of Ca doping on the superconductivity of NdBa2Cu3Oy oxides

Two series of single phase triple-perovskite superconducting samples with nominal compositions of (Nd1−xCax)Ba2Cu3Oy and Nd(Ba2−xCax)Cu3Oy are prepared by the solid-state reaction method. It is found that both the Tc and the orthorhombicity of the unit cell for all the samples decrease with increasing Ca content. Tc is also correlated to the distance of Cu(2)-Cu(2) along the c-axis, which decreases linearly with increasing Ca doping.