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 T-c and the orthorhombicity of the unit cell for all the samples decrease with increasing Ca content. T-c is also correlated to the distance of Cu(2)-Cu(2) along the c-axis, which decreases linearly with increasing Ca doping. (C) 2004 Elsevier B.V. All rights reserved.