Rietveld analysis on Gd(Ba(2-x)A(x))Cu3Oy (A = Ca, Sr) superconductors

Two series of single phase triple-perovskite superconducting samples with n ominal compositions of Gd(Ba2-xCax)Cu3Oy (Ca series, 0 less than or equal t o x less than or equal to 0.30) and Gd(Ba2-x,Sr-x,)Cu3Oy (Sr series, 0 less than or equal to x' less than or equal to 1.0) were prepared. Orthorhombic ity decreases with increasing amount of Ca or Sr substitution. Part of Ca i ons occupy R site and push the same amount of Gd3+ ion into Ba site, attrac ting negative oxygen ions to randomly occupy 0(4) and 0(5) sites on the bas al plane which leads to a further reduction of orthorhombicity in Gd(Ba2-xC ax)Cu3Oy series compared with the same amount of substitution in Sr series, in which, Sr only occupies the Ba site. T-c is dependent on the orthorhomb icity of these samples, no matter whether it is Ca or Sr substitution.