A series of single phase La1.5CaxBa1.5−xCu3Oy (0 ≤x≤ 0.50) compounds with tetragonal triple-perovskite structure is studied by Rietveld analysis. For x≤ 0.40, all the Ca2+ ions enter the center site, the Y3+ site of the tetragonal YBa2Cu3Oy phase. For x= 0.50, occupation factor of Ca2+ ion in the Y3+ site (OFCa/Y) is 0.466(2). The maximum allowed OFCa/Y is close to 0.50 which limits further substitution of Ca2+ ion to the Ba2+ ion for the La1.5CaxBa1.5−xCu3Oy series. Tc can be explained by the difference between OFCa/Y and OFLa/Ba, (OF of La3+ ion in the Ba2+ site). In other words, superconductivity is determined by the amount of Ca2+ ions in the Y3+ site and La3+ ions in the Ba2+ site in the unit-cell.
Physica C: Superconductivity and its Applications 282-287(2), pp.1069-1070