Layer-Engineering of High-Tc Superconductors: (Cu,Mo)Sr2(Ce,Y)4Cu2O13+δ with a Quadruple-Fluorite-Layer Block Between CuO2 Planes

Among high-Tc superconductive copper oxides, there have been known phases that contain fluorite-structured layers as an additional "blocking block" between adjacent CuO2 planes. Here, we report that even a phase with the CuO2 planes separated by a 12-A thick quadruple-fluorite-layer block can be synthesized in a single phase and strongly oxygenated form to exhibit superconductivity with a Tc value as high as 55 K. The new phase is the fourth member of the (Cu,Mo)Sr2(Ce,Y)sCu2O(5+2s+delta) or (Cu,Mo)-12s2 homologous series. Comparison with the previously known s = 1, 2, and 3 members of the series reveals the amazing conclusion that Tc remains essentially unaffected upon inserting additional fluorite-structured layers between the two CuO2 planes as long as the hole-doping level of the planes is kept constant.