Homologous series of copper-oxide superconductors: Synthesis of members up to

Here we establish the fifth and sixth members of the (Cu,Mo)-12 s 2 homologous series of superconductive copper oxides. Samples of the (Cu0.75Mo0.25) Sr 2 Y Ce s − 1 Cu 2 O 5 + 2 s + δ system for the s = 1 , 2 , 3 , 4 , 5 , and 6 cation compositions were synthesized. The first four members already reported in previous studies were obtained in essentially single-phase form. Formation of the higher homologues proceeds through intercalation reactions of additional Ce–O2 layers into the fluorite-structured (Y 0.5Ce0.5)–O2–[Ce–O2]s−2-(Y 0.5Ce0.5) block between two adjacent CuO2 planes, such that with increasing s the phase formation becomes increasingly slow. Samples were however realized where the s = 5 phase content was high enough for superconductivity–property characterization. It was revealed that the trend of essentially constant T c value of ∼55 K for similarly oxygenated samples continues up to the s = 5 homologue in the (Cu,Mo)-12 s 2 homologous series.