High pressure synthesis and superconducting properties of Sr 2Ca n−1Cu nO y (n=1∼4) and Sr 2Ca n−1Cu nO 2n+δF 2±y (n=2∼5)

Abstract

We prepared two series of superconductors, Sr 2Ca n−1Cu nO y (02(n−1)n; n=1∼4) and Sr 2Ca n−1Cu nO 2n+δF 2±y (02(n−1)n-F; n=2,3) under high pressure and investigated their superconducting properties. The former series were prepared under 5∼6 GPa. The n=1 member, Sr 2CuO 3+δ, is not superconducting, while the n=2∼4 members show superconducting transitions at 77, 109 and 83 K, respectively. The latter series were prepared at 1250 °C under 5.5 GPa and showed T c of 99 K (n=2), 111 K (n=3) and ∼40K (n=4, 5). In this series, T c was dependent on both the oxygen and fluorine contents.