Homologous series of iron pnictide oxide superconductors (Fe2As2)[Can+1(Sc,Ti)nOy] (n=3,4,5) with extremely thick blocking layers

We have discovered homologous series of iron pnictide superconductors (Fe2As2)[Can+1(Sc,Ti)nOy] (n=3,4,5). These compounds have extremely thick blocking layers up to quintuple perovskite layers sandwiched by the Fe2As2 layers. These samples exhibited bulk superconductivity with relatively high Tc up to 42 K. The relationship between Tc and the iron-plane interlayer distance suggested that Tc of the iron based superconductor is basically determined by the local structure of Fe2As2 layer.