New Iron Arsenide Oxides (Fe2As2)(Sr-4(Sc, Ti)(3)O-8), (Fe2As2)(Ba4Sc3O7.5), and (Fe2As2)(Ba3Sc2O5)

We synthesized new layered iron arsenide oxides (Fe2As2)(Sr-4(Sc, Ti)(3)O-8), (Fe2As2)(Ba4Sc3O7.5), and (Fe2As2)(Ba3Sc2O5). The crystal structures of these compounds are tetragonal with a space group of I4/mmm. The structure of (Fe2As2)(Sr-4(Sc, Ti)(3)O-8) and (Fe2As2)(Ba4Sc3O7.5) consists of the alternate stacking of antifluorite Fe2As2 layers and triple perovskite-type oxide layers. The interlayer distance between the Fe planes of (Fe2As2)(Ba4Sc3O7.5) is similar to 18.7 angstrom. Moreover, the a-axis of (Fe2As2)(Ba3Sc2O5) is the longest among the layered iron pnictides, indicating the structural flexibility of the layered iron pnictide containing perovskite-type layers. The bulk sample of (Fe2As2)(Sr-4(Sc0.6Ti0.4)(3)O-8) exhibited diamagnetism up to 28 K in susceptibility measurements. (C) 2010 The Japan Society of Applied Physics