Structural features of layered iron pnictide oxides (Fe2As2)(Sr4M2O6)

Structural features of newly found perovskite-based iron pnictide oxide system have been studied. Compared to REFePnO system, perovskite-based system tend to have smaller Pn-Fe-Pn angle and higher pnictogen height owing to low electronegativity of alkaline earth metal and small repulsive force between pnictogen and oxigen atoms. As-Fe-As angles of (Fe2As2)(Sr4Cr2O6), (Fe2As2)(Sr4V2O6) and (Fe(2)Pn(2))(Sr4MgTiO6) are close to ideal tetrahedron and those pnictogen heights of about 1.40 A are close to NdFeAsO with optimized carrier concentration. These structural features of this system may lead to realization of high-T-c superconductivity in this system. (C) 2009 Elsevier B.V. All rights reserved.