Structure and magnetic properties of a new anion-deficient perovskite Pb2Ba2BiFe4ScO13 with crystallographic shear structure

• Pb 2 Ba 2 BiFe 4 ScO 13 was obtained by solid state synthesis. • Its structure was refined from combination of XPD and TEM. • It is a new member of the perovskite-related homologous series A n B n O 3 n −2 with n = 5. • Pb 2 Ba 2 BiFe 4 ScO 13 is antiferromagnetically ordered below T N ≈350 K. Pb 2 Ba 2 BiFe 4 ScO 13 , a new n = 5 member of the oxygen-deficient perovskite-based A n B n O 3 n −2 homologous series, was synthesized using a solid-state method. The crystal structure of Pb 2 Ba 2 BiFe 4 ScO 13 was investigated by a combination of synchrotron X-ray powder diffraction, electron diffraction, high-angle annular dark-field scanning transmission electron microscopy and Mössbauer spectroscopy. At 900 K, it crystallizes in the Ammm space group with the unit cell parameters a = 5.8459(1) Å, b = 4.0426(1) Å, and c = 27.3435(1) Å. In the Pb 2 Ba 2 BiFe 4 ScO 13 structure, quasi-two-dimensional perovskite blocks are periodically interleaved with ½[1 1 0] ( 1 ¯ 0 1 ) p crystallographic shear (CS) planes. At the CS planes, the corner-sharing FeO 6 octahedra are transformed into chains of edge-sharing FeO 5 distorted tetragonal pyramids. B-positions of the perovskite blocks between the CS planes are jointly occupied by Fe 3+ and Sc 3+ . The chains of the FeO 5 pyramids and (Fe,Sc)O 6 octahedra delimit six-sided tunnels that are occupied by double columns of cations with a lone electron pair (Pb 2+ ). The remaining A-cations (Bi 3+ , Ba 2+ ) occupy positions in the perovskite block. According to the magnetic susceptibility measurements, Pb 2 Ba 2 BiFe 4 ScO 13 is antiferromagnetically ordered below T N ≈350 K.