title: Varied roles of Pb in transition-metal PbMO3perovskites (M= Ti, V, Cr, Mn, Fe, Ni, Ru).
abstract: Different structural chemistries resulting from the Pb2+lone-pair electrons in the PbMO3perovskites are reviewed. The Pb2+lone-pair electrons enhance the ferroelectric transition temperature in PbTiO3, stabilize vanadyl formation in PbVO3, and induce a disproportionation reaction of CrIVin PbCrO3. A Pb2++ NiIV= Pb4++ NiIIreaction in PbNiO3stabilizes the LiNbO3structure at ambient pressure, but anA-site Pb4+in an orthorhombic perovskite PbNiO3is stabilized at modest pressures at room temperature. In PbMnO3, a ferroelectric displacement due to the lone pair electron effect is minimized by the spin-spin exchange interaction and the strong octahedral site preference of the MnIV/IIIcation. PbRuO3is converted under pressure from the defective pyrochlore to the orthorhombic (Pbnm) perovskite structure where Pb-Ru interactions via a common O -2p orbital stabilize at low temperature a metallicImmaphase at ambient pressure. AbovePc[Formula: see text] a covalent Pb-Ru bond is formed by Pb2++ RuIV= Pb4++ RuIIelectron sharing.
authors.affiliation: Materials Science and Engineering Program and Texas Materials Institute, University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: John B
authors.initials: JB
authors.lastname: Goodenough
authors.affiliation: Materials Science and Engineering Program and Texas Materials Institute, University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Jianshi
authors.initials: J
authors.lastname: Zhou
keywords: crystal structure; lone pair electrons; perovskites