A-Site and B-Site Charge Orderings in an s–d Level Controlled Perovskite Oxide PbCoO₃

Abstract

Perovskite PbCoO synthesized at 12 GPa was found to have an unusual charge distribution of PbPbCoCoO with charge orderings in both the A and B sites of perovskite ABO. Comprehensive studies using density functional theory (DFT) calculation, electron diffraction (ED), synchrotron X-ray diffraction (SXRD), neutron powder diffraction (NPD), hard X-ray photoemission spectroscopy (HAXPES), soft X-ray absorption spectroscopy (XAS), and measurements of specific heat as well as magnetic and electrical properties provide evidence of lead ion and cobalt ion charge ordering leading to PbPbCoCoO quadruple perovskite structure. It is shown that the average valence distribution of PbCoO between PbCrO and PbNiO can be stabilized by tuning the energy levels of Pb 6s and transition metal 3d orbitals.

Reentrant Structural Transitions and Collapse of Charge and Orbital Orders in Quadruple Perovskites

“…In conclusion, we find that quadruple perovskites,already widely studied because of their outstanding physical and chemical properties, [21,22] show intriguing structural properties,namely,reentrant structural transitions in BiCu x Mn 7Àx O 12 solid solutions.Moreover,reentrant structural transitions can be triggered by am agnetic field even without long-range magnetic order and without changes in electronic states,a nd the reentrant phases show nearly zero thermal expansion. These properties can have implications for practical applications,a nd BiCu x Mn 7Àx O 12 solid solutions deserve further detailed studies.…”

Novel catalytic properties of quadruple perovskites

“…Unusual A -site ions in this series are Mn 2+ and Cu + ions for A Cu 3 V 4 O 12 [27,28], and the most remarkable example is ζ-Mn 2 O 3 (MnMn 3 Mn 4 O 12 ) [29]. Recently, quadruple perovskite PbCoO 3 (Pb 2+ Pb 4+ 3 Co 2+ 2 Co 3+ 2 O 12 ), in which both A - and B -site aliovalent ions are simultaneously ordered, has been reported [30]. Several examples with B -site ordering of a different kind of cations in Pn symmetry (space group No.…”

Valence State of Pb in Transition Metal Perovskites PbTMO3 (TM = Ti, Ni) Determined From X‐Ray Absorption Near‐Edge Spectroscopy

“…Magnetic ferroelectric materials in which ferroelectricity and magnetism coexist and charge disproportionation as well as the pressure‐induced insulator‐metal transition in Lead‐transition metal perovskites PbTMO 3 (TM = transition metals) attract research attention recently . Pb has the charge degree of freedom stemming from the possibility of having either the 6s 2 (Pb 2+ ) or the 6s 0 (Pb 4+ ) electronic configurations.…”

“…Because the 6s 1 configuration (Pb 3+ ) is prohibited, Lead is called valence‐skipping (or negative‐ U ) ion, a characteristic that is also typically observed for the Bi ion, that can have either Bi 3+ (6s 2 ) or Bi 5+ (6s 0 ) valence. The application of high‐pressure synthesis in recent years has made available PbTMO 3 with TM covering almost all 3d transition metals, with TM = Ti, V, Cr, Mn, Fe, Co, and Ni and a 4d transition metal Ru in PbRuO 3 . Starting from the left end of the periodic table, PbTiO 3 is expected to have charge state Pb 2+ /Ti 4+ , while to the right end, PbNiO 3 is expected to have the Pb 4+ /Ni 2+ charge state .…”

“…Starting from the left end of the periodic table, PbTiO 3 is expected to have charge state Pb 2+ /Ti 4+ , while to the right end, PbNiO 3 is expected to have the Pb 4+ /Ni 2+ charge state . In between, for TM = Cr, Fe and Co a mixed valence state 6s 2 (Pb 2+ )/6s 0 (Pb 4+ ) has been inferred from the valence determination on the TM ions or the Pb core‐level X‐ray photoemission spectroscopy . PbMnO 3 (P4 mmm −1 ) is special with the claim of Pb 2+ Mn 4+ O 3 (6s 2 ), which requires further confirmation with spectroscopic methods.…”