Glassy Distribution of Bi³⁺/Bi⁵⁺ in Bi_1–xPb_xNiO₃ and Negative Thermal Expansion Induced by Intermetallic Charge Transfer

Abstract

The valence distribution and local structure of Bi 1−x Pb x NiO 3 (x ≤ 0.25) were investigated by comprehensive studies of Rietveld analysis of synchrotron X-ray diffraction (SXRD) data, X-ray absorption spectroscopy (XAS), hard X-ray photoemission spectroscopy (HAXPES), and pair distribution function (PDF) analysis of synchrotron X-ray total scattering data. Disproportionation of Bi ions into Bi 3+ and Bi 5+ was observed for all the samples, but it was a longranged one with distinct crystallographic sites in the P1̅ triclinic structure for x ≤ 0.15, while the ordering was short-ranged for x = 0.20 and 0.25. An intermetallic charge transfer between Bi 5+ and Ni 2+ , leading to large volume shrinkage, was observed for all the samples upon heating at ∼500 K.

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

“…Such a distribution leads to the “overscreening” observed in our experiment (i.e., to the binding energies of the 4 f levels of Pb 2+ appearing to be higher than those of the 4 f levels of Pb 4+ ) and is the consequence of the specific electronic density of states of this compound (Figure b), where the bottom of the conduction band consists mainly of Pb 4+ s states hybridized with oxygen p states. It should be noted that in other compounds such as PbO, PbO 2 and Bi 1– x Pb x NiO 3 experiments also yield higher binding energies for the 4 f levels of Pb 2+ (Bi 3+ ) and lower ones for Pb 4+ (Bi 5+ ) ions.…”

Enhanced Negative Thermal Expansion Induced by Simultaneous Charge Transfer and Polar–Nonpolar Transitions

“…These results mean that the ordering of Bi 3+ /Bi 5+ is short ranged, probably because of the deviation from the 1:1 ratio. It should be noted that such an absence of Bi 3+ /Bi 5+ long-range ordering was reported in Bi 1– x Pb x NiO 3 and Bi 1– x Sb x NiO 3 . ,, …”

“…It should be noted that such an absence of Bi 3+ /Bi 5+ long-range ordering was reported in Bi 1−x Pb x NiO 3 and Bi 1−x Sb x NiO 3 . 8,9,12 The Bi 3+ 0.5(1+x) Bi 5+ 0.5(1−x) Ni 2+ 1−x Fe 3+…”

“…Inver, a low thermal expansion alloy, is used in clocks to keep precise time, while β-eucryptite is used in glass ceramics to compensate for the thermal expansion of glass matrix. In fact, a large number of NTE materials have been reported over the last few decades. − In particular, compounds with perovskite (BiNiO 3 derivatives, − LaCu 3 Fe 4 O 12 , , SrCu 3 Fe 4 O 12 , PbTiO 3 -based ferroelectrics, − and electron-doped PbVO 3 ) or related structures, such as antiperovskite (Mn nitrides), , layered perovskite (Ca 2 RuO 4– y ), , and ReO 3 -type (ScF 3 ) structures, , have been found to be giant NTE materials. NTE in these materials has a variety of origins, such as intermetallic charge transfer, ferroelectric–paraelectric transitions, the magneto-volume effect, microstructural effects, and flexible networks.…”

Hydrothermal synthesis and crystal structure of a mixed-valence pyrochlore-type strontium bismuthate, (Sr_0.75Bi_0.25)₂Bi₂O_6.83

“…Journal of the Ceramic Society of Japan 128 [9] 660-663 2020 JCS-Japan 157.6 and 158.8 eV) were attributed to Bi 5+ and Bi 3+ , respectively, as indicated in the previous report for Bi 0.75 -Pb 0.25 NiO 3 . 17) The average valence of Bi atoms was found to be 4.26, with 63 % of Bi 5+ and 37 % of Bi 3+ . This pyrochlore-type strontium bismuthate follows the linear relationship between the lattice parameter of the cubic unit cell and the sum of the ionic radii of the Aand B-site cations, as shown in various pyrochlore-type oxides [Fig.…”