High-pressure synthesis, crystal structure, and magnetic properties of KSbO₃-type 5doxides K_0.84OsO₃and Bi_2.93Os₃O₁₁

Abstract

5d Solid-state oxides K0.84OsO3 (Os5.16+; 5d 2.84) and Bi2.93Os3O11 (Os4.40+; 5d 3.60) were synthesized under high-pressure and high-temperature conditions (6 GPa and 1500–1700 °C). Their crystal structures were determined by synchrotron x-ray diffraction and their 5d electronic properties and tunnel-like structure motifs were investigated. A KSbO3-type structure with a space group of Im-3 and Pn-3 was determined for K0.84OsO3 and Bi2.93Os3O11, respectively. The magnetic and electronic transport properties of the polycrystalline compounds were compared with those obtained theoretically. It was revealed that the 5d tunnel-like structures are paramagnetic with metallic charge conduction at temperatures above 2 K. This was similar to what was observed for structurally relevant 5d oxides, including Bi3Re3O11 (Re4.33+; 5d 2.66) and Ba2Ir3O9 (Ir4.66+; 5d 4.33). The absence of long-range magnetic order seems to be common among 5d KSbO3-like oxides, regardless of the number of 5d electrons (between 2.6 and 4.3 per 5d atom).

Quantum materials with strong spin–orbit coupling: challenges and opportunities for materials chemists

“…and A 4 M 6 O 19 , can be prepared through control of the synthesis method and the choice of A-site cation. 94 In both edge-and face-sharing multimers the M-M distances are relatively short, and this may allow for sufficient direct interaction between the valence orbitals of the cations of neighbouring octahedra that they form multi-site molecular orbitals over which the valence d electrons delocalise. In other words, the magnetic 'units' of the structure may no longer be the individual MO 6 octahedra but multimer 'molecules'.…”

High-Pressure Synthesis and Magnetic and Electrical Properties of Fe-Doped Bi3Re3O11 and Bi3Os3O11

“… a BVS = Σ i =1 N ν i , v i = exp­[( R 0 – l i )/B], N is the coordination number, B = 0.37, R 0 (B i 3+ ) = 2.094, R 0 (F e 3+ ) = 1.759, R 0 (Os 5+ ) = 1.868, R 0 (Re 5+ ) = 1.86 …”

“…Due to the close proximity of the octahedra, the Os(Fe)− Os(Fe) and Re(Fe)−Re(Fe) distances were found to be short (2.658 and 2.602 Å, respectively). The values for osmium oxide are close to the bond length of undoped Bi 2.93 Os 3 O 11 (2.6610 Å), 34 suggesting that a metallic bond is formed. The Re(Fe)−Re(Fe) distance is longer than the distance for Bi 3 Re 3 O 11 (2.456 Å), 8 but since it is shorter than the Os−Os bond distance (2.6610 Å), 34 it is inferred that metallic bonding is also involved in the chemical bonding of Bi 3 Re 2.13 Fe 0.87 O 11 .…”

Os4+ Instability in the Pyrochlore Structure: Tl2–xBixOs2O7–y

“…Osmium in the system studied prefers to exist in a mixed valence state, following precedent. 5,8,9,18,19 A high level of mixed valence would be difficult to stabilize in a pyrochlore containing only Bi 3+ at the A site, causing the instability of the single-phase bismuth osmate pyrochlore. Rather than adopting the pyrochlore structure, bismuth osmate will instead preferentially form the KSbO 3 structure type (Bi 3 Os 3 O 11 ), which allows for Os to remain mixed valent.…”

“…Among the osmate compounds, bismuth osmate with an equal Bi to Os mole ratio was suspected to belong to the KSbO 3 structure type . This was proven through a later study involving neutron diffraction experiments and was found to be a slightly bismuth deficient material with the final formula of Bi 2.93 Os 3 O 11 , or Bi 1.95 Os 2 O 7.33 . Recently Bi 2 Ir 2 O 6.815 was studied as a potential topological insulator .…”