Investigation of the high-temperature redox chemistry of Sr₂Fe_1.5Mo_0.5O_6−δvia in situ neutron diffraction

Abstract

The composition of Sr2Fe1.5Mo0.5O6−δ, a SOFC electrode material, is investigated by neutron diffraction in both highly oxidizing and reducing conditions, and correlated with measured physical properties.

Mixed-Conductor Sr2Fe1.5Mo0.5O6−δ as Robust Fuel Electrode for Pure CO2 Reduction in Solid Oxide Electrolysis Cell

“…The results showed that the reduced SFM has a slightly larger lattice constant of a = b = c = 3.925 Å than the oxidized SFM ( a = b = c = 3.916 Å), Table . Such fully disordered distribution over the Fe and Mo sites with space group Pm 3̅ m has already reported for SFM structure by several groups, − such as Liu and co-workers using powder X-ray diffraction method . However, Muñoz-García suggested an orthorhombic structure with Pnma for SFM based on powder neutron diffraction analysis .…”

“…However, Muñoz-García suggested an orthorhombic structure with Pnma for SFM based on powder neutron diffraction analysis . In addition, a tetragonal I 4/ mcm and a Fe–Mo ordered structure with Fm 3̅ m have been also reported for SFM. , The observed discrepancy between the different research groups could be attributed to the differences in the material preparation conditions …”

“…22 In addition, a tetragonal I4/mcm and a Fe−Mo ordered structure with Fm3̅ m have been also reported for SFM. 34,36 The observed discrepancy between the different research groups could be attributed to the differences in the material preparation conditions. 34 The particle size of the SFM powder was in the range of 200−300 nm, as indicated by the TEM image in Figure 3a.…”

Nano-domain states of strontium ferrites SrFe1−MO2.5+ (M=V, Mo; y≤0.1; x≤0.2)

“…So, displacements occur in all sublattices, that lead to diffuse scattering. These diffraction effects were also observed by Bugaris and coauthors in their structural investigations of tetragonal phase SrFe 0.75 Mo 0.25 O 3 À δ (3 43 À δ42.75) [11], where they call it "unusual strain broadening". Perhaps, they also deal with the nanodomain state of this phase in a perovskite matrix, that manifested as diffuse scattering.…”

“…The "order-disorder" phase transitions in case of nanostructured oxides do not lead to destruction of the materials. At the same time, despite the presence of high-charged cations, which are obstacles to the motion of vacancies, doping has a weak inhibitory effect on oxygen diffusion [9][10][11], and in cases of relatively low substitution degree, for example M ¼Mo 6 þ and y¼ 0.05, even improves the diffusion [9].…”