2 research outputs found
Combining Multiscale Approaches for the Structure Determination of an Iron Layered Oxysulfate: Sr<sub>4</sub>Fe<sub>2.5</sub>O<sub>7.25</sub>(SO<sub>4</sub>)<sub>0.5</sub>
The
new iron layered oxysulfate Sr<sub>4</sub>Fe<sub>2.5</sub>O<sub>7.25</sub>(SO<sub>4</sub>)<sub>0.5</sub> has been prepared by a solid-state
reaction in closed ampules into the form of ceramics and single crystals.
Its atomic structure has been solved by means of spectroscopy, diffraction
techniques, and high-resolution electron microscopy. Sr<sub>4</sub>Fe<sub>2.5</sub>O<sub>7.25</sub>(SO<sub>4</sub>)<sub>0.5</sub> is
a layered structure that derives from the RuddelsdenāPopper
(RP) phases with the layer stacking sequence SrO/SrFeO<sub>2.5</sub>/SrFe<sub>0.5</sub>(SO<sub>4</sub>)<sub>0.5</sub>O<sub>1.25</sub>/SrFeO<sub>2.5</sub>. Within the mixed Fe<sup>3+</sup>/SO<sub>4</sub><sup>2ā</sup> layer, the sulfur atoms are slightly shifted
from the B site of the perovskite and each sulfate group shares two
corners with iron pyramids in the basal plan without any order phenomenon.
The electronic conductivity is thermally activated, while no ionic
conductivity is detected
Single Sublattice Endotaxial Phase Separation Driven by Charge Frustration in a Complex Oxide
Complex
transition-metal oxides are important functional materials
in areas such as energy and information storage. The cubic ABO<sub>3</sub> perovskite is an archetypal example of this class, formed
by the occupation of small octahedral B-sites within an AO<sub>3</sub> network defined by larger A cations. We show that introduction of
chemically mismatched octahedral cations into a cubic perovskite oxide
parent phase modifies structure and composition beyond the unit cell
length scale on the B sublattice alone. This affords an endotaxial
nanocomposite of two cubic perovskite phases with distinct properties.
These locally B-site cation-ordered and -disordered phases share a
single AO<sub>3</sub> network and have enhanced stability against
the formation of a competing hexagonal structure over the single-phase
parent. Synergic integration of the distinct properties of these phases
by the coherent interfaces of the composite produces solid oxide fuel
cell cathode performance superior to that expected from the component
phases in isolation