Neutron structural characterization and transport properties of oxidized and reduced La0.5Sr0.5M0.5Ti0.5O3 (M = Mn, Fe) perovskites: Possible electrode materials in solid-oxide fuel cells

Abstract

Oxygen-stoichiometric La 0.5 Sr 0.5 M 0.5 Ti 0.5 O 3 (M ¼ Mn, Fe) perovskites and the corresponding reduced specimens, of La 0.5 Sr 0.5 M 0.5 Ti 0.5 O 3-d composition, have been prepared and characterized by x-ray diffraction and neutron powder diffraction (NPD), in complement with thermal analysis, electrical conductivity, and thermal expansion measurements. NPD data show that these perovskites are all orthorhombic, space group Pbnm (No. 62). The total reduction of M 3þ to M 2þ in the reduced phases is accompanied with the occurrence of oxygen vacancies, which was confirmed by thermogravimetric analysis (TGA). Above room-temperature, these phases undergo two structural phase transitions studied in situ from NPD data; the former to a tetragonal (I4/mcm) structure, and the second one to a cubic (Pm-3m) phase. All the oxides display a semiconductorlike behavior with a maximum conductivity value of 15 SÁcm

Synthesis, structure, and magnetic properties of the perovskite La0.3Sm0.2Sr0.5Ti0.5Fe0.5O3

“…The reliable parameters R wp , R p and v 2 ( Table 1) are reasonable for assigning the structure to the phase on the basis of the Rietveld analysis. The lattice parameters and unit cell volume of La 0.3 Sm 0.2 Sr 0.5 Ti 0.5 Fe 0.5 O 3 were found to be smaller than those of the reported phase La 0.5 Sr 0.5 Ti 0.5-Fe 0.5 O 3 [17]. This is attributed to the effective ionic radius of Sm 3?…”

“…The angles Ti/Fe-O(1)-Ti/Fe and Ti/Fe-O(2)-Ti/Fe in the ideal cubic perovskite structure are equal to 180°, but in our investigated perovskite (Table 2), they differ from this value because of octahedra tilting. The octahedral tilting in our sample is found to be greater than that in La 0.5 Sr 0.5 Ti 0.5 Fe 0.5 O 3 [17] where bond angles Ti/Fe-O(1)-Ti/Fe and Ti/Fe-O(2)-Ti/ Fe are 163.69°and 168.2°, respectively, while in our sample these bond angles are smaller ( Table 2).…”

“…Recently, Martinez-Coronado et al [17] reported that oxygen-stoichiometric La 0.5 Sr 0.5 M 0.5 Ti 0.5 O 3 (M = Mn, Fe) perovskites and the corresponding reduced specimens crystallize with the orthorhombic space group Pbnm (No. 62) and display a semiconductor-like behavior with a maximum conductivity value of 15 S cm -1 for the oxidized La 0.5 Sr 0.5 Mn 0.5 Ti 0.5 O 3 phase at 850°C.…”

A Highly Efficient and Robust Perovskite Anode with Iron–Palladium Co‐exsolutions for Intermediate‐Temperature Solid‐Oxide Fuel Cells

“…Typical values for LSFN are 2.05, 1.79, and 1.55 S cm −1 at T =800, 750, and 700 °C, respectively, whereas the conductivity values for LSFNP are 2.18, 1.95, and 1.71 S cm −1 at the same temperatures. LSFN and LSFNP both possess competitive electrical conductivity among common perovskite oxides under a reducing atmosphere . The increased conductivity of LSFNP would be helpful for a fast charge‐transfer process.…”

Pr and Ti co-doped Strontium Ferrite as a Novel Hydrogen Electrode for Solid Oxide Electrolysis Cell

“…Martínez-Coronado et al [12] electrolysis [13,14]. In fact, SrFeO 3−δ -based perovskites have been studied for more than 10 years.…”