Pure and Zr-doped YMnO_3+δas a YSZ-compatible SOFC cathode: a combined computational and experimental approach

Abstract

Zr doping stabilizes the interstitial oxygen in layered manganite YMnO3 and provides O2− migration path with a lower energy barrier. The resulting material is of high interest as a YSZ compatible SOFC cathode.

Oxygen Absorption in Nanocrystalline h-RMnO3 (R = Y, Ho, Dy) and the Effect of Ti Donor Doping

“…The layered hexagonal manganites are prone to anti-Frenkel defect formation and can also incorporate excess oxygen on interstitial sites, which is possible due to the structure being less close-packed than the perovskite structure. − Oxygen interstitials move through an interstitialcy mechanism with a low energy barrier compared to those reported for vacancy migration in perovskites, ,− enabling oxygen transport and exchange at lower temperatures. Remsen and Dabrowski first reported this reversible absorption and release of oxygen for Dy 1– x Y x MnO 3+δ (0 ≤ δ ≤ 0.35), and similar large excess oxygen values have later been reported for other R MnO 3 compositions. ,− …”

“…The P 6 3 cm structure is composed of alternating layers of seven-coordinated R 3+ and five-coordinated Mn 3+ in corner-sharing trigonal bipyramids, shown in Figure . Interstitial oxygen sites are located between three Mn 3+ ions in the triangular lattice of MnO 5 bipyramids and are charge-compensated by the oxidation of two out of three nearest-neighbor Mn 3+ to Mn 4+ , as described by eq in the Kröger–Vink notation 1 2 normalO 2 ( g ) + 2 Mn Mn x → normalO normali ″ + 2 Mn Mn • For high oxygen contents, interstitial oxygen in the MnO 5 layers gives rise to new hexagonal superstructures depending on the value of δ. ,, Partial substitution of Y 3+ in YMnO 3 with larger R 3+ such as Tb, Ce, Nd, and Sm improves the oxygen storage and transport properties of these materials, as oxygen absorption and ionic radius of R 3+ are strongly correlated. − ,− Donor dopants like Ti 4+ on the Mn sublattice can also further increase the maximum storage capacity, , as oxygen interstitials (eq ) are energetically favored as a charge compensation mechanism for Ti 4+ compared to the reduction of Mn 3+ to Mn 2+ (eq ) 2 0.25em TiO 2 → 2 Ti Mn • + 3 0.25em normalO normalO x + normalO normali ″ TiO …”

“…15,24,28 Partial substitution of Y 3+ in YMnO 3 with larger R 3+ such as Tb, Ce, Nd, and Sm improves the oxygen storage and transport properties of these materials, as oxygen absorption and ionic radius of R 3+ are strongly correlated. 28−30,39−41 Donor dopants like Ti 4+ on the Mn sublattice can also further increase the maximum storage capacity, 42,43 as oxygen interstitials (eq 2) are energetically favored as a charge compensation mechanism for Ti 4+ compared to the reduction of Mn 3+ to Mn 2+ (eq 3) 27 2 TiO 2Ti 3 O O…”

Colloidal Processing of Y0.08Zr0.92O2/La0.80Sr0.20MnO3 Semi-Cells Using a Sr-Doped Lanthanum Manganite Synthesized by a Citrate Route

“…The stoichiometric oxygen content values are 66 atom% and 60 atom%, very similar to those obtained by EDX, in spite of the semi-quantitative character of this tool. In the YSZ layer, Zr concentration is much higher than that of Y, as expected, and both concentrations fall at a very short distance, below 0.5 µm in the coating, demonstrating that the diffusion of the substrate elements is negligible [37] and even lower than that reported for similar materials using the same approach [38]. Nevertheless, in contact with the YSZ, Mn and La of LSM diffuse into the substrate and a cubic zirconia solid solution with divalent manganese and trivalent lanthanum ions is formed, as proposed elsewhere [39].…”

New apatite‐type oxide ion conductors Ce9.33+xSi6O26+δ: Structures, phase stabilities, electrical properties, and conducting mechanisms

“…Due to its high operating temperature, it has high technical requirements for the selection of electrode materials and long‐term stability. This limits the development of SOFCs 5‐10 and, therefore, gives impetus to explore new types of oxide ion conductors with high conductivity in the middle‐ and low‐temperature range (400–700℃) 7,11,12 …”