Challenges Imposed by Thermochemical Expansion of Solid State Electrochemical Materials

Mixed Ionic-Electronic Conductivity, Redox Behavior and Thermochemical Expansion of Mn-Substituted 5YSZ as an Interlayer Material for Reversible Solid Oxide Cells

“…In the low-temperature range below ~400 °C, when the oxygen exchange with the gas phase is frozen, the observed expansion of oxide materials corresponds to the “true” thermal expansion of the lattice originating from the anharmonicity of atomic vibrations. Increasing temperature gives rise to a “chemical” contribution to the thermochemical expansion [ 64 , 65 ] associated with the increase in [Mn 2+ ]/[Mn 3+ ] ratio on heating due to oxygen losses from the lattice and the reduction of Mn cations, and consequently an increase in their average ionic radius. The changes in the slope of dilatometric curves reflect the corresponding inflections in temperature dependencies of the oxygen nonstoichiometry and the mean manganese valence ( Figure 15 A).…”

Strongly coupled thermal and chemical expansion in the perovskite oxide system Sr(Ti,Fe)O3−α

“…(The CCEs are still lower than those reported for Cebased uorite-structured oxides, typically $0.1. 21 ) The many factors controlling chemical expansion in perovskites make generalizations difficult, but Frade 29 has noted a trend in some cases towards increasing CCE with increasing perovskite tolerance factor (t). STF35 has a tolerance factor of 0.995 (calculated for all Fe 3+ , all high spin and neglecting oxygen vacancies), which should place it towards the upper end of perovskite CCE values by that relationship.…”

Tailoring chemical expansion by controlling charge localization: in situ X-ray diffraction and dilatometric study of (La,Sr)(Ga,Ni)O3−δ perovskite

“…In the present work, the more anisotropic expansion observed in the sample with higher Ni content (x ¼ 0.5) could be one factor contributing to a lower macroscopic chemical expansion coefficient vs. x ¼ 0.05. If signicant, this effect also suggests that one may observe a greater inuence of charge delocalization on macroscopic CCEs Along those lines, Frade 43 had demonstrated a correlation between tolerance factor (aer reduction) and CCE for some perovskite-structured mixed ionic and electronic conductors with t < 1, implying larger chemical expansion coefficients when the cubic perovskite phase becomes more stable (t / 1) upon reduction. In the present work the XRD results suggest that at high temperatures the structures appear to be quite similar for low and high Ni contents (Fig.…”