Change in the Thermal Expansion of a Perovskite‐Type Mixed Conductor Upon Sample Density

Abstract

Thermal expansions (TEs) of dense and porous samples were studied for mixed conductor Sr(Co 0.9 Nb 0.1 )O 3Àd (SCNb). In Ar, the TEs of the porous samples were almost the same as those of a dense sample, which had the character of conventional TEs. In air, on the other hand, the TEs of porous samples were larger than the dense sample. The difference of TE in air resulted from a change in the chemical expansion, which originated from the variation of oxygen vacancy concentration. On decreasing the density, oxygen incorporation from air into SCNb took place at a lower temperature, and the length change upon chemical expansion was increased.

LaNi0.6Co0.4−xFexO3−δ as Air-Side Contact Material for La0.3Ca0.7Fe0.7Cr0.3O3−δ Reversible Solid Oxide Fuel Cell Electrodes

“…On the other hand, thermal expansion originates from the anharmonicity of the lattice vibrations and is dependent on the electrostatic attraction forces within the lattice. The concentrations of positive and negative charges and their distances within the lattice influence the electrostatic attraction forces [32,[37][38][39].…”

Thermal properties of (Gd0.6Sr0.4)0.99Fe1-xCoxO3-δ cathodes for intermediate temperature solid oxide fuel cells

“…Conventional expansion results from the anharmonicity of atomic vibrations, which is related to the atomic bond strength [50]. Chemical expansion is induced by the aforementioned oxygen vacancy caused by the thermal reduction of Co ions to lower oxidation states [51].…”

Synchrotron Radiation Shed Light to <i>In Situ </i>and Dynamic Observation of High-Temperature Processes

“…The reversible change in the density can be attributed to the change in the density of the Sr-Fe-O oxides. It is reasonable to consider that the density change during the redox cycles is caused by chemical expansion and contraction of the perovskite-type SrFeO 3−δ and Sr 4 Fe 6 O 13−δ phases in response to changes in the oxygen deficiency (δ), which is typically found in oxides with perovskite-type structures, such as La 1−x Sr x MnO 3+δ [29], SrCo 0.9 Nb 0.1 O 3−δ [30], Nd 2−x Sr x NiO 4+δ [31], and Ca 0.5 Sr 0.5 Mn 1−b Fe b O 3−δ [32]. The observed change in the normalized density, ρ norm , can be concluded to indicate the change in the oxygen deficiency δ that is located in the perovskite-type SrFeO 3−δ or Sr 4 Fe 6 O 13−δ .…”