Dependence of thermal expansion of LaNi0.6Fe0.4O3 (- delta) and La0.6Sr0.4Co0.2Fe0.8O3 (-) (delta) on oxygen partial pressure

作者：Niwa Eiki; Hashimoto Takuya

来源：Solid State Ionics, 2016, 285: 187-194.

DOI：10.1016/j.ssi.2015.09.019

• LaNi0.6Fe0.4O3- (delta)
• La0.6Sr0.4Co0.2Fe0.8O3 (-) (delta)
• Thermal expansion
• Dilatometry
• Oxygen nonstoichiometry
• Chemical expansion coefficient

The linear thermal expansion behavior of LaNi0.6Fe0.4O3 (- delta) and La0.6Sr0.4Co0.2Fe0.8O3 (- delta), which have attracted much interest as cathode material for solid oxide fuel cell, was measured with dilatometer under various oxygen partial pressures, P(O-2). Thermal expansion coefficient of LaNi0.6Fe0.4O3 (- delta) is independent on P(O-2) and between 120 x 10(-5) K-1 and 135 x 10(-5) K-1 in the measurement conditions of this study. Thermal expansion coefficient of La0.6Sr0.4Co0.2Fe0.8O3 (- delta) is much larger than that of LaNi0.6Fe0.4O3 (- delta) and increases with decreasing P(02). The difference of P(O-2) dependence of thermal expansion behavior between LaNi0.6Fe0.4O3 (- delta) and La0.6Sr0.4Co0.2Fe0.8O3 (- delta) could be ascribed to the difference of the dependence of oxygen nonstoichiometry on temperature and P(O-2). Due to little variation of delta by temperature at constant P(O-2) in LaNi0.6Fe0.4O3 (- delta), chemical expansion due to generation of scarcely contributes to total expansion, while chemical expansion largely contributes to total expansion of La0.6Sr0.4Co0.2Fe0.8O3 (- delta) especially under low P(O-2) owing to larger variation of S by temperature at constant P(02). By comparison with thermal expansion behavior of 8 mol% yttria stabilized ZrO2, 8YSZ, under various P(02), it was concluded that mechanical compatibility of LaNi0.6Fe0.4O3 (- delta) against 8YSZ was better since La0.6Sr0.4Co0.2Fe0.8O3 (- delta) showed not only much larger thermal expansion coefficient than 8YSZ but also large P(O-2) dependence. Chemical expansion coefficients, epsilon(chem.). of LNF64 and LSCF6428 were also evaluated. The epsilon(chem), of LNF64 was almost zero whereas those of LSCF6428 were order of 10(-2), showing fair agreement with so far reported epsilon(chem). of LSCF and other oxide materials frequently used for SOFC.

• 出版日期2016-2