Chemical stability of La _1-xSr _xCrO ₃ in oxidizing atmospheres

The single-phase region of La _1-xSr _xCrO ₃ (x=0.1, 0.2, 0.3) was precisely determined as a function of temperature, P _O2 and Sr content. The powders with the nominal composition of La _1-xSr _xCrO ₃ were equilibrated under various conditions, and then identified by XRD analyses. To confirm the equilibration, two independent experiments were performed for each composition observing (i) the precipitation of the second phase from a single-phase solid solution, and (ii) the formation of the single phase from the constituent oxides. Two kinds of second phases, SrCrO ₄ and an unknown phase, were observed depending on the conditions. The second phases tended to appear at low temperature, in high P _O2 and with a large Sr content. The single-phase regions obtained via the two equilibration routes were in good agreement with each other. The thermodynamic calculations on the supposition of ideality of the solid solution essentially reproduced the experimental results. When this material is used as the interconnects of solid oxide fuel cells, much attention should be paid to its relatively narrow solubility range of Sr; for example, the solubility limit is approximately 0.1 under a typical cathode-side condition (1273K, air).