| 초록 |
The present paper reports on improved catalytic activity of (La0.75Sr0.25)(Mn0.95-xFexNi0.05)O3+δ (x = 0.1 – 0.3 mole) perovskite-type cathodes. The samples were prepared by the Pechini method using metal acetates. A perovskite-type phase was formed at calcination temperature ~700oC and a rhombohedral symmetry of R – 3c space group was stabilized at ~1100oC. An increase in x increased the unit cell volume as observed by the XRD and FT-IR spectroscopy studies. Two temperature regions, I (＜ 300oC) and II (300-1100oC), were observed in the TG, thermal expansion, and electrical and ionic conductivities variations. The TG was increased to 106-107% for region – I due to a large increase in oxygen vacancies and then slightly increased to ~107-110 % for region – II, confirming the excess oxygen content (3+δ). The region – II possessed high ionic and electronic conductivities. The samples with x = 0.1 mole exhibited the optimal values, namely unit cell volume, 351.21 Å3; relative density, 0.88; crystallite size, ~286 nm; BET surface area, 1.21 m2/g; BET particle size, 0.77 μm; electrical conductivity, ~49 S/cm at ~600oC; and activation energy, ~0.13 eV, similar to those of traditionally applied cathode, La0.75Sr0.25MnO3+δ (LSM), however, with superior parameters, namely high coefficient of thermal expansion, ~12.1 ppm/oC, and exceptionally high ionic conductivity, ~6×10-2 S/cm and low interfacial polarization resistance at ~600oC, making it suitable for intermediate-temperature solid oxide fuel cell application. This sample was also found chemically inert to the solid electrolytes. |
