Abstract
Phase evolution, structure, thermal property, morphology, electrical property and reactivity of a perovskite-type cathode system, La0.75Sr0.25 Mn0.95-xCoxNi0.05O3+delta (0.1 <= x <= 0.3), are reported. The samples are synthesized using metal acetates by the Pechini method. A perovskite-type phase is formed after calcination at similar to 700 degrees C and a rhombohedral symmetry of R - 3c space group is stabilized at similar to 1100 degrees C. An increase in x decreases the unit cell volume linearly, accompanying with a linear decrease in bond lengths and tilt angle. The differential thermal analysis suggests the phase stabilization for a temperature range, 50-1100 degrees C. The thermo-gravimetric, thermal expansion, and electrical and ionic conductivities studies suggest presence of a Jahn-Teller transition at similar to 260-290 degrees C. The samples with x = 0.1 mol exhibit electrical conductivity of similar to 55 S cm(-1) at similar to 600 degrees C, activation energy of similar to 0.13 eV, coefficient of thermal expansion of similar to 12 x 10(6) C-1, crystallite size of similar to 45 nm, Brunauer-Emmett-Teller (BET) surface area of 1.26 m(2) g(-1) and average particle size of similar to 0.9 mu m. A fairly high ionic conductivity, 5-9 x 10(-2) S cm(-1) makes the sample with x = 0.1 mole suitable for intermediate-temperature solid oxide fuel cell cathode applications. The experimental results are discussed with the help of the defect models proposed for La1-xSrxMnO3+delta. (C) 2008 Elsevier B.V. All rights reserved.