III International Conference

PP-II-41fell cell – with the required performances (high mixed ionic-electronic conductivity, stabilityunder working condition and compatibility with other parts of fuel cell, anode and electrode)is an important problem to solve for the intermediate temperature SOFCs.Nanocomposites comprised of fluorite-like oxides (good ionic conductors) andperovskites (electronic conductors) appear to be promising for these applications due tocombination of these needed for cathode material properties [2]. A low cost of these materialsrequired for the practical application can be ensured by using industrially availableinexpensive mixed oxides of lanthanides LnO x (Ln=Ce(51%)+La(26%)+Pr(5%)+Nd(12.8%)+Sm(1%)) and an efficient preparation technique - mechanochemicaltreatment (MC) of their mixture with simple transition metal oxides in high power planetaryball mills followed by short annealing [3]. The most apparent advantage of this method is theabsence of wastewaters that is very important from the ecological point of viewThis work aims at development of inexpensive nanocomposite cathode materials withhigh oxygen mobility for application in IT SOFC using low cost LnO x and MC preparationroute.According to XRD all synthesized samples consist of two phases: doped CeO 2 * with thefluorite-like and LnMeO 3 (Ln=La, Nd; Ме=Mn, Co, Fe) with the perovskite-like structures.HRTEM revealed the nanocomposite particle structure of prepared samples: particles (theaverage particle size is nearly 450 nm) consist of domains (domain size is in the range of 50-100 nm) with perovskite and fluorite structures.According to H 2 TPR the increase in calcinations temperature leads to a small change inthe total hydrogen consumption for Ln-Co-O and Ln-Mn-O composites and to decrease forLn-Fe-O composite.According to CH 4 reduction rates in H 2 and CH 4 of Ln-Me-O nanocomposites are higherthan that observed for individual perovskite and for pure or doped fluorite-like phases [4,5].Moreover, synthes-gas was formed during the reduction CH 4 of some samples (Ln-Mn-O, Ln-Fe-O, Ln-Co-O with the stoichiometry La:Me=1:1, annealed at 1100 0 C). It means that thesenanocomposites can be also used in membrane processes.The highest mixed ionic-electronic conductivity was revealed for Ln-Co-O material.Compatibility of Mn-containing nanocomposites preliminary supported as thin layers onthe surface of single-crystalline corundum disc (a) or porous thin stainless-steel foils (b) wasstudied. Since the thermal expansion coefficient of both corundum and stainless steel is closeto that of Sc-doped ceria (~9-11x 10 -6 ).239