Versatile Application of Redox Processes for REBaCoMnO5+δ (RE: La, Pr, Nd, Sm, Gd, and Y) Oxides

Belonging to the not fully explored REBaCo2-xMnxO5+delta system, a series of REBaCoMnO5+delta (RE: selected rare earth elements) oxides having perovskite-type structure is synthesized and studied in terms of their structural properties, oxygen content, stability, thermal expansion, and transport properties. Impact of RE3+ on physicochemical properties of the compounds is derived, with smaller cations causing a decrease of the unit cell volume, lowering of the total oxygen content and thermal expansion, but also suppressing electrical conductivity. It is shown that a proper chemical modification enables to successfully utilize REBaCoMnO5+delta in applications, in which redox processes associated with oxygen reduction/oxidation and transport determine the effectiveness of the working material. In particular, NdBaCoMnO5+delta (with larger Nd3+) shows good chemical stability in relation to Ce0.8Gd0.2O2-delta and La0.8Sr0.2Ga0.8Mg0.2O3-delta solid electrolytes and moderate thermal expansion, 20.04(4).10(-6) K-1 in 300-900 degrees C. In symmetrical configuration with La0.8Sr0.2Ga0.8Mg0.2O3-delta electrolyte its cathodic polarization resistance is found to be only 0.036 Omega cm(2) at 900 degrees C, making it an excellent candidate cathode for solid oxide fuel cells. At the same time, YBaCoMnO5+delta (with small and cheap Y3+) delivers reversible oxygen storage capacity surpassing 3.4 wt % during the oxygen partial pressure swing process between air and 5 vol % H-2 in Ar at 500 degrees C.