Evaluation of BaY sub(1 - x)Pr sub(x)Mn sub(2)O sub(5 + delta ) oxides for oxygen storage technology

• Published in: Solid state ionics Vol. 262; pp. 659 - 663
• Main Authors: Klimkowicz, Aliga, Swierczek, Konrad, Zheng, Kun, Baranowska, Monika, Takasaki, Akito, Dabrowski, Bogdan
• Format: Journal Article
• Language: English
• Published: 01-09-2014
• Subjects: Crystal structure; Lanthanides; Oxidation; Oxides; Reduction; Storage capacity; Symmetry; Unit cell
• ISSN: 0167-2738
• DOI: 10.1016/j.ssi.2013.11.001

Crystal structure and oxygen storage properties of A-site ordered BaY sub(1 - x)Pr sub(x)Mn sub(2)O sub(5 + delta ) (x = 0,0.25, 0.5,0.75 and 1) perovskite-type oxides are reported, showing almost complete and reversible change ([Delta] delta > 0.94 mol mol super(-1)) occurring between fully reduced BaY, sub(1 - x)Pr sub(x)Mn sub(2)O sub(5) and oxidized BaY sub(1 - x) sub(x)Pr sub(x) Mn sub(2)O sub(6) during reduction in 5 vol.% H sub(2) in Ar atmosphere and oxidation in air at 500 [degrees]C. All reduced compounds, as well as oxidized ones for x > or = 0.5 possess tetragonal structure with P4/nmm (or P4/mmm for BaPrMn sub(2)O sub(6)) symmetry at room temperature. In the case of BaY sub(0.75)Pr sub(0.25)Mn sub(2)O sub(6) and BaYMn sub(2)O sub(6), good Rietveld refinements of XRD data were obtained assuming either monoclinic P121 or triclinic P-1 symmetry. The oxidation process causes a significant decrease of unit cell volume, which is additionally linearly dependent on average ionic radius of Y sub(1 - x)Pr sub(x). Due to a higher molar mass, an increasing Pr content causes a decrease of reversible oxygen storage capacity; nevertheless, Pr-containing materials show improved reduction rate and oxidize at lower temperatures. The optimized BaY sub(0.75)Pr sub(0.25)Mn sub(2)O sub(5)-BaY sub(0.75)Pr sub(0.25)Mn sub(2)O sub( 6) system showed very stable performance for 50 cycles. The obtained results indicate that by an appropriate chemical modification, it is possible to enhance oxygen storage-related properties of BaY sub(1 - x)Ln sub(x)Mn sub(2)O sub(5 + delta ) (Ln - lanthanides) oxides, and such materials are promising for oxygen storage technology application.