In-situ structural analysis of the oxygenation of YBaCo₄O₇₊

Full text: In this work, the oxygenation of YBaCo₄O_7+δ is further explored through neutron diffraction studies. The 114-compound material of YBaCo₄O₇ is a mixed cobalt valence system that exists in a hexagonal arrangement (space group P 6₃ mc). Mixed Co²⁺/³⁺ valance allows the structure to accommodate additional oxygen through a structural transition to an orthorhombic arrangement. Neutron powder diffraction patterns revealed the evolution of the oxygenated YBaCo₄O_7+δ, δ = 1 phase when exposed to oxygen at 320℃. This is paired with a decrease in the YBaCo₄O_7+δ, δ = 0 phase due to the one formula equivalent of Co²⁺ fully oxidising to Co³⁺. It results in a bulk mixture containing both δ = 0 and 1 phases. After 1 hour of exposure to oxygen at 320℃, more than 97 % of the phase mixture is now δ = 1. The diffraction results here show that thermogravimetric studies, while convenient, do not give the complete picture of what is happening. And understanding what exact phases of YBaCo₄O_7+δ are present can help with potential oxygen storage applications. (author)