A Crystallographic Shear Driven by Oxygen Insertion in (LuFeO ₃ ) n LuFe ₂ O ₄

Herein, a structural shearing behavior in heterolayered (LuFeO 3 ) n LuFe 2 O 4 ( n = 0, 1) upon oxygen uptake is reported. Using advanced X‐ray and electron diffraction techniques, it is found that when (LuFeO 3 ) n LuFe 2 O 4 absorbs oxygen, only the LuFe 2 O 4 layer is affected, transforming into LuFe 2 O 4.5 , while the LuFeO 3 layer remains chemically unchanged. Magnetic susceptibility and Mössbauer spectroscopy corroborate this local oxygen uptake in the LuFe 2 O 4 layer by confirming the mixed oxidation state of the iron site. Interestingly, even though the LuFeO 3 layer in the n = 1 compound does not directly absorb oxygen, it significantly influences how the structure evolves during oxidation. The n = 1 compound (Lu 2 Fe 3 O 7 ) is active for oxygen absorption at a lower temperature than the n = 0 compound LuFe 2 O 4 (110 °C vs. 150 °C from thermal gravimetric measurement). The LuFeO 3 layer in Lu 2 Fe 3 O 7 acts as a buffer zone that reduces strain and chemical pressure within the LuFe 2 O 4 layer thereby enhancing the rate of oxygen absorption. The findings reveal a common behavior in the (LuFeO 3 ) n LuFe 2 O 4 series that provides new insights into the design of ternary oxides active at low temperatures for fast oxygen uptake. This crystallographic study can therefore lead to further improvements in the oxygen storage capability and oxygen absorption rates.