High‐Temperature Structural and Electrical Characterization of Reduced Oxygen‐Deficient Ruddlesden–Popper Nickelates

Abstract

High-temperature characterization of oxygen-deficient Sr-rich (La 1-x Sr x ) 2 NiO 4-δ (x = 0.5-0.8) solid solutions under mildly reducing conditions with p(O 2 ) ≈ 5 × 10 -5 atm was performed by employing structural and thermal analysis, TEM, and electrical conductivity measurements. Oxygen losses from the crystal lattice on reduction were found to result in a reversible transition from the tetragonal (I4/mmm) to the orthorhombic (Immm) structure and shrinkage of the crystal lattice for the compositions with x > 0.5. TEM and thermogravimetric analysis evidenced slow kinetics of the structural transition. The increase[a] CICECO -