A Comprehensive Multimodal Study of La 0.45 Sr 0.45 TiO 3 Structure as Matrix for the Exsolution Process: From the Average to the Local Scale

ABSTRACT We report a comprehensive structural investigation of La 0.45 Sr 0.45 TiO 3 (LSTO) as a ceramic matrix for exsolution‐based fuel electrodes in solid oxide fuel cells and electrolyzers. Synchrotron radiation powder diffraction reveals an average cubic perovskite structure from room temperature to 900°C, even under the reducing exsolution conditions (5% H 2 /Ar), where Ti ions occupy centrosymmetric sites. However, pre‐edge features of X‐ray Absorption Spectroscopy spectra at the Ti K‐edge indicate Ti off‐centering. Combined Pair Distribution Function analysis of synchrotron and neutron diffraction uncovers local distortion on the 2–3 nm scale. An a − a − c + octahedral‐tilting, coupled with Sr/La ordering in alternating planes perpendicular to the c axis, reduces the local symmetry to the orthorhombic P 2 1 am space group. Ti ions shift away from La 3+ ‐rich planes, exerting stronger electrostatic repulsion than Sr 2+ ‐rich ones, while oxygen ions are drawn toward them. This asymmetric environment creates the observed Ti off‐centering. Local distortions persist up to 900°C under a reducing atmosphere. Density Functional Theory calculations support this structural model and clarify the material's electronic structure. The highest occupied electronic states are primarily Ti‐derived, consistent with Ti reduction observed by XPS. Excess charge preferentially localizes on two of four Ti ions per orthorhombic cell, exhibiting weak ferromagnetic coupling.