Local Structural Environments in Cubic Sr ₂ ScGaO ₅ : A Multinuclear Solid-State NMR Study

Oxygen-deficient perovskites exhibit promising ionic conductivity for electrochemical applications, but understanding their structure–property relationships requires detailed knowledge of local atomic environments. In this study, we employ multinuclear (17O, 45Sc, and 71Ga) solid-state NMR spectroscopy to investigate the local structure of cubic Sr2ScGaO5 (c-SSGO). 17O NMR signals were assigned based on 17O{45Sc} transfer of population double resonance experiments (TRAPDOR) and ab initio chemical shift calculations using the CASTEP code. Our results provide compelling evidence that despite its cubic average structure determined by X-ray Bragg diffraction, the local atomic arrangement in c-SSGO closely resembles the orthorhombic brownmillerite structure, as previously proposed from neutron diffraction pair distribution (PDF) analysis. Furthermore, we demonstrate how solid-state NMR, together with DFT calculations of 17O NMR chemical shifts can serve to discriminate between alternative structural scenarios for defect perovskite structures. The study highlights the power of solid-state NMR in elucidating local structural details in complex oxides with local variations in their crystal structures.