Local Structural Environments in Cubic Sr2ScGaO5: A Multinuclear Solid-State NMR Study

Abstract

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, and71Ga) solid-state NMR spectroscopy to investigate the local structure of cubic Sr2ScGaO5(c-SSGO).17O NMR signals were assigned based on17O{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 of17O 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.