Solid-State NMR of Spin-9/2 Nuclei 115In and 209Bi in Functional Inorganic Complex Oxides

Indium and bismuth are technologically important elements, in particular as oxides for optoelectronic applications. 115In and 209Bi are both I = 9/2 nuclei with high natural abundances and moderately high frequencies but large nuclear electric quadrupole moments. Leveraging the quadrupolar interaction as a measure of local symmetry and polyhedral distortions for these nuclei could provide powerful insights on a range of applied materials. However, the absence of reported NMR parameters on these nuclei, particularly in oxides, hinders their use by the broader materials community. In this contribution, solid-state 115In and 209Bi NMR of three recently discovered quaternary bismuth or indium oxides are reported, supported by density functional theory calculations, numerical simulations, diffraction, and additional multinuclear (27Al, 69,71Ga, 121Sb) solid-state NMR measurements. The compounds LiIn2SbO6, BiAlTeO6, and BiGaTeO6 are measured without special equipment at 9.4 T, demonstrating that wideline techniques such as the QCPMG pulse sequence and frequency-stepped acquisition can enable straightforward extraction of quadrupolar tensor information in I = 9/2 115In and 209Bi even in sites with large quadrupolar coupling constants. Relationships are described between the NMR observables and local site symmetry. These are amongst the first reports of the NMR parameters of 115In, 121Sb, and 209Bi in oxides.