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.