Solid-state nuclear magnetic resonance of spin-9/2 nuclei ¹¹⁵ In and ²⁰⁹ Bi in functional inorganic complex oxides

Indium and bismuth are technologically important elements, in particular as oxides for optoelectronic applications. ¹¹⁵ In and ²⁰⁹ Bi 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 nuclear magnetic resonance (NMR) parameters on these nuclei, particularly in oxides, hinders their use by the broader materials community. In this contribution, solid-state ¹¹⁵ In and ²⁰⁹ Bi NMR of three recently discovered quaternary bismuth or indium oxides are reported, supported by density functional theory calculations, numerical simulations, diffraction and additional multinuclear (²⁷ Al, ^69,71 Ga, and ¹²¹ Sb) solid-state NMR measurements. The compounds LiIn₂ SbO₆ , 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 = 9/2 ¹¹⁵ In and ²⁰⁹ Bi 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 ¹¹⁵ In, ¹²¹ Sb, and ²⁰⁹ Bi in oxides.