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

Abstract

Indium and bismuth are technologically important elements, in particular as oxides for optoelectronic applications. <sup>115</sup>In and <sup>209</sup>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 NMR parameters on these nuclei, particularly in oxides, hinders their use by the broader materials community. In this contribution, solid-state <sup>115</sup>In and <sup>209</sup>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 (<sup>27</sup>Al, <sup>69,71</sup>Ga, <sup>121</sup>Sb) solid-state NMR measurements. The compounds LiIn<sub>2</sub>SbO<sub>6</sub>, BiAlTeO<sub>6</sub>, and BiGaTeO<sub>6</sub> 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 <sup>115</sup>In and <sup>209</sup>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 <sup>115</sup>In, <sup>121</sup>Sb, and <sup>209</sup>Bi in oxides.