Local Structure in Disordered Melilite Revealed by Ultrahigh Field ⁷¹Ga and ¹³⁹La Solid-State Nuclear Magnetic...

Multinuclear Nuclear Magnetic Resonance (NMR) spectroscopy of quadrupolar nuclei at ultrahigh magnetic field provides compelling insight into the short-range structure in a family of fast oxide ion electrolytes with La_1+xSr_1-xGa₃O_7+0.5x melilite structure. The striking resolution enhancement in the solid-state ⁷¹Ga NMR spectra measured with the world's unique series connected hybrid magnet operating at 35.2 T distinctly resolves Ga sites in four- and five-fold coordination environments. Detection of five-coordinate Ga centers in the site-disordered La_1.54Sr_0.46Ga₃O_7.27 melilite is critical given that the GaO₅ unit accommodates interstitial oxide ions and provides excellent transport properties. This work highlights the importance of ultrahigh magnetic fields for the detection of otherwise broad spectral features in systems containing quadrupolar nuclei and the potential of ensemble-based computational approaches for the interpretation of NMR data acquired for site-disordered materials.