For NMR spectroscopy measurements, these were taken at three different fields 16.4 T, 11.8 T, and 23.5 T as outlined below. 16.4 T & 11.8 T: Al NMR spectra were acquired using Bruker 4 mm HXY MAS probes. 1D spectra were acquired using a regular one-pulse pulse program with a small flip angle (𝜋/6) on Bruker 700 MHz (16.4 T) and 500 MHz (11.8 T) magnets with Avance III consoles. Two-dimensional Al 3QMAS (triple quantum MAS) NMR spectra were acquired on a Bruker 700 MHz (16.4 T) magnet. Quadrupolar pulse optimization was performed on γ-Al2O3 powder (Acros Organics). 23.5 T: Al NMR spectra were acquired using a Bruker 1.9 mm HXY MAS probe. Spectra were acquired using a rotor-synchronised ( Bruker Topspin software was used for raw data handling and processing. The 27 Al spectra were fitted with DMFIT software to obtain integrated ratios and values of average 𝛿 !"# , average 𝐶 $ and ΔCS using the CzSimple model with d=5 for the Gaussian Isotropic Model (GIM) case. The best fit is obtained using the GIM case of the Czjzek model , corresponding to a distribution of local environments that lead to a spread of quadrupolar coupling constants and chemical shifts.