Magic Angle Spinning NMR Study on Inversion Behavior and Vacancy Disorder in Alumina-Rich Spinel.

Solid state magic angle spinning nuclear magnetic resonance (NMR) and X-ray diffraction (XRD) were used to investigate the inverse behavior and vacancy disorder in alumina-rich spinel, MgAlO (0 ≤ x ≤ 0.86). Simulation and integration of NMR spectra have been developed for probing the population of Al located in different coordinated environments. Rietveld profile refinements were performed for powder XRD spectra by combining with NMR analysis. With changes in the composition, inversion disorder and cationic vacancies coexisting in tetrahedral and octahedral coordinations fluctuate in amount in the crystal lattice. The coordination polyhedra in the crystal structure can adjust the volume to variations of composition, anion parameter, and inverse parameter. This opens a window to the design and functionalization of spinel materials.