Structural characterization of ceramic phases with high-resolution ²⁷Al NMR

High-resolution solid-state ²⁷Al NMR spectra have been obtained from ALON, β′-sialon and yttrium aluminate phases. The usefulness of ²⁷Al magic-angle spinning NMR in phase characterization is shown by comparing different preparations of the yttrium aluminates. The sensitivity of the ²⁷Al resonance position to the local environment means different units (e.g. AlN₄, AlO₄, AlO₆) can readily be distinguished allowing oxynitride structures, containing elements of similar scattering factor, to be refined. This is exemplified for the β′-sialon phase. For quadrupolar nuclei (nuclear spin, I ≥ 1) such as ²⁷Al (I = ), interaction with the local electric field gradient can cause extensive broadening of the resonance such that the NMR spectrum may not precisely quantify the aluminium distribution.