A 27Al MAS NMR study of a sol-gel produced alumina: Identification of the NMR parameters of the θ-Al2O3 transition alumina phase

27Al MAS NMR has been used to study a sol-gel prepared alumina annealed at various temperatures. Two-field simulation of the sample heated to 1200 °C confirmed the presence of corundum, as suggested by XRD, and also the presence of nanocrystalline θ-Al2O3. 27Al MAS NMR chemical shifts, quadrupolar coupling constants and asymmetry parameters are reported for the tetrahedral and octahedral aluminium sites within θ-Al2O3.