Al2O3 solubility in the fast ion conductor 0.88ZrO2–(0.12−x)Sc2O3–xAl2O3 determined by 27Al NMR

27Al NMR has been used to investigate the solubility limit of alumina (α-Al2O3) in the fast ion conductor 0.88ZrO2–0.12Sc2O3. It is found that approximately 0.6 mol% alumina is retained in the ZrO2/Sc2O3 host lattice and that at higher doping levels the alumina exists in the specimen as a separate α-Al2O3 phase. Further 27Al NMR evidence is presented to support a view that the incorporated Al replaces Sc in the cubic zirconia-scandia structure.