Self-segregation and solubility in nonstoichiometric MgAl2O4 nanoparticles

Magnesium aluminate spinel (MAS) has a wide range of technological applications owing to its exceptional mechanical properties and good chemical stability. MAS phase diagrams indicate that only stoichiometric MgAl2O4 is stable at similar to 25 degrees C and Mg2+ and Al3+ exhibit solubility in nonstoichiometric MAS only at temperatures higher than similar to 1200 degrees C. In this study, the synthesis of nonstoichiometric single-phase spinel nanopowders at low temperatures is reported, and the role of the chemical distribution of Al3+ and Mg2+ excess on the stability of these nanopowders is examined. We performed selective lixiviation to examine the surface segregation of Mg2+ and Al3+ in nonstoichiometric MAS to investigate its effect on interfacial solubility and consequently the stability of nonstoichiometric MAS. Furthermore, we plotted an experimental phase diagram of nano MAS that predicts the crystallite size limits for the nonstoichiometric single-phase MAS.