Stoichiornetry defect at grain boundary observed by nano-scale TEM microanalysis in spinel MgAl2O4

The stoichiometry defect at grain boundary in spinel MgAl2O 4 observed by nano-scale TEM microanalysis was presented. A Hot Isostatic Press (HIP) of a commercial stoichiometric powder allowed obtaining a near dense spinel with an average grain size value of 0.61 μ. For the determination of the chemical composition, a STEM equipped with a windowless energy dispersive X-ray detector was used. The X-ray analysis operated across the grain boundary exhibited an increase of the Al/Mg and O/Mg ratio at the grain coupled with an unchanged O/Al ratio. The result shows that due to to the stoichiometric change a positive space charge cloud near the boundary exists.