All
samples presented Mg2Si as major crystalline
phase; the presence of MgO and Si was also
detected. The raw starting materials are affected by
the presence of MgO, as previously reported.14
Rietveld refinement of the XRD patterns of the raw
starting materials and ball-milled powders did not
show any significant differences in MgO content
(about 6%). The oxidation processes which affected
Mg2Si occurred during sintering and further
increased the amount of MgO (up to 15 wt.%) and of
Si (up to 4 wt.%). The crystallite size was within the
range of 100 nm to 140 nm for all sintered samples.
As an example, Fig. 2 shows a FE-SEM image of the
x = 0.04 sample, showing the typical morphology of
the Al-doped Mg2Si samples with micron-sized
grains. FE-SEM, EDS, and XRD analyses did not