Synthesis and structure of aluminum substituted MoSi2

Effect of Al addition on the microstructure and low-temperature reactivity to oxygen of pre-formed MoSi2

“…This is consistent with the fact that Al atoms (143 pm) have a larger radius compared to Si (117 nm) and that the lattice will expand if a substitutional solid solution is formed. These values are similar to those found in the literature [26] and they differ only slightly from those of Dasgupta et al [25] and Tabaru et al [41]. As mentioned above, the diffraction peaks of the a-MoSi 2 phase does not vary with the Al content and their values are a = 3.212 Ǻ and c = 7.878 Ǻ .…”

“…The same method has been used to study the evolution of the various phases formed in the Mo-Si-Al system [25,26]. From the XRD patterns of several samples of Mo(Si 1-x , Al x ) 2 , Ghayoumabadi et al [26] concluded that (i) nearly pure tetragonal (a-MoSi 2 ) is formed when x = 0.0; (ii) Al leaving the low-temperature phase (a-MoSi 2 ) devoid of Al.…”

“…This means that the ratio (Si ? Al)/Mo is not fixed at 2.0 as in [25,26], but increases steadily from 2.0 to 2.4 as x is increased from 0.0 to 0.4. The primary question at stake here is to demonstrate if Al can substitute Si atoms in pre-formed MoSi 2 .…”

“…Several preparation methods have been designed specifically to take advantage of the exothermicity of the reaction. This is the case for MoSi 2 prepared by combustion and self-propagating high temperature synthesis [25,26] and by mechanical alloying [27][28][29][30][31][32][33][34][35][36].…”

Thermal properties of MoSi2 with minor aluminum substitutions

“…In our earlier work Al addition in MoSi 2 was shown to change the crystal structure from C11 b tetragonal phase to C40 hexagonal phase, with an intermediate biphasic region [17]. The aluminum addition expands the lattice in both C11 b and C40 phases.…”