Crystal structure of a solid
solution in the Mg–Pd–Al system
Chem.
Met. Alloys 12 (2019)
29-32
https://doi.org/10.30970/cma12.0391
Vasyl STOTSKYI, Svitlana PUKAS, Roman GLADYSHEVSKII
A search for new ternary palladium aluminides was carried out in the system Mg–Pd–Al. A new phase was observed in two
alloys of nominal compositions Mg7.1Pd28.6Al64.3
and Mg11.1Pd33.3Al55.6; phase and structural analyses were performed based on
X-ray powder diffraction data. A crystal structure corresponding to partial substitution of Mg in the
binary compound Pd8Al21 (Pt8Al21-type,
Pearson symbol tI116, space
group I41/a) was established.
The approximate composition Mg5Pd8Al16 was determined by
energy-dispersive X-ray
spectroscopy for the phase in the
Mg-poor sample (a = 13.0429(2), c = 10.6880(1) Å) and it was assumed, based on geometrical
arguments, that Mg atoms replace Al atoms in Wyckoff position 4a and one of the seven positions 16f. The phase in the Mg-rich sample (a = 13.1928(4), c = 10.6488(5) Å)
was found to contain more Mg,
indicating the existence of a solid solution. Compared to the binary compound
Pd8Al21, the a-parameter is also larger but the c-parameter shorter, leading to an
overall increase of the cell volume with increasing Mg content.
Projection of the structure of Mg5Pd8Al16
along [001].
Keywords
Ternary palladium aluminide
/ X-ray powder diffraction / Energy-dispersive X-ray spectroscopy / Crystal
structure