Quaternary phases R1-xAexT2Ge2 (R = La, Ce, Gd,
Yb; Ae = Ca, Sr; T = Fe, Co,
Ni) with CeAl2Ga2 (122) structure type
Chem.
Met. Alloys 8 (2015) 123-128
https://doi.org/10.30970/cma8.0331
Volodymyr Gvozdetskyi, Viktor Hlukhyy, Roman Gladyshevskii
New quaternary phases crystallizing with the
CeAl2Ga2 (I4/mmm) structure type (122 phases) were
synthesized by arc melting in the R–Ae-T–Ge (R = La, Ce, Gd, Yb; Ae = Ca, Sr; T = Fe, Co, Ni) systems. The structures of La0.590Ca0.410Fe2Ge2
(a = 4.0662(6), c = 10.625(2) Å) and La0.805Sr0.195Fe2Ge2
(a = 4.1101(2), c = 10.654(1) Å) were refined on X-ray single-crystal diffraction
data. Several new 122 phases were identified on X-ray powder diffraction data
in the {Ce,Gd,Yb}-Ca-{Fe,Co,Ni}-Ge systems. The
structures are built up from layers of rare-earth or alkaline-earth atoms,
alternating with deformed [TGe4]
tetrahedra with tetahedral
angles in the range 110° < α < 122°
(compared to the ideal value of 109.5°). The influence of the d‑metal and the Ae content on the
degree of deformation of the tetrahedra is discussed.
Crystal structures of the quaternary 122 phases
La0.590(7)Ca0.410(7)Fe2Ge2
and La0.805(2)Sr0.195(2)Fe2Ge2,
comparing with the ternary compound LaFe2Ge2
Keywords
Multicomponent phases / Crystal structure / CeAl2Ga2
type / X-ray powder and single-crystal diffraction