Quaternary phases R_1-xAe_xT₂Ge₂ (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 La_0.590Ca_0.410Fe₂Ge₂ (a = 4.0662(6), c = 10.625(2) Å) and La_0.805Sr_0.195Fe₂Ge₂ (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 La_0.590(7)Ca_0.410(7)Fe₂Ge₂ and La_0.805(2)Sr_0.195(2)Fe₂Ge₂, comparing with the ternary compound LaFe₂Ge₂

Keywords

Multicomponent phases / Crystal structure / CeAl₂Ga₂ type / X-ray powder and single-crystal diffraction