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

 

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 RAe-TGe (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.

 

image description

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