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Ternary Rare Earth ( R ) Transition Metal Aluminides R 3 T 4 Al 12 ( T = Ru and Os) with Gd 3 Ru 4 Al 12 Type Structure
Author(s) -
Niermann Jens,
Jeitschko Wolfgang
Publication year - 2002
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/1521-3749(200211)628:11<2549::aid-zaac2549>3.0.co;2-x
Subject(s) - intermetallic , crystallography , ternary operation , crystal structure , transition metal , alkaline earth metal , diffractometer , gallium , metal , rare earth , aluminium , materials science , chemistry , metallurgy , alloy , computer science , programming language , catalysis , biochemistry
The isotypic intermetallic compounds R 3 Ru 4 Al 12 ( R = Y, Pr, Nd, Sm, Gd—Tm) and R 3 Os 4 Al 12 ( R = Y, Ce—Nd, Sm, Gd—Tm) were prepared by reaction of the elemental components in an arc‐melting furnace. Their crystal structure was determined from four‐circle X‐ray diffractometer data of Y 3 Ru 4 Al 12 : P 6 3 / mmc , a = 877.7(1) pm, c = 952.3(1) pm, Z = 2, R = 0.028 for 361 structure factors and 28 variable parameters. It was also refined for Nd 3 Os 4 Al 12 ( a = 889.2(1) pm, c = 960.3(1) pm, R = 0.021 for 425 F values and 30 variables) and Gd 3 Os 4 Al 12 ( a = 884.7(1) pm, c = 955.3(2) pm, R = 0.020; 427 F values, 30 variables). The refinements of the occupancy parameters revealed mixed T /Al occupancy for some of the aluminum sites resulting in the compositions Y 3 Ru 4.060(3) Al 11.940(3) , Nd 3 Os 4.43(1) Al 11.57(1) , and Gd 3 Os 4.44(1) Al 11.56(1) , respectively. The structure is related to those found for Y 2 Co 3 Ga 9 , Er 4 Pt 9 Al 24 , CeOsGa 4 , Ho 3 Ru 4 Ga 15 , YbFe 2 Al 10 , TbRe 2 Al 10 , LuRe 2 Al 10 , and CaCr 2 Al 10 . Topologically all of these structures may be viewed as consisting of atomic layers, although chemical bonding within and between the layers is of similar character. Two kinds of layers can be distinguished in these structures. One kind contains all of the rare earth (occasionally also alkaline earth) and in addition aluminum or gallium atoms. The other kind of layers consists of the transition metal atoms and again aluminum or gallium atoms. These latter layers are hexa gonally close packed and slightly puckered. The three different structures of the disilicides TiSi 2 , CrSi 2 , and MoSi 2 also contain these layers; however, in the disilicides these layers are flat.