Gd₅Si₂B₈: A Ternary Rare‐Earth‐Metal Silicide Boride Compound

Abstract

In spite of the extensive experimental attention devoted to the various structural and physical properties of binary borides [1] and silicides [2] of the rare-earth metals (RE), there are comparatively few investigations of ternary silicide borides. Indeed, only a few boron-rich rare-earth metal silicide borides such as RESiB 44 , RESi 4.6 B 17.6 , RESi 1.2 B 41 (RE = Gd!Er, Y), [3] and Tb 3Àx C 2 Si 8 B 36[4] containing icosahedral B 12 cages, are known. This situation is in contrast with the ternary boride carbide phases of rare-earth metals which have received increasing attention over these last few years both experimentally and theoretically. [5] In an attempt to extend this chemistry to the RE-Si-B systems, we have explored different synthesis techniques, such as tin flux, and novel silicon-rich compounds, such as Er 8 Si 17 B 3 , have thus been characterized.

The ternary RE–Si–B systems (RE=Dy, Ho, Er and Y) at 1270K: Solid state phase equilibria and magnetic properties of the solid solution REB2−xSix (RE=Dy and Ho)

“…The line compound RE 5 Si 2 B 8 of Gd 5 Si 2 B 8 -type structure exhibits an intergrown structure, which is formed by the stacking of ThB 4 -and U 3 Si 2 -type slabs alternating along the c axis of the tetragonal lattice [3,20]. The crystal structures of all the RE 5 Si 2 B 8 phases (RE = Dy, Ho and Y) were recently reported [21].…”

Portraits of some representatives of metal boride carbide and boride silicide compounds

“…This is supported by the DOS computed at the LMTO DFT level. The Fermi level cuts a rather high peak of DOS, showing that the compound should be metallic in character [42]. The different projected DOS indicate participation of all constituting elements, Gd, B 6 , B 2 , and Si 2 , all over the DOS.…”

“…Recent works have shown that substituting silicon for carbon leads to compounds with strongly different structural arrangements [41,42]. Several years ago when we thought about extending the RE-B-C chemistry to that of RE-B-Si, a look at the literature on ternary RE-B-Si compounds showed very few results [43].…”

Solid state phase equilibria in the Gd–Si–B system at 1270K

“…The boron and silicon subnets are independent of each other in such a way that no boron-silicon bond occurs in the structure, contrary to the numerous and strong Si-Si and B-B covalent bonds. A more detailed description of the structural type Gd 5 Si 2 B 8 (and isostructural R 5 Si 2 B 8 compounds with R=Sm and Tb) together with theoretical calculations is proposed elsewhere [43]. The ternary phase Gd 5 Si 3 B 0.64 has been obtained from boron-poor samples.…”