Mn5Si3-type host-interstitial boron rare-earth metal silicide compounds RE5Si3 : Crystal structures, physical properties and theoretical considerations

• Published in: Journal of solid state chemistry 2006-08, Vol.179 (8), p.2310-2328
• Main Authors: ROGER, Jérome, BEN YAHIA, Mouna, BABIZHETSKYY, Volodymyr, BAUER, Joseph, CORDIER, Stéphane, GUERIN, Roland, HIEBL, Kurt, ROCQUEFELTE, Xavier, SAILLARD, Jean-Yves, HALET, Jean-Francois
• Format: Article
• Language: English
• Subjects: Chemical Sciences; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Halides, chalcogenides and analogous compounds of group vb; Inorganic compounds; Magnetic properties and materials; Magnetically ordered materials: other intrinsic properties; Material chemistry; Physics; Saturation moments and magnetic susceptibilities; Structure of solids and liquids; crystallography; Structure of specific crystalline solids
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2006.04.023

A series of binary rare-earth metal silicides RE5Si3 and ternary boron-interstitial phases RE5Si3Bx (RE ¼ Gd, Dy, Ho, Lu, and Y) adopting the Mn5Si3-type structure, have been prepared from the elemental components by arc melting. Boron ''stuffed'' phases were subsequently heated at 1750K within a high-frequency furnace. Crystal structures were determined for both binary and ternary series of compounds from single-crystal X-ray data: hexagonal symmetry, space group P63/mcm, Z ¼ 2. Boron insertion in the host binary silicides results in a very small decrease of the unit cell parameters with respect to those of the binaries. According to X-ray data, partial or nearly full boron occupancy of the interstitial octahedral sites in the range 0.6-1 is found. The magnetic properties of these compounds were characterized by the onset of magnetic ordering below 100 K. Boron insertion induces a modification of the transition temperature and yp values in most of the antiferromagnetic binary silicides, with the exception of the ternary phase Er5Si3Bx which was found to undergo a ferromagnetic transition at 14 K. The electrical resistivities for all binary silicides and ternary boron-interstitial phases resemble the temperature dependence of metals, with characteristic changes of slope in the resistivity curves due to the reduced electron scattering in the magnetically ordered states. Zintl-Klemm concept would predict a limiting composition RE5Si3B0.6 for a valence compound and should then preclude the stoichiometric formula RE5Si3B. Density functional theory calculations carried out on some RE5Si3Zx systems for different interstitial heteroatoms Z and different x contents from 0 to 1 give some support to this statement.