Synthesis, crystal growth and structure of Mg containing β-rhombohedral boron: MgB17.4

✍ Scribed by Volker Adasch; Kai-Uwe Hess; Thilo Ludwig; Natascha Vojteer; Harald Hillebrecht

• Book ID: 104029560
• Publisher: Elsevier Science
• Year: 2006
• Tongue: English
• Weight: 508 KB
• Volume: 179
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1016/j.jssc.2006.03.009

✦ Synopsis

For the first time, single crystals of Mg containing b-rhombohedral boron MgB 17.4 were synthesised from the elements in a Mg/Cu melt at 1600 1C. The crystal structure determined by the refinement of single crystal data (space group R-3m, a ¼ 10:991ð2Þ Å, c ¼ 24:161ð4Þ Å, 890 reflections, 123 variables, R 1 ðF Þ ¼ 0:049, wR 2 ðIÞ ¼ 0:122) improves and modifies the former structure model derived from earlier investigations on powder samples. Mg is located on four different positions with partial occupation. While the occupation of the sites D (53.3%), E (91%) and F (7.2%) is already known from other boron-rich borides related to b-rhombohedral boron, the occupation of the fourth position (18h, 6.7%) is observed for the first time. Two boron positions show partial occupation. The summation reveals the composition MgB 17.4 and Mg 5.85 B 101.9 , respectively, confirmed by WDX measurements. The single crystals of MgB 17.4 show the highest Mg content ever found. Preliminary measurements indicate no superconductivity.