aMatériaux et Phénomènes Quantiques - UMR 7162, Université Paris 7, 2 place Jussieu, F-75251 Paris Cedex 05, France bDepartment of Metallurgy, University of Belgrade, VJ12, 19210 Bor, Serbia and Montenegro
Received 26 January 2006; revised 25 May 2006; accepted 29 May 2006. by J.F. Sadoc. Available online 21 June 2006.
Superhard materials have many industrial applications, wherever resistance to abrasion and wear are important. The synthesis of new superhard materials is one of the great challenges to scientists. We re-examined the phase diagram of the binary osmium–boron system and confirmed the existence of two hexagonal phases, OsB1.1, Os2B3, and an orthorhombic phase, OsB2. Almost nothing is known about the physical properties of osmium borides. Microhardness measurements show that OsB2 is extremely hard. Ab initio calculations show that this is due to formation of covalent bonds between boron atoms. OsB2 is also a low compressibility material. It can be used as hard coating.
Keywords: A. Superhard materials; A. Osmium diboride; D. Electronic properties; E. Ab initio calculations