Journal of Alloys and Compounds 448 (2008) L1–L4 Letter Study of Ti 2 SC under compression up to 47 GPa Shrinivas R. Kulkarni a,∗ , R. Selva Vennila a , Nishad A. Phatak a , S.K. Saxena a , C.S. Zha b , T. El-Raghy c , M.W. Barsoum d , W. Luo e , R. Ahuja e a Center for Study of Matter at Extreme Conditions (CeSMEC), Florida International University, VH-140, University Park, Miami, FL 33199, United States b Cornell High Energy Synchrotron Source (CHESS), Wilson Laboratory, Cornell University, Ithaca, NY 14853, United States c 3-ONE-2, LLC, Voorhees, NJ, United States d Department of Materials Science and Engineering, Drexel University, Philadelphia, PA 19104, United States e Condensed Matter Theory Group, Physics Department, Uppsala University, Box 530, 751 21 Uppsala, Sweden Received 5 October 2006; received in revised form 11 October 2006; accepted 12 October 2006 Available online 28 November 2006 Abstract The pressure dependence of the lattice parameters of the ternary layered carbide, Ti 2 SC, was measured by using synchrotron radiation X-ray diffraction and a diamond anvil cell setup. The experiment was conducted at room temperature and no phase transformation was observed up to the maximum pressure of 47 GPa. The a and c lattice parameters at room condition are 3.216 ˚ A and 11.22 ˚ A, respectively. The bulk modulus, calculated using the Birch–Murnaghan equation of state, is 191 ± 3 GPa, with a pressure derivative of 4.0 ± 0.3 and that obtained by our ab initio calculations is 183GPa, with a pressure derivative of 4.1. Like the majority of the ternary layered carbides (MAX phases), compressibility along the c-axis was higher than that along the a-axis. Published by Elsevier B.V. Keywords: Ti 2 SC; High pressure; Diamond anvil cell; Bulk modulus 1. Introduction The history of the ternary layered carbides traces long back when Nowotny and coworkers [1] synthesized a large number of these materials, which were called H– or Hagg phases. Most of these materials have a M 2 AX stoichiometry, where, M is an early transition metal, A is an A-group element and X is C or N. They are hexagonal with a space group of P6 3 /mmc [1,2]. After this pioneering work, these phases were essentially ignored until a decade ago, when Barsoum and El-Raghy, reported their work on Ti 3 SiC 2 . More compounds with different stochiometries were found afterwards and it was discovered that all these compounds belonged to the same family and were called M n+1 AX n (MAX) phases, where n =1, 2 or 3 and M, A and X have the same meaning, respectively, as mentioned above. Depending on the value of n these compounds were further referred to as 211, 312 or 413 MAX phases [3]. ∗ Corresponding author. E-mail address: skulk004@fiu.edu (S.R. Kulkarni). These materials possess unusual, and sometimes unique, combinations of properties. On one hand, they behave as metals in terms of their machinability, electrical and thermal conduc- tivities, on the other hand they behave as ceramics in terms of their specific stiffnesses [4–7]. Onodera et al. [8] reported on the bulk moduli, K 0 , of these phases. They showed that K 0 of Ti 3 SiC 2 was quite high and that the compressibility along the c-axis was higher than that along the a-axis. Since then the bulk moduli of Ti 3 Si 0.5 Ge 0.5 C 2 [9], Zr 2 InC [10], Nb 2 AsC [11], Ti 2 AlN [12], Ti 3 GeC 2 [13], Ti 4 AlN 3 [14] and M 2 AlC [15] (M=Ti, Cr, V, Nb, Ta) have been determined. In general all these phases have K 0 around 200 ± 20 GPa, except for Cr 2 AlC and Zn 2 InC, and the compressibilities along the a-axis are higher than those along the c-axis, except for Nb 2 AsC, Nb 2 AlC and Cr 2 AlC. For the Ta-containing phases, the compressibilities in both directions are almost identical [15,16]. All the phases were stable up to pressures ≈50 GPa. If the pressure is not hydrostatic, however, a strain induced  to  type phase transition is observed at 26.6 GPa for Ti 3 GeC 2 [13]. A similar transition was theoretically predicted for Ti 3 SiC 2 [17] 0925-8388/$ – see front matter. Published by Elsevier B.V. doi:10.1016/j.jallcom.2006.10.086