Journal of Solid State Chemistry 160, 156 }166 (2001) doi:10.1006/jssc.2001.9210, available online at http://www.idealibrary.com on New Ternary Phases in the Mo+Ni+P System: Synthesis and Crystal Structures S. V. Oryshchyn,*- C. Le Se H ne H chal,* S. De H putier,* J. Bauer,* R. Gue H rin,* and L. G. Akselrud- *Laboratoire de Chimie du Solide et Inorganique Mole & culaire, UMR CNRS 6511, CNRS}Universite & de Rennes 1, Institut de Chimie, Campus de Beaulieu, Avenue du Ge & ne & ral Leclerc, 35042 Rennes Ce & dex, France; and -Analytical Chemistry Department, Ivan Franko State University, Kyrylo and Mefodij Street 6, 290005 L'viv, Ukraine E-mail: roland.guerin@univ-rennes1.fr Received December 16, 2000; in revised form March 29, 2001; accepted April 12, 2001; published online June 12, 2001 A reinvestigation of the ternary system Mo+Ni+P has been established using X-ray di4raction, scanning electron micros- copy, and electron probe microanalysis. This up-to-date system shows 10 ternary phosphides, which were mostly structurally characterized from X-ray powder or single-crystal data. Among these phosphides, three new ternary phases are reported for the 5rst time: triclinic Mo 8.58 Ni 7.42 P 6 (a  7.0079(4) A  , b  7.0290(4) A  , c  7.0308(4) A  ,   68.893(3)3,   73.196(3)3,   60.149(3)3, space group P1  , new structure type), cubic Mo 3 Ni 2 P 1.18 (a  10.846(2) A  , space group F4  3m, Mn 3 Ni 2 Si- type structure), and tetragonal Mo 2.675 Ni 0.325 P(a  9.733(1) A  , b  4.7805(7) A  , space group I4  , Mo 3 P-type derivative struc- ture). These phases were prepared from the elements by high- temperature annealing at 13503C, and their crystal structures exhibit numerous strong metal+metal bonds in agreement with their metal-to-nonmetal ratio higher than 2.5. Indeed, in a gen- eral way, the phosphorus coordination number for Mo and Ni atoms is relatively small so that metallic arrangements as [Ni 4 ] tetrahedra and [Mo 6 ] octahedra can be considered as examples in the structures of Mo 8.58 Ni 7.42 P 6 and Mo 3 Ni 2 P 1.18 , respectively.  2001 Academic Press Key Words: molybdenum nickel phosphides; crystal data; structural relationship; electron probe microanalysis. INTRODUCTION The "rst results on the ternary Mo}Ni}P system were obtained at the end of the 1970's when the composition lines NiP}MoP and Ni  P}&&Mo  P'' were studied at 10003C by Gue H rin and Sergent (1, 2). Two ternary phases, namely MoNiP  and MoNiP, with hexagonal symmetry, were dis- covered at that time. The "rst one, a new structural type, exhibited strong linear and in"nite }Mo}Ni}Mo} chains (3), whereas the second one, MoNiP, was found to be in fact the Mo-rich limit of a solid solution Ni  Mo  P (04x41) of Fe  P type (4). Approximately at the same time, Oryshchyn et al. estab- lished at 8503C the isothermal section of the Mo}Ni}P phase diagram by means of X-ray analysis (5). In addition to the phases mentioned above, "ve new phosphides were isolated and labeled from I to V:I}Mo  Ni  P, II&Mo  Ni  P  , III}Mo  Ni  P  , IV&Mo  Ni  P  , and V&Mo  NiP. In a second step, the crystal structures of I}Mo  Ni  P and III}Mo  Ni  P  were solved by X-ray pow- der and single-crystal determination, respectively (5, 6). In contrast, in the absence of single crystals or pure samples, no crystallographic data for the last three phases II&Mo  Ni  P  , IV&Mo  Ni  P  , and V&Mo  NiP could be obtained. The goal of this study was therefore to synthesize at higher temperature the last three phosphides in order to obtain single crystals suitable for their structure determina- tion. This paper deals with the results that were obtained after successive anneals of the samples at 1150 and 13503C, using X-ray di!raction (XRD), scanning electron micros- copy (SEM), and electron probe microanalysis (EPMA). In addition, for the "rst time the crystal structures of the new ternary phases Mo  Ni  P  , Mo  Ni  P  , and Mo  Ni  P are described. EXPERIMENTAL Sample Preparation The samples were prepared either as powders or as single crystals. The required amounts of the constituent elements, all as powders (Mo and Ni, purity 99.9%; and red phos- phorus, purity 99.99%) were mixed, cold-pressed as pellets, and "rst annealed at 10003C for two days in vacuum-sealed silica tubes. After cooling, samples were ground to powder, cold-pressed again, and reannealed at 11503C under the same conditions for one week. After quenching, they were pulverized for X-ray powder di!raction. To obtain single crystals, a second step was necessary. The previous samples were cold-pressed again and loaded 156 0022-4596/01 $35.00 Copyright  2001 by Academic Press All rights of reproduction in any form reserved.