Ternary phosphides

The ternary phosphide Cu4SnPio, prepared by direct synthesis from the elements, contains the highly symmetrical adamantane-type Pjq cage unit (8.25b). Each P atom is tetrahedrally coordinated to metal atoms and other P atoms at distances corresponding to covalent linkages. If the structure is regarded as ionic, the anion corresponds to Pjo . 

The structure of VP4 contains chains as in (8.26a). These consist of distorted edge-sharing [VPg] octahedra which are also linked by V-V bonds. In C0P2, edge-sharing of [CoP]g octahedra occurs without the formation of Co-Co bonds (8.26b) [42]. 

There are many ternary phosphides containing rare earth elanents and a number of these exhibit very varied and interesting magnetic properties. Isostructural series are formed by compounds of types MNi4P2, 

Some Ternary Phosphides with FejP or Co2P-Type Structures 

FIGURE 8.14 Structure of Ca2Cu4P2. (Adapted from A. Mewis, ZAC, 545, 43,1987.) 

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A number of binary phosphides and polyphosphides (compounds containing P—P bonds), for instance those of Mn, Tc, Re, Fe, Ru, Os can be prepared, often in well crystallized form, by the tin-flux technique. The mixture generally containing an excess of P (red P) and a high excess of tin is heated, possibly at a slow rate, to the required temperature (600°-1000°C) and maintained at that temperature for several days and then slowly cooled. In several cases the products may be recovered by dissolving the tin-rich residue in hydrochloric acid. The preparation of several ternary phosphides and of arsenides and antimonides has also been described (see 6.11.3). 

In the review by Kanatzidis et al. (2005), the preparation by the tin-flux method is mentioned also for several ternary phosphides and polyphosphides of rare-earth and transition metals. Typically the components (R metal, T metal, P and Sn in an atomic ratio of about 1 4 20 50) in sealed silica tubes were slowly heated, to avoid violent reactions, up to 800°C, annealed at that temperature for 1 week and slowly (2 K/h) cooled to ambient temperature. The tin-rich matrix was dissolved in diluted hydrochloric acid. The authors described the preparation of compounds corresponding for instance to the formula MeT4P12 (Me = heavy rare-earth metals and Th and U, T = Fe, Ru, etc.) and to the series of phases MeT2P2 (Me is a lanthanide or an actinide and T a late transition metal) having a structure related to the BaAl4 or ThCr2Si2 types. 

The phosphide IrP2 is isomorphous with RI1P2 fr2P and IrPs adopt the anti-CnF2 and skuttemdite stmctures, respectively. Crystalline IrAss and IrSbs also possess a skuttemdite stmcture. Ternary phosphides and arsenides include Ca2fri2P7 andCa5fri9Pi2. ... 

Figure 21 Crystal structures of various ternary phosphide halides. Europium (cadmium, mercmy), phosphorus, and halogeu atoms are drawn as large light grey, filled, and open circles, respectively. Some relevant coordination polyhedra aroimd the phosphorus atoms and the P-P bonds are shown. The HgBr4 tetrahedra in the (Hg2P)2HgBr4 strucmre fill the channels of the three-dimensional [Hg2P] network...

Lithium phosphide reacts with MP (M = Ce or Pr) in the presence of phosphorous vapour to form the ternary phosphides Li2MP2. X-Ray investigation showed... 

In the ternary phosphides (Fei M,t)2P, when M = Mn or Cr it replaces iron at square-pyramidal sites, but when M = Co or Ni it replaces at tetrahedral sites. The magnetically ordered phases give complex spectra which have not been fully interpreted as yet [109]. 

Figure 5 Examples of ternary phosphides with different coordination numbers of heteroatomic bonded metal atoms, (a) Linear unit [BP2] (M3M P2, NasBP2 type), isosteric with CO2 (b) [M (P2)I zig-zag chain with P2 dumbbells (M2M P2, K2PdAs2 type) (P atoms, open...

The ternary phosphide FeTiP (mineral name floren-... 

AlInP. Reacting PH3 with the trimethyl or trIethyl derivatives of aluminium and indium leads to the formation of ternary phosphide films of the two metals [50, 214 to 218], see also [219, 220]. 

GaInP. Of the ternary phosphides of main group 3, films and layers comprising the metals gallium and indium have been investigated most thoroughly. These films are quite often... 

Chikhrii, S.I., Orishchin, S.V., Kuzma, Yu.B. Glovyak,T. (1990). New Ternary Phosphides R3NiyP5 and Their Crystal Structure, Sov.Phys.Crystallogr. 34, 681-684. 

Binary phosphides with nine-fold coordination of P include FCjP, MUjP, NijP, ZrjP, C02P, RujP, RejP, MUjP, FejP, NijP, TijPj and Nb7P4. Nine-fold coordination of P is found in ternary phosphides such as Fei2Zr2P7 and Co4Hf2P3 which have crystal structures closely related to that of FOjP (Figure 8.3) [12,13]. 

The different types of crystal structure found amongst the ternary phosphides are far too numerous to be systematically dealt with here [43-45]. When one component is an alkali or alkaline earth metal, complex anions are liable to be formed (Section 8.4). Most of the ternary phosphides already cited involve replacement one metal atom by alternative atoms while retaining the original type of structure (Figures 8.3, 8.4 and 8.11). 

There are a number of ternary phosphides of composition MM P, which adopt an Fe2P-type (or the closely related C02P type) crystal structure (Table 8.11) (see also Figure 8.3 for Fe2P-type structures). In the MM P structures each P atom has a nine-fold TKD-type coordination (Figure 3.4) by metal atoms, and each metal atom is 12 or more coordinated using both P and metal atoms. Some of these have uses in metallurgy (Chapter 12.19) [44,46]. 

Small amounts of ternary metal phosphides are important for special purposes. Thus, Florenskyite, FeTiP [22], is utilised for precipitation hardening in interstitial-free ferrite steels [23]. Other ternary phosphides with similar (FcjP type) crystal structures (Chapter 8.1), for example, NiCrP, MoNiP and FeNiP can strongly inflnence the microstructure and mechanical properties of glassy metal alloys. 

Krypyakevych (1977) has proposed the systematics of structure types of intermetallic and related compounds based on the analysis of the coordination polyhedra of the smallest atom. This author distinguishes 17 groups to which the coordination polyhedra of the smallest atoms belong. In analyzing the crystal structures of intermetallic compounds some problems, connected with choice of the smallest atom, arise. In the case of the metal compounds with boron, carbon, silicon, and phosphorus the nonmetal element is always the smallest. Kuz ma (1983) successfully used this concept for the analysis of the structure types of borides. In analyzing the structure types of the binary and ternary phosphides we will hold to the systematics developed by Krypyakevych (1977) also because the CPs of phosphorus atoms are given in the figures. 

As illustrated in fig. 32, ternary compounds in R-M-P systems are situated in the part of the diagram system with 0-33.3 at.% of R. Substitution of R by a transition metal with a close atomic radius (Zr, Hf) does not cause an essential change in the number of ternary phosphides formed La-Ni-P (10 compounds), Ce-Ni-P (15), Tb-Ni-P (9) and Zr-Ni-P (12). However, as was shown by Lomnitskaya and Kuz ma (1991b), ternary... 

The structure types of the ternary and quaternary phosphides are presented in order of increasing phosphorus content and at the same P content in order of increasing rare-earth content. Some closely related STs are also discussed. Information about the structure types of ternary phosphides is reported similarly as for binary phosphides above. 

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