Rare ternary

The structure and models describing chemical reactions are almost trivial. Chemical kinetics generally takes into consideration binary and, rarely, ternary interactions among the molecules. It is a natural tendency to decompose complex phenomena into binary, or perhaps ternary interactions. Therefore the formal theory of chemical kinetics can be extended to describe transformation phenomena (using the term in a broad sense) in populations whose basic components are not molecules. 

In ternary systems, we distinguish between two common types. In type II, two binaries are partially miscible and the third binary is completely miscible in type I, only one binary is partially miscible. (A third type, where all three binaries are only partially miscible, is relatively rare and not considered here.)... 

The GdAlgB O QiCe ", Tb " is synthesized by a soHd-state firing of the rare-earth coprecipitated oxide plus boric acid and MgCO at 900° C in a slightly reducing atmosphere. As in the case of the lanthanum phosphate phosphor, a flux is usually used. The synthesis of this phosphor is further comphcated, however, by the fact that it is a ternary system and secondary phases such as gadolinium borate form and must then react to give the final phosphor. 

Although there are several hundred biaary nitrides, only a relative few ternary bimetallic metal nitrides are known (6). A group of ternaries of the composition where M is an alkah, alkaline-earth, or a rare-earth metal and M is a transition or post-transition metal, have been synthesized (6). 

Azeotropic compositions are rare for terpolymerization and Ham 14 has shown that it follows from the simplified eqs. 38-40 that ternary azeotropes should not exist. Nonetheless, a few systems for which a ternary azeotrope exists have now been described (this is perhaps a proof of the limitations of the simplified equations) and equations for predicting whether an azeotropic composition will exist for copolymerizations of three or more monomers have been formulated.20113 This work also shows that a ternary azeotrope can, in principle, exist even in circumstances where there is no azeotropic composition for any of the three possible binary copolymerizations of tire monomers involved. 

The crystal structures of the borides of the rare earth metals (M g) are describedand phase equilibria in ternary and higher order systems containing rare earths and B, including information on structures, magnetic and electrical properties as well as low-T phase equilibria, are available. Phase equilibria and crystal structure in binary and ternary systems containing an actinide metal and B are... 

Figure 1. Formation of ternary borides MreMj3B2 and different structure types (Mre = rare-earth element, M-p = transition-metal element). , CeCo3B2 type ErIr3B2 type O, URujBj type El, Ndo7,Rh3 29B2 type IS, YOS3B2 type B, Laofi3Rh3B2 type , compound formation observed, but structure type unknown. Refs a , b , c , d e , f g , h , i , j ", k , 1 , m , r, s - , t u = 45 see also ref. 62.

Because they exhibit interplay of magnetic and superconducting properties, the formation and crystal chemistry of MRgMy4B4 compounds have been examined. Ternary rare-earth and actinide (Th, U, Pu)-transition metal borides of the approxi-... 

Figure 2. Formation of ternary borides MREMT4B4 (Mre = rare-earth element, Mj = transition metal) and different structure types. B, CeCo4B4 type B, LURU4B4 type a, NdCo4B4 type H, YOS4B4 type 8, Sm,4.eFe4B4 type MRcRe4B4 type , LuRh4B4type. Refs b, c , d", e, f , g , h, il l ...

For the larger rare-earth metals ternary diborides are formed, having tKe CeCr2B6 structure. Here puckered B nets are incompletely developed, with Bj groups in the form of loosely attached 6 -network fragments (B—B 210 pm). There is a resemblance to the structures of W3lrB6 and W2C0B2 (see Fig. 4). 

We were one of the first groups to report a ternary selenophosphate of a rare-earth metal [11-13]. Since that time, we have uncovered a host of rare-earth metal chalcophosphates [1, 13, 14] that complement the transition-metal compounds found by the Kanatzidis group [15-31]. Despite the host of publications in the area of metal chalcophosphate chemistry, there have only been our systematic studies of the quaternary phase space of the rare-earth metal chalcophosphates [1, 13, 14]. 

When the fact that ternary collisions are relatively rare occurrences is combined with the fact that there will probably be severe geometric restrictions on such reactions, one concludes that these reactions must have relatively low activation energies or else their reaction rates would be vanishingly small. This expectation is confirmed by experimental data on such reactions. 

After the discovery of the Al6Mn i-QC [1], development of QCs were limited for almost a decade to ternary systems with a major A1 constituent, such as Al-(Pd,Mn)-Si, Al-Zn-(Li,Mg), Al-Cu-TM (TM = Fe, Ru, Os), Al-Pd-(Mn,Re) [2,25,26], (This may be the reason why jargon such as Al-based QCs was coined.) After all, most QC discoveries were achieved by chemical additions to, or substitutions in, known compounds. From the mid-1990s to about 2000, QCs were also found in Zn-Mg-R (R = rare-earth-metal), Cd-Mg-R, and (Yb,Ca)-Cd systems, the last being the first stable binary i-QC at room temperature. Experience and insight are worth a lot — Tsai and coworkers produced 90% of these i-QCs [27],... 

The transition-metal monopnictides MPn with the MnP-type structure discussed above contain strong M-M and weak Pn-Pn bonds. Compounds richer in Pn can also be examined by XPS, such as the binary skutterudites MPn , (M = Co, Rh, Ir Pn = P, As, Sb), which contain strong Pn-Pn bonds but no M-M bonds [79,80], The cubic crystal structure consists of a network of comer-sharing M-centred octa-hedra, which are tilted to form nearly square Pnn rings creating large dodecahedral voids [81]. These voids can be filled with rare-earth atoms to form ternary variants REM Pnn (RE = rare earth M = Fe, Ru, Os Pn = P, As, Sb) (Fig. 26) [81,82], the antimonides being of interest as thermoelectric materials [83]. 

As a final comment on terminology, we note that elemental semiconductors are formed from a single element, e.g., Si or Ge, whereas compound semiconductors are formed from two binary), three ternary), four quaternary), or, rarely, more elements. Semiconductor alloys refer to solid solutions where either one anion or one cation can substitute for another, or possibly two or more such substitutions can occur for a binary semiconductor AB a simple alloy with C would be represented as Ai CjcB. Semiconductors are often classified by the group numbers in the periodic table. Thus, for example, I-VII semiconductors include Cul and AgBr, II-VI semiconductors include ZnS, CdTe, and HgTe, III-V semiconductors include GaAs, GaN, InP, and InSb, and IVx-VIv semiconductors include PbSe and Sn02. Fundamental physical properties are compiled in a recent handbook [22]. 

In the ideal case, the structure of the ternary complex is known by X-ray crystallography or NMR. This would be of great help in designing the linker by molecular modeling. Unfortunately, this ideal case is rather rare. Fortunately, there are several other clues to designing a successful linkage with the help of NMR. The atoms on both fragments to which the linker should be attached can be identified by a combination of various techniques ... 

Typically, binary Laves compounds AM2 are formed in several systems of A metals such as alkaline earths, rare earths, actinides, Ti, Zr, Hf, etc., with M = Al, Mg, VIII group metals, etc. Laves phases are formed also in several ternary systems either as solid solution fields extending from one binary phase (or possibly connecting the binary phases of two boundary systems) or as true ternary phases, that is forming homogeneity fields not connected with the boundary systems. 

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