Ternary compounds, formation

Figure 5.41. Schemes of ternary compound formation in ternary alloys. For a few metal pairs (Al-Cu, Al-Fe, etc.) the third elements are indicated (defined by their position in the Periodic Table) with which true ternary phases are formed that is, phases are formed which are homogeneous in internal regions of the composition triangle not connected with the corners or edges. Compare these data with those shown for the formation of binary compounds in the figures relevant to the involved metals.

Just as an example about the ternary intermetallic reactivity, a few schemes of ternary compound formation for aluminium are given in Fig. 5.41, summarizing the formation capability of (true) ternary compounds. Data are generally available (although partial) about ternary aluminium alloys with selected metals (Fe, Mg, Si, etc.), owing to their relevant applications and commercial interest. With reference to the indicated metal pairs (Al-Fe, Al-Co, Al-Cu, etc.), the preferential formation of compounds with metals is evident. 

Reactions of Compounds and Sulfur-Additive Mixtures. When additives and compounds are used to retain sulfur in the positive electrode there are other possible reactions, in addition to the usual electrochemical reactions, that can take place at the positive electrode. These include electrochemical oxidation and reduction of the additive (or compound ) and interaction of the additive with the electrolyte. In addition, there is the possibility of ternary compound formation from a reaction between the discharge product, Li2S, and sulfur compounds. Because the arsenic—sulfur system has undergone the most intensive investigation for use in lithium—sulfur cells, examples of the aforementioned reactions using arsenic are shown below ... 

The reaction of NH3 with gallium double oxides gives no ternary compound formation. At low temperatures, however, two modifications of the new phase Gai- /sD c/sNi- cOx, where x l, can be isolated. ... 

The regularities of ternary compound formation in ternary systems ... 

It has been found that the most influential factors for ternary compound formation are Z,/(Rj+R ) and R /Rj in this type of systems. Larger zy(R +R ) and larger R /Rj correspond to ternary intermediate compound formation. This fact can be explained as follows According to Pauling s first rule of the crystal structure of complex ionic... 

Figure 2. Formation of ternary borides and phase equilibria within ternary boride systems of the type M-M-B or M-Y-B (M = metal, Y = honmetal). , complete isothermal section established B, part of a diagram only. Numbers in the lower part of each square correspond to the refs, to the ternary section. The number of ternary compounds observed is indicated in the right upper corner of each square.

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.

ArV is not necessarily positive, and to compare the relative stability of the different modifications of a ternary compound like AGSiOs the volume of formation of the ternary oxide from the binary constituent oxides is considered for convenience. The pressure dependence of the Gibbs energies of formation from the binary constituent oxides of kyanite, sillimanite and andalusite polymorphs of A SiOs are shown in Figure 1.10. Whereas sillimanite and andalusite have positive volumes of formation and are destabilized by pressure relative to the binary oxides, kyanite has a negative volume of formation and becomes the stable high-pressure phase. The thermodynamic data used in the calculations are given in Table 1.7 [3].1... 

Fig. 2. The Bonnichsen, Chance, and Theorell 34) mechanism for the dismutation of hydrogen peroxide by catalase. (A) The simple ping-pong mechanism (ferric-peroxide compound (ycle) involves only the successive formation and decomposition of the compound 1 intermediate by two successive molecules of H2O2. (B) Reversible ES(Fe -H202) and ternary (compound I-H2O2]) complexes are added to the mechanism in A.

During this period, various aspects of Miedema s methods for predicting the heat of formation of binary compounds were assembled and eventually published in book form (de Boer et al. 1988). This included the application of the technique to predict the thermodynamic behaviour of some ternary compounds. Whilst only applicable to a restricted set of crystallographic structures, this was nevertheless a significant development, as a common objection to the CALPHAD approach was that the existence of ternary compounds could never be predicted solely from binary data. 

The incorporation of Cu ions in the perovskite structure is known for only a few examples since this particular structure is normally stabilized by or requires a B atom in a high formal oxidation state such as Ti4+ in BaTiOs, or Rhs+ in LaRhOs. Further, since Cu can not be readily stabilized in its Cu(m) state, and is unknown in the tetravalent state, the simple formation of ternary compounds such as LaCuOg or BaCuOs is not expected. Even in the K2NiF4 structure, the stabilization of Cu4+ as in Ba2Cu04 is not expected, but the formation of a stable Cu(II) state is a distinct possibility, as in La2Cu04. Copper(II), however, has been introduced in the doubled-or tripled-perovskite structure. Examples of these, which include structural distortions from cubic symmetry, are listed ... 

Table 2.3 lists ternaries that have been deposited, together with indication of when clear single compounds formation was verified. While solid solution formation is usually the goal of these smdies, it should be kept in mind that separate phases, either as a composite or as separate layers, may be required for some purposes. For example, bilayers of CdS/ZnO and CdS/ZnS have been deposited from single solutions. These depositions depend on the preferential deposition of CdS over ZnS and, in the case of the former, the often-encountered greater ease of formation of the oxide (hydroxide) than the sulphide of Zn. 

By depositing two (or more) different layers and annealing them, intermixing of the layers can lead to ternary and multinary compounds, although clear compound formation does not always occur. Thus, annealing (at 150°C, a relatively low temperature) ZnS-Cuj S and BbS-Cu S films resulted in extensive interdiffusion of the metallic elements but no XRD confirmation of solid solution formation [199]. On the other hand, Sb2S3-CuS layers converted fully to CuSbS2 at 400°C, which ex-... 

It is fair to state that the understanding of deposition of ternary compounds lags behind that of binaries. A better understanding of the factors that control codeposition, as well as solid solution formation, is needed. However, it is also clear that there is scope for deposition of a wide range of compounds, not only ternaries, but quaternaries and even higher-multinary materials. Additionally, the scope for deposition of mixed-phase fdms, either as consecutive layers (as shown earlier) or as composites, is great, and this aspect of CD will undoubtedly be pursued. 

Ionic compounds consist of positive ions (cations) and negative ions (anions) hence, ionic compounds often consist of a metal and nonmetal. The electrostatic attraction between a cation and anion results in an ionic bond that results in compound formation. Binary ionic compounds form from two elements. Sodium chloride (NaCl) and sodium fluoride (NaF) are examples of binary ionic compounds. Three elements can form ternary ionic compounds. Ternary compounds result when polyatomic ions such as carbonate (C032 ), hydroxide (OH-), ammonium (NH4+), form compounds. For example, a calcium ion, Ca2+, combines with the carbonate ion to form the ternary ionic compound calcium carbonate, CaC03. Molecular compounds form discrete molecular units and often consist of a combination of two nonmetals. Compounds such as water (H20), carbon dioxide (C02), and nitric oxide (NO) represent simple binary molecular compounds. Ternary molecular compounds contain three elements. Glucose ( 12 ) is a ternary molecular compound. There are several distinct differences between ionic and molecular compounds, as summarized in Table 1.2. 

Sleight and Jeitschko (107) studied the Bi-Fe-Mo oxide system by X-ray diffraction. They reported the formation of a ternary compound, Bis(Fe04) (Mo04)2. The X-ray pattern of this compound was similar to that reported for compound X by Batist (106). 

Formation of Ternary Oxides12 Many compounds of mineralogical importance are ternary compounds of oxygen with a formula ABaO +, where A = Ca, Mg, Mn, Fe, Co, and Ni, and B = Si, W, C, and S. These compounds may be considered to be formed from the reaction of the binary oxides. That is... 

As the two binary compounds approach each other in acid/base character, the enthalpy of formation gets less negative. For ternary compounds formed from very similar binary oxides (for which the data are not shown), such as (AI2O3 + SiC>2), (CuO + Fe2C>3), and (Fe2C>3 + TiC>2), the AtH values are, in fact, endothermic. 

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