Formation of Ternary Oxides

Figure 7.15 (a) Enthalpy of formation of ternary oxides and nitrides from their binary constituent compounds as a function of the ratio of ionic potential [16]. Reprinted with permission from [16] Copyright (1997) American Chemical Society, (b) Gibbs energy of the oxide-sulfide equilibrium for group 1 and 2 metals at 1773 K as a function of the optical basicity of the metal. 

We will focus on looking for factors that determine the energy (or enthalpy) of formation of ternary oxide compounds. Oxides can be characterized on an acid/base scale. An acidic oxide, AnO, is an oxide ion donor, while a basic oxide, B 0, is one that accepts another oxide ion. The two reactions can be represented as... 

The Reaction of Am02 and Ani203 with the Oxides of Group V Elements. In its reactions with group V elements americium behaves like a typical rare earth element. When using Am02 as the americium component there is always loss of oxygen and the formation of ternary oxides... 

Formation of mixed oxides Formation of ternary oxides or sulfides... 

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. 

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... 

Conclusions These experiments support a hypothesis that acid/base considerations determine the energetics and stabilities of ternary oxide formation. The enthalpies of formation of the ternary oxides from the constituent binary oxides support this hypothesis, since the enthalpies get increasingly more exothermic with increasing strength of the acids and bases that react. Across the... 

General reviews of the use of oxide semiconductors for the photoelectrolysis of water are contained in Refs. 62 and 65 (see Table 1). Eleven binary and ternary oxides were examined in Ref. 62. Linear correlations were presented between the flat band potential, Vtb of these oxides and their band gap energy (Eg) and between Vm and the heat of formation of the oxide per metal atom per metal-oxygen bond. Aligning all the oxide energy levels on a common scale, these authors noted62 that the position of the conduction band varies much more than those of valence bands - a trend expected from the cationic (d-band) character of the conduction band in the oxide while the valence band is mainly of 0(2p) character. The latter should be relatively independent of the oxide parentage in terms of the metal. 

Analogous to the formation of ternary oxosilicates by reaction of an alkaline metal oxide with an acidic nonmetal oxide the synthesis of a ternary phosphorus nitride is possible (Scheme 1). 

In a similar way, it seems difficult to explain how Cu is bound to the manganese oxides that are formed in the water column and would thus have to scavenge Cu from solution at these low [Cu2+] levels. Straightforward competition between complexation in solution and on surfaces may be too simplistic. The formation of ternary complexes of metal ions with surfaces and organic ligands is a possible binding mechanism. It was demonstrated in some model systems (39), but is poorly known for natural systems. 

The Barin tables are far more complete in coverage than any of the sources described above. All of the natural elements and their compounds are included. In addition to the substance types listed in USBM Bull 677, the Barin tables include a large number of ternary oxides - aluminates, arsenates, borates, chromates, molybdates, nitrates, oxy-halides, phosphates, titanates, tungstates, selenates, vanadates, zirconates, etc. - as well as cyanides, hydroxides, complex silicates and inter-metallic compounds. The only substances not included by Barin, for which tables can be found elsewhere, are the ionized-gas species and a limited number of gas species important only at very high temperatures, which are listed in the JANAF tables. For each table Dr. Barin gives references for each of the major thermochemical values employed (enthalpy of formation and entropy at 298 K, and heat capacity). Like the USBM Bulletins, no attempt is made to discuss the choice between conflicting data sources. 

Bonneviot L, Clause O, Che M, Manceau A, Dexpert H (1989b) EXAFS characterization of the adsorption sites of nickel ammine and ethyldiamine complexes on a silica surface. Catalysis Today 6 39-46 Bomebusch H, Clausen BS, Steffensen G, Liitzenkirchen-Hecht D, Frahm R (1999) A new approach for QEXAFS data acquisition. J Synchrotron Rad 6 209-211 Bostick BC, Fendorf S, Barnett MO, Jardine PM, Brooks SC (2002) Uranyl surface complexes formed on subsurface media from DOE facilities. Soil Sci Soc Am J (2002) 66 99-108 Bottero JY, Manceau A, Villieras F, Tchoubar D (1994) Structure and mechanisms of formation of iron oxide hydroxide (chloride) polymers. Langmuir 10 316-319 Bourg ACM, Joss S, Schindler PW, (1979) Ternary surface complexes 2. Complex formation in the system silica-Cu(II)-2,2 bipyridyl . Chimia 33 19-21... 

C. J., and Ceder, G. (2012) Accuracy of density functional theory in predicting formation energies of ternary oxides from binary oxides and its implication on phase stability. Phys. Rev. B, 85 (15), 155208. 

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