Complete solid solutions

FIG. 22-1 phase diagram for components exhibiting complete solid solution. (Zief and Wilcox, Fractional Solidification, -ool. 1, Marcel Dehher, New York, 1967, p. 31. )... 

When solid alloys have a positive heat of mixing, AHm, complete solid solution occurs above the temperature where TASm is more negative than the heat... 

AO-BO Sodium chloride MgO-NiO, complete solid solution often possible... 

Many minerals show exsolution textures. For these minerals, there is complete solid solution at sufficiently high temperatures, but a miscibility gap at lower temperatures. The alkali feldspar, (Na, K)AlSi30s, is an example. Suppose a roughly homogenous mineral of intermediate composition cools down and into... 

Fluorapatite is a highly insoluble calcium phosphate phase. The solubility product of stoichiometric fluorapatite at 37°C is 3.19 0.14x10 " mol 1 (for Cas(P04)3F as reported by Moreno et al. [53]) and appears significantly lower than that of HA in the same conditions (7.36 0.93 x 10 ° mol for Ca5(P04)30H). Asuggested explanation for this very low solubility product is that cohesive forces are stronger in fluorapatite than in other apatites due to smaller unit-cell dimensions. The complete solid solution Ca-,o(P04)6(OH)2-xFx can be obtained. Initial solubility determinations have shown a solubility minimum for x close to 1 [54], related to the formation of hydrogen bonding between F and OH ions. These results were subsequently... 

Trivalent Solutes. It has proven difficult to find a trivalent cation that substitutes exclusively for Fca ions over a complete solid-solution range. However, Dehe et al." have compared Mossbauer, neutron-diffiaction, and saturation magnetization data to arrive at the following formulations ... 

There has been only one report to date on superconductivity in the BaPbj S Oj perovskite series (11). From BaPbOs, where no superconductivity is observed, Tc rises to approximately 3.5K for x=0.25-0.3 and drops rapidly to below 1.5K for larger values of x. Because the BaSbOs perovskite does not exist, a complete solid solution is not expected. The limiting Sb concentration appears to be x=0.5. The electronic properties have not been studied in any detail, but the visual appearance of the materials suggests considerable changes within the solid solution... 

Ningyoite is an orthorhombic hexagonal phosphate (Hikichi et al. 1989). Because of structural differences, a complete solid solution between... 

One important aspect of experimental studies is the ease with which alkali or other ions are exchanged in a given zeolite structure. It would appear that complete solid solution in a given crystal structure is frequently possible (Zhdanov, 1970 Breck, 1970 Taylor and Roy, 1964 ... 

Zircon, complete solid-solution behavior is observed, and a plot of the unit cell volume against x shows that Vdgard s Law is followed. When the end members are not is structural, a systematic change in the solubility range in both structures is found as A is varied, and the data have been systematized in terms of a simple, potentially predictive, structure-field map. The pervasive polymorphism of these ABO4 compounds, involving both reconstructive and displacive transformations and metastable structures produced by different sample preparation methods, indicates that the crystal structural stability of substituted compounds needs to be carefully evaluated as a function of temperature to assess the structural integrity of waste-form materials. 

Of the Cr—Mo—S, Cr—W—S, and Mo—W—S ternary systems, only Mo—W—S has been studied from 500—1000 °C, by Moh and Udubasa371. Details of the binary systems Mo—S and W—S are given above. The metallic system Mo—W is characterized by a complete series of solid solutions between the endmembers with continuous liquidus and solidus relations381. Complete solid solution series were also found to occur be-... 

The quaternary phase relations have been briefly discussed44,4S. The phase relations within the Fe—Cu—Mo—S system are influenced by the complete solid solution series between X-phase ( CuMo2S3) and Y-phase ( FeMo4S6), Fig. 24. 

Series of experiments were performed to outline the high-temperature phase relations of the X—Y phase solid solution series5, Fig. 25. Details of the individual ternary reactions have been discussed above. Both endmembers, the X-phase and the Y-phase, stable above 594 4 °C and 535 15 °C, respectively, form a complete solid solution series of pseudo-character, ie., at low temperatures Cu + MoS2 +... 

In most compounds containing two cation types some variability in composition is possible. This varies from less than 0.1% in compounds such as BaTi03, in which there is a marked difference in charge and size between the two cations corresponding to differences between their lattice sites, to complete solid solutions over the whole possible range where the ions are identical in charge and close in size and can only occupy one type of available lattice site such as, for instance, Zr4+ and Ti4+ in Pb(ZrvTi v)()3. 

Microstructurally, alloys are composed of alloy constituents that include alloy phases and, in some cases, unalloyed metals. Crystalline alloy phases can be subdivided into intermetallic phases, metal-nonmetal compounds such as borides or carbides see Borides Solid-state Chemistry Carbides Transition Metal Solid-state Chemistry), and terminal or complete solid solutions. 

The monazite structure is dimorphous with xenotime (zircon stmcture-t5q)e), and is one of the major natural hosts of Th and U in cmstal rocks the tetravalent actinides can be accommodated in conjunction with a large divalent cation in a coupled substitution for lanthanide elements, e.g., complete solid solution is found between brabantite, (Cao sTho 5)P04, and monazite-(Ce), CeP04 [51]. Ternary compositions, and partial occupancy are also mechanisms of actinide substitution (Table 5). 

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