Solid Solution Range

Niobium-Molybdenum The addition of molybdenum to niobium within the solid solution range gives improved corrosion resistance to hydrochloric and sulphuric acids. 

TABLE 4.2 Some Mineral Systems Showing Broad Solid Solution Ranges... 

The F center absorption maximum for KC1 is at 565 nm and that for KF is 460 nm (Table 9.1). (a) What is the composition of a natural crystal with color centers showing an absorption peak at 500 nm (b) If the absorption peak for KF corresponds to the promotion of an electron from the F center to the conduction band, determine the energy of the color center with respect to the conduction band. (The band gap in KF is 10.7 eV.) If the relative position of the color center energy level remains the same throughout the KF-KC1 solid solution range, estimate (c) the band gap of KC1 and (d) the band gap for the natural crystal. 

The given ratios and compositions are short indications of solid solution ranges, which can even overlap. It has to be noted, moreover, that the number of electrons to be considered may be uncertain. The VEC values, therefore, indicate only a composition range where one of the aforementioned structure types may occur. 

A few general remarks about a group of metal-hydrogen phases have been included in 3.8.4.1 where interstitial hydrogen solutions in metallic structures have been described. However, as previously observed, a number of intermediate phases are also formed in several systems. A short summary of these is shown in Table 5.2 where their formulae very often have only an indicative character and several structure types correspond to more or less extended solid solution ranges. 

Table 5.2. Structures of a few selected hydrogen-metal compounds. The formulae very often have only an indicative character. Solid solution ranges are frequently observed.

Compounds with the 16th group elements. Among the various phases formed with these non-metal elements, the normal valence compounds, NaCl type, may be mentioned. Some of them have been described as point compounds (for instance BaS, BaSe, BaTe) a few others as corresponding to a solid solution range (for instance, EuS 43-50 at.% S, EuTe 50-57 at.% Te). 

Ru and Os alloys. A specimen of structure types observed in the alloys of these metals (very often as solid solution ranges) is shown in Table 5.48a. The formation of Laves-type phases, a phases and several CsCl-type phases can be underlined. Notice the formation of marcasite and pyrite type compounds with the semimetals and non-metals of the 15th and 16th groups. 

Characteristics and implementation of the treatments depend on the expected results and on the properties of the material considered a variety of processes are employed. In ferrous alloys, in steels, a eutectoid transformation plays a prominent role, and aspects described by time-temperature-transformation diagrams and martensite formation are of relevant interest. See a short presentation of these points in 5.10.4.5. Titanium alloys are an example of the formation of structures in which two phases may be present in comparable quantities. A few remarks about a and (3 Ti alloys and the relevant heat treatments have been made in 5.6.4.1.1. More generally, for the various metals, the existence of different crystal forms, their transformation temperatures, and the extension of solid-solution ranges with other metals are preliminary points in the definition of convenient heat treatments and of their effects. In the evaluation and planning of the treatments, due consideration must be given to the heating and/or cooling rate and to the diffusion processes (in pure metals and in alloys). 

Introductory remarks. Phases related to the 1 3 stoichiometry and their derivative structures, either as point compounds or as solid solution ranges, are frequently found in binary and ternary intermetallic alloy systems. 

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 ... 

Figure 1.3 Proposed CH4-H2O T-x phase diagram with the solid solution range (P 5 MPa). Regions expanded for ease of viewing. (Reproduced from Huo, Z., Hester, K.E., Sloan, E.D., Miller, K.T., AlChE. /., 49, 1300 (2003). With permission.)...

Superconductivity has been found in metallic elements and intermetallic compounds and within their solid-solution-range. But, superconductivity has not been found in an alloy with an arbitrary composition. 

Fig. 11. The shaded area represent compound, Nb3Al with the solid solution ranged from 75 to about 82 at.% of niobium. It should be noted that there is no solid solution that exists on the Al rich side.

Fig. 12. The SSR (Solid Solution Range) for the 28 A3B compounds are indicated by the solid line with arrows. Solid circles indicate no SSR. The numerical value of Tc for each compound is indicated. N indicates no superconductivity found down to 0.015 K.

Nordberg, L.O., Shen, Z.J., Nygren, M. and Ekstrom, T., (1997b), On the extension of the CX-SiAlON solid solution range and anisotropic grain growth in Sm-doped a-SiAlON ceramics , J. Eur. Ceram. Soc., 17(4), 575-580. 

Y-Si-AI-O-N Janecke prism showing crystalline phases and solid solution ranges. 

A great variety of formulas for this phase can be found, e.g. 48 s°). Some of these data are dubious, others are only correct in respect of the temperature-dependent solid solution range of the Y-phase. However, the Y-phase should be described as a compound with a Fe Mo ratio of 1 4, as this represents the only formula valid for the temperature stability range from slightly below 800 °C up to its melting point. The Y-phase can only be synthesized above 535 15 °C46 it is quench-able and probably remains metastable at room temperature. 

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