- Solid solution
A solid solution is a solid-state solution of one or more solutes in a solvent. Such a mixture is considered a solution rather than a compound when the crystal structure of the solvent remains unchanged by addition of the solutes, and when the mixture remains in a single homogeneous phase. This often happens when the two elements (generally metals) involved are close together on the periodic table; conversely, a chemical compound is generally a result of the non-proximity of the two metals involved on the periodic table.
The solute may incorporate into the solvent crystal lattice substitutionally, by replacing a solvent particle in the lattice, or interstitially, by fitting into the space between solvent particles. Both of these types of solid solution affect the properties of the material by distorting the crystal lattice and disrupting the physical and electrical homogeneity of the solvent material.
Some mixtures will readily form solid solutions over a range of concentrations, while other mixtures will not form solid solutions at all. The propensity for any two substances to form a solid solution is a complicated matter involving the chemical, crystallographic, and quantum properties of the substances in question. Solid solutions, in accordance with the Hume-Rothery rules, may form if the solute and solvent have:
- Similar atomic radii (15% or less difference)
- Same crystal structure
- Similar electronegativities
- Similar valency
The phase diagram in Fig. 1 displays an alloy of two metals which forms a solid solution at all relative concentrations of the two species. In this case, the pure phase of each element is of the same crystal structure, and the similar properties of the two elements allow for unbiased substitution through the full range of relative concentrations.
Solid solutions have important commercial and industrial applications, as such mixtures often have superior properties to pure materials. Many metal alloys are solid solutions. Even small amounts of solute can affect the electrical and physical properties of the solvent.
The binary phase diagram in Fig. 2 at right shows the phases of a mixture of two substances in varying concentrations, α and β. The region labeled "α" is a solid solution, with β acting as the solute in a matrix of α. On the other end of the concentration scale, the region labeled "β" is also a solid solution, with α acting as the solute in a matrix of β. The large solid region in between the α and β solid solutions, labeled "α and β", is not a solid solution. Instead, an examination of the microstructure of a mixture in this range would reveal two phases — solid solution α-in-β and solid solution β-in-α would form separate phases, perhaps lamella or grains.
In the phase diagram, the unalloyed extreme left and right concentrations, and the dip in the center, the material will be solid and become liquid as heat is added, where at other proportions the material will enter a mushy or pasty phase. The mixture at dip point of the diagram is called a eutectic alloy. Lead-tin mixtures formulated at that point (37/63 mixture) are useful when soldering electronic components, particularly if done manually, since the solid phase is quickly entered as the solder cools. In contrast, when lead-tin mixtures were used to solder seams in automobile bodies a pasty state enabled a shape to be formed with a wooden paddle or tool, so a 70-30 lead to tin ratio was used. (Lead is being removed from such applications owing to its toxicity and consequent difficulty in recycling devices and components that include lead.)
When a solid solution becomes unstable — due to a lower temperature, for example — exsolution occurs and the two phases separate into distinct microscopic to megascopic lamellae. This is mainly caused due to difference in cation size. Cations who have a large difference in radii are not likely to readily substitute.
Take the alkali feldspar minerals for example, whose end members are albite, NaAlSi3O8 and microcline, KAlSi3O8. At high temperatures Na+ and K+ readily substitute for each other and so the minerals will form a solid solution, yet at low temperatures albite can only substitute a small amount of K+ and the same applies for Na+ in the microcline, this leads to exsolution where they will separate into two separate phases. In the case of the alkali feldspar minerals, thin white albite layers will alternate between typically pink microcline.
- Chen, Jing; Xu, Zhi-qin; Chen, Z-Z.; Li, T-F.; Chen, F-Y. (December 2005). "Pargasite and ilmenite exsolution texture in clinopyroxene from the Hujialing Garnet-Pyroxenite, Su-lu U.H.P. Terrane, Central China: A geodynamic Implication". European Journal of Mineralogy 17 (6): 895–903. doi:10.1127/0935-1221/2005/0017-0895. http://www.uni-graz.at/IEC-7/PDF-files/Chen.pdf.
- Petersen, U.. "Introduction to Ore Microscopy II; Mineral Paragenesis". http://www.mines.utah.edu/~wmep/59298/592PDF/rlm2.pdf.
- ^ Cottrell, Alan Howard (1967). An Introduction to Metallurgy. Institute of Materials. ISBN 0844807672.
- ^ Callister Jr., William D. (2006). Materials Science and Engineering: An Introduction (7th ed.). John Wiley & Sons. ISBN 0471354465.
- ^ a b Nesse, William D. (2000). Introduction to Mineralogy. New York: Oxford University Press. p91-92. ISBN: 978-0-19-510691-6
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Solid solution — Solid solution. См. Твердый раствор. (Источник: «Металлы и сплавы. Справочник.» Под редакцией Ю.П. Солнцева; НПО Профессионал , НПО Мир и семья ; Санкт Петербург, 2003 г.) … Словарь металлургических терминов
solid solution — 1. a solid, homogeneous mixture of substances, as glass or certain alloys. 2. (in a crystal structure) the more or less complete substitution of one kind of atom, ion, or molecule for another that is chemically different but similar in size and… … Universalium
solid solution — noun a homogeneous solid that can exist over a range of component chemicals; a constituent of alloys that is formed when atoms of an element are incorporated into the crystals of a metal • Syn: ↑primary solid solution • Hypernyms: ↑solution •… … Useful english dictionary
solid solution — kietasis tirpalas statusas T sritis fizika atitikmenys: angl. solid solution vok. Festlösung, f; Mischkristall, m rus. твёрдый раствор, m pranc. solution solide, f … Fizikos terminų žodynas
solid solution — kietasis tirpalas statusas T sritis chemija apibrėžtis Kristalinis ar amorfinis homogeninis kietųjų medžiagų mišinys. atitikmenys: angl. solid solution rus. твердый раствор … Chemijos terminų aiškinamasis žodynas
solid solution — noun any homogenous crystalline solid, consisting of more than one type of molecule or atom randomly dispersed, in which the structure is independent of its composition … Wiktionary
solid solution — noun Chemistry a solid mixture containing a minor component uniformly distributed within the crystal lattice of the major component … English new terms dictionary
solid solution — sol′id solu′tion n. phs cry/mir a solid, homogeneous mixture, as glass, certain alloys and chemical compounds, or minerals in which ionic substitution has occurred • Etymology: 1890–95 … From formal English to slang
solid solution — /sɒləd səˈluʃən/ (say soluhd suh loohshuhn) noun 1. a solid homogeneous mixture of two or more substances, as some alloys, glasses, etc. 2. Chemistry a mixed crystal of two or more isomorphous substances … Australian English dictionary
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