Impurities in solids

The addition of impurity atoms to a metal results in the formation of a solid solution and/or a new second phase, depending on the kinds of impurity, their concentrations, and the temperature of the alloy. The present discussion is concerned with the notion of a solid solution treatment of the formation of a new phase is deferred to Chapter 9. 

Several terms relating to impurities and solid solutions deserve mention. With regard to alloys, solute and solvent are terms that are commonly employed. Solvent is the element or compound that is present in the greatest amount on occasion, solvent atoms are also called host atoms. Solute is used to denote an element or compound present in a minor concentration. 

Figpre 4.2 Two-dimensional schematic representations of substitutional and interstitial impurity atoms. 

The Structure and Properties of Materials, Vol. 1, Structure, p. 77. Copyright 1964 by John Wiley Sons, New York, NY. Reprinted by permission of John Wiley Sons, Inc.) 

What are the Differences behveen Interstitial and Substitutional Solid Solutfons  

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MJ Pikal, DJW Grant. A theoretical treatment of changes in energy and entropy of solids caused by additives or impurities in solid solution. Int J Pharm 39 243-253, 1987. 

Another defect problem to which the ion-pair theory of electrolyte solutions has been applied is that of interactions to acceptor and donor impurities in solid solution in germanium and silicon. Reiss73>74 pointed out certain difficulties in the Fuoss formulation. His kinetic approach to the problem gave results numerically very similar to that of the Fuoss theory. A novel aspect of this method was that the negative ions were treated as randomly distributed but immobile while the positive ions could move freely. 

Rebane, K. K., 1974. Some problems of the vibrational structure of optical spectra of impurities in solids, in Optical Properties of Ions in Solids, B. DiBartolo (Ed.), Plenum, New York, pp. 247-258. 

In the first Section, attention is paid to distinguishing between reactive and non-reactive systems from the point of view of wettability. Then, after describing wetting and bonding of non-reactive couples, we discuss the effect on these characteristics of oxygen, which is the most common impurity in solid/liquid/vapour systems, as well as the effect of reactive and non-reactive alloying elements. Finally, in a short Section, we consider some results for the wetting of fluorides which like oxides are very ionic. 

Gupta R. P., Wall T. F., and Baxter L. A. (eds.) (1999) The Impact of Mineral Impurities in Solid Fuel Combustion. Plenun, New York, 768pp. 

Our first steps toward the single-molecule regime arose from work at IBM Research in the early 1980s on persistent spectral hole-burning effects in the optical transitions of impurities in solids (for a review, see [20]). Briefly, if a molecule with a strong zero-phonon transition and minimal Franck-Condon distortion is doped into a solid and cooled to liquid helium temperatures, the optical absorption becomes inhomogeneously broadened (Fig. 2.2A). The width of the lowest electronic transition for any one molecule (homogeneous width, Yjj) becomes very small because few phonons are present, while at the... 

Moilanen, A., Kurkela, E., Laatikainen-Luntama, J. (1999). Ash behaviour in biomass fluidised-bed gasification. In Gupta et al. (eds.). Impact of mineral impurities in solid fuel combustion. New York Kluwer Academic / Plenum Publishers. Pp. 555 - 567. 

Virtanen M. E., ct al. (1999) A Novel Approach to Use CCSEM when Studying Agglomeration in Fluidized Bed Combustion. In Impact of Mineral impurities in Solid Fuel Combustion, (Ed. by R. P, Gupta, Wall, T.F., and Baxter, L.L.) 147-154. Kluwer Academic f Plenum Publishers, New York. 

Tiainen M. S., et al. (1999) Determination of Amorphous Material in Peat Ash by X-ray Diffraction. In Impact of mineral impurities in solid fitle combustion, (Ed. by R. P. Gupta, T. F. Wall and L. Baxter) 217-224. Kluwer Academic Plenum Publisher, New York. 

PJT Instabilities of Monoatomic Impurities in Solids Survey of Experimental Results... 

Dipolar instabilities of impurities in solids were discovered in 1965 by Lombardo and Pohl in Li-doped KCl [49]. Since then, a large amount of off-centre and on-centre instabilities of monoatomic impurities in insulator and semiconductor materials have been reported. In many cases the impurity centres are not well characterized and the observed instabilities could be due to close defects. In this article we only consider centres with spontaneous instabilities driven by PJT mechanisms. An exhaustive review of all these centres is beyond the scope of this report and we have selected representative examples based on the authors interest. Some early reviews can be found in [93,152,153]. 

In this article experimental and theoretical work on spontaneous instabilities of impurities in solids driven by PIT vibronic coupling mechanisms is reviewed. Particular attention is paid to the results of calculations addressed to understand the microscopic origin of off-centre and on-centre instabilities and also to quantify the involved distortions. Especially, we aim to help to overcome a paradigm taken root among many researchers of physics and chemistry of solids that the instabilities of atoms and ions in pure and doped solids are due to difference of atomic sizes. On the contrary, we have presented a great quantity of experimental evidences and theoretical results showing that it is an effect of the vibronic coupling. 

Assuming that there is thermodynamic equilibrium at the solid/liquid interface, no diffusion of impurities in solid, and complete mixing in the liquid,... 

The solubility is defined with respect to a second precipitated phase. The solubility of an impurity is the maximum concentration, which can be incorporated in the liquid or solid phase without precipitating a second phase. For most impurities in solid silicon at high-temperatures, equilibrium is achieved with the liquid phase governed by the liquidus in the phase diagram. Solid solubility is temperature-dependent as represented by the solidus or solvent curves in the phase diagram. At lower temperatures, the reference phase is usually a compound or an impurity-rich alloy. When the impurity is volatile, the saturated crystal is in equilibrium with the vapor, and the impurity solubility also depends on its vapor pressure. 

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