Alloyage of two solid substances can lead to formation of solid solution, an intermediate phase or chemical compound. Solid solution can have structure of subtraction, replacement or introduction.
Looking at solid substance, it is difficult to present that it can have different phases. It – so! At alloyage of two solid substances the firm phase which can be solid solution, an intermediate phase or chemical compound is with each other formed. Scientific definition of firm solutions it: solid solutions are phases in which atoms of one substance are located in a crystal lattice of another, without changing its type. Therefore substance which crystal lattice remains after alloyage call solvent. Solid solutions are formed only of ionic connections. Depending on arrangement of the dissolved substance distinguish solutions of introduction, subtraction or replacement. Most often the arrangement of atoms of the dissolved substance has chaotic character.
Solid solutions of introduction
This type is formed if the sizes of parts of the dissolved substance there is less than the size of crystal lattice that provides steadily situation in interstices. Examples of solid solutions of introduction – all this the connections formed by elements with small atomic radiuses with metals of transitional groups. The most widespread solution of introduction – carbon in iron or hydrogen in platinum. Stability of such solutions is provided with the small radius of the dissolved substance because of which surrounding atoms of solvent in a crystal lattice are not too displaced and which does not allow to adjoin to them.
Solid solutions of subtraction
This type of solid solutions is formed only of chemical compounds, for example, oxygen solution in oxide of iron (FeO). Solution of subtraction is characterized by availability of metal with a different valency. The above-stated oxide of iron is a typical example of solid solution of subtraction. In it all oxygen positions are entertaining, but a part of positions of ions of iron is free. Oxygen fills a free vacancy. In this example the case with a defective metal sublattice is considered, but also the nonmetallic sublattice can be defective. For example, there is a number of titanium dioxides with the content of oxygen of 38-56%. With increase keeping of the titan, the amount of defects in an oxygen sublattice increases. With reduction of keeping of the titan the total amount of defects decreases that leads to uniform distribution them between sublattices. However in oxides with the maximum content of oxygen the defects are completely located in a metal sublattice.
Solid solutions of replacement
In this type of solid solution the ions of one element are replaced with ions of akin other element. Such solutions are formed at coincidence of charges and the sizes of the exchanging parts. Distribution of the dissolved substance in a crystal lattice happens chaotically. The example of solid solution of replacement is the NaCl system – KCl in which potassium replaces sodium.