What is substitutional solid solution?

Substitutional solid solutions are those in which the atoms of the minor component (solute) are substituted for the atoms of the major component (solvent) on the lattice positions normally occupied by the solvent atoms.

What are the factors that govern substitutional solid solution?

Substitutional solid solution rules

• The atomic radius of the solute and solvent atoms must differ by no more than 15%:
• The crystal structures of solute and solvent must be similar.
• Complete solubility occurs when the solvent and solute have the same valency.
• The solute and solvent should have similar electronegativity.

In which case do substitutional solid solutions occur?

Substitutional solid solutions are formed by the replacement of atoms A in a host lattice by foreign atoms of element B (the atoms are substituted). In many cases, the solubility of an atom species B in A is limited.

What are the 4 characteristic parameter for solid solution?

Solid solutions can be categorized on the basis of some of the physical parameters, such as structure, concentration, solubility and order.

What are the four factors affecting the formation of a substitutional solid solution?

Hume-Rothery Rules

• Atomic Size: The sizes of the two atoms must be similar.
• Crystal Structure: The two atoms must crystallize in the same way.
• Electronegativity: Electronegativity is a measure of an atom’s ability to attract electrons.
• Valence: Valence is a measure of an atom’s ability to combine with other atoms.

Which of the following requirements has to be satisfied for a substitutional solid solution?

For complete substitutional solubility the following criteria must be met: 1) the difference in atomic radii between Ni and the other element (∆R%) must be less than ±15%, 2) the crystal structures must be the same, 3) the electronegativities must be similar, and 4) the valences should be the same, or nearly the same.

What are the differences between interstitial and substitutional solid solutions?

The difference between substitutional and interstitial solid solution is that in the formation of a substitutional solid solution, it involves the substitution of a solvent atom by a solute atom whereas in the formation of interstitial solid solutions, there is no displacement of solvent atoms by solute atoms, instead.

What conditions favor formation of substitutional alloys?

When a molten metal is mixed with another substance, there are two mechanisms that can cause an alloy to form: (1) atom exchange or (2) interstitial mechanism. The relative size of each element in the mix plays a primary role in determining which mechanism will occur.

What is Hume-Rothery rules to form a substitute alloy?

The Hume-Rothery rules for such alloys are: – The difference between the atomic radius of the solute and the solvent atoms should not be greater than 15%. – The crystal structure of the solute and the solvent elements should be similar.

What differences in properties result from the formation of a substitutional alloy?

The main difference between substitutional and interstitial alloys is that substitutional alloys are formed by substituting one metal atom for another metal atom of similar size whereas interstitial alloys are formed by inserting smaller atoms into holes of the metal lattice.

How does diffusion occur in substitutional alloy?

Substitutional diffusion occurs by the movement of atoms from one atomic site to another. In a perfect lattice, this would require the atoms to “swap places” within the lattice.

What are two characteristics of a metal required for a substitutional alloy to form?

Substitutional alloys are formed when the two metallic components have similar atomic radii and chemical-bonding characteristics. For example, silver and gold form such an alloy over the entire range of possible compositions. When two metals differ in radii by more than about 15 percent, solubility is more limited.

Why are Hume-Rothery rules followed?

1. Why are Hume Rothery’s rules followed? Explanation: To form an extensive solid solution, Hume Rothery’s rules are obeyed. An extensive solid solution is generally considered as one that is greater than 10 atomic percent soluble.

What are the necessary conditions for substitutional diffusion?

Substitutional diffusion occurs only if a vacancy is present. A vacancy is a “missing atom” in the lattice. If a vacancy is present, one of the adjacent atoms can move into the vacancy, creating a vacancy on the site that the atom has just left.

Do Hume-Rothery rules apply only to solid solutions?

The Hume-Rothery rules are a set of basic rules describing the conditions under which an element could dissolve in a metal, forming a solid solution. There are two sets of rules, one which refers to substitutional solid solutions, and another which refers to interstitial solid solutions.

Which diffusion is faster interstitial or substitutional?

Interstitial diffusion is generally faster and there are many more interstitial sites than vacancy sites to jump to. 2. Substitutional Diffusion: At high temperature many atoms in the semiconductor move out of their lattice site, leaving vacancies into which impurity atoms can move.