types of solid solutions

2. Contents :
•Methods of prepartation
• Solid solution :
oSubstitutional Solid solutions
oInterstetial Solid solution
oComplex Solid Solution
oMechanistic approach : study by X-ray powder
diffraction

3. Methods of preparation
• Solid solutions
• When in a solid, the atoms of solute are present in the
lattice of the solvent, it is known as solid solution.
• A solid solution is basically a crystalline phase that can
have variable composition.
• Often, it have certain properties of materials ,
eg.conductivity, ferromagentism.
• By modifying its composition in such a way that a solid
solution forms and used may be made of designing new
materials having specific properties.

4. • Simple solid solution series are one of he two types :
• Substitutional solid solutions (the atom or ion
introduced directly replaces an atom or ion of same
change in parent structure)
• Interstetial solid solutions(introduced species
occupied a site i.e. normally empty in crystal
structure and no atoms or ions are set out)

5. Formation of Substitutional solid
solutions
• When the atoms of solute substitute for the atoms of
the solvent in its lattice, the solution is known as
Substitutional solid solution.
• If a range of simple substitutional solid solutions is to
form there are certain requirements that must be met :
1. The ions that are replacing each other must have the
same charge (otherwise vacancies would be created)
and be fairly similar in size.
From a review of exp. results on alloy formation,
it has been suggested that a difference of 15% is
radii is most that can be tolerated.

6. 2.It is essential that the two end member phases be
isostructural. The reverse is not necessarily true,
however just two phases are isostructral it doesn’t
follow that they form solid solutions with each other
in crystalline state.
• eg. LiF and CaO both have the rock salt structure but
they are not miscible with each other in crystalline
state.
• It form only if the solute atoms are larger enough to
replace the solvent atoms in the lattice.

7. 3. In system where two ions that are replacing each
other are of considerably of different size,it is usually
found that a larger ion can be partially replaced by a
smaller one , but it much more difficult to do reverse
and replace a smaller ion by a larger ion.
• eg. – in alkali metasilicates, rather none than half
Na+ ions in Na2SiO3 replaced by Li+ at higher temp.
(~800°c) to give solid solutions.

8. Interstetial Solid Solutions
• This type of reaction occurs when the solute
atom is equal to or the slightly smaller than the
solvent atom.
• The solute atom occupies an interstetial position
in the crystal latex.
• An example of interstetial solid solution is
carbon in iron.

9. Complex solid solution
• Substitution by higher valence cations
Cation interstetial
Vacancies anions
• Substitution by lower valence cations
anion interstetial
Vacancies cations

10. • Cation vacancies
If the replaceable cation of the host structure has a
lower charge than that of the cation which is
replacing it, additional charge nedded in order to
preserve of electroneutrality.
• Interstetial anion
The other mechanism by cation of higher charge
may substitute one of the lower charge to create, at
same time,interstetial anion.

11. • Anion vacancies
If the replaceabale cation of the host structure has a
higher charge than that of the replacing cation ,
charge balance may be maintained by creating either
anion vacancies or interstetial cations.anion vacancies
occur in cubic,lime stabilized zirconia.
• Interstitial cations
The alternative mechanism to anion vacancies is to
create interstitial cations at the same time as a
cation of lower charge substitute for one of higher
charge.

12. Experimental methods fore
studying solid solutions
• X-Ray diffraction
 One is as a simple fingerprint method in a qualitative
phase analysis is carried out.to determine the
crystalline phases that are present in a sample and
necessary measuring the pattern very accurately.
 The second way to measure the powder pattern
accurately in order to obtain information about
composition of solid solution is the unit cell
undergoes a small contraction or expansion & then
composition will vary across a solid solution series
by calibration graph.

13. Applications
• X-ray powder diffraction is most widely used for the
identification of unknown crystalline materials.
• Determination of unknown solids is critical to studies in
geology, environmental science, material science.
• Characterisation of crystalline materials.
• identification of fine-grained minerals such as clays.
• determination of unit cell dimensions.
• measurement of sample purity.
• Limitations
• Homogeneous and single phase material is best for
identification of an unknown.
• For mixed materials, detection limit is ~ 2% of sample.

14. Referances :
• E.Zimmer and H.D.Ringel,Nucl,Technol 45(1979)
pg no.-287
• Synthesis of inorganic material by Ulrich,Nicold
hissing ,Pg no. 102
• Solid state chemistry and its applications
Anthony R. west,pg. no. 30-34
• Solid state (new revised sixth edition)- by
S.O.Pillai.

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