Defects in Solids - Solid State Video Lecture | Physical Chemistry

defects in solids defects are mainly two
types they are point effects and
defects point defects are due to
deviation around the point or an atom in
a crystal line defects are due to
deviation in the entire rows of lattice
points one point defects point defects
impurity non stoichiometric and
stoichiometric defects a impurity defect
this defect is due to the impurity in
the crystal for example in molten NaCl
if SR CL 2 is present then some of the
na plus ions are occupied by SR plus 2
each SR plus 2 replaces 2 na plus ions
one of the sites is occupied and the
other remains vacant the vacancies are
equal to number of SR plus 2 ions
another example is solid solution of cl2
chlorine and AG CL silver chloride be
non stoichiometric defect these are two
types metal excess defect and metal
deficient defect metal exist defect due
to an ion a vacancy
it is due to the absence of an ion from
lattice site leaving a hole which is
occupied by electron to maintain
electrical neutrality the anionic sites
occupied by unpaired electrons a call F
centers German word fab is entus means
color Center more number of F centers
more will be the intensity of color NaCl
sodium chloride is an L o L I CL lithium
chloride is pink
metal excess defect due to presence of
extra time at interstitial sites example
Zn o zinc oxide
this is due to the movement of metal
ions to interstitial sites and the
electrons the neighboring interstitial
site example Zn o zinc oxide is white
when cold and yellow when hot because it
loses oxygen and Zn plus two ions occupy
the interstitial sites
metal deficiency defect example fel
ferrous oxide
this is due to absence of a metal iron
from its lattice site and charge is
balanced by iron having higher positive
charge generally transition elements
exhibit this defect fel ferrous oxide is
mostly found with a composition of Fe
0.96 o it may range from Fe 0.93 o 2f Fe
0.96 o stoichiometric defects vacancy
defects an interstitial defect these do
not affect the stoichiometry of solids
these are called intrinsic or
thermodynamic defects it is of two types
a vacancy and B interstitial defects
they can see an interstitial defects are
shown by non ionic solids they can see
defect when some of the lattice sites
are vacant it exhibit they can see
defect
this results in decrease in density of
the substance
interstitial defects when some of the
Constituent particles occupy an
interstitial site it exhibit
interstitial defect this results an
increase in the density of the substance
ionic solids have to maintain electrical
neutrality so they exhibit frontal and
Schottky defects Frenkel defect this is
observed when the smaller iron cation is
dissociated from its normal site and
occupy interstitial site this does not
change the density of the substance this
is shown by ionic solids where there is
large difference in the size of ions and
low coordination number four to six
example Z&S zinc sulfide agcl silver
chloride silver iodide AG BR silver
bromide short key defect this is due to
a vacancy at cationic site an equal
number of vacancies at an iron site in
order to maintain electrical neutrality
this decreases the density of solids
this is shown by ionic solids where
cation and anion are having almost equal
size and high coordination number six to
eight example NaCl sodium chloride cacl2
zim chloride AG BR silver bromide KCl
potassium chloride AG BR silver bromide
exhibit both Frankel and Schottky defect
solids have a good range of electrical
conductivity 10 power minus 22 10 power
7 o hm inverse M inverse solids are
classified into three types based on
conductivities