Effect of plastic deformation on
of ice that had undergone 15 and 30% plastic deforma-
electrical properties of ice
tion (Fig. 37). These changes were confirmed later by
Dislocations introduced during the process of plas-
Mae and Higashi (1973), after they conducted very de-
tic deformation can affect the electrical properties of
tailed and careful investigations on the effect of plastic
ice (as well as other materials) in a variety of ways.
deformation on ice electrical conductivity and dielectric
permittivity in wide temperature (10 to 100C) and
They can generate new point defects such as vacan-
cies, interstitials and Bjerrum defects; they can also
capture point defects by their elastic field and make
mation of pure single crystals of ice, the dislocation
density in their experiments rose from 104 to 107 cm2.
defects immobile. All this can change the charge carri-
er concentrations. But this is not the whole story yet.
Mae and Higashi found that plastic deformation left un-
Owing to their long-range elastic and electrical fields,
dislocations can effectively scatter charge carriers. As
duced significant changes in low-frequency conductivi-
ty σs. This can be easily explained, as the plastic defor-
a result the charge carrier mobility usually decreases
after plastic deformation. Moreover, charged disloca-
mation generated a concentration of new charge carriers
tions may, in principle, move under the action of these
that was comparable with the minority charge carrier
electrical fields, contributing to both electrical conduc-
concentration but was much less than the majority
tivity and dielectric permittivity.
charge carrier concentration. That would also explain
the failure of Brill and Camp, who measured ε in the
The first known, but unsuccessful, attempt to find
the effect of plastic deformation on the electrical prop-
region of majority charge carrier frequency.
A typical change in σs found by Mae and Higashi,
erties of ice was made by Brill and Camp (1957). They
after introducing a dislocation density of 107/cm2, was 2
reported no changes induced by plastic deformation in
1010/Ω . cm. Notice that this number, when recalcu-
the dielectric properties of ice at 1 kHz. On the con-
trary, Higashi (1969) reported preliminary results ob-
lated into the number of elementary charges per inter-
molecular length on a dislocation, gives 5 103, which
tained by Mae, who found a very profound increase in
low-frequency conductivity and dielectric permittivity
is in the range of the experimental magnitude of qa/e.
30%
Compression
600
1.0 C.P.S.
15%
400
0%
t
ou
t
in
pr
200
"
al
n
gi 50
0
i
100
90
80
70
60
40
30
ourre (C)
Temper"t
a
ith
w
2.0
30%
d
ce
Compression
a
pl
re
15%
be
to
1.0
0%
1.0 C.P.S.
0
100
90
80
70
60
50
40
30
Temperature (C)
Figure 37. Effect of compressive strain on the electric properties
of ice single crystals, measured at 1 Hz (after Higashi 1969).
26
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