Syamaprasad, U; Dr.Girijavallabhan,C P(Cochin University of Science And Technology, December , 1981)
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Abstract:
The thesis aims to present the results of the
experimental investigations on the electrical properties like
electrical conductivity, dielectric constant and ionic thermo~
currents in certain ammonium containing ferroelectric crystals
viz. LiNH4SO4, (NH4)2SO4 and (NH4)5H(SO4)2. Special attention
has been paid in revealing the mechanisms of electrical conduction
in the various phases of these crystals and those asso~
ciated with the different phase transitions occurring in them,
by making studies on doped, quenched and deuterated crystals.
The report on the observation of two new phase transitions in
(NH4) S O2 and of a similar one in ( NH4 ) H (2SO4 ) are included. The relaxation mechanisms of the impurity-vacancy complexes and the space charge phenomena in pure and doped crystals of LiNH4SO4 and (NH4)2SO4 and the observation of a new type of ionic thermo-current viz. Protonic Thermo-Current (PTC) in these crystals are also presented here.
Description:
Department of Physics, Cochin University of Science and Technology
Junaid, Bushiri M; Mahadevan Pillai, V P; Ratheesh, R; Nayar, V U(Elsevier, April 23, 1999)
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Abstract:
Raman spectra of the KTP single crystal are recorded in electric fields (dc and ac) applied along the polar axis c. Spectra with
the laser beam focused near the cathode end, anode end and the centre of the crystal are recorded. The cathode end of the crystal
develops a spot ‘grey track’ where the laser beam is focused after a lapse of 5 h from the application of a dc electric field of
38 V/cm. The spectra recorded at the cathode end after the application of field show variations in intensity of bands. A new band
appears at 177 cm21. Changes in band intensities are explained on the basis of changes in polarizability of the crystal due to the
movement of K1 ions along the polar axis. K1 ions accumulate at the cathode end, where the ‘Grey track’ formation occurs.
The intensity enhancement observed for almost all bands in the ac field is attributed to the improvement of crystalline quality.
Description:
Journal of Physics and Chemistry of Solids 60 (1999) 1983–1988
Santhakumari, N C; Dr.Girijavallabhan,C P(Cochin University Of Science And Technology, February 15, 1992)
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Abstract:
Solid electrolytes for applications like
chemical sensing, energy storage, and conversion have been
actively investigated and developed since the early
sixties. Although of immense potential, solid state
protonic conductors have been ignored in comparison with
the great interest that has been shown to other ionic
conductors like lithium and silver ion conductors. The
non-availability of good, stable protonic conductors could
be partly the reason for this situation. Although organic
solids are better known for their electrical insulating
character, ionic conductors of organic origin constitute a
recent addition to the class of ionic conductors.
However, detailed studies (N1 such conductors are scarce.
Also the last decade has witnessed an unprecedented boom
in research on organic "conducting polymers". These newly
devised materials show conductivity spanning from
insulator to metallic regimes, which can be manipulated by
appropriate chemical treatment. They find applications in
devices ranging from rechargeable batteries to "smart
windows".
This thesis mainly deals with the synthesis and
investigations on the electrical properties of (i) certain organbc protonic conductors derived from ethylenediamine
and (ii) substituted polyanilines
Description:
Department
of Physics, Cochin University of Science and Technology