dc.description.abstract |
This project has been directed towards investigations on the
preparation and study of the new high temperature
superconductors. Various types of superconducting materials
(e.g. Yttrium and Bismuth based) were prepared under a variety
of conditions and finally a suitable (Melt-Textured-Growth)
process was idPnlified as the method which delivered the best
quality samples. 'rhe samples were characterized according Lo
t.h e i r- c r i t.ical temperatures, (where they lose all electrical
resistance), magnetjzation behaviour, and transport propertjes
,1nder. varying conditions of magnetic fields and currents. In
these studies most of which are the first of their kind in
Pakistan, we were able to identify the important parameters
which lim i L U1e ab i I i ty of these materials to carry large
currPnls and Lo withstand high magnetic fields. It was
df'lerminPd LhaL grain boundaries and absence of directional
order in polycrystalline materials are the major drawbacks. The
melL LexLured superconductors prepared by us provided very good
i n t.o r-g r a i n conlacts, large grains and well defined
d j rec 1. i o n a l j Ly. The last feature, viz. directionality enabled
us Lo study Lheir uniqu? two dimensional behaviour. A number of
interesting and important features were observed in Lhe
anisotropy of their magnetic responses, which also illustrate
the complexity of their behaviour.
Measurements of magnetization changes with time, were performed
which yiPlded further insight into the dynamical behaviour of
Lhese materials, and the role of defects in enhancing critical
currents. The results obtained during the period of this
project have been published ·internationally in the form of
Eleven (11) research publications. Additionally they were
presented in both local and international conferences and
seminars. Seven experimental and two theoretical M.Phil Theses
were completed on various aspects of this problem. Two
experimental Ph.D? Theses are nearing completion. The principal
InvestigaLor was awarded the A. Salam Prize in Physics for
1989 on the basis of some of the work done in this project.
Finally, ?hese studies have an important bearing on our ability
to understand the electrodynamics of the new high temperature
superconductors, so as to enable their applications. Large
critical currents, high critical fields and temperatures are
Lhe parameters whjch are crucial to the fabrication of super-
conducting wires and thence to the fabrication of
superconouct.ing magnets. |
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