About 20 years ago, researchers still had not found a
metallic
superconductor with a critical temperature above 23K. They
also had
not identified an oxide superconductor with a critical
temperature
over 11K. In those days, many researchers began to theorize
that they
would not be able to find new superconductors with high
critical
temperatures. But in 1986, Prof. Kitazawa read a paper
by K. A. Muller
and J. G. Bednorz, in which the two IBM researchers pointed
out that
barium oxides containing divalent copper ions could possibly
be
superconductors. Like other experts in the field at the
time, Prof.
Kitazawa had not looked at materials with magnetic ions
because the
spin magnetic moment of magnetic ions was thought to work
against
superconductivity.
Prof. Kitazawa thought that barium oxides might become
superconductors at low temperature and instructed a senior
undergraduate student to
study the possibility for his graduation thesis. An oxide
prepared by
the student showed a Meissner effect at 23K, indicating
that the
material was superconductive. Almost no experts in this
field paid
attention to the paper by Muller and Bednorz because they
were not
superconductivity specialists. However, Prof. Kitazawa
led the world's
largest and best team studying oxide superconductors. His
team not
only showed that the oxide was a superconductor but also
found that
the material had a layered structure based on copper and
oxygen. The
announcement of the team's research results immediately
triggered a
worldwide superconductor boom. Prof. Kitazawa started searching
for
new oxide superconductors jointly with his students. At
3 a.m. on the
third day of his team's efforts, he received a phone call
at home from
one of his students. The student said he had observed unusual
signals
and asked Prof. Kitazawa to come to the lab immediately.
The student
was so excited about what he had seen and wanted Prof.
Kitazawa to
come to the lab right away without waiting for the first
train in the
morning. Prof. Kitazawa says, "When I arrived at the
lab, I saw
signals which indicated without a doubt that the material
being tested
was a superconductor. It was a strontium-based superconductor,
and its
critical temperature was 40K. Although I did not show the
students how
excited I was, I think the staff in the laboratory knew
because there
had been no progress for a long time."
The study of superconductors usually takes one of two
forms: searching
for superconductors with higher critical temperatures and
studying
commercial applications of superconductors with relatively
low
critical temperatures. Prof. Kitazawa wants to study future
commercial
applications. Although materials with higher critical temperatures
have been found, they currently must be cooled with liquid
nitrogen to
become superconductors. What commercial applications are
worth the
cost of cooling superconductors to liquid nitrogen temperatures?
Prof.
Kitazawa has high expectations for a "Superconducting
Global Power
Network."
Through the use of superconducting electric power grids
that waste no
power during transmission, extra power can be transmitted
freely to
any place where power is in short supply. This would mean,
for example,
that problems with solar and wind power generation, which
depend
heavily on weather conditions and terrain, could be resolved.
Prof.
Kitazawa says, "If enough people wanted to use an
environmentally-
friendly renewable energy source that costs twice as much
as current
sources, then a global power network of superconductors
could make it
possible. High-temperature superconductors were discovered
unexpectedly, but the manufacture of commercial products
based on them
requires advanced technology. Technological developments
in this field
are so rapid that the huge number of power transmission
cables
currently in use could be cut by two to three every month.
It won't be
long before technology based on superconductivity is applied
commercially." For Prof. Kitazawa, superconductors
are tools to be
used to create a better future for our children, grandchildren
and
beyond. He hopes to see these materials contribute to the
future of
mankind.
(Interviewer: Kuniko Ishiguro, Cosmopia Inc.)
For more information,
http://www.nanonet.go.jp/english/mailmag/2005/043a.html
