Scientists have been searching for decades
for more efficient ways to convert heat to electricity. Thermoelectric
materials generate electricity when heated and turn cold in the presence
of electrical current.
The measure of success for converting materials is the ZT factor,
a formula that includes thermal power, electrical conductivity, thermal
conductivity and temperature. A ZT factor over three would make thermoelectric
power generation competitive with home refrigerators and power generators.
Forty years ago the best ZT factor in existence was 0.6. After four decades
of research, it stood at one.
Researchers from Michigan State University, the University of
Michigan at Ann Arbor, and Aristotle University of Thessaloniki in Greece
have discovered a new family of thermoelectric semiconductor materials
that raises the bar considerably. The researchers' material has a ZT factor
of 2.2 at 527 degrees Celsius, which may be high enough for practical
The high temperature rules out refrigeration applications, however.
The researchers' material is a mix of silver, lead, antimony and
tellurium. One of the keys to its utility is very tiny areas, or nano
dots, where the crystal structure of the material is rich in silver and
antimony and surrounded by a silver-antimony-poor region.
There is evidence that the material could be further improved,
according to the researchers. The work appeared in the February 5, 2004
issue of Science.
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