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Deassy Novita began her
groundbreaking research as a grad student.
Photo: UC Engineering |
"We find that when networks become flexible
their electrical conductivity increases precipitously," says Deassy
Novita. "Now we will be able to chemically tune these materials for
specific applications. For example, the batteries implanted in
patients who have heart pacemakers make use of a solid electrolyte."
Novita is a third-year doctoral student working in
the lab of Punit Boolchand, professor of electrical engineering in the
University of Cincinnati's College of Engineering. Originally from
Indonesia and now a U.S. citizen, Novita began the ground-breaking
research as part of her doctoral thesis.
"This system has been studied by about 35 groups
all over the world over the past two decades. We are the first to make
these samples in a 'dry' state," says Boolchand. "Most people who
studied these materials produced them unwittingly in the laboratory
ambient environment where the relative humidity is typically 50%, and
that leads to samples that are - so to speak - in a 'wet' state. By
special handling of the materials, we were able to produce them in a
dry state, where we can see the intrinsic behavior of these materials."
The intrinsic behavior shows samples to exist in
three elastic domains. In the first domain, at low AgI (silver iodide)
content (less than 9.5%) they form networks that are rigid but
stressed. In the second domain, called the "intermediate phase," at a
slightly higher content of AgI (9.5 to 37.8%), they form networks that
are rigid but unstressed. And finally in the third domain, at AgI
content of 37.8% and higher, their networks become flexible.
The UC research team showed for the first time that
such intermediate phases also exist in networks that are ionically
conducting. In the flexible phase of these materials, "silver ions
move like fish through water," says Boolchand.
We synthesized materials of the composition
(AgI)x(AgPO3)1-x in a glassy or disordered state, and then examined
their thermal, optical and electrical properties as a function of
chemical composition. (Here "x" represents the amount of AgI
electrolyte, and 1-x the fraction of the base AgPO3 glass or
disordered solid.)
The next step in their research will be to
understand why traces of water change the behavior of these
electrolytes so drastically and to understand if the behavior observed
here of three elastic domains is a general feature of all electrolyte
glasses or is it peculiar to this very well studied material.
"We think the behavior will be observed in general
in solid electrolytes," says Boolchand. |
