The issue of how to improve the thermoelectric figure of merit (ZT) in oxide semiconductors has been challenging for more than 20 years. In this work, we report an effective path to substantial reduction in thermal conductivity and increment in carrier concentration, and thus a remarkable enhancement in the ZT value is achieved. The ZT value of In2O3 system was enhanced 4-fold by nanostructuing (nano-grains and nano-inclusions) and point defect engineering. The introduction of point defects in In2O3 results in a glass-like thermal conductivity. The lattice thermal conductivity could be reduced by 60%, and extraordinary low lattice thermal conductivity (1.2 W m−1 K−1 @ 973 K) below the amorphous limit was achieved. Our work paves a path for enhancing the ZT in oxides by both the nanosturcturing and the point defect engineering for better phonon-glasses and electron-crystal (PGEC) materials.
A solution rheology method has been applied to resolve component friction dynamics in
polymer mixtures. The approach consists of separately evaluating viscoelastic properties of entangled
“object” solutions of polymeric A in oligomeric B and “mirror” solutions of polymeric B in oligomeric A. At
various compositions, the friction coefficients ζA and ζB associated with both components A and B are
obtained by applying the well-established reptation theory to analyze the oscillatory shear measurements
of storage and loss moduli of these object and mirror solutions. It is found that ζA(φ,T) and ζB(φ,T) exhibit
different temperature and composition dependencies. Specifically, the low-T
g component A, which is low
vinylbutadiene (1,4-PB) in the present case, has considerably weaker temperature and composition
dependencies in comparison with the high-T
g component B, which is a high vinyl butadiene (1,2-PB).
Further analysis indicates the presence of two consecutive glass transitions in the mixtures. A revised
free volume theory (FVT) is proposed to assign different levels of free volume to the components in a
mixture as the origin of the separable glass transitions.
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