발간논문

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Electrical and thermoelectric properties of the undoped (100-x)% Bi₂Te₃-x% Sb₂Te₃ (x≥66.7) pseudo-binary single crystals grown by the zone melting method were measured over the temperature range from 77 to 600K. For the (100-x)% Bi₂Te₃-x% Sb₂Te₃ (x≥66.7) alloys, the temperature dependence of the Hall mobility was T^(-1.0) regardless the Sb₂Te₃ contents. The temperature dependences of (m^*/m_o)^(3/2)·μ_c and the effective mass were proportional to T^(-1.5) and T^(-1/3), respectively. The saturated hole concentration decreased with increasing temperature and the slope of the Seebeck coefficient changed at about 350K, which implied the two sub-bands in the valence band. While the 33.3% Bi₂Te₃-66.7% Sb₂Te₃ alloy exhibited the highest figure-of-merit among the undoped Bi₂Te₃-Sb₂Te₃ alloys, the maximum figure-of-merit could be expected fur the 22.5% Bi₂Te₃-77.5% Sb₂Te₃ alloy with optimizing the carrier concentration.

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Both the experimental and analytical methods are employed in this study to elucidate the effect of the fluid viscosity and velocity on the die filling characteristics. Two difffrent fluids, i.e. pseudoplastic fluid(paint) and Newtonian fluid(water), were chosen as the model fluids to monitor the flow patterns during die filling. The flow patterns shown by these two fluids were recorded using a high speed camera to compare their flow behavior during die filling. In the case of the pseudoplastic fluid flow exhibited by the paint die filling was observed to proceed in a laminar manner while maintaining its free surface. In the case of the water however, the leading edge of the fluid was completely shattered even at a relatively low injection speed resulting in die filling accompanied by turbulence. Such experimental observations were then compared with the analytical results obtained from computer simulations.

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