Papers by Author: Yung Kang Kuo

Abstract: Single crystals of Pb_1-xCd_xSe compounds with x = 0, 0.01, 0.03, 0.05, 0.07 and 0.1 were grown by vertical Bridgman method. The crystalline phase and stochiometry for these crystals were investigated by X-ray diffraction, SEM and electron-probe microanalysis (EPMA). The thermoelectric behaviors for the Pb_1-xCd_xSe crystals were studied by means of thermal and carrier transport measurements in the temperature range between 50K and 400K. X-ray diffraction and SEM analysis confirmed that as-grown Pb_1-xCd_xSe crystals are simgle phase. The experimental results showed that the PbTe sample is p-type semiconductor but Pb_1-xCd_xSe samples with x = 0.01, 0.03, 0.05, 0.07 and 0.1 are n-type semiconductors. Temperature dependences of resistivity, Seebeck coefficient, and thermal conductivity for the various compositions of Pb_1-xCd_xSe were analyzed. The dimensionless thermoelectric figure of merit ZT for these compounds was evaluated and discussed. It was found that Pb_0.95Cd_0.05Se exhibits the best thermoelectric performance. The maximum figure of merit (ZT) of Pb_0.95Cd_0.05Se is about 0.47 at 290 K.

Abstract: In this study, Bi2Te3 was selected as a matrix material and an immiscible semiconductor material CdTe with a wider energy band gap was precipitated to form microstructures in it. For this purpose, a series of two-component composites (Bi2Te3)1-x/(CdTe)x, with x = 0.01, 0.05, 0.1, 0.15, 0.2 were prepared by melting, high speed rocking and quenching technique. The composition and microstructure of these two-component composites were examined by X-ray and SEM. Thermoelectric properties including Seebeck coefficient, electric resistivity, and thermal conductivity were measured from 30 K to 400 K. The compositional and temperature dependence of the microstructure and thermoelectric properties of (Bi2Te3)1-x/(CdTe)x composites were discussed. It is found that (Bi2Te3)0.99/(CdTe)0.01 exhibits a better thermoelectric performance than that of Bi2Te3 at elevated temperatures. The figure of merit (ZT) of (Bi2Te3)0.99/(CdTe)0.01 is about 0.64 at 400 K.