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Thermoelectric properties of the Si doped SiC were measured. It is intended to reduce the thermal conductivity by addition of isoelectric element Si. Measurements of electrical resistivity, thermoelectric power and thermal conductivity were made on SiC thermoelectric semiconductor as a function of both Si doping concentration (over the range of 1.0 wt.%•`40.0 wt.%) and temperature (from room temperature to 750•Ž). Measurements of Hall coefficient, X-ray crystallography and EPMA were also made on these samples. The thermal conductivity decreases with increase of Si concentration. At Si concentration of 40.0 wt.%, minimum thermal conductivity reached to 13 W/mK. The figure of merit Z was calculated from electrical resistivity, thermoelectric power and thermal conductivity. The maximum value of the figure of merit reaches 2•~10-4K-1 at 750•Ž and Si concentration of 40.0 wt.%.

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Both the thermoelectric power and the resistivity of the oxygen deficient YBa 2 Cu 3 O 61x samples were measured. The rare-earth-doped samples, such as Sm and Dy, whose magnetic moments in the 13 valence state are different, were studied. Then the power factor of the thermoelectric ability was calculated. The power factor of the Dy-doped samples is smaller than those of the other samples, especially at high temperature. This smallness of the power factor is the main reason why the Dy-doped samples have larger resistivity. We try to analyze the data by the theoretical expression under the variable range hopping conduction model. The expression of the thermoelectric power could be fit for the nondoped and Sm-doped samples, except at low temperature. In this situation, the thermoelectric power increases as temperature increases, and this temperature dependence is good for the thermoelectric materials at high temperature where the resistivity decreases with temperature increasing.

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