ABSTRACT
This chapter deals with the thermoelectric effect of porous materials. Porous materials are supposed to have the property of slowing down heat flow. When a temperature gradient exists across a porous thermoelectric material, an electrical voltage is induced due to the difference in the energy levels of the electrons on the hot side versus the electrons on the cold side. An electrical voltage due to a temperature gradient exists due to the Seebeck effect. However, how to sustain the temperature gradient remains to be resolved. It is hypothesized that porous materials should have much lower heat conductivity than their bulk counterparts without sacrificing the electrical conductivity. In this study, three porous thermoelectric samples were produced by infiltration casting of bismuth tin (Bi-Sn) in a porous medium. The samples varied in their levels of porosity. The voltage output was measured for each sample at various temperature gradients over a period of 40 s at 0.1 s intervals. The Seebeck coefficient and the figure of merit (ZT) value of each sample were calculated. The average Seebeck coefficients for the three samples, from least porous to most porous, were –1.64 × 10-5, –2.55 × 10-5, and –1.54 × 10-5 V/K. The average figure of merit values for the three samples, from least porous to most porous, were 0.012, 0.031, and 0.010.
