Substantial transverse Peltier cooling has been reported for synthetic composites consisting of layers of bismuth telluride and either bismuth or lead. Ideally, the two materials in such a composite should have very different values for the electrical and thermal conductivities. If this condition is satisfied, the transverse figure of merit, Z ϕ , for the optimum orientation is not much smaller than the longitudinal figure of merit, Z, for the two materials when used as a conventional thermocouple. A second condition is that Z should be as large as possible. We have shown that the two conditions can be met simultaneously if one of the components is porous or otherwise discontinuous. Thus, a highly efficient transverse thermoelement could be made from porous p-type and dense n-type bismuth telluride. Effective transverse thermoelements could also be made from less porous p-type bismuth telluride in conjunction with either single crystal bismuth or YbAl2.96Mn0.04. It is shown that a dimensionless transverse figure of merit, Z ϕ T, in excess of 0.6 should easily be obtained with these configurations. It should be possible to observe temperature depressions in excess of 100° by the use of suitably shaped synthetic transverse thermoelements.
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