Experimental study of the thermoelectric power factor enhancement in composites

D. J. Bergman and L. J. Fel [J. Appl. Phys. 85, 8205 (1999)] calculated that in composites the thermoelectric power factor, the product of the square of the thermopower and the electrical conductivity, can be enhanced over that of the individual constituents, but the figure of merit cannot. This is demonstrated here experimentally in the elemental bismuth-silver system, and ascribed to the fact that inclusions of a highly electrically conducting material (Ag) in a matrix of a material with a high thermopower (Bi) enhance the conductivity of the composite more than they reduce its thermopower. The power factor is technologically important in transient thermoelectric cooling.