Is Thermoelectric Conversion Efficiency of a Composite Bounded by its Constituents?
We analyze the conversion efficiency of thermoelectric composites, and conclude that thermoelectric figure of merit ZT as we know it is ill-defined for composites, and is irrelevant for their conversion efficiency. In addition, we prove that thermoelectric conversion efficiency of a composite is not bounded by its constituents, and can be higher than all its constituents in the absence of size and interface effects, in contrast to previous claim.