The B factor in multilayer thermionic refrigeration

The figure of merit for multilayer thermionic refrigeration is discussed in terms of an effective B factor, which has a similar definition as the B fa ctor in thermoelectrics. We show that high efficiencies for cooling or powe r generation are only obtained with very high values of this B factor. Such high values can only be attained because of the low thermal conductivity o f multilayers. The B factor for thermionics is usually less than the one fo r thermoelectrics. (C) 1999 American Institute of Physics. [S0021-8979(99)0 5824-7].