Thermoelectric properties of chalcogenides with the spinel structure

Many compounds with the spinel structure type have been analyzed for their thermoelectric properties. Published data was used to augment experimental results presented here and to select promising thermoelectric spinels. Comp ounds studied here include Cu0.5Al0.5Cr2Se4, Co0.5Co0.5Cr2Se4 Cu0.5In0.5Cr2 Se4, and CuIr2Se4. Many exhibit low lattice thermal conductivity of about 2 0 mW/cmK, independent of temperature. Two representative series of compound s GaxCu1-xCr2Se4 0 less than or equal tox less than or equal to0.6 and CuxZ n1-x Cr2Se4 0 less than or equal tox less than or equal to 0.3 have been st udied to examine the doping region of interest for both high and low temper ature thermoelectric applications. Ferromagnetic, small polaron semiconduct ors are found in both series of compounds. G(a)xCu(1-x)Cr(2)Se(4) shows a m etal insulator transition, from a p-type metal at x=0 to a p-type and then n-type semiconductor as x crosses 1/2. The maximum figure of merit ZT is of order 0.1. CuxZn1-xCr2Se4 transitions from a p-type semiconductor to a p-t ype metal as x increases.