Thermoelectric properties of CoSb/sub 3/ with oxide particles dispersion

We have prepared (1-x)CoSb/sub 3/-x(oxide) composite (x=0.1-0.3) where the oxide particles are dispersed in the CoSb/sub 3/ matrix by the MG (mechanical grinding) technique. The electrical resistivity of CoSb/sub 3/ is reduced by addition of MoO/sub 2/ or WO/sub 2/, but it is enhanced by addition of Al/sub 2/O/sub 3/. This is because the electrical resistivity of MoO/sub 2/ or WO/sub 2/ is smaller than that of CoSb/sub 3/, while Al/sub 2/O/sub 3/ is an insulator. The electrical resistivity increases with an increase of the MG time. The thermal conductivity is reduced by the addition of oxide and it decreases with increasing MG time. As a result, 0.7CoSb/sub 3/-0.3MoO/sub 2/ composite exposed to 3h MG treatment or 0.9CoSb/sub 3/-0.1WO/sub 2/ composite exposed to 7h MG treatment has a maximum figure of merit of 3.6/spl times/10/sup -4/ K/sup -1/ at about 580K, which is slightly larger than that of CoSb/sub 3/ at 482K, 3.2/spl times/10/sup -4/.