Thermoelectric properties of n-type Ag-Pb-Sb-Te compounds

It was recently reported that the bulk AgPb_mSbTe_2+m exhibits very high thermoelectric performance: ZT=2.2 at 800 K [Kuei Fang Hsu et al, "Cubic AgPb_mSbTe_2+m: bulk thermoelectric materials with high figure of merit", Science, vol. 303, (2004), pp. 818-821]. Our group was trying to prepare the same composition of material by melting elements/compounds followed by hotpressing. At first the samples with the formula of (PbTe)_1-x(AgSbTe₂)_x (x=0.05, 0.09, 0.2) was prepared, as a result, the single phase of material was obtained only for (PbTe)_1-x(AgSbTe₂)_x (x=0.05, 0.09). Second, the samples with the formula of AgPb₁₈SbTe₂₀, AgPb_18+xSbTe₂₀, AgPb₁₈SbTe_20+y were prepared. The obtained phase contains small amounts of Ag dispersion. The thermoelectric properties of the obtained samples were evaluated in the temperature range from RT to 673 K, by using the measured electrical resistivity, Seebeck coefficient and thermal conductivity. The maximum ZT was 1.07 obtained for the formula of Ag_0.7Pb₁₈Sb_0.8Te₂₀ at 673 K.