Thermoelectric properties of p-type Ag1−x(Pb1−ySny)mSb1−zTem+2

Abstract

The thermoelectric properties of Ag1−x(Pb1−ySny)mSb1−zTem+2 (4≤m≤16, −0.1≤x≤0.3, 1/3≤y≤2/3, 0.2≤z≤0.4; Lead Antimony Silver Tellurium Tin, LASTT-m) compositions were investigated in the temperature range of 300 to ~670K. All samples crystallize in the average NaCl-type structure without any noticeable second phase and exhibit very narrow bandgaps of <0.1eV. We studied a range of m values, silver concentrations (x), Pb/Sn ratios (y), and antimony concentrations (z) to determine their effects on the thermoelectric properties. The samples were investigated as melt grown polycrystalline ingots. Varying the Ag contents, the Pb/Sn ratios, and the Sb contents off-stoichiometry allowed us to control the electrical conductivity, the Seebeck coefficient, and the thermal conductivity. The electrical conductivity tends to decrease with decreasing m values. The highest ZT of ~1.1 was achieved at ~660K for Ag0.9Pb5Sn5Sb0.8Te12 mainly due to the very low lattice thermal conductivity of ~0.4W/(mK) around 660K. Also, samples with charge-balanced stoichiometries, Ag(Pb1−ySny)mSbTem+2, were studied and found to exhibit a lower power factor and higher lattice thermal conductivity than the Ag1−x(Pb1−ySny)mSb1−zTem+2 compositions.