Synthesis and thermoelectric properties of Mn-doped AgSbTe2 compounds

Polycrystalline p-type Ag0.9Sb1.1-xMnxTe2.05 (x = 0.05, 0.10, and 0.20) compounds have been prepared by a combined process of melt-quenching and spark plasma sintering. The sample composition of Ag0.9Sb1.1xMnxTe2.05 has been specially designed in order to achieve the doping effect by replacing part of Sb with Mn and to present the uniformly dispersed Ag2Te phase in the matrix by adding insufficient Te, which is beneficial for optimizing the electrical transport properties and enhancing the phonon scattering effect. All the samples have the NaCl-type structure according to our X-ray powder diffraction analysis. After the treatment of spark plasma sintering, only the sample with x = 0.20 has a small amount of MnTe2 impurities. The thermal analysis indicates that a tiny amount of Ag-2 Te phase exists in all these samples. The presence of the MnTe2 impurity with high resistance and high thermal conductivity leads to the deteriorative thermoelectric performance of the sample with x = 0.20 due to the decreased electrical transport properties and the increased thermal conductivity. In contrast, the sample with x - 0.10 exhibits enhanced thermoeletric properties due to the Mn-doping effect. A dimensionless thermoelectric figure of merit of 1.2 is attained for the sample with x = 0.10 at 573 K, showing promising thermoelectric properties in the medium temperature range.