Impact of In Situ Generated Ag2Te Nanoparticles on the Microstructure and Thermoelectric Properties of AgSbTe2 Compounds

A series of ternary (Ag2Te) x (Sb2Te3)100−x (x = 44 to 54) bulk materials with in situ generated Ag2Te nanoparticles were prepared from high-purity elements by combining the melt-quench technique with the spark plasma sintering technique. The influence of the Ag2Te nanoparticles on the thermoelectric transport properties, and the mechanism of nanoparticle formation were investigated. With increasing x, the concentration of the Ag2Te nanoparticles increased monotonically, but their diameter remained nearly unchanged. Due to the possible carrier energy filtering effect caused by the Ag2Te nanoparticle inclusions, the Seebeck coefficient of the sample with x = 50 was two times higher than that of the sample prepared by the melting method. Moreover, notable scattering of mid-to-long wavelength phonons arising from the evenly distributed Ag2Te nanoparticles led to a large reduction of the lattice thermal conductivity. All these effects led to the enhancement of the ZT value of the x = 50 sample (AgSbTe2) compared with the single-phase sample (x = 44).