Synthesis dependent phase segregation in thermoelectric material AgSbTe2

Polycrystalline AgSbTe2 was synthesized from high purity elements in evacuated sealed quartz tubes by two different procedures: (i) slow cooling and (ii) annealing and quenching. Here we discuss the effect of annealing and quenching on the structural properties of the compound. XRD measurements confirmed the principal AgSbTe2 phase crystallizing with cubic space group Fm-3m. However, depending on the preparation technique, varying amounts of secondary phases Ag2Te and Sb2Te3 were observed. The morphology and composition of the compound were also investigated by FESEM. Understanding the phase segregation is crucial for controlling the stability of the parent compound in high temperature thermoelectric applications. The formation of synthesis dependent secondary phases is a consequence of the metastable nature of the parent compound and may lead to enhanced phonon scattering, lower thermal conductivity and improved thermoelectric performance.