Facile synthesis of Ag2Te nanowires and thermoelectric properties of Ag2Te polycrystals sintered by spark plasma sintering

Abstract

Ag₂Te nanowires with a diameter of approximately 200 nm and a length of several micrometers were prepared using a simple one-step solvothermal method without templates and surfactants. Ag(NO)₃ and Na₂TeO₃ were used as the Ag and Te sources, respectively, and N₂H₄·H₂O was used as the reducing agent. Based on the study of the morphology and composition of the Ag₂Te nanowires obtained under different hydrothermal conditions, a possible formation mechanism of Ag₂Te nanowires was proposed. An Ag-rich Ag₂Te sample was prepared by adjusting the molar ratio of Ag and Te. Furthermore, Ag₂Te nanowire powders were condensed to bulk materials by spark plasma sintering at 673 K for 5 min. The thermoelectric properties of the Ag₂Te bulk materials were measured between 323 K and 673 K. The phase transition temperature of the transformation from α-Ag₂Te to β-Ag₂Te was determined to be 419 K by differential scanning calorimetry. The highest ZT values of pure Ag₂Te and Ag self-doped Ag₂Te bulk samples reached 0.9 and 1.1 at 623 K, respectively. These results indicate that this one-pot technique for preparing the Ag self-doped Ag₂Te sample with enhanced thermoelectric performance may be widely used in other thermoelectric systems that can be fabricated by solution methods.