Thermoelectric properties of Sb$_{2}$Te$_{3}$-based nanocomposites with graphite

Antimony-telluride-based nanocomposite samples containing different weight fractions of graphite (Sb$_{2}$Te$_{3}$ + $x$% graphite, where $x$ = 0.0, 0.5, 1.0, and 2.5%) are synthesized and studied. The samples are produced by a solid-state reaction with the use of a ball mill. X-ray diffraction measurements show that the Sb$_{2}$Te$_{3}$ phase is present in the nanocomposites. All of the diffraction peaks are identified as corresponding to the rhombohedral structure of symmetry $R\bar3m$. No additional peaks related to graphite are observed because of its low content. Moreover, the X-ray data show the insolubility of graphite in Sb$_{2}$Te$_{3}$: the peaks related to Sb$_{2}$Te$_{3}$ remain unchanged upon the addition of graphite. The thermal conductivity, thermoelectric power, and resistivity of the samples are studied in the temperature range 80 K $\le T \le$ 320 K. The thermal conductivity $k$ of the nanocomposite decreases several times compared to the thermal conductivity of single-crystal Sb$_{2}$Te$_{3}$ and reaches $k\approx$ 0.95 W m$^{-1}$ K$^{-1}$ at $x$ = 0.5%. The parameter $k$ unsteadily depends on the content of graphite. The thermoelectric power of the nanocomposites with graphite at $x$ = 1.0% is higher compared to that of nanostructured Sb$_{2}$Te$_{3}$.