Thermoelectric Properties of Hot-Pressed Ba₃Cu_14−δTe₁₂

The aim of this study was to investigate the thermoelectric properties of hot-pressed Ba₃Cu_14−δTe₁₂ as well as its stability with regards to Cu ion movement. For the latter, two single crystals were picked from pellets after they were measured up to 573 and 673 K, which showed no significant changes in the occupancies of any of the Cu sites. All investigated Ba₃Cu_14−δTe₁₂ materials displayed low thermal conductivity values (<1 W m^–1 K^–1) and appropriate electrical conductivity values (300–600 Ω^–1 cm^–1). However, the thermopower values were comparably low (<+65 μV K^–1), resulting in uncompetitive zT values, with the highest being achieved for Ba₃Cu_13.175Te₁₂, namely zT = 0.12 at 570 K. In an attempt to decrease the thermal conductivity, and thereby enhance the figure of merit, a brief alloying study with Ag was undertaken. The incorporation of Ag, however, did not produce any significant improvements.