Significant enhancement of the dimensionless thermoelectric figure of merit of the binary Ag₂Te

Effect of Phase Transition on the Thermoelectric Properties of Ag₂Te

“…The ¬ was very sensitive to the phase transition like the µ and the S. The ¬ exhibited a maximum to be 1.8 W m ¹1 K ¹1 before the phase transition and rapidly decreased to 0.9 W m ¹1 K ¹1 after the phase transition. These values obtained in the present study were slightly higher than the previously reported values, 9,10) which would be caused by the differences of the sample density and the Ag-doping content between the present and the previous samples. It has been expected that the silver ion conduction will scatter heat carrying phonons leading to the reduction of the ¬ lat .…”

“…8) Here, we will discuss the effect of the silver ion conduction on the TE properties of Ag 2 Te which is known to show relatively good TE performance. 9) In addition, it is also known that Ag 2 Te has a phase transition at around 420 K from ¢-Ag 2 Te (monoclinic structure) to ¡-Ag 2 Te (BCC structure) and shows an increase of ionic conductivity at the temperature about 10 2 times. Although the TE properties of Ag 2 Te were examined previously in our group, 10) the sample density was too low (only 85% of the theoretical density) to make a precise evaluation of the effect of silver ion conduction on the TE properties.…”

The effect of Ag concentration on the structural, electrical and thermal transport behavior of Pb:Te:Ag:Se mixtures and improvement of thermoelectric performance via Cu doping

“…perature dependent, while above the transition it becomes more negative with increasing temperature. The absolute values of the thermopower for both x = 2.0 and x = 2.01 samples, in the temperature range 50 • C ≤ T ≤ 400 • C, are smaller than the corresponding values of pure Ag 2 Te [16][17][18][19] but this is most probably due to the presence of impurities. The sign of the thermopower though is in agreement.…”

“…The magnitude of the thermopower in that sample, at high temperature, is comparable to the magnitude observed in these composites, which offers further proof that the Ag 2 Te stabilizes in a cubic phase. The thermopower of the stoichiometric Ag 2 Te remains negative through the transition [19] which implies that in the Ag 1.9 Te sample, the composition of the cubic phase is ␤-Ag 1.9 Te and not ␤-Ag 2 Te and that the p-type behavior in the composites is associated with the reduction in Ag concentration.…”

Alloying to increase the band gap for improving thermoelectric properties of Ag2Te

“…In addition, the intrinsic low thermal conductivity 24 has inspired research interest in this system as a thermoelectric material, [25][26][27] and a maximum zT of $0.6 was achieved. 26 Due to the small band gap (#0.2 eV, depending on the phase modification) of this material, 23,28 the observed nearly intrinsic conduction (decreasing or flattening S with increasing T) 23,26,29 behavior strongly suggests that the potential of this material as a thermoelectric is not fully realized.…”