X-Ray Study of the Structural Phase Transitions in Ge1–xAgx/2Bix/2 Te Solid Solutions

Abstract

The rhombohedral–cubic phase transition in the system Ge1–xAgx/2BIx/2 Te is studied by means of high temperature X‐ray analysis. The temperature and composition changes of the rhombohedral lattice parameters are found. Conclusions are made about the chemical bonds in the case of GeTe‐based solid solution with heterovalent [Ag and Sb(Bi)] and isovalent [Pb(Sn)] replacing the Ge cations.

High-Performance (Ag x SbTe x/2+1.5)15(GeTe)85 Thermoelectric Materials Prepared by Melt Spinning

“…This can be ascribed to the rhombohedral to cubic polymorphic transformation widely recognized in the TAGS system. [18][19][20] The region of this phase transition moves to lower temperature as the Ag content increases, in agreement with previous results reported.…”

Electrical Resistivity and Scattering Mechanisms of GeTe-Rich Thermoelectric Materials in the System GeTe-AgBiTe2

“…0:05 in bulk samples and hot-pressed samples, the product r 0 L 1 2 F * ; b versus 1=T deviates from the linear dependence. This is probably connected with the approach to the phase transition region and the associated phenomena, as the phase transition temperature rapidly decreases with increasing the AgBiTe 2 content [2]. So for these compositions the Matthiessen's rule is not valid.…”

“…The crystal structure of AgBiTe 2 is cubic (Fm3m). The GeTe-rich (GeTe) 1Àx (AgBiTe 2 ) x solid solutions (SS) keep the crystal structure of GeTe, but the phase transition temperature decreases with increasing content of introduced Ag and Bi atoms in cation sublattice from 700 K for pure GeTe to room temperature for composition containing 23% AgBiTe 2 [2]. The temperature dependencies of thermoelectric power S of (GeTe) 1Àx (AgBiTe 2 ) x SS for bulk samples of compositions x with 0:02 x 0:20 and for hot-pressed samples with x 0:03; 0.05; 0.10; 0.15; 0.20 were measured in the temperature interval 80 to 800 K. The Fermi energy and degree of degeneracy for different compositions were obtained and discussed earlier [3].…”

(GeTe)1–x(AgSnSe2)x: Strong Atomic Disorder-Induced High Thermoelectric Performance near the Ioffe–Regel Limit

“…Traditionally, I-V-VI 2 compounds (I = Ag, Cu, Na; V = Sb, Bi; VI = Te, Se) are usually adopted as the effective alloying species to enhance the atomic disorder in GeTe, especially the (GeTe) 1– x (AgSbTe 2 ) x , i.e. , TAGS alloys. − These (GeTe) 1– x (I-V-VI 2 ) x alloys exhibit superior TE performance and have been used in radioisotope TE generators for deep space because of the following reasons. The foremost reason is the resulted ultralow κ L stems from the atomic disorder of (GeTe) 1– x (I-V-VI 2 ) x alloys.…”