Zone Leveling Crystal Growth of Thermoelectric PbTe Alloys with Sb₂Te₃ Widmanstätten Precipitates

Abstract

Unidirectional solidification of PbTe-rich alloys in the pseudobinary PbTe-Sb2Te3 system using the zone leveling technique enables the production of large regions of homogeneous solid solutions for the formation of precipitate nanocomposites as compared with Bridgman solidification. (PbTe)0.940(Sb2Te3)0.060 and (PbTe)0.952(Sb2Te3)0.048 alloys were successfully grown using (PbTe)0.4(Sb2Te3)0.6 and (PbTe)0.461(Sb2Te3)0.539 as seed alloys, respectively, with 1 mm h–1 withdrawal velocity. In the unidirectionally solidified regions of both alloys, Widmanstätten precipitates are formed due to the decrease in solubility of Sb2Te3 in PbTe. To determine the compositions of the seed alloys for the zone leveling experiments, the solute distribution in solidification in the PbTe-richer part of the pseudobinary PbTe-Sb2Te3 system has been examined from the concentration profiles in the samples unidirectionally solidified by the Bridgman method.

A combinatorial approach to microstructure and thermopower of bulk thermoelectric materials: the pseudo-ternary PbTe–Ag2Te–Sb2Te3 system

“…The composition where solidification starts in the Bridgman-type experiments reflects the solidus composition that is in equilibrium with the liquid at the initial composition, assuming that the chemical diffusion in the solid states does not affect the resulting compositional variations along the solidification direction. 37 Therefore, the higher content of PbTe for BM-3a than -3b is qualitatively consistent with the reported phase diagram, 15 where both the solidus and liquidus temperatures decrease with composition varying from PbTe to AgSbTe 2 . The only difference from the previous study is that the solidus compositions in this study are slightly PbTe-richer than the reported phase diagram.…”

“…The resulting compositional distributions are also shown in Fig. 1 37 Therefore, the higher content of PbTe for BM-3a than -3b is qualitatively consistent with the reported phase diagram, 15 where both the solidus and liquidus temperatures decrease with composition varying from PbTe to AgSbTe 2 . The only difference from the previous study is that the solidus compositions in this study are slightly PbTe-richer than the reported phase diagram.…”

The Thermoelectric Properties of Bismuth Telluride

“…Zone melting was chosen as the processing technique due to the control of solute segregation and sample homogeneity. The ampoules were placed in a home built vertical zone melting furnace with a solidification rate of 2.7 mm h −1 which resulted in oriented polycrystalline material. With great care one can achieve single crystals via zone melting, however, polycrystalline samples have the same transport behavior as single crystal Bi 2 Te 3 provided the orientation is complete …”

Ternary eutectic growth of nanostructured thermoelectric Ag-Pb-Te materials

“…[1][2][3] Embedded nanosized phases that created extra interfaces with submicron spacing length are capable of scattering the phonons with mid-to-long mean-free-path. 4 Approaches to synthesize bulk nanostructured materials include solid-state precipitation, 5,6 eutectoid decomposition, 7,8 spinodal decomposition, 9,10 and eutectic reaction, 11,12 etc.…”