Thermoelectric efficiency in graded indium-doped PbTe crystals

Abstract

High efficiency thermoelectric conversion is achieved by using materials with a maximum figure of merit Z=S2σ/k, where S is the Seebeck coefficient, σ and k, the electrical and thermal conductivities, respectively. High quality homogeneous thermoelectric materials, based on PbTe crystals, usually display an elevated value of Z over a narrow temperature range. A maximal value of figure of merit Z, as a function of electron density, is attained only for one specific location of the Fermi level, EF, with respect to the conduction band edge, EC. In order to maintain this optimal Z value, namely, maintain a constant location of the Fermi level, the electron density, which is determined by the dopant concentration, must increase with increasing temperature. We present a method for the generation of a dopant (indium) concentration profile in n-type PbTe crystals that gives rise to a constant location of the Fermi level, and hence, to an optimal value of Z over a wide temperature range. The resulting functionally graded material, based on PbTe〈In〉, displays a practically constant value of the Seebeck coefficient, over the 50–600 °C temperature range.

Anomalous transport properties of the half-metallic ferromagnets Co 2 TiSi, Co 2 TiGe and Co 2 TiSn

“…It can also be achieved, e.g. in PbTe crystals, with a sophisticated and experimentally complex graded indium doping through the crystal [13]. This report will show that the Heusler compounds Co 2 TiSi, Co 2 TiGe and Co 2 TiSn combine all the requirements of half-metallic ferromagnets with a constant Seebeck coefficient that can be used in future for spincaloric devices.…”

“…The rather large constant Seebeck coefficients above the Curie temperatures up to at least 950 K could be achieved by filling up the flat band in the D direction in the minority spin channel just above e F (figure 1c). The constant Seebeck coefficients above the Curie temperatures mean that the energy of the Fermi level is pinned in a wide temperature range in these compounds [13,39] and therefore the thermovoltages have a linear temperature dependence that makes these compounds suitable materials for future thermoelectric devices such as thermocouples. With an Al doping of the Z -position in the Co 2 TiZ (Z = Si, Ge or Sn) compounds, one can tune their Curie temperature to lower values [40] and therefore tune the working temperature of thermocouples designed using these materials.…”

Electrical Transport and Thermoelectric Properties of PbTe Prepared by HPHT

“…In order to enhance the thermoelectric properties of PbTe, many methods have been used including hot-pressing and finegrain size with heavy doping. [3][4][5][6] At the same time, there are many low-dimensional structures made from PbTe for the purpose of enhancing its thermoelectric properties. [7][8][9] Comparing to the other preparation methods for thermoelectric materials, the method of high pressure and high temperature (HPHT) has many advantages.…”

Visible-active photocatalytic behaviors observed in nanostructured lead chalcogenides PbX (X = S, Se, Te)

“…[15][16][17] These unusual characteristics make them practical in various technological applications, such as infrared opto-electronic devices, thermoelectric devices, photo-voltaic cells, infrared lasers and light-emitting devices. [18][19][20][21][22][23][24] Narrow band gaps and high carrier mobilities identify lead chalcogenides potential materials for photocatalysis.…”