Ohad Ben-Yehuda

Highly textured Bi2Te3-based materials for thermoelectric energy conversion

This work is concerned with Bi2Te3-based compounds known as being highly effective materials for thermoelectric applications near room temperature. These compounds are characterized by a remarkable anisotropy linked to their R3¯m crystal structure. Two textured p-type Bi0.4Sb1.6Te3 samples were prepared using a powder metallurgy approach, with the c axis parallel to the pressing direction. One sample was undoped while the second was doped with Pb which acts as an acceptor. The electrical conductivity, Hall coefficient, and magnetoresistivity were measured from room temperature down to 6K. The Seebeck coefficient α and electrical conductivity σ were measured along and perpendicular to the c axis from 300 up to 550K, and the thermal conductivity κ was measured at 300K. Different values of Seebeck coefficient were observed along and perpendicular to the c axis at temperatures above Ti, the beginning of intrinsic region in which the influence of the minority carriers becomes significant. Below Ti, the Seebeck...

Highly Efficient Segmented p-type Thermoelectric Leg

In the past years, energy demands in the entire world have been constantly increasing. This fact, coupled with the requirement for decreasing the world’s dependence on fossil fuels, has given rise to the need for alternative energy sources. While no single alternative energy source can solely replace the traditional fossil fuels, the combination of several alternative power sources can greatly decrease their usage. Thermoelectricity is one way to produce such energy via the harvesting of waste heat into electricity. One common example is the automobile industry which in the past few years had been looking into the option of harvesting the waste heat created by the engine, around the exhaust pipe and in the catalytic converter. Thermoelectricity is ideal for such application since it can convert the energy directly into electric current without any moving parts, thereby extending the life cycle of the operation.

Functionally Graded Bi 2 Te 3 based material for above ambient temperature application

This study is concerned with the preparation of Bi0.4Sb1.6Te3 functionally graded (FG) samples by a powder metallurgical approach for above ambient temperature applications. The FG sample is based on two components with different carrier concentration. The first is designed for a maximal figure of merit at room temperature, the second, doped with Pb, is meant for operation at higher temperatures. The transport properties of the two components of the FG sample, namely the Seebeck coefficient and electrical resistivity, have been determined from room temperature up to 550 K. The preparation of FG samples, their chemical stability and their transport properties over this temperatures range were examined and will be discussed.

Improved power factor of Bi0.4Sb1.6Te3 - based samples prepared by cold pressing and sintering

Anisotropic thermoelectrical Bi0.4Sb1.6Te 3 samples were prepared by powder metallurgy procedures. A strong correlation was observed between the morphological anisotropy of the powder particles and the crystal anisotropy of the compound. By using this correlation and taking a particle size range in which the morphological anisotropy was dominant, the thermoelectrical anisotropy was maximized. This desirable particle size was determined by SEM and XRD measurements, while sample anisotropy was determined by XRD measurements on sample facets that had been oriented in parallel and in perpendicular to the applied compression, respectively. Two types of samples, one anisotropic with a high orientation factor (~0.77) of the c-axis parallel to the compressing direction and the other pseudo-isotropic, were fabricated. This study is the first step toward a fabrication of functionally graded (FGM) thermoelectric samples, based on two Bi0.4Sb1.6Te3 ingots, each with a different carrier concentration. The first ingot was designed so that its maximum efficiency is at room temperature, while the second ingot, doped with Pb, is designed for a higher temperature. The results indicate that a power factor of 40 muWcm-1K-2 can be achieved for a sample aimed to operate at the lower temperature. This value is comparable to that observed in single crystals