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Thermoelectric properties of rare-earth lead selenide alloys and lead chalcogenide nanocomposites

Thiagarajan, Suraj Joottu
http://rave.ohiolink.edu/etdc/view?acc_num=osu1196263620

Abstract Details

2007, Master of Science, Ohio State University, Mechanical Engineering.
The three transport properties that make up the thermoelectric figure of merit can be decoupled by the use of certain techniques. In this work, we investigate the effect of two such methods on the thermoelectric properties: (1) Use of rare earth dopants with f-orbitals situated close to the Fermi level, thus resulting in a high thermopower, and (2) use of nanostructured bulk materials with size quantization effects that would affect transport properties of the material. In the first part, we examine the effect of rare-earth dopant in PbSe by using a sequence of samples of pure PbSe (for reference), and PbSe doped with Ce, Pr, Nd, Eu, Gd and Yb. We report the magnetic susceptibility data, as well as a full set of galvanomagnetic and thermomagnetic measurements, from which we deduce the carrier’s transport properties, specifically density, mobility, density-of-states effective mass and scattering exponent. In short, the trivalent rare earth atoms act as donors; the mobility of the rare-earth alloys is decreased by mechanisms that we will discuss, while the scattering exponent is not affected. The effective mass is increased, but not sufficiently to overcome the mobility decrease and increase the weighted mobility or improve the thermoelectric performance of the material, except potentially Pb 1-xNd xSe. In the second part, we developed a nanocomposite of PbTe and PbSe, made from core-shell structured nanoparticles sintered together. At a core size of ~20 nm, the core is expected to show size-quantization effects, and confine energy levels at discrete values. Such a confinement would lead to an enhancement in the Seebeck coefficient through the interaction of the discrete energy levels with the host density of states. Moreover, the nanostructures in the matrix should lead to a reduction in the lattice thermal conductivity. In the nanocomposite samples, we did not find the expected Seebeck enhancement, presumably due to the wide size distribution of the cores leading to little size-quantization. However, we found a favorable reduction in the lattice thermal conductivity, lower than an alloy of the same composition. Unfortunately, this gain by the thermal conductivity reduction comes at the cost of the carrier mobility.
Joseph Heremans (Advisor)
80 p.
Thermoelectric; Figure of merit; Seebeck Coefficient; thermoelectric power; quantum dot; nanocomposite; rare-earth; lead telluride; lead selenide

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Citations

  • Thiagarajan, S. J. (2007). Thermoelectric properties of rare-earth lead selenide alloys and lead chalcogenide nanocomposites [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1196263620

    APA Style (7th edition)

  • Thiagarajan, Suraj. Thermoelectric properties of rare-earth lead selenide alloys and lead chalcogenide nanocomposites. 2007. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1196263620.

    MLA Style (8th edition)

  • Thiagarajan, Suraj. "Thermoelectric properties of rare-earth lead selenide alloys and lead chalcogenide nanocomposites." Master's thesis, Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=osu1196263620

    Chicago Manual of Style (17th edition)

osu1196263620
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© 2007, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.