Thesis (Ph. D.)--University of Michigan, 1938. / Caption title. Thesis note on label attached to p. 437. "Reprinted from Economic Geology, vol. XXXIV, no.4, June-July, 1939." eContent provider-neutral record in process. Description based on print version record.

Thesis (Ph. D.)--University of Oregon, 2004. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 171-176). Also available for download via the World Wide Web; free to University of Oregon users.

Thesis (Ph. D.)--University of Michigan, 1938. / Caption title. Thesis note on label attached to p. 437. "Reprinted from Economic Geology, vol. XXXIV, no.4, June-July, 1939."

Thesis (Ph. D.)--University of Pennsylvania, 1928.

Neutron diffraction experiments on europium telluride/lead telluride super-lattice systems reveal pronounced correlations between the antiferromagnetic EuTe layers. The results from an assortment of varying experimental conditions (applied magnetic field, temperature, etc.) and their relevance to the physical mechanism underlying this striking phenomena are discussed. Stochastic computer simulations are compared to this real data to examine the effects of varying the neutron coherence length and the amount of correlations in the model sample. There are rising theoretical efforts to determine the physical mechanism causing the observed correlations and a laconic overview of current theories in interlayer coupling is given herein. The investigated structures do not exhibit perfect correlations between the magnetic layers but most samples clearly show correlation effects. The description of these partial correlations, characterized by an order parameter p, is examined and a straightforward method for determining p is derived. / Graduation date: 1998

Thermoelectric power generators can convert a temperature gradient into electrical energy, serving as a new energy resource by utilizing solar energy or by utilizing more waste heat. Thermoelectric coolers have the advantage of no moving parts, are quiet and release no gases that are harmful to the atmosphere, in contrast to compression-based refrigeration. While the low efficiency of “classical” thermoelectric devices limits their wide applications, the exploration of better thermoelectric materials is of great importance to improve the efficiency of thermoelectric devices. Good thermoelectric materials are usually narrow band gap semiconductors with a large Seebeck coefficient, reasonably high electrical conductivity and low thermal conductivity. This thesis deals with the exploration of new thermoelectric materials based on transition metal tellurides and the optimization of bulk materials based on oxides of low toxicity and high stability in air. In the first project, seven new ternary or quaternary tellurides, crystallizing in three different structure types, were synthesized and characterized. Single crystal X-ray diffraction was used for crystal structure determination; powder X-ray diffraction and energy dispersive X-ray analysis (EDAX) were used for phase and composition analyses. Physical properties of these compounds were predicted by electronic structure calculations and confirmed by physical property measurements. In the second project, two series of n-type doped perovskite SrTiO3 were prepared in a high temperature tube furnace under dynamic high vacuum of the order of 10–6 mbar, namely SrTi1-x(Nb,Ta)xO3, and Sr1-xLaxTi1-x(Nb,Ta)xO3. The phase purity was characterized by means of powder X-ray diffraction and electron probe micro analysis (EPMA). Rietveld refinements were performed to check for purity and symmetry reduction. The physical properties, such as Seebeck coefficient, electrical conductivity, and thermal conductivity, were measured at high temperatures for all the samples. Of the series of Nb/Ta-doped strontium titanates SrTi1-x(Nb,Ta)xO3, SrTi0.90Ta0.10O3 exhibits the highest ZT value, namely 0.17 for at 752 K. Of the double substituted series, Sr0.99La0.01Ti0.99Ta0.01O3 was best with ZT = 0.13 at 660 K. The rapid increases imply that higher ZT values are likely to occur at higher temperatures.

Thermoelectric power generators can convert a temperature gradient into electrical energy, serving as a new energy resource by utilizing solar energy or by utilizing more waste heat. Thermoelectric coolers have the advantage of no moving parts, are quiet and release no gases that are harmful to the atmosphere, in contrast to compression-based refrigeration. While the low efficiency of “classical” thermoelectric devices limits their wide applications, the exploration of better thermoelectric materials is of great importance to improve the efficiency of thermoelectric devices. Good thermoelectric materials are usually narrow band gap semiconductors with a large Seebeck coefficient, reasonably high electrical conductivity and low thermal conductivity. This thesis deals with the exploration of new thermoelectric materials based on transition metal tellurides and the optimization of bulk materials based on oxides of low toxicity and high stability in air. In the first project, seven new ternary or quaternary tellurides, crystallizing in three different structure types, were synthesized and characterized. Single crystal X-ray diffraction was used for crystal structure determination; powder X-ray diffraction and energy dispersive X-ray analysis (EDAX) were used for phase and composition analyses. Physical properties of these compounds were predicted by electronic structure calculations and confirmed by physical property measurements. In the second project, two series of n-type doped perovskite SrTiO3 were prepared in a high temperature tube furnace under dynamic high vacuum of the order of 10–6 mbar, namely SrTi1-x(Nb,Ta)xO3, and Sr1-xLaxTi1-x(Nb,Ta)xO3. The phase purity was characterized by means of powder X-ray diffraction and electron probe micro analysis (EPMA). Rietveld refinements were performed to check for purity and symmetry reduction. The physical properties, such as Seebeck coefficient, electrical conductivity, and thermal conductivity, were measured at high temperatures for all the samples. Of the series of Nb/Ta-doped strontium titanates SrTi1-x(Nb,Ta)xO3, SrTi0.90Ta0.10O3 exhibits the highest ZT value, namely 0.17 for at 752 K. Of the double substituted series, Sr0.99La0.01Ti0.99Ta0.01O3 was best with ZT = 0.13 at 660 K. The rapid increases imply that higher ZT values are likely to occur at higher temperatures.

Abstract The main focus of this work was on exploratory preparation of thermoelectric materials and analyses of their physical properties. A thermoelectric material is capable of converting heat to electricity or vice versa. Usually, narrow band gap semiconductors are good candidates for thermoelectric applications, because such materials have large Seebeck coefficient, reasonably high electrical conductivity and low thermal conductivity. In this work, two different systems were studied, ternary layered tellurides and quaternary derivatives of Tl9BiTe6. I tried to prepare Pb1−xBi2+xTe4 with x = 0.30, 0.10, −0.10 and = 0.30 and Pb1−xBi4+xTe7 with x = 0.15, 0.00, −0.15 and −0.35, and two pure compounds, Pb0.8Bi2.2Te4 and Pb0.9Bi2.1Te4 were obtained. Powder X-ray diffraction was used to confirm the purity of the compounds, and physical properties were measured on cold-pressed samples with densities around 80% of the theoretical value. The figure of merit of the ternary tellurides is comparable to the published values of PbBi2Te4 (0.5 at 600 K). I also investigated the quaternary series Tl8.67PbxBi1.33−xTe6 with x between 0.50 and 1.00. The purity was confirmed by powder X-ray diffraction data, and physical properties were measured on Spark Plasma Sintered (SPS) samples. Low thermal conductivity was observed as well as competitive power factors. The highest ZT value was 0.57 for the compound Tl8.67Pb0.60Bi0.73Te6 at 575 K.

Thesis (M.S.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains x, 84 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 79-83).

Abstract The main focus of this work was on exploratory preparation of thermoelectric materials and analyses of their physical properties. A thermoelectric material is capable of converting heat to electricity or vice versa. Usually, narrow band gap semiconductors are good candidates for thermoelectric applications, because such materials have large Seebeck coefficient, reasonably high electrical conductivity and low thermal conductivity. In this work, two different systems were studied, ternary layered tellurides and quaternary derivatives of Tl9BiTe6. I tried to prepare Pb1−xBi2+xTe4 with x = 0.30, 0.10, −0.10 and = 0.30 and Pb1−xBi4+xTe7 with x = 0.15, 0.00, −0.15 and −0.35, and two pure compounds, Pb0.8Bi2.2Te4 and Pb0.9Bi2.1Te4 were obtained. Powder X-ray diffraction was used to confirm the purity of the compounds, and physical properties were measured on cold-pressed samples with densities around 80% of the theoretical value. The figure of merit of the ternary tellurides is comparable to the published values of PbBi2Te4 (0.5 at 600 K). I also investigated the quaternary series Tl8.67PbxBi1.33−xTe6 with x between 0.50 and 1.00. The purity was confirmed by powder X-ray diffraction data, and physical properties were measured on Spark Plasma Sintered (SPS) samples. Low thermal conductivity was observed as well as competitive power factors. The highest ZT value was 0.57 for the compound Tl8.67Pb0.60Bi0.73Te6 at 575 K.