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Full-Text Articles in Physics

Toward High-Performance Nanostructured Thermoelectric Materials: The Progress Of Bottom-Up Solution Chemistry Approaches, Yixin Zhao, Jeffrey S. Dyck, Clemens Burda Dec 2012

Toward High-Performance Nanostructured Thermoelectric Materials: The Progress Of Bottom-Up Solution Chemistry Approaches, Yixin Zhao, Jeffrey S. Dyck, Clemens Burda

Jeffrey Dyck

Significant research effort has recently gone into the synthesis of thermoelectric nanomaterials through different chemical approaches since nanomaterials chemistry became a promising strategy for improving thermoelectric performance. Different thermoelectric nanocrystals, especially PbTe, Bi2Te3 and CoSb3, with various compositions and morphologies have been successfully prepared by solvo/hydrothermal, electrochemical, and ligand-based synthesis methods. Such nanoscale materials show not only substantial reduction in thermal conductivity due to increased phonon scattering at nanoscale grain boundaries and lower densities of phonon states but possibly also an enhancement in thermopower due to electronic quantum size effects. More recently, the notoriously low power factors of thermoelectric ...


Structure Inhomogeneities, Shallow Defects, And Charge Transport In The Series Of Thermoelectric Materials K2bi8−Xsbxse13, Jeffrey S. Dyck, T. Kyratski, E. Hatzikraniotis, K. M. Paraskevopoulos, C. D. Malliakas, C. Uher, M. G. Kanatzidis Dec 2012

Structure Inhomogeneities, Shallow Defects, And Charge Transport In The Series Of Thermoelectric Materials K2bi8−Xsbxse13, Jeffrey S. Dyck, T. Kyratski, E. Hatzikraniotis, K. M. Paraskevopoulos, C. D. Malliakas, C. Uher, M. G. Kanatzidis

Jeffrey Dyck

The charge transport properties of the low-dimensional thermoelectric materials K2Bi8-xSbxSe13 (02Bi8-xSbxSe13 was analyzed on the basis of the classical semiconductor theory and discussed in the context of recent band calculations. The results suggest that the K2Bi8-xSbxSe13 materials possess coexisting domains with semimetallic and semiconducting characters whose ratio is influenced by the value of x and by local defects. The extent and relative distribution of these domains control the charge transport properties. Electron diffraction experiments performed on samples of K2Bi8-xSbxSe13 with x=1.6 show evidence for such domains by indicating regions with long range ordering of K+/Bi3+ atoms and ...


Improving Thermoelectric Properties Of Chemically Synthesized Bi2te3-Based Nanocrystals By Annealing, Yixin Zhao, Jeffrey Dyck, Brett Hernandez, Clemens Burda Jul 2010

Improving Thermoelectric Properties Of Chemically Synthesized Bi2te3-Based Nanocrystals By Annealing, Yixin Zhao, Jeffrey Dyck, Brett Hernandez, Clemens Burda

Jeffrey Dyck

The power factors of chemically synthesized Bi2Te3 and Bi0.5Sb1.5Te3 nanocrystals (NCs) were improved up to 2.4 and 7.8 μW cm−1 K−2, respectively, which are significantly higher than previously reported values for chemically synthesized Bi2Te3 NCs and even comparable to the recently reported highest power factor of 5 μW cm−1 K−2 for Bi2Te3 NCs consolidated by spark plasma sintering. This improvement was achieved by annealing the NCs under argon protection, and the crystal structures and morphologies of these annealed NCs were characterized via XRD, SEM, and TEM measurements. The temperature-dependent thermoelectric properties of ...


Lattice Thermal Conductivity Of K2(Bi1_Zsbz)8se13 Solid Solutions, Jeffrey S. Dyck, Theodora Kyratsi, Evripides Hatzikraniotis, M Paraskevopoulous, H. K. Shin, Ctirad Uher, Mercouri Kanatzidis Apr 2004

Lattice Thermal Conductivity Of K2(Bi1_Zsbz)8se13 Solid Solutions, Jeffrey S. Dyck, Theodora Kyratsi, Evripides Hatzikraniotis, M Paraskevopoulous, H. K. Shin, Ctirad Uher, Mercouri Kanatzidis

Jeffrey Dyck

The family of solid solutions of the type B -K2(Bi1_zSbz)8Se13 (0


Cubic : Bulk Thermoelectric Materials With High Figure Of Merit, Kuei Hsu, Sim Loo, Fu Guo, Wei Chen, Jeffrey Dyck, Cterid Uher, Tim Hogan, E. Polychroniadis, Mercouri Kanatzidis Feb 2004

Cubic : Bulk Thermoelectric Materials With High Figure Of Merit, Kuei Hsu, Sim Loo, Fu Guo, Wei Chen, Jeffrey Dyck, Cterid Uher, Tim Hogan, E. Polychroniadis, Mercouri Kanatzidis

Jeffrey Dyck

The conversion of heat to electricity by thermoelectric devices may play a key role in the future for energy production and utilization. However, in order to meet that role, more efficient thermoelectric materials are needed that are suitable for high-temperature applications. We show that the material system may be suitable for this purpose. With m = 10 and 18 and doped appropriately, n-type semiconductors can be produced that exhibit a high thermoelectric figure of merit of ~2.2 at 800 kelvin. In the temperature range 600 to 900 kelvin, the material is expected to outperform all reported bulk thermoelectrics, thereby earmarking ...


Synthesis, Crystal Structure And Thermoelectric Properties Of Β-K2bi8se13 Solid Solutions, Theodora Kyratsi, Duck-Young Chung, Jeff Dyck, Ctirad Uher, Sangeeta Lal, Sim Loo, Tim Hogan, John Ireland, Carl Kannewurf, Evripides Hatzikraniotis, Konstantinos Paraskevopoulos, Mercouri Kanatzidis Dec 2003

Synthesis, Crystal Structure And Thermoelectric Properties Of Β-K2bi8se13 Solid Solutions, Theodora Kyratsi, Duck-Young Chung, Jeff Dyck, Ctirad Uher, Sangeeta Lal, Sim Loo, Tim Hogan, John Ireland, Carl Kannewurf, Evripides Hatzikraniotis, Konstantinos Paraskevopoulos, Mercouri Kanatzidis

Jeffrey Dyck

Solid solution series of the type K2Bi8-xSbxSe13, K2-xRbxBi8Se13 as well as K2Bi8Se13-xSx were prepared and the distribution of the atoms (Bi/Sb, K/Rb and Se/S) on different crystallographic sites, the band gaps and their thermoelectric properties were studied. The distribution Se/S appears to be more uniform than the distribution of the Sb and Rb atoms in the β-K2Bi8Se13 structure that shows preference in specific sites in the lattice. Band gap is mainly affected by Sb and S substitution. Seebeck coefficient measurements showed n-type character for of all Se/S members. In the Bi/Sb series an enhancement ...


Micro Thermoelectric Cooler Fabrication: Growth And Characterization Of Patterned Sb2te3 And Bi2te3 Films ., Luciana Da Silva, M. Kaviany, A. Dehennis, Jeffrey Dyck Dec 2002

Micro Thermoelectric Cooler Fabrication: Growth And Characterization Of Patterned Sb2te3 And Bi2te3 Films ., Luciana Da Silva, M. Kaviany, A. Dehennis, Jeffrey Dyck

Jeffrey Dyck

A column-type micro thermoelectric cooler is being fabricated using p-type Sb2Te3 and n-type Bi2Te3 films (approximately 4 μm thick). The films are grown by thermal co-evaporation and patterned on Cr/Au/Ti/Pt (hot) connectors, which are deposited onto a silicon dioxide coated wafer. The column height is limited by control of the Te deposition rate. Although a high substrate temperature during thermoelectric film deposition is desired, it has been limited by the degradation of the photoresist used for patterning. The measured Seebeck coefficient and electrical resistivity of the thermoelectric films are reported, and preliminary results show that excess tellurium ...


Transport Coefficients Of Titanium-Doped Sb2te3 Crystals., P. Svanda, P. LošŤÁK, Č. Drašar, Jeffrey Dyck Dec 2002

Transport Coefficients Of Titanium-Doped Sb2te3 Crystals., P. Svanda, P. LošŤÁK, Č. Drašar, Jeffrey Dyck

Jeffrey Dyck

Titanium-doped single crystals (cTi = 0 to 2×1020 atoms cm-3) were prepared from the elements Sb, Ti, and Te of 5N purity by a modified Bridgman method. The obtained crystals were characterized by measurements of the temperature dependence of the electrical resistivity, Hall coefficient, Seebeck coefficient and thermal conductivity in the temperature range of 5-300 K. It was observed that with an increasing Ti content in the samples the electrical resistance, the Hall coefficient and the Seebeck coefficient increase. This means that the incorporation of Ti atoms into the Sb2Te3 crystal structure results in a decrease in the concentration of ...


Highly Anisotropic Crystal Growth And Thermoelectric Properties Of K2bi8_Xsbxse13 Solid Solutions: Band Gap Anomaly At Low X, Jeffrey S. Dyck, Theodora Kyratsi, Wei Chan, Duck-Young Chung, Ctirad Uher, Konstantinos Paraskevopoulos, Mercouri Kanatzidis Jul 2002

Highly Anisotropic Crystal Growth And Thermoelectric Properties Of K2bi8_Xsbxse13 Solid Solutions: Band Gap Anomaly At Low X, Jeffrey S. Dyck, Theodora Kyratsi, Wei Chan, Duck-Young Chung, Ctirad Uher, Konstantinos Paraskevopoulos, Mercouri Kanatzidis

Jeffrey Dyck

The thermoelectric properties of solid solutions of the type B -K2Bi8_xSbxSe13 (0


Thermoelectric Properties Of The N-Type Filled Skutterudite Ba0.3co4sb12 Doped With Ni, Jeffrey Dyck, Wei Chen, Ctirad Uher, Lidong Chen, Xinfeng Tang, Toshio Hirai Mar 2002

Thermoelectric Properties Of The N-Type Filled Skutterudite Ba0.3co4sb12 Doped With Ni, Jeffrey Dyck, Wei Chen, Ctirad Uher, Lidong Chen, Xinfeng Tang, Toshio Hirai

Jeffrey Dyck

Synthesis and electrical and thermal transport properties are reported for several filled skutterudite compounds doped with Ni: Ba0.3NixCo4_xSb12 with 0


Thermoelectric Properties Of K[Subscript 2]Bi[Subscript 8-X]Sb[Subscript X]Se[Subscript 13] Solid Solutions And Se Doping [Et Al.], Theodora Kyratski, Jeffrey Dyck, Wei Chen Dec 2001

Thermoelectric Properties Of K[Subscript 2]Bi[Subscript 8-X]Sb[Subscript X]Se[Subscript 13] Solid Solutions And Se Doping [Et Al.], Theodora Kyratski, Jeffrey Dyck, Wei Chen

Jeffrey Dyck

Our efforts to improve the thermoelectric properties of β-K2Bi8Se13, led to systematic studies of solid solutions of the type β-K2Bi8−xSbxSe13. The charge transport properties and thermal conductivities were studied for selected members of the series. Lattice thermal conductivity decreases due to the mass fluctuation generated in the lattice by the mixed occupation of Sb and Bi atoms. Se excess as a dopant was found to increase the figure-of merit of the solid solutions.


Anomalous Barium Filling Fraction And N-Type Thermoelectric Performance Of Ba[Sub Y]Co[Sub 4]Sb[Sub 12]., L. Chen, T. Kawahara, X. Tang, T. Goto, T. Hirai, Jeffrey Dyck, W. Chen, C. Uher Aug 2001

Anomalous Barium Filling Fraction And N-Type Thermoelectric Performance Of Ba[Sub Y]Co[Sub 4]Sb[Sub 12]., L. Chen, T. Kawahara, X. Tang, T. Goto, T. Hirai, Jeffrey Dyck, W. Chen, C. Uher

Jeffrey Dyck

Barium-filled skutterudites BaCoSb with an anomalously large filling fraction of up to y=0.44 have been synthesized. The lattice parameters increase linearly with Ba content. Magnetic susceptibility data show that BaCoSb is paramagnetic, which implies that some of the Co atoms in BaCoSb have acquired a magnetic moment. The presence of the two different valence states of Co (Co3+ and Co2+) leads to the anomalously large barium filling fraction even without extra charge compensation. All samples show n-type conduction. The electrical conductivity increases with increasing the Ba filling fraction. The lattice thermal conductivity of BaCoSb is significantly depressed as ...


Multi-Filling Approach For The Improvement Of Thermoelectric Properties Of Skutterudites., L. Chen, X. Tang, T. Kawahara, Jeffrey Dyck Dec 2000

Multi-Filling Approach For The Improvement Of Thermoelectric Properties Of Skutterudites., L. Chen, X. Tang, T. Kawahara, Jeffrey Dyck

Jeffrey Dyck

Several skutterudite antimonides filled with atoms of different kinds, (Ba, M)yCo4Sb12 (M=Ce, La, Sr), have been synthesized by the combination of solid state reaction and melting methods. Thermal conductivity of (Ba,Sr)yCo4 Sb12 samples shows a behavior similar to that of BayCo4Sb12. Adding a small amount of Ce or La to the BayCo4Sb12 system is effective in further reducing the lattice thermal conductivity. The difference in the ionic radii of the two co-filler atoms is the most sensitive factor for scattering of phonons. The multi-filled (Ba, M)yCo4Sb12 (M=Sr, Ce, La) show lower Seebeck coefficients as ...


Thermoelectric Properties Of Yb-Filled And Sn-Compensated Skutterudites ., Jihui Yang, Gregory Meisner, Wei Chen, Jeffrey Dyck, Ctirad Uher Dec 2000

Thermoelectric Properties Of Yb-Filled And Sn-Compensated Skutterudites ., Jihui Yang, Gregory Meisner, Wei Chen, Jeffrey Dyck, Ctirad Uher

Jeffrey Dyck

The effect of alloying tin on the antimony site of ytterbium-filled skutterudites is examined. We performed measurements of Hall effect, electrical resistivity, Seebeck coefficient and thermal conductivity on the series Yb0.5Co4Sb12-x Snx, with x=0.5, 0.6, 0.8 and 0.83. We find that the substitution of tin does not alter the position of the Fermi level with respect to the conduction band of these heavily doped semiconducting samples, but rather it gives rise to a p-type band. Experimental data for x=0.83 can be understood in the context of a two-carrier electrical conduction. Thermal conductivity ...


Transport And Magnetic Properties Of Co1-Xnixsb3 With X Less Than 0.01, Jeffrey Dyck, W. Chen, Y. Yang, G. Meisner, C. Uher Dec 2000

Transport And Magnetic Properties Of Co1-Xnixsb3 With X Less Than 0.01, Jeffrey Dyck, W. Chen, Y. Yang, G. Meisner, C. Uher

Jeffrey Dyck

The filled skutterudite compounds based on the binary skutterudite CoSb3 are currently being investigated for their potential application as thermoelectric materials. One route to optimization of these compounds is by doping on the Co site. An obvious candidate for an n-type dopant is Ni, because it has one more electron in its valence shell than Co. We present electrical resistivity, thermopower, Hall effect and magnetic susceptibility measurements on polycrystalline, n-type Co1-xNixSb3 with x less than 0.01. A model which takes into account conduction of electrons residing in the conduction band in addition to hopping conduction within an impurity "band ...


Growth Of Bulk, Polycrystalline Gallium And Indium Nitride At Sub-Atmospheric Pressures, John Angus, Alberto Argoitia, Cliff Hayman, Long Wang, Jeffrey Dyck, Kathleen Kash Dec 1996

Growth Of Bulk, Polycrystalline Gallium And Indium Nitride At Sub-Atmospheric Pressures, John Angus, Alberto Argoitia, Cliff Hayman, Long Wang, Jeffrey Dyck, Kathleen Kash

Jeffrey Dyck

Bulk polycrystalline gallium nitride and indium nitride were crystallized at sub-atmospheric pressures by saturating the pure metals with nitrogen from a microwave electron cyclotron resonance source. Saturation of Ga/In melts with nitrogen led only to the crystallization of gallium nitride. The polycrystralline samples were wurtzitic. The gallium nitride was well faceted, with narrow Raman lineshapes, and showed near-band-edge and yellow band photo-luminescence at both 4K and 300K. The indium nitirde was formed in smaller amounts, was less well faceted, and showed no photoluminescence.