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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 ...


Defect Structure Of Sb2−Xcrxte3 Single Crystals, Jeffrey Dyck, J. HoráK, P. C. Quayle, Č. DrašAr, P. LošT’ÁK, C. Uher Nov 2012

Defect Structure Of Sb2−Xcrxte3 Single Crystals, Jeffrey Dyck, J. HoráK, P. C. Quayle, Č. DrašAr, P. LošT’ÁK, C. Uher

Jeffrey Dyck

Single crystals of Sb2Te3 doped with Cr (cCr=0–6×1020 cm-3) were prepared by the Bridgman method. The measurements of the Hall coefficient reveal a nonmonotonous dependence of hole concentrations on the Cr content in the crystal. The hole concentration decreases at low content of Cr, while at higher content of Cr it increases again. However, according to magnetic measurements, Cr atoms enter the structure and form uncharged substitutional defects CrSb×, which cannot affect the free carrier concentration directly. The observed dependence can be elucidated by means of a point defect model. The model is based on an assumption ...


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 ...


Enhancing Thermoelectric Performance Of Ternary Nanocrystals Through Adjusting Carrier Concentration., Yixin Zhao, Jeffrey Dyck, Brett Hernandez, Clemens Burda Mar 2010

Enhancing Thermoelectric Performance Of Ternary Nanocrystals Through Adjusting Carrier Concentration., Yixin Zhao, Jeffrey Dyck, Brett Hernandez, Clemens Burda

Jeffrey Dyck

The carrier concentration of chemically synthesized Bi2Te3-based nanocrystals (NCs) is for the first time reported to be adjusted by forming ternary Bi2−xSbxTe3 NCs (x = 0.02, 0.05, 0.10, 0.20, 0.50, and 1.50) through partial substitution of Bi with Sb. Carrier concentrations of ternary Bi2−xSbxTe3 NCs were successfully adjusted by a factor of more than 10 controlled by the stoichiometric partial Sb/Bi substitution level. The power factors of the stoichiometric ternary Bi2−xSbxTe3 NCs improved three times compared to the parent Bi2Te3 due to the carrier concentration adjustment.


Significant Suppression Of Ferromagnetism By Hydrostatic Pressure In The Diluted Magnetic Semiconductor Sb2-Xvxte3 With X <~ 0.03, Jeffrey Dyck, T J. Mitchell, A J. Luciana, P C. Quayle, C DrašAr, P LošŤÁK Dec 2006

Significant Suppression Of Ferromagnetism By Hydrostatic Pressure In The Diluted Magnetic Semiconductor Sb2-Xvxte3 With X <~ 0.03, Jeffrey Dyck, T J. Mitchell, A J. Luciana, P C. Quayle, C DrašAr, P LošŤÁK

Jeffrey Dyck

The authors report on the hydrostatic pressure dependence of the magnetotransport properties of ferromagnetic Sb2-xVxTe3 single crystals with x=0.02—0.03. Pressure significantly increases the free hole concentration in these compounds. In turn, the Curie temperature is suppressed by roughly 40%, which goes against many models that would predict an increase in Curie temperature with increasing carrier concentration. These results indicate that the ferromagnetism in these materials is carrier mediated and that a full Ruderman-Kittel-Kasuya-Yosida model that takes into account the oscillatory nature of the indirect exchange interaction among localized spins is needed in order to explain the ...


Nanostructured Bi2se3 Films And Their Thermoelectric Transport Properties., Xiaofeng Qiu, Leah Austin, Philip Muscarella, Jeffrey Dyck, Clemens Burda Aug 2006

Nanostructured Bi2se3 Films And Their Thermoelectric Transport Properties., Xiaofeng Qiu, Leah Austin, Philip Muscarella, Jeffrey Dyck, Clemens Burda

Jeffrey Dyck

No abstract provided.


Substantial Pressure Effect On The Resistivity And Curie Temperature For The Diluted Magnetic Semiconductor Sb2–X Vx Te3., Jeffrey Dyck, K. Ahilan, M. Aronson, C. Uher, P. Lošťák Jun 2006

Substantial Pressure Effect On The Resistivity And Curie Temperature For The Diluted Magnetic Semiconductor Sb2–X Vx Te3., Jeffrey Dyck, K. Ahilan, M. Aronson, C. Uher, P. Lošťák

Jeffrey Dyck

The influence of hydrostatic pressure on the electrical resistivity ρ and ferromagnetic transition temperature T C of bulk, single crystal Sb1–x Vx Te3 with x = 0.03 is presented. Pressure strongly suppresses ρ at all temperatures, with an overall decrease of about 35% at 1.6 GPa. The peak in ρ , a signature of T C, moves to lower temperature with increasing pressure. An overall suppression of T C near 40% at 1.6 GPa is observed. The results are discussed within the context of a carrier-mediated ferromagnetic exchange interaction.


Defect Structure Of Sb2−Xmnxte3 Single Crystals., Jaromír Horák, Petr LošŤÁK, Čestmír Drašar, Jeffrey Dyck, Zengzua Zhou, Cterid Uher Aug 2005

Defect Structure Of Sb2−Xmnxte3 Single Crystals., Jaromír Horák, Petr LošŤÁK, Čestmír Drašar, Jeffrey Dyck, Zengzua Zhou, Cterid Uher

Jeffrey Dyck

Incorporation of the transition metal elements in the tetradymite structure of Sb2Te3 has a strong influence on electronic properties. Recent studies have indicated that Mn substitutes on the Sb sublattice increases the carrier concentration of holes. However, the doping efficiency of Mn appears rather low in comparison to what it should be based on the measurements of magnetization, structural analysis, and transport properties. In this paper we address this issue by making detailed studies of the Hall effect and electrical resistivity and we explain the results with the aid of a model that takes into account interactions of the Mn ...


Transport Coefficients Of Titanium-Doped Sb2te3 Single Crystals., Č. Drašar, M. Steinhart, P. Lošťák, H.-K. Shin, Jeffrey Dyck, C. Uher Mar 2005

Transport Coefficients Of Titanium-Doped Sb2te3 Single Crystals., Č. Drašar, M. Steinhart, P. Lošťák, H.-K. Shin, Jeffrey Dyck, C. Uher

Jeffrey Dyck

Titanium-doped single crystals (cTi=0–2×1020atomscm−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 3–300K. It was observed that with an increasing Ti content in the samples the electrical resistivity, 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 holes in ...


Low-Temperature Ferromagnetic Properties Of The Diluted Magnetic Semiconductor Sb2-X Crx Te3 ., Jeffrey Dyck, Č. Drašar, P. LošŤÁK, C. Uher Mar 2005

Low-Temperature Ferromagnetic Properties Of The Diluted Magnetic Semiconductor Sb2-X Crx Te3 ., Jeffrey Dyck, Č. Drašar, P. LošŤÁK, C. Uher

Jeffrey Dyck

We report on magnetic and electrical transport properties of Sb2-x Crx Te3 single crystals with 0⩽x⩽0.095 over temperatures from 2 K to 300 K . A ferromagnetic state develops in these crystals at low temperatures with Curie temperatures that are proportional to x (for x>0.014 ), attaining a maximum value of 20 K for x=0.095 . Hysteresis below TC for the applied field parallel to the c axis is observed in both magnetization and Hall-effect measurements. Magnetic as well as transport data indicate that Cr takes the 3+ (3 d3 ) valence state, substituting for antimony in ...


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


Conduction Band Splitting And Transport Properties Of Bi2se3., J. Navrátil, J. Horák, T. Plecháček, S. Kamba, P. LošŤÁK, Jeffrey Dyck, W. Chen, C. Uher Mar 2004

Conduction Band Splitting And Transport Properties Of Bi2se3., J. Navrátil, J. Horák, T. Plecháček, S. Kamba, P. LošŤÁK, Jeffrey Dyck, W. Chen, C. Uher

Jeffrey Dyck

Detailed transport studies of single crystals of Bi2Se3 were made in the temperature range of 2–300K, and the data were analyzed in terms of a model consisting of two groups of electrons—a centrosymmetrical lower conduction band and an upper conduction band located away from the Γ-point. Very good agreement with the experimental data is obtained assuming the electrons are scattered on acoustic phonons and ionized impurities. A rather strong influence of the latter mechanism is attributed to a large number of charged selenium vacancies in Bi2Se3. The fitted transport parameters were used to calculate the electronic portion of ...


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 ...


Magnetic And Transport Properties Of The V2– Vi3 Diluted Magnetic Semiconductor Sb2_Xmnxte3, Jeffrey Dyck, P. Svanda, P. Lostak, J. Horak, W. Chen, C. Uher Dec 2003

Magnetic And Transport Properties Of The V2– Vi3 Diluted Magnetic Semiconductor Sb2_Xmnxte3, Jeffrey Dyck, P. Svanda, P. Lostak, J. Horak, W. Chen, C. Uher

Jeffrey Dyck

We have measured electrical and magnetic properties of single crystals of Sb2_xMnxTe3 with x =0 – 0.045 at temperatures of 2 K to 300 K. Hall effect measurements indicate that each manganese atom donates approximately one hole to the valence band. The magnetic susceptibility is paramagnetic down to 2 K, and both Curie–Weiss and Brillouin analyses show that manganese substitutes for Sb and takes the Mn2+ state with S=5/2. Contrary to the case of III–V host matrices, manganese does not stimulate ferromagnetic order in the family of bulk layered V2– VI3 diluted magnetic semiconductors, at least ...


Effect Of Sn Substituting For Sb On The Low-Temperature Transport Properties Of Ytterbium-Filled Skutterudites, J. Yang, D. Morelli, G. Meisner, W. Chen, Jeffrey Dyck, C. Uher Apr 2003

Effect Of Sn Substituting For Sb On The Low-Temperature Transport Properties Of Ytterbium-Filled Skutterudites, J. Yang, D. Morelli, G. Meisner, W. Chen, Jeffrey Dyck, C. Uher

Jeffrey Dyck

We examine the effect of alloying Sn on the Sb site of ytterbium-filled skutterudites, a promising class of thermoelectric materials. We report measurements of the Hall effect, electrical resistivity, Seebeck coefficient, and thermal conductivity between 2 and 300 K on two series of samples having different ytterbium filling fractions: Yb0.19Co4Sb12-xSnx, with x=0, 0.05, 0.1, and 0.2, and Yb0.5Co4Sb12-xSnx, with x=0.5, 0.6, 0.8, 0.83, and 0.9. We find that the substitution of Sn does not lower the electron concentration of these samples, but rather gives rise to a p-type ...


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 ...


Heat Transport In Sb2àXvxte3 Single Crystals, Jeffrey Dyck, W. Chen, C. Uher, Č. DrašAr, P. LošŤÁK Sep 2002

Heat Transport In Sb2àXvxte3 Single Crystals, Jeffrey Dyck, W. Chen, C. Uher, Č. DrašAr, P. LošŤÁK

Jeffrey Dyck

Antimony telluride doped with small concentrations of vanadium was recently identified as a diluted magnetic semiconductor. We present a study of the heat transport in single crystals of [formula] with [formula] 0.01, 0.02, and 0.03. Thermopower and thermal conductivity were measured from 1.5 K to 300 K. The thermopower is positive for all samples investigated and has a modest dependence on vanadium content. At low temperatures, the lattice thermal conductivity has an approximate [formula] dependence and the data up to 100 K can be fitted well assuming that phonons scatter on boundaries, point defects, charge carriers ...


Electrical Conductivity And Thermopower Of Cu–Sio[Sub 2] Nanogranular Films., W. Chen, J. Lin, X. Zhang, H. Shin, Jeffrey Dyck, C. Uher Jul 2002

Electrical Conductivity And Thermopower Of Cu–Sio[Sub 2] Nanogranular Films., W. Chen, J. Lin, X. Zhang, H. Shin, Jeffrey Dyck, C. Uher

Jeffrey Dyck

We have measured the thermopower S and electrical conductivity σ in a series of Cu[sub x](SiO[sub 2])[sub 1-x] nanogranular films between 2 and 300 K with Cu volume fraction x varying from 0.43 up to 1.0. At low temperatures, disorder-enhanced electron-electron interaction effects dictate the behavior of σ. A crossover of the temperature dependence from σ∝ √T to σ∝ T[sup 1/3] is observed as x is lowered and the metal-insulator transition is approached. S is small, shows linear temperature dependence, and is rather insensitive to the change of x. Effects of annealing ...


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


Transport Properties Of Polycrystalline Type-I Sn Clathrates, G. S. Nolas, J. L. Cohn, Jeffrey Dyck, C. Uher, J. Lang Apr 2002

Transport Properties Of Polycrystalline Type-I Sn Clathrates, G. S. Nolas, J. L. Cohn, Jeffrey Dyck, C. Uher, J. Lang

Jeffrey Dyck

Thermal conductivity, resistivity, Seebeck coefficient, and Hall measurements on polycrystalline Sn-clathrate compounds with the type-I hydrate crystal structure are reported. Interstitial alkali-metal atoms in these compounds reside inside polyhedral cavities formed by the tetrahedrally bonded Sn network atoms. Localized disorder associated with “rattling” motion of these interstitial atoms contributes to the low thermal conductivity of these semiconducting compounds. The Hall coefficient and resistivity for some compounds exhibit nonmonotonic temperature dependences consistent with a crossover with decreasing temperature from conduction-band to impurity-band conduction. The carrier mobility is found to be low even in the absence of interstitial atoms within the Sn ...


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


Diluted Magnetic Semiconductors Based On Sb2àXvxte3 „0.01ïXï0.03., Jeffrey Dyck, Pavel Hájek, Petr LošŤÁK, Ctirad Uher Mar 2002

Diluted Magnetic Semiconductors Based On Sb2àXvxte3 „0.01ïXï0.03., Jeffrey Dyck, Pavel Hájek, Petr LošŤÁK, Ctirad Uher

Jeffrey Dyck

We report on a diluted magnetic semiconductor based on the [formula] tetradymite structure doped with very low concentrations of vanadium (1—3 at. %). The anomalous transport behavior and robust magnetic hysteresis loops observed in magnetotransport and magnetic measurements are experimental manifestations of the ferromagnetic state in these materials. The [formula] exchange between holes and vanadium [formula] spins is estimated from the behavior of the magnetoresistance. A Curie temperature of at least 22 K is observed for [formula] This discovery offers possibilities for exploring magnetic properties of other tetradymite structure semiconductors doped with a wide range of [formula] transition metals.


Effect Of Ni On The Transport And Magnetic Properties Of Co1àXnixsb3, Jeffrey Dyck, Wei Chen, Jihui Yang, Gregory P. Meisner, Ctirad Uher Mar 2002

Effect Of Ni On The Transport And Magnetic Properties Of Co1àXnixsb3, Jeffrey Dyck, Wei Chen, Jihui Yang, Gregory P. Meisner, Ctirad Uher

Jeffrey Dyck

The filled skutterudite compounds based on the binary skutterudite [formula] are currently being investigated for their potential applications 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, since it has one more electron in its valence shell than Co. Up to now, however, only high concentrations of Ni in [formula] have been studied; and the valence of Ni in this compound and its influence on the transport and magnetic properties has been an open question. We present electrical resistivity, thermopower, Hall effect, magnetoresistance ...


Low-Temperature Ferromagnetism And Magnetic Anisotropy In The Novel Diluted Magnetic Semiconductor Sb2−Xvxte3, Jeffrey Dyck, Wei Chen, Pavel Hájek, Petr Lošt’Ák, Ctirad Uher Feb 2002

Low-Temperature Ferromagnetism And Magnetic Anisotropy In The Novel Diluted Magnetic Semiconductor Sb2−Xvxte3, Jeffrey Dyck, Wei Chen, Pavel Hájek, Petr Lošt’Ák, Ctirad Uher

Jeffrey Dyck

We report on a novel diluted magnetic semiconductor based on the Sb2Te3 tetradymite structure doped with very low concentrations of vanadium (1–3at%). Anisotropy in the magnetic hysteresis loops and magnetoresistance are observed at temperatures below the ferromagnetic ordering temperature. A Curie temperature of 24K is observed for Sb1.97V0.03Te3.


Influence Of Electron-Phonon Interaction On The Lattice Thermal Conductivity Of Co1àXnixsb3, J. Yang, D. T. Morelli, G. P. Meisner, W. Chen, Jeffrey Dyck, C. Uher Feb 2002

Influence Of Electron-Phonon Interaction On The Lattice Thermal Conductivity Of Co1àXnixsb3, J. Yang, D. T. Morelli, G. P. Meisner, W. Chen, Jeffrey Dyck, C. Uher

Jeffrey Dyck

We have investigated the effect of electron-phonon scattering in a series of n-type nickel-doped [formula] skutterudite materials. Samples were polycrystalline of the form [formula] with [formula] 0.001, 0.003, 0.005, 0.0075, and 0.01. The lattice thermal conductivity decreases dramatically with increasing Ni doping for [formula] For higher Ni concentration the reduction of the lattice thermal conductivity saturates. Our theoretical analysis indicates that this reduction of the lattice thermal conductivity cannot be explained solely by point-defect scattering of the phonons. Rather, we can fit the lattice thermal conductivity of Ni-doped [formula] by introducing an electron-phonon scattering mechanism ...


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.


Transport Properties Of Bi2−Xinxse3 Single Crystals., J. Navrátil, T. Plecháček, J. Horák, S. Karamazov, P. LošŤÁK, Jeffrey Dyck, W. Chen, C. Uher Aug 2001

Transport Properties Of Bi2−Xinxse3 Single Crystals., J. Navrátil, T. Plecháček, J. Horák, S. Karamazov, P. LošŤÁK, Jeffrey Dyck, W. Chen, C. Uher

Jeffrey Dyck

The paper reports on the temperature dependence of the electrical and thermal conductivity, Hall constant, and Seebeck coefficient of Bi2−xInxSe3 (x=0, 0.2, 0.4) single crystals measured over the temperature range from 2 to 300 K. One single-valley conduction band model is used to interpret relations among transport coefficients. The data analysis relies on the use of a mixed carrier scattering mechanism consisting of acoustic scattering and scattering on ionized impurities. The effect of In incorporation into the Bi2Se3 crystal lattice on the individual components of thermal conductivity is evaluated and discussed. Copyright 2001 Academic Press.