scholarly journals Thermoelectric performance enhancement by manipulation of Sr/Ti doping in two sublayers of Ca3Co4O9

2020 ◽  
Vol 9 (6) ◽  
pp. 769-781
Author(s):  
Li Zhang ◽  
Yichen Liu ◽  
Thiam Teck Tan ◽  
Yi Liu ◽  
Jian Zheng ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Seebeck Coefficient ◽  
Photoelectron Spectroscopy ◽  
Performance Enhancement ◽  
Phonon Scattering ◽  
Electronic Conductivity ◽  
Deep Understanding ◽  
Electronic System ◽  
Spin Entropy ◽  
Doping Effects

AbstractThermoelectric (TE) performance of Ca3Co4O9 (CCO) has been investigated extensively via a doping strategy in the past decades. However, the doping sites of different sublayers in CCO and their contributions to the TE performance remain unrevealed because of its strong correlated electronic system. In this work, Sr and Ti are chosen to realize doping at the [Ca2CoO3] and [CoO2] sublayers in CCO. It was found that figure of merit (ZT) at 957 K of Ti-doped CCO was improved 30% than that of undoped CCO whereas 1 at% Sr doping brought about a 150% increase in ZT as compared to undoped CCO. The significant increase in electronic conductivity and the Seebeck coefficient are attributed to the enhanced carrier concentration and spin-entropy of Co4+ originating from the Sr doping effects in [Ca2CoO3] sublayer, which are evidenced by the scanning electron microscope (SEM), Raman, Hall, and X-ray photoelectron spectroscopy (XPS) analysis. Furthermore, the reduced thermal conductivity is attributed to the improved phonon scattering from heavier Sr doped Ca site in [Ca2CoO3] sublayer. Our findings demonstrate that doping at Ca sites of [Ca2CoO3] layer is a feasible pathway to boost TE performance of CCO material through promoting the electronic conductivity and the Seebeck coefficient, and reducing the thermal conductivity simultaneously. This work provides a deep understanding of the current limited ZT enhancement on CCO material and provides an approach to enhance the TE performance of other layered structure materials.

Synthesis and Thermoelectric Properties of Co4-XFeXSb12-YSnY Skutterudites

2011 ◽  
Vol 695 ◽  
pp. 65-68 ◽  
Author(s):  
Kwan Ho Park ◽  
Il Ho Kim
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Seebeck Coefficient ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Phonon Scattering ◽  
Charge Compensation ◽  
Fe Doping ◽  
Sn Doping ◽  
Double Doping

Co4-xFexSb12-ySny skutterudites were synthesized by mechanical alloying and hot pressing, and thermoelectric properties were examined. The carrier concentration increased by doping and thereby the electrical conductivity increased compared with intrinsic CoSb3. Every specimen had a positive Seebeck coefficient. Fe doping caused a decrease in the Seebeck coefficient but it could be enhanced by Fe/Sn double doping possibly due to charge compensation. The thermal conductivity was desirably very low and this originated from ionized impurity-phonon scattering. Thermoelectric properties were improved remarkably by Fe/Sn doping, and a maximum figure of merit, ZT = 0.5 was obtained at 723 K in the Co3FeSb11.2Sn0.8 specimen.

Thermoelectric Properties of Carbon Nanotubes Added n-type CoSb3 Compound

2011 ◽  
Vol 1314 ◽  
Author(s):  
Takashi Itoh ◽  
Masashi Tachikawa
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Electrical Resistivity ◽  
Seebeck Coefficient ◽  
Thermoelectric Properties ◽  
Phonon Scattering ◽  
Pulse Discharge ◽  
Molar Ratios ◽  
Performance Reduction ◽  
Compound Matrix

ABSTRACTCobalt triantimonide compounds are well known as materials with good thermoelectric properties over temperature range of 550-900 K. For further improving thermoelectric performance, reduction of thermal conductivity is required. In this study, we attempted to disperse carbon nanotubes (CNTs) homogeneously into the n-type CoSb3 compound for lowering lattice thermal conductivity by the phonon scattering. Powders of Co, Ni, Sb and Te were blended with molar ratios of n-type Co0.92Ni0.08Sb2.96Te0.04 compound, and the compound was synthesized through a pulse discharge sintering (PDS) process. After coarsely grinding the synthesized compound, CNTs were mixed with the compound powder at different mass% (0, 0.01, 0.05 and 0.1 mass%). Then, the mixture was mechanically ground with a planetary ball milling equipment. The ground composite powder was compacted and sintered by PDS. Thermoelectric properties (Seebeck coefficient, electrical resistivity and thermal conductivity) of the sintered samples were measured. It was confirmed that the fibrous CNTs existed homogeneously in the compound matrix. The absolute value of Seebeck coefficient slightly decreased with increase of CNT content. The minimum thermal conductivity was obtained at addition of 0.01mass%CNT, and the electrical resistivity was a little increased with CNT content. The maximum ZT of 0.98 was achieved at 853 K in the 0.01mass%CNT-added sample.

Phonon Scattering in the Complex Strain Field of a Dislocation in PbTe

2021 ◽  
Author(s):  
Ben Xu ◽  
Yandong Sun ◽  
Yanguang Zhou ◽  
Ramya L Gurunathan ◽  
Jin-Yu Zhang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Strain Field ◽  
Performance Enhancement ◽  
Phonon Scattering ◽  
Strain Engineering ◽  
Thermoelectric Devices ◽  
Complex Strain

Strain engineering is critical to the performance enhancement of electronic and thermoelectric devices because of its influence on the material thermal conductivity. However, current experiments cannot probe the detailed physics...

scholarly journals Ce Filling Limit and Its Influence on Thermoelectric Performance of Fe3CoSb12-Based Skutterudite Grown by a Temperature Gradient Zone Melting Method

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 6810
Author(s):  
Xu-Guang Li ◽  
Wei-Di Liu ◽  
Shuang-Ming Li ◽  
Dou Li ◽  
Jia-Xi Zhu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Temperature Gradient ◽  
Seebeck Coefficient ◽  
Density Functional ◽  
Lattice Thermal Conductivity ◽  
Phonon Scattering ◽  
Zone Melting ◽  
Impurity Level ◽  
Filling Fraction ◽  
Gradient Zone

CoSb3-based skutterudite is a promising mid-temperature thermoelectric material. However, the high lattice thermal conductivity limits its further application. Filling is one of the most effective methods to reduce the lattice thermal conductivity. In this study, we investigate the Ce filling limit and its influence on thermoelectric properties of p-type Fe3CoSb12-based skutterudites grown by a temperature gradient zone melting (TGZM) method. Crystal structure and composition characterization suggests that a maximum filling fraction of Ce reaches 0.73 in a composition of Ce0.73Fe2.73Co1.18Sb12 prepared by the TGZM method. The Ce filling reduces the carrier concentration to 1.03 × 1020 cm−3 in the Ce1.25Fe3CoSb12, leading to an increased Seebeck coefficient. Density functional theory (DFT) calculation indicates that the Ce-filling introduces an impurity level near the Fermi level. Moreover, the rattling effect of the Ce fillers strengthens the short-wavelength phonon scattering and reduces the lattice thermal conductivity to 0.91 W m−1 K−1. These effects induce a maximum Seebeck coefficient of 168 μV K−1 and a lowest κ of 1.52 W m−1 K−1 at 693 K in the Ce1.25Fe3CoSb12, leading to a peak zT value of 0.65, which is 9 times higher than that of the unfilled Fe3CoSb12.

MeV Si Ions Bombardment Effects on the Thermoelectric Properties of Si/Si+Ge Multi-Layer Superlttice Nanolayered Films

2010 ◽  
Vol 1267 ◽  
Author(s):  
Marcus Pugh ◽  
S. Budak ◽  
Cydale Smith ◽  
John Chacha ◽  
Kudus Ogbara ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Seebeck Coefficient ◽  
Thermoelectric Materials ◽  
Phonon Scattering ◽  
Ion Beam ◽  
Absolute Temperature ◽  
Inelastic Interaction ◽  
Before And After ◽  
The Cross

AbstractEffective thermoelectric materials have a low thermal conductivity and a high electrical conductivity. The performance of the thermoelectric materials and devices is shown by a dimensionless figure of merit, ZT = S2σT/K, where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature and K is the thermal conductivity. ZT can be increased by increasing S, increasing σ or decreasing K. MeV ion bombardment caused defects and disorder in the film and the grain boundaries of these nano-scale clusters increase phonon scattering and increase the chance of an inelastic interaction and phonon annihilation. We have prepared 100 alternating layers of Si/Si+Ge nanolayered superlattice films using the ion beam assisted deposition (IBAD). The 5 MeV Si ions bombardments have been performed using the AAMU Pelletron ion beam accelerator to make quantum clusters in the nanolayered superlattice films to decrease the cross plane thermal conductivity, increase the cross plane Seebeck coefficient and cross plane electrical conductivity. We have characterized the thermoelectric thin films before and after Si ion bombardments as we measured the cross-plane Seebeck coefficient, the cross-plane electrical conductivity, and the cross-plane thermal conductivity for different fluences

scholarly journals Effects of the Interface between Inorganic and Organic Components in a Bi2Te3–Polypyrrole Bulk Composite on Its Thermoelectric Performance

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3080
Author(s):  
Cham Kim ◽  
David Humberto Lopez
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Thermal Properties ◽  
Seebeck Coefficient ◽  
Power Factor ◽  
Energy Band ◽  
Phonon Scattering ◽  
Thermoelectric Performance ◽  
High Seebeck Coefficient ◽  
Fabrication Condition

We provided a method to hybridize Bi2Te3 with polypyrrole, thus forming an inorganic/organic bulk composite (Bi2Te3–polypyrrole), in which the effects of energy band junction and phonon scattering were expected to occur at the interface of the two components. Bi2Te3–polypyrrole exhibited a considerably high Seebeck coefficient compared to pristine Bi2Te3, and thus it recorded a somewhat increased power factor despite the loss in electrical conductivity caused by the organic component, polypyrrole. Bi2Te3–polypyrrole also exhibited much lower thermal conductivity than pristine Bi2Te3 because of the phonon scattering effect at the interface. We successfully brought about the decoupling phenomenon of electrical and thermal properties by devising an inorganic/organic composite and adjusting its fabrication condition, thereby optimizing its thermoelectric performance, which is considered the predominant property for n-type binary Bi2Te3 reported so far.

Phase Transformation and Thermoelectric Properties of Sn-Filled/Fe-Doped CoSb3 Skutterudites

2011 ◽  
Vol 312-315 ◽  
pp. 223-228
Author(s):  
Il Ho Kim
Keyword(s):  
Thermal Conductivity ◽  
Electrical Resistivity ◽  
Seebeck Coefficient ◽  
Phonon Scattering ◽  
Induction Melting ◽  
X Ray Diffraction ◽  
Scattering Centers ◽  
Δ Phase ◽  
Increasing Temperature ◽  
P Type

Sn-filled and Fe-doped CoSb3 skutterudites were synthesized by encapsulated induction melting. A single δ-phase was obtained by subsequent annealing, as confirmed by X-ray diffraction. The as-solidified ingot consisted of mixed phases of -CoSb, -CoSb2, δ-CoSb3 and elemental Sb. The phases could be transformed by annealing, and the phases of the as-solidified ingot annealed at 773 K for 24 h transformed to δ-CoSb3. The temperature dependence of the Seebeck coefficient, electrical resistivity and thermal conductivity were examined from 300 K to 700 K. The positive Seebeck coefficient confirmed p-type conduction. The electrical resistivity increased with increasing temperature, which showed that the SnzCo3FeSb12 skutterudite is highly degenerate. The thermal conductivity was reduced by Sn-filling because the filler atoms acted as phonon scattering centers in the skutterudite lattice. The thermoelectric figure of merit was enhanced by Sn filling and its optimum composition was considered to be Sn0.3Co3FeSb12.

scholarly journals Synthesis and Thermoelectric Properties of C60/Cu2GeSe3Composites

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Degang Zhao ◽  
Jiai Ning ◽  
Shuyu Li ◽  
Min Zuo
Keyword(s):  
Thermal Conductivity ◽  
Electrical Resistivity ◽  
Seebeck Coefficient ◽  
Grain Boundaries ◽  
Ball Milling ◽  
Thermoelectric Properties ◽  
Phonon Scattering ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Average Size

Nanosized C60powder was sufficiently incorporated with Cu2GeSe3powder by ball milling and C60/Cu2GeSe3composites were prepared by spark plasma sintering. C60distributed uniformly in the form of clusters and the average size of cluster was lower than 1 μm. With the addition of C60increasing, the electrical resistivity and Seebeck coefficient of C60/Cu2GeSe3composites increased while the thermal conductivity decreased significantly which resulted from the phonon scattering by C60clusters locating on the grain boundaries of Cu2GeSe3matrix. The maximumZTof 0.20 was achieved at 700 K for 0.9% C60/Cu2GeSe3sample.

Synthesis and Transport Properties of Polycrystalline Co-Filled Type-I Clathrate Compound (Sr,Ba)8Ga16Ge30

2009 ◽  
Vol 610-613 ◽  
pp. 441-445
Author(s):  
Li Wang ◽  
De Gang Zhao ◽  
Xiao Ya Shi ◽  
Wan Jiang ◽  
Li Dong Chen
Keyword(s):  
Thermal Conductivity ◽  
Seebeck Coefficient ◽  
Temperature Dependence ◽  
Spark Plasma Sinter ◽  
High Purity ◽  
Electronic Conductivity ◽  
Thermoelectric Performance ◽  
Type I ◽  
Clathrate Compound ◽  
Spark Plasma

Ga-substituted Ge based type-I clathrates with the general formula A8X16Y30 display promising thermoelectric performance. Using high purity elemental Sr, Ba, Ga, and Ge as starting materials, polycrystalline co-filled type-I clathrate compound (Sr,Ba)8Ga16Ge30 were successfully achieved by combining melting and Spark Plasma Sinter (SPS) method. The temperature dependence of thermal conductivity, electronic conductivity and Seebeck coefficient were reported. The calculated ZTmax is 0.28 at 700K. Enhanced thermoelectric performance would be expected through adjusting Sr/Ba ratio and framework atoms.

scholarly journals The Effect of Crystal Mismatch on the Thermoelectric Performance Enhancement of Nano Cu2Se

2021 ◽  
Vol 7 ◽  
Author(s):  
Yunus Demirci ◽  
Aminu Yusuf ◽  
Bejan Hamawandi ◽  
Muhammet S. Toprak ◽  
Sedat Ballikaya
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Seebeck Coefficient ◽  
Transport Properties ◽  
Performance Enhancement ◽  
Sem Analysis ◽  
Total Thermal Conductivity ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Two Phases

In the past decades, Cu2−xSe compounds have attracted great attention due to the inclusion of non-toxic and abundant elements, besides having a promising thermoelectric (TE) performance. In this work, we investigated the effect of a crystal mismatch of a nanoinclusion phase on the TE properties of Cu2−xSe. Nano-Cu2Se was synthesized using microwave assisted thermolysis, while the p-type skutterudite, Fe3.25Co0.75Sb12 (FeCoSb), compound was synthesized using a chemical alloying route. Nano-Cu2Se, and (nano-Cu2Se)1−x(nano-FeCoSb)x composites, where x = 0.05 and 0.1, were prepared via mechanical alloying followed by Spark Plasma Sintering process. Structural properties were evaluated by PXRD and SEM analysis, while the high temperature transport properties were examined via electrical conductivity, Seebeck coefficient, and thermal conductivity measurements in the temperature range of 300–800 K. Powder X-ray diffraction (PXRD) confirmed a single phase of nano Cu2Se, while the samples with FeCoSb inclusion consist of two phases as Cu2Se and CoSb3. SEM micrographs of all samples show that Cu2Se has randomly oriented grains with different sizes. Cu2Se samples with a FeCoSb inclusion show a rather different structure. In these samples, a rod-shaped FeCoSb phase, with a size varying between 20 and 100 nm, showed an inhomogeneous distribution in the structure and stacked between the Cu2Se layers. Transport data indicate that crystal mismatch between Cu2Se and FeCoSb has a strong effect on the TE transport properties. Electrical conductivity decreases but Seebeck coefficient enhances with nano FeCoSb inclusion. Total thermal conductivity was suppressed by 30% and ZT value enhanced by 15% with 5% nano FeCoSb inclusion at 750 K, likely due to a decrease in the electronic contribution of the thermal conductivity. Structural and transport data show that small amount of nanoinclusion of FeCoSb has a beneficial effect on the TE performance of nano Cu2Se at temperatures below 800 K.

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