Effects of Mg Substitution on the Thermoelectric Properties of Ca3Co4O9-Based Materials

2011 ◽  
Vol 84-85 ◽  
pp. 671-675 ◽  
Author(s):  
Xiao Ling Qi ◽  
You Yu Fan ◽  
Ling Ke Zeng ◽  
Dong Sheng Zhu
Keyword(s):  
Thermal Conductivity ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Lattice Thermal Conductivity ◽  
Sol Gel ◽  
Dopant Content ◽  
Mg Doping ◽  
Mg Content ◽  
Mg Substitution

Polycrystalline Ca3-xMgxCo4O9(x=0-0.3)ceramics were prepared by the sol–gel method combined with the ordinary pressing sintering and the thermoelectric properties were measured from room temperature to 673 K. The substitution of Mg2+for Ca2+had a greater impact on the thermoelectric properties of Ca3Co4O9. The electrical conductivity and the thermal conductivity reduced significantly with increasing Mg content, and the Seebeck coefficient increased simultaneously. The influence of Mg doping on the thermal conductivity is mainly embodied in the lattice thermal conductivity of Ca3Co4O9. The lattice thermal conductivity showed a significant change with the increase of the dopant content, while the carrier thermal conductivity had no obvious change with the doping increasing. These results indicated that the thermoelectric properties of the material could be optimized remarkably with the substitution of Mg. The figure of meritZreached 1.08×10-4K-1at 573 K for the sample of Ca2.8Mg0.2Co4O9.

Thermal Transport Properties of Ca3Co4O9 with Mg Substitution

2011 ◽  
Vol 71-78 ◽  
pp. 959-962
Author(s):  
Xiao Ling Qi ◽  
Ling Ke Zeng ◽  
You Yu Fan
Keyword(s):  
Thermal Conductivity ◽  
Transport Properties ◽  
Room Temperature ◽  
Sol Gel ◽  
Dopant Content ◽  
Gel Method ◽  
Sol Gel Method ◽  
Mg Doping ◽  
Mg Substitution ◽  
Thermal Conductivities

Polycrystalline Ca3-xMgxCo4O9（x=0-0.3）ceramics were prepared by the sol–gel method combined with the ordinary pressing sintering and the thermal conductivities were measured from room temperature to 673 K. The influence of Mg2+ substitution for Ca2+ on the thermal conductivities of Ca3Co4O9 ceramics was investigated systematically. The influence of Mg doping on the thermal conductivities is mainly embodied in the lattice thermal conductivities, which shows a significant decrease with the increase of the dopant content for the samples with x ≤ 0.2, while the carrier thermal conductivity had no obvious change with Mg doping increasing. These results indicated that the thermal conductivities of the material could be reduced remarkably with the substitution of Mg from 1.427 W/m·K to 0.731 W/m·K at 573 K with x = 0.2.

Thermoelectric Properties of CoSb3-based Skutterudite Compounds

2010 ◽  
Vol 1267 ◽  
Author(s):  
Adul Harnwunggmoung ◽  
Ken Kurosaki ◽  
Hiroaki Muta ◽  
Shinsuke Yamanaka
Keyword(s):  
Thermal Conductivity ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Lattice Thermal Conductivity ◽  
Filling Ratio ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Figure ◽  
Alloy Scattering ◽  
Skutterudite Compound

AbstractCoSb3 is known as a skutterudite compound that could exhibit high thermoelectric figure of merit. However, the thermal conductivity of CoSb3 is relatively high. In order to enhance the thermoelectric performance of this compound, we tried to reduce the thermal conductivity of CoSb3 by substitution of Rh for Co and by Tl-filling into the voids. The polycrystalline samples of (Co,Rh)Sb3 and Tl-filled CoSb3 were prepared and the thermoelectric properties such as the Seebeck coefficient, electrical resistivity, and thermal conductivity were measured in the temperature range from room temperature to 750 K. The Rh substitution for Co reduced the lattice thermal conductivity, due to the alloy scattering effect. The minimum value of the lattice thermal conductivity was 4 Wm-1K-1 at 750 K obtained for (Co0.7Rh0.3)Sb3. Also the lattice thermal conductivity rapidly decreased with increasing the Tl-filling ratio. T10.25Co4Sb12 exhibited the best ZT values; the maximum ZT was 0.9 obtained at 600 K.

Thermoelectric Properties of Tl-X-Te (X=Pb, Sn, Ge) Systems

2005 ◽  
Vol 886 ◽  
Author(s):  
Atsuko Kosuga ◽  
Ken Kurosaki ◽  
Hiroaki Muta ◽  
Shinsuke Yamanaka
Keyword(s):  
Thermal Conductivity ◽  
Electrical Resistivity ◽  
Solid State ◽  
Electrical Properties ◽  
Seebeck Coefficient ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Lattice Thermal Conductivity ◽  
Dimensionless Figure Of Merit

ABSTRACTPolycrystalline-sintered samples of Tl2GeTe3, Tl4SnTe3, and Tl4PbTe3 were prepared by a solid-state reaction. Their thermoelectric properties were evaluated at temperatures ranging from room temperature to ca. 700 K by using the measured electrical resistivity (ρ), Seebeck coefficient (S), and thermal conductivity (κ). Despite their poor electrical properties, the dimensionless figure of merit ZT of all the compounds was relatively high, i.e., 0.74 at 673 K for Tl4SnTe3, 0.71 at 673 K for Tl4PbTe3, 0.29 at 473 K for Tl2GeTe3, due to the very low lattice thermal conductivity of the compounds.

scholarly journals Local ferroelectric polarization switching driven by nanoscale distortions in thermoelectric $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Aastha Vasdev ◽  
Moinak Dutta ◽  
Shivam Mishra ◽  
Veerpal Kaur ◽  
Harleen Kaur ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Lattice Thermal Conductivity ◽  
Direct Evidence ◽  
Temperature Dependent ◽  
Force Microscopy ◽  
Ferroelectric Domains ◽  
Pdf Analysis ◽  
Ferroelectric Transition Temperature

AbstractA remarkable decrease in the lattice thermal conductivity and enhancement of thermoelectric figure of merit were recently observed in rock-salt cubic SnTe, when doped with germanium (Ge). Primarily, based on theoretical analysis, the decrease in lattice thermal conductivity was attributed to local ferroelectric fluctuations induced softening of the optical phonons which may strongly scatter the heat carrying acoustic phonons. Although the previous structural analysis indicated that the local ferroelectric transition temperature would be near room temperature in $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te , a direct evidence of local ferroelectricity remained elusive. Here we report a direct evidence of local nanoscale ferroelectric domains and their switching in $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te using piezoeresponse force microscopy(PFM) and switching spectroscopy over a range of temperatures near the room temperature. From temperature dependent (250–300 K) synchrotron X-ray pair distribution function (PDF) analysis, we show the presence of local off-centering distortion of Ge along the rhombohedral direction in global cubic $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te . The length scale of the $${\text {Ge}}^{2+}$$ Ge 2 + off-centering is 0.25–0.10 Å near the room temperatures (250–300 K). This local emphatic behaviour of cation is the cause for the observed local ferroelectric instability, thereby low lattice thermal conductivity in $${\text {Sn}}_{0.7}{\text {Ge}}_{0.3}{\text {Te}}$$ Sn 0.7 Ge 0.3 Te .

Effects of Ce filling fraction and Fe content on the thermoelectric properties of Co-rich CeyFexCo4−xSb12

2001 ◽  
Vol 16 (3) ◽  
pp. 837-843 ◽  
Author(s):  
Xinfeng Tang ◽  
Lidong Chen ◽  
Takashi Goto ◽  
Toshio Hirai
Keyword(s):  
Thermal Conductivity ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Single Phase ◽  
Lattice Thermal Conductivity ◽  
Hole Concentration ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Figure ◽  
Filling Fraction ◽  
Fe Content

Single-phase filled skutterudite compounds, CeyFexCo4−xSb12 (x = 0 to 3.0, y = 0 to 0.74), were synthesized by a melting method. The effects of Fe content and Ce filling fraction on the thermoelectric properties of CeyFexCo4−xSb12 were investigated. The lattice thermal conductivity of Ce-saturated CeyFexCo4−xSb12, y being at the maximum corresponding to x, decreased with increasing Fe content (x) and reached its minimum at about x = 1.5. When x was 1.5, lattice thermal conductivity decreased with increasing Ce filling fraction till y = 0.3 and then began to increase after reaching the minimum at y = 0.3. Hole concentration and electrical conductivity of Cey Fe1.5Co2.5Sb12 decreased with increasing Ce filling fraction. The Seebeck coefficient increased with increasing Ce filling fraction. The greatest dimensionless thermoelectric figure of merit T value of 1.1 was obtained at 750 K for the composition of Ce0.28Fe1.52Co2.48Sb12.

Thermoelectric Properties of K2Bi8−xSbxSe13Solid Solutions and Se Doping

2001 ◽  
Vol 691 ◽  
Author(s):  
Theodora Kyratsi ◽  
Jeffrey S. Dyck ◽  
Wei Chen ◽  
Duck-Young Chung ◽  
Ctirad Uher ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Charge Transport ◽  
Transport Properties ◽  
Thermoelectric Properties ◽  
Solid Solutions ◽  
Figure Of Merit ◽  
Lattice Thermal Conductivity ◽  
Se Doping ◽  
Mass Fluctuation ◽  
Thermal Conductivities

ABSTRACTOur 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.

Thermoelectric Properties of Bi2Te3-ySey Bulk Materials Synthesized by Melting-Grinding Process

2018 ◽  
Vol 773 ◽  
pp. 145-151
Author(s):  
Min Soo Park ◽  
Gook Hyun Ha ◽  
Hye Young Koo ◽  
Yong Ho Park
Keyword(s):  
Thermal Conductivity ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Thermal Characteristics ◽  
Grinding Process ◽  
Alloy Scattering ◽  
Temperature Range ◽  
P Type ◽  
Optimal Effect

The Bi–Te thermoelectric system shows an excellent figure of merit (ZT) near room temperature. Research on increasing the ZT value for n‑type Bi–Te is imperative because the thermoelectric properties of this compound are inferior to those of the p-type material. For this purpose, n-type Bi2Te3-ySey powders with various amounts of Se dopant (0.3 ≤ y ≤ 0.6) were synthesized by a vacuum melting-grinding process to improve the physical properties. The ZT value of the sintered bodies was investigated in the temperature range of 298–423 K with regard to the electrical and thermal characteristics. As the Se content increased, the electrical conductivity decreased owing to a reduction in the carrier concentration, which improved the overall value of ZT. The thermal conductivity clearly decreased as the Se content increased in the temperature range of 298–373 K due to increased alloy scattering, as well as a reduction in the lattice thermal conductivity caused by crystal grain boundary scattering. At room temperature, Bi2Te2.7Se0.3 (y = 0.3) exhibited the highest ZT of 0.85. At increased temperatures, the ZT value was highest for Bi2Te2.55Se0.45 (y = 0.45), indicating that the optimal effect of the Se dopants varies depending on the temperature range.

Thermoelectric Properties of Composite PbTe – PbSnS2 Materials

2010 ◽  
Vol 1267 ◽  
Author(s):  
Steven N Girard ◽  
Jiaqing He ◽  
Vinayak P Dravid ◽  
Mercouri Kanatzidis
Keyword(s):  
Thermal Conductivity ◽  
Thermoelectric Properties ◽  
Room Temperature ◽  
Lattice Thermal Conductivity ◽  
Preliminary Characterization ◽  
New Phase ◽  
Sn Substitution

AbstractThe thermoelectric (Pb1-mSnmTe)1-x(PbS)x where m = 0.05 and x = 0.08 has been shown to produce PbS nanostructures that effectively scatter phonons, enhancing ZT. As Sn substitution is increased, a new phase of PbSnS2 precipitates. We find that incorporation of PbSnS2 in PbTe results in a significant reduction in lattice thermal conductivity around 0.6 W/mK at room temperature. We present preliminary characterization and thermoelectric properties.

Improved thermoelectric properties of gadolinium intercalated compounds GdxTiS2 at the temperaturesfrom 5 to 310 K

2006 ◽  
Vol 21 (2) ◽  
pp. 480-483 ◽  
Author(s):  
D. Li ◽  
X.Y. Qin ◽  
J. Zhang
Keyword(s):  
Thermal Conductivity ◽  
Electrical Resistivity ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Lattice Thermal Conductivity ◽  
Substantial Decrease ◽  
Intercalated Compounds

The thermoelectric properties of Gd intercalated compounds GdxTiS2 have been investigated at the temperatures from 5 to 310 K. The results indicate that Gd intercalation into TiS2 leads to substantial decrease of both its electrical resistivity and its lattice thermal conductivity κL (κL is lowered by 20% and 46% at 300 K for x = 0.025 and 0.05, respectively). Specially, as compared to the pristine TiS2 the figure of merit ZT of the intercalated compound GdxTiS2 has been improved at all temperatures investigated, and specifically, the ZT value of Gd0.05TiS2 at 300 K is about three times as large as that of TiS2.

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