The Experts below are selected from a list of 25068 Experts worldwide ranked by ideXlab platform
Li-dong Zhao - One of the best experts on this subject based on the ideXlab platform.
-
Anharmoncity and Low Thermal Conductivity in thermoelectrics
Materials Today Physics, 2018Co-Authors: Cheng Chang, Li-dong ZhaoAbstract:The thermoelectric (TE) efficiency is evaluated by the material thermoelectric figure of merit (ZT), which can be usually improved by enhancing the electrical transport properties and/or reducing the Thermal Conductivity. Seeking the material with Low Thermal Conductivity is crucial for thermoelectrics, which enable us simplify complex thermoelectric parameters and focus on the optimization of electrical transport properties alone. Here, we summarized the relationship between anharmonicity and Low Thermal Conductivity in thermoelectrics. Several strategies which yield anharmonicity are also suggested, including lone pair electron, resonant bonding and rattling model. At last, some intuitive methods were proposed and summarized to evaluate the anharmonicity.
-
high thermoelectric performance in n type biagses due to intrinsically Low Thermal Conductivity
Energy and Environmental Science, 2013Co-Authors: Haijun Wu, Celine Barreteau, David Bérardan, Nita Dragoe, Jiaqing He, Jing Li, Li-dong ZhaoAbstract:BiAgSeS shows intrinsically Low Thermal Conductivity in the temperature range from 300 K (∼0.46 W m−1 K−1) to 823 K (∼0.29 W m−1 K−1). Low Thermal Conductivity coupling with enhanced electrical transport properties achieved through partially substituting S2− by Cl− leads to a high ZT of ∼1.0 at 823 K for BiAgSeS0.97Cl0.03, indicating that the BiAgSeS system is promising for thermoelectric power generation applications.
-
high thermoelectric performance of oxyselenides intrinsically Low Thermal Conductivity of ca doped bicuseo
Npg Asia Materials, 2013Co-Authors: Jiaqing He, Celine Barreteau, David Bérardan, Nita Dragoe, Jing-feng Li, Fu Li, Li-dong ZhaoAbstract:We report on the high thermoelectric performance of p-type polycrystalline BiCuSeO, a layered oxyselenide composed of alternating conductive (Cu2Se2)2− and insulating (Bi2O2)2+ layers. The electrical transport properties of BiCuSeO materials can be significantly improved by substituting Bi3+ with Ca2+. The resulting materials exhibit a large positive Seebeck coefficient of ∼+330 μV K−1 at 300 K, which may be due to the ‘natural superlattice’ layered structure and the moderate effective mass suggested by both electronic density of states and carrier concentration calculations. After doping with Ca, enhanced electrical Conductivity coupled with a moderate Seebeck coefficient leads to a power factor of ∼4.74 μW cm−1 K−2 at 923 K. Moreover, BiCuSeO shows very Low Thermal Conductivity in the temperature range of 300 (∼0.9 W m−1 K−1) to 923 K (∼0.45 W m−1 K−1). Such Low Thermal Conductivity values are most likely a result of the weak chemical bonds (Young’s modulus, E∼76.5 GPa) and the strong anharmonicity of the bonding arrangement (Gruneisen parameter, γ∼1.5). In addition to increasing the power factor, Ca doping reduces the Thermal Conductivity of the lattice, as confirmed by both experimental results and Callaway model calculations. The combination of optimized power factor and intrinsically Low Thermal Conductivity results in a high ZT of ∼0.9 at 923 K for Bi0.925Ca0.075CuSeO. Li-Dong Zhao, Jiaqing He and co-workers have gained insight into the highly thermoelectric properties of a bismuth–copper oxyselenide (BiCuSeO), a polycrystalline, layered compound. BiCuSeO's ability to produce a significant electric potential from a temperature difference, and vice versa, arises from its intrinsically Low Thermal Conductivity, and can be further improved by boosting the material's electrical Conductivity through doping with strontium or barium, or introducing copper deficiencies. The researchers have now carried out an extensive characterization of the oxyselenide and propose that its conveniently Low Thermal Conductivity results from the weak chemical bonds that exist between two different kinds of layers, and a particular bonding arrangement, in the material's lattice. Moreover, by substituting bismuth ions (Bi3+) with calcium ions (Ca3+) the Thermal Conductivity of the lattice could be Lowered further, leading to an improvement in the oxyselenide's thermoelectric properties. We report on the promising thermoelectric performance of p-type polycrystalline BiCuSeO, which is a layered oxyselenide composed of conductive (Cu2Se2)2− layers that alternate with insulating (Bi2O2)2+ layers. Electrical transport properties can be optimized by substituting Bi3+ with Ca2+. Moreover, BiCuSeO shows very Low Thermal Conductivity in the temperature ranges of 300 (∼0.9 W m−1K−1) to 923 K (∼0.45 W m−1 K−1). These intrinsically Low Thermal Conductivity values may result from the weak chemical bonds of the material as well as the strong anharmonicity of the bonding arrangement. The combination of the optimized power factor and the intrinsically Low Thermal Conductivity results in a high ZT of ∼0.9 at 923 K for Bi0.925Ca0.075CuSeO.
-
High thermoelectric performance of oxyselenides: Intrinsically Low Thermal Conductivity of Ca-doped BiCuSeO
NPG Asia Materials, 2013Co-Authors: Yan Ling Pei, Qijun Liu, Celine Barreteau, David Bérardan, Nita Dragoe, Jiaqing He, Wei Pan, Jing-feng Li, Li-dong ZhaoAbstract:We report on the high thermoelectric performance of p-type polycrystalline BiCuSeO, a layered oxyselenide composed of alternating conductive (Cu2Se2)2? and insulating (Bi2O2)2þ layers. The electrical transport properties of BiCuSeO materials can be significantly improved by substituting Bi3þ with Ca2þ. The resulting materials exhibit a large positive Seebeck coefficient of Bþ330lVK?1 at 300K, which may be due to the ‘natural superlattice’ layered structure and the moderate effective mass suggested by both electronic density of states and carrier concentration calculations. After doping with Ca, enhanced electrical Conductivity coupled with a moderate Seebeck coefficient leads to a power factor of B4.74lWcm?1K?2 at 923K. Moreover, BiCuSeO shows very Low Thermal Conductivity in the temperature range of 300 (B0.9Wm?1K?1)to 923K(B0.45Wm?1K?1). Such Low Thermal Conductivity values are most likely a result of the weak chemical bonds (Young’s modulus, EB76.5GPa) and the strong anharmonicity of the bonding arrangement (Gruneisen parameter, cB1.5). In addition to increasing the power factor, Ca doping reduces the Thermal Conductivity of the lattice, as confirmed by both experimental results and Callaway model calculations. The combination of optimized power factor and intrinsically Low Thermal Conductivity results in a high ZT of B0.9 at 923K for Bi0.925Ca0.075CuSeO.
David R. Clarke - One of the best experts on this subject based on the ideXlab platform.
-
Low Thermal Conductivity without oxygen vacancies in equimolar YO1.5 + TaO2.5- and YbO1.5 + TaO2.5-stabilized tetragonal zirconia ceramics
Acta Materialia, 2010Co-Authors: Yang Shen, Rafael M. Leckie, Carlos G Levi, David R. ClarkeAbstract:Abstract A narrow range of composition exists along both the ZrO 2 –YTaO 4 and ZrO 2 –YbTaO 4 quasi-binaries over which the tetragonal zirconia phase can be retained on cooling. Unlike other stabilized zirconia materials which have Low Thermal Conductivity as a result of phonon scattering by oxygen vacancies, these compositions do not contain oxygen vacancies and yet an equimolar YO 1.5 + TaO 2.5 composition has been reported to also exhibit Low Thermal Conductivity [1] . We find that zirconia compositions along the quasi-binaries have Low and temperature-independent Thermal conductivities, and that the Thermal conductivities and their temperature dependence are consistent with a defect scattering model that takes into account a minimum phonon mean free path due to the inter-atomic spacing. Furthermore, the conductivities of the Yb and Y trivalent-doped compositions scale in a predictable manner with atomic site disorder effects on the cation sub-lattice associated with the lighter Y 3+ ions and the heavier Yb 3+ and Ta 5+ ions. The Lowest Thermal Conductivity measured was ∼1.4 W mK –1 at 900 °C. The Low Thermal Conductivity and phase stability makes these systems promising candidates for Low Conductivity applications, such as Thermal barrier coatings.
-
Low Thermal Conductivity without oxygen vacancies in equimolar YO1.5+ TaO2.5- and YbO1.5+ TaO2.5-stabilized tetragonal zirconia ceramics
Acta Materialia, 2010Co-Authors: Yang Shen, Rafael M. Leckie, Carlos G Levi, David R. ClarkeAbstract:A narrow range of composition exists along both the ZrO2- YTaO4and ZrO2-YbTaO4quasi-binaries over which the tetragonal zirconia phase can be retained on cooling. Unlike other stabilized zirconia materials which have Low Thermal Conductivity as a result of phonon scattering by oxygen vacancies, these compositions do not contain oxygen vacancies and yet an equimolar YO1.5+ TaO2.5composition has been reported to also exhibit Low Thermal Conductivity [1]. We find that zirconia compositions along the quasi-binaries have Low and temperature- independent Thermal conductivities, and that the Thermal conductivities and their temperature dependence are consistent with a defect scattering model that takes into account a minimum phonon mean free path due to the inter-atomic spacing. Furthermore, the conductivities of the Yb and Y trivalent-doped compositions scale in a predictable manner with atomic site disorder effects on the cation sub-lattice associated with the lighter Y3+ions and the heavier Yb3+and Ta5+ions. The Lowest Thermal Conductivity measured was ∼1.4 W mK-1at 900 °C. The Low Thermal Conductivity and phase stability makes these systems promising candidates for Low Conductivity applications, such as Thermal barrier coatings. © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
-
Oxide materials with Low Thermal Conductivity
Journal of the American Ceramic Society, 2007Co-Authors: Michael R Winter, David R. ClarkeAbstract:A heuristic approach to identifying candidate materials with Low, temperature-independent Thermal Conductivity above room temperature is described. On the basis of this approach, a number of compounds with Thermal conductivities Lower than that of 8 mol% yttria-stabilized zirconia and fused silica have been found. Three compounds, in particular, the Zr3Y4O12 delta phase, the tungsten bronzes, and the La2Mo2O9 phase, exhibit potential for Low Thermal Conductivity applications. As each can exhibit extensive substitutional solid solution with other, high atomic mass ions, there is the prospect that many more compounds with Low Thermal Conductivity will be discovered.
Shinsuke Yamanaka - One of the best experts on this subject based on the ideXlab platform.
-
Thermoelectric Properties of Thallium Compounds with Extremely Low Thermal Conductivity
Journal of The Japan Society of Powder and Powder Metallurgy, 2020Co-Authors: Shinsuke Yamanaka, Ken Kurosaki, Hiroaki MutaAbstract:We have prepared polycrystalline bulk samples of various thallium compounds and measured their thermoelectric properties. Almost all the thallium compounds exhibit extremely Low values of the Thermal Conductivity (∼0.5 Wm−1K−1). This extremely Low Thermal Conductivity leads a great advantage for an enhancement of the thermoelectric performance. In this paper, we review the thermoelectric properties of various thallium compounds selected for study as novel thermoelectric materials. One of them seems to have a high thermoelectric figure of merit comparable to those of state-of-the-art materials.
-
Ag9TlTe5 and AgTlTe: High ZT Materials With Extremely Low Thermal Conductivity
2020Co-Authors: Ken Kurosaki, Atsuko Kosuga, Hiroaki Muta, Keita Goto, Shinsuke YamanakaAbstract:We have studied the thermoelectric properties Ag9TlTe5 and AgTlTe. The thallium compounds have extremely Low Thermal conductivities around 0.25 Wm -1 K -1 from room temperature to about 700 K. The thallium compounds indicate very high ZT values; especially the highest ZT value of Ag9TlTe5 is 1.23 obtained at 700 K. Ag9TlTe5 is a unique material combining extremely Low Thermal Conductivity and relatively Low electrical resistivity.
-
Extremely Low Thermal Conductivity Substances as Novel Thermoelectric Materials
MRS Proceedings, 2011Co-Authors: Shinsuke Yamanaka, Atsuko Kosuga, Ken Kurosaki, Keita Goto, Hiroaki MutaAbstract:We have prepared polycrystalline bulk samples of various thallium compounds and measured their thermoelectric properties. The most remarkable point of the thermoelectric properties of the thallium compounds is the extremely Low Thermal Conductivity. The state-of-the-art thermoelectric materials such as Bi 2 Te 3 and TAGS materials indicate relatively Low the Thermal Conductivity, around 1.5 W/m/K. However, the Thermal Conductivity of the thallium compounds is beLow 0.5 W/m/K; especially that of silver thallium tellurides is around 0.25 W/m/K at room temperature. This extremely Low Thermal Conductivity leads a great advantage for an enhancement of the thermoelectric performance. In this paper, we report on the properties of some thallium compounds selected for study as novel thermoelectric materials. One of these compounds seems to have a thermoelectric figure of merit comparable to those of state-of-the-art materials.
-
Thallium-Free Thermoelectric Materials with Extremely Low Thermal Conductivity
MRS Proceedings, 2011Co-Authors: Shinsuke Yamanaka, Anek Charoenphakdee, Ken Kurosaki, Hideaki Mastumoto, Hiroaki MutaAbstract:With the goal of developing high-performance bulk thermoelectric materials, we have characterized ternary silver thallium tellurides. The ternary silver thallium tellurides exhibit extremely Low Thermal Conductivity ( −1 K −1 ) and consequently their thermoelectric performance is excellent. Although the extremely Low Thermal Conductivity materials, as typified by the ternary silver thallium tellurides, would be a new class of next-generation thermoelectric materials, thallium compounds are unsuitable for practical application because of their toxicity. Against such a background, we are currently exploring thallium-free thermoelectric materials with extremely Low Thermal Conductivity. In this paper, we will briefly summarize the thermoelectric properties of ternary thallium tellurides obtained in our group. Further experiments aimed at improving the ZT of these materials will be presented. Finally, we will propose two candidates: Ag 8 GeTe 6 and Ga 2 Te 3 as thallium-free Low Thermal Conductivity materials.
-
Ag8SiTe6: A New Thermoelectric Material with Low Thermal Conductivity
Japanese Journal of Applied Physics, 2009Co-Authors: Anek Charoenphakdee, Ken Kurosaki, Hiroaki Muta, Shinsuke YamanakaAbstract:Here, we introduce a new thermoelectric material: Ag8SiTe6. Ag8SiTe6 indicated p-type semiconductor characteristics. The crystal structure of Ag8SiTe6 was quite complicated, which led to a very Low Thermal Conductivity of 0.23 W m-1 K-1 at room temperature. A relatively high thermoelectric figure of merit of 0.48 was obtained at 800 K, which was mainly due to the very Low Thermal Conductivity.
Ken Kurosaki - One of the best experts on this subject based on the ideXlab platform.
-
Thermoelectric Properties of Thallium Compounds with Extremely Low Thermal Conductivity
Journal of The Japan Society of Powder and Powder Metallurgy, 2020Co-Authors: Shinsuke Yamanaka, Ken Kurosaki, Hiroaki MutaAbstract:We have prepared polycrystalline bulk samples of various thallium compounds and measured their thermoelectric properties. Almost all the thallium compounds exhibit extremely Low values of the Thermal Conductivity (∼0.5 Wm−1K−1). This extremely Low Thermal Conductivity leads a great advantage for an enhancement of the thermoelectric performance. In this paper, we review the thermoelectric properties of various thallium compounds selected for study as novel thermoelectric materials. One of them seems to have a high thermoelectric figure of merit comparable to those of state-of-the-art materials.
-
Ag9TlTe5 and AgTlTe: High ZT Materials With Extremely Low Thermal Conductivity
2020Co-Authors: Ken Kurosaki, Atsuko Kosuga, Hiroaki Muta, Keita Goto, Shinsuke YamanakaAbstract:We have studied the thermoelectric properties Ag9TlTe5 and AgTlTe. The thallium compounds have extremely Low Thermal conductivities around 0.25 Wm -1 K -1 from room temperature to about 700 K. The thallium compounds indicate very high ZT values; especially the highest ZT value of Ag9TlTe5 is 1.23 obtained at 700 K. Ag9TlTe5 is a unique material combining extremely Low Thermal Conductivity and relatively Low electrical resistivity.
-
Extremely Low Thermal Conductivity Substances as Novel Thermoelectric Materials
MRS Proceedings, 2011Co-Authors: Shinsuke Yamanaka, Atsuko Kosuga, Ken Kurosaki, Keita Goto, Hiroaki MutaAbstract:We have prepared polycrystalline bulk samples of various thallium compounds and measured their thermoelectric properties. The most remarkable point of the thermoelectric properties of the thallium compounds is the extremely Low Thermal Conductivity. The state-of-the-art thermoelectric materials such as Bi 2 Te 3 and TAGS materials indicate relatively Low the Thermal Conductivity, around 1.5 W/m/K. However, the Thermal Conductivity of the thallium compounds is beLow 0.5 W/m/K; especially that of silver thallium tellurides is around 0.25 W/m/K at room temperature. This extremely Low Thermal Conductivity leads a great advantage for an enhancement of the thermoelectric performance. In this paper, we report on the properties of some thallium compounds selected for study as novel thermoelectric materials. One of these compounds seems to have a thermoelectric figure of merit comparable to those of state-of-the-art materials.
-
Thallium-Free Thermoelectric Materials with Extremely Low Thermal Conductivity
MRS Proceedings, 2011Co-Authors: Shinsuke Yamanaka, Anek Charoenphakdee, Ken Kurosaki, Hideaki Mastumoto, Hiroaki MutaAbstract:With the goal of developing high-performance bulk thermoelectric materials, we have characterized ternary silver thallium tellurides. The ternary silver thallium tellurides exhibit extremely Low Thermal Conductivity ( −1 K −1 ) and consequently their thermoelectric performance is excellent. Although the extremely Low Thermal Conductivity materials, as typified by the ternary silver thallium tellurides, would be a new class of next-generation thermoelectric materials, thallium compounds are unsuitable for practical application because of their toxicity. Against such a background, we are currently exploring thallium-free thermoelectric materials with extremely Low Thermal Conductivity. In this paper, we will briefly summarize the thermoelectric properties of ternary thallium tellurides obtained in our group. Further experiments aimed at improving the ZT of these materials will be presented. Finally, we will propose two candidates: Ag 8 GeTe 6 and Ga 2 Te 3 as thallium-free Low Thermal Conductivity materials.
-
Ag8SiTe6: A New Thermoelectric Material with Low Thermal Conductivity
Japanese Journal of Applied Physics, 2009Co-Authors: Anek Charoenphakdee, Ken Kurosaki, Hiroaki Muta, Shinsuke YamanakaAbstract:Here, we introduce a new thermoelectric material: Ag8SiTe6. Ag8SiTe6 indicated p-type semiconductor characteristics. The crystal structure of Ag8SiTe6 was quite complicated, which led to a very Low Thermal Conductivity of 0.23 W m-1 K-1 at room temperature. A relatively high thermoelectric figure of merit of 0.48 was obtained at 800 K, which was mainly due to the very Low Thermal Conductivity.
Jiaqing He - One of the best experts on this subject based on the ideXlab platform.
-
origin of Low Thermal Conductivity in snse
Physical Review B, 2016Co-Authors: Yu Xiao, Kunling Peng, Jiaqing He, Cheng Chang, Xiaoyuan Zhou, Shengkai Gong, Yongsheng Zhang, Di Wu, Zhi ZengAbstract:We provide direct evidence to understand the origin of Low Thermal Conductivity of SnSe using elastic measurements. Compared to state-of-the-art lead chalcogenides $\mathrm{Pb}Q(Q=\mathrm{Te}$, Se, S), SnSe exhibits Low values of sound velocity $(\ensuremath{\sim}1420\phantom{\rule{0.28em}{0ex}}\mathrm{m}/\mathrm{s})$, Young's modulus $(E\ensuremath{\sim}27.7\phantom{\rule{0.28em}{0ex}}\mathrm{GPa})$, and shear modulus $(G\ensuremath{\sim}9.6\phantom{\rule{0.28em}{0ex}}\mathrm{GPa})$, which are ascribed to the extremely weak Sn-Se atomic interactions (or bonds between layers); meanwhile, the deduced average Gr\"uneisen parameter \ensuremath{\gamma} of SnSe is as large as \ensuremath{\sim}3.13, originating from the strong anharmonicity of the bonding arrangement. The calculated phonon mean free path (l \ensuremath{\sim} 0.84 nm) at 300 K is comparable to the lattice parameters of SnSe, indicating little room is left for further reduction of the Thermal Conductivity through introducing nanoscale microstructures and microscale grain boundaries. The Low elastic properties indicate that the weak chemical bonding stiffness of SnSe generally causes phonon modes softening which eventually sLows down phonon propagation. This work provides insightful data to understand the Low lattice Thermal Conductivity of SnSe.
-
Origin of Low Thermal Conductivity in SnSe
Physical Review B, 2016Co-Authors: Yu Xiao-zhu, Yan Ling Pei, Kunling Peng, Jiaqing He, Cheng Chang, Xiaoyuan Zhou, Shengkai Gong, Yongsheng Zhang, Di Wu, Zhi ZengAbstract:© 2016 American Physical Society. We provide direct evidence to understand the origin of Low Thermal Conductivity of SnSe using elastic measurements. Compared to state-of-the-art lead chalcogenides PbQ(Q=Te, Se, S), SnSe exhibits Low values of sound velocity (∼1420m/s), Young's modulus (E∼27.7GPa), and shear modulus (G∼9.6GPa), which are ascribed to the extremely weak Sn-Se atomic interactions (or bonds between layers); meanwhile, the deduced average Grüneisen parameter γ of SnSe is as large as ∼3.13, originating from the strong anharmonicity of the b onding arrangement. The calculated phonon mean free path (l ∼ 0.84 nm) at 300 K is comparable to the lattice parameters of SnSe, indicating little room is left for further reduction of the Thermal Conductivity through introducing nanoscale microstructures and microscale grain boundaries. The Low elastic properties indicate that the weak chemical bonding stiffness of SnSe generally causes phonon modes softening which eventually sLows down phonon propagation. This work provides insightful data to understand the Low lattice Thermal Conductivity of SnSe.
-
high thermoelectric performance in n type biagses due to intrinsically Low Thermal Conductivity
Energy and Environmental Science, 2013Co-Authors: Haijun Wu, Celine Barreteau, David Bérardan, Nita Dragoe, Jiaqing He, Jing Li, Li-dong ZhaoAbstract:BiAgSeS shows intrinsically Low Thermal Conductivity in the temperature range from 300 K (∼0.46 W m−1 K−1) to 823 K (∼0.29 W m−1 K−1). Low Thermal Conductivity coupling with enhanced electrical transport properties achieved through partially substituting S2− by Cl− leads to a high ZT of ∼1.0 at 823 K for BiAgSeS0.97Cl0.03, indicating that the BiAgSeS system is promising for thermoelectric power generation applications.
-
high thermoelectric performance of oxyselenides intrinsically Low Thermal Conductivity of ca doped bicuseo
Npg Asia Materials, 2013Co-Authors: Jiaqing He, Celine Barreteau, David Bérardan, Nita Dragoe, Jing-feng Li, Fu Li, Li-dong ZhaoAbstract:We report on the high thermoelectric performance of p-type polycrystalline BiCuSeO, a layered oxyselenide composed of alternating conductive (Cu2Se2)2− and insulating (Bi2O2)2+ layers. The electrical transport properties of BiCuSeO materials can be significantly improved by substituting Bi3+ with Ca2+. The resulting materials exhibit a large positive Seebeck coefficient of ∼+330 μV K−1 at 300 K, which may be due to the ‘natural superlattice’ layered structure and the moderate effective mass suggested by both electronic density of states and carrier concentration calculations. After doping with Ca, enhanced electrical Conductivity coupled with a moderate Seebeck coefficient leads to a power factor of ∼4.74 μW cm−1 K−2 at 923 K. Moreover, BiCuSeO shows very Low Thermal Conductivity in the temperature range of 300 (∼0.9 W m−1 K−1) to 923 K (∼0.45 W m−1 K−1). Such Low Thermal Conductivity values are most likely a result of the weak chemical bonds (Young’s modulus, E∼76.5 GPa) and the strong anharmonicity of the bonding arrangement (Gruneisen parameter, γ∼1.5). In addition to increasing the power factor, Ca doping reduces the Thermal Conductivity of the lattice, as confirmed by both experimental results and Callaway model calculations. The combination of optimized power factor and intrinsically Low Thermal Conductivity results in a high ZT of ∼0.9 at 923 K for Bi0.925Ca0.075CuSeO. Li-Dong Zhao, Jiaqing He and co-workers have gained insight into the highly thermoelectric properties of a bismuth–copper oxyselenide (BiCuSeO), a polycrystalline, layered compound. BiCuSeO's ability to produce a significant electric potential from a temperature difference, and vice versa, arises from its intrinsically Low Thermal Conductivity, and can be further improved by boosting the material's electrical Conductivity through doping with strontium or barium, or introducing copper deficiencies. The researchers have now carried out an extensive characterization of the oxyselenide and propose that its conveniently Low Thermal Conductivity results from the weak chemical bonds that exist between two different kinds of layers, and a particular bonding arrangement, in the material's lattice. Moreover, by substituting bismuth ions (Bi3+) with calcium ions (Ca3+) the Thermal Conductivity of the lattice could be Lowered further, leading to an improvement in the oxyselenide's thermoelectric properties. We report on the promising thermoelectric performance of p-type polycrystalline BiCuSeO, which is a layered oxyselenide composed of conductive (Cu2Se2)2− layers that alternate with insulating (Bi2O2)2+ layers. Electrical transport properties can be optimized by substituting Bi3+ with Ca2+. Moreover, BiCuSeO shows very Low Thermal Conductivity in the temperature ranges of 300 (∼0.9 W m−1K−1) to 923 K (∼0.45 W m−1 K−1). These intrinsically Low Thermal Conductivity values may result from the weak chemical bonds of the material as well as the strong anharmonicity of the bonding arrangement. The combination of the optimized power factor and the intrinsically Low Thermal Conductivity results in a high ZT of ∼0.9 at 923 K for Bi0.925Ca0.075CuSeO.
-
High thermoelectric performance of oxyselenides: Intrinsically Low Thermal Conductivity of Ca-doped BiCuSeO
NPG Asia Materials, 2013Co-Authors: Yan Ling Pei, Qijun Liu, Celine Barreteau, David Bérardan, Nita Dragoe, Jiaqing He, Wei Pan, Jing-feng Li, Li-dong ZhaoAbstract:We report on the high thermoelectric performance of p-type polycrystalline BiCuSeO, a layered oxyselenide composed of alternating conductive (Cu2Se2)2? and insulating (Bi2O2)2þ layers. The electrical transport properties of BiCuSeO materials can be significantly improved by substituting Bi3þ with Ca2þ. The resulting materials exhibit a large positive Seebeck coefficient of Bþ330lVK?1 at 300K, which may be due to the ‘natural superlattice’ layered structure and the moderate effective mass suggested by both electronic density of states and carrier concentration calculations. After doping with Ca, enhanced electrical Conductivity coupled with a moderate Seebeck coefficient leads to a power factor of B4.74lWcm?1K?2 at 923K. Moreover, BiCuSeO shows very Low Thermal Conductivity in the temperature range of 300 (B0.9Wm?1K?1)to 923K(B0.45Wm?1K?1). Such Low Thermal Conductivity values are most likely a result of the weak chemical bonds (Young’s modulus, EB76.5GPa) and the strong anharmonicity of the bonding arrangement (Gruneisen parameter, cB1.5). In addition to increasing the power factor, Ca doping reduces the Thermal Conductivity of the lattice, as confirmed by both experimental results and Callaway model calculations. The combination of optimized power factor and intrinsically Low Thermal Conductivity results in a high ZT of B0.9 at 923K for Bi0.925Ca0.075CuSeO.
