Remarkable Enhancement in Thermoelectric Performance of BiCuSeO by Cu Deficiencies

Liu, Yong; Zhao, Li‐Dong; Liu, Yaochun; Lan, Jinle; Wei, Xianfu; Li, Fu; Zhang, Bo Ping; Bérardan, David; Dragoe, Nita; Lin, Yuan; Nan, Ce Wen; Li, Jing‐Feng; Zhu, Hongmin

doi:10.1021/ja211769z

Cited by 44 publications

(61 citation statements)

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“…As shown in Figure 5a, BiCuSeO exhibits low electrical conductivity over the entire temperature range and a semiconducting electrical transport behavior. After doping with Ca, the electrical transport changes to a metallic-like behavior and the electrical conductivity shows a significant increase with increasing Ca fraction, from B1.12 S cm À1 (BiCuSeO) to B270 S cm À1 (Bi 0.90 Ca 0.10 CuSeO) at 300 K. The electrical conductivity of Bi 0.90 Ca 0.10 CuSeO is higher than that of BiCu 0.975 SeO 22 and is comparable to that of Bi 0.90 Sr 0.10 CuSeO. 21 This result indicates that Ca doping can effectively enhance the electrical conductivity of BiCuSeO by introducing holes in the valence band.…”

Section: Structural and Thermoelectric Propertiesmentioning

confidence: 97%

“…[21][22][23][24][25] Stoichiometric mixtures of Bi 2 O 3 (3 N), Bi (4 N), CaO (3 N), Cu (3 N) and Se (5 N) powders were thoroughly ground up by hand and then heated to 973 K for 12 h in a sealed evacuated quartz tube. The total sample mass was maintained at B10 g; for example, when x ¼ 0.075 Ca, 3.8778 g of Bi 2 O 3 , 2.1622 g of Bi, 0.1135 g of CaO, 1.7195 g Cu, and 2.1269 g of Se are used.…”

Section: Experimental Procedures Synthesismentioning

confidence: 99%

“…The combined electrical conductivity and positive temperature-dependent Seebeck coefficient result in a power factor (S 2 s) peak at a high temperature of 923 K. As shown in Figure 5c, the highest power factor is B4.74 mW cm À1 K À2 for the Bi 0.925 Ca 0.075 CuSeO sample at 923 K, High thermoelectric performance of oxyselenides Y-L Pei et al which is higher than B4.10 mW cm À1 K À2 at 923 K for the BiCu 0.975-SeO sample. 22 Figure 5d shows the total thermal conductivity as a function of temperature for Bi 1-x Ca x CuSeO samples. The total thermal conductivity of undoped BiCuSeO decreases with increasing temperature from 0.89 Wm À1 K À1 at 300 K to 0.45 Wm À1 K À1 at 923 K (heat capacity (Supplementary Figure S2) and thermal diffusivity (Supplementary Figure S3)).…”

Section: Structural and Thermoelectric Propertiesmentioning

confidence: 99%

“…20 Recently, we reported a quaternary BiCuSeO compound that exhibits very low thermal conductivity. [21][22][23][24][25] High ZT values were achieved using this system by optimizing the electrical transport properties. Specifically, electrical conductivity was increased by Sr doping, introducing Cu deficiencies and Ba heavy metal doping.…”

Section: Introductionmentioning

confidence: 99%

“…Specifically, electrical conductivity was increased by Sr doping, introducing Cu deficiencies and Ba heavy metal doping. [21][22][23][24][25] Although promising thermoelectric properties have been observed with BiCuSeO compounds, [21][22][23][24][25] surprisingly little is known about their microstructure and the main cause of their low thermal conductivity. In this paper, we perform a systematic evaluation of the BiCuSeO system, including the structural, transport, optical and elastic properties, using a combination of electron microscopy observations and electronic structure calculations.…”

Section: Introductionmentioning

confidence: 99%

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High thermoelectric performance of oxyselenides: intrinsically low thermal conductivity of Ca-doped BiCuSeO

et al. 2013

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We report on the high thermoelectric performance of p-type polycrystalline BiCuSeO, a layered oxyselenide composed of alternating conductive (Cu 2 Se 2 ) 2 À and insulating (Bi 2 O 2 ) 2 þ layers. The electrical transport properties of BiCuSeO materials can be significantly improved by substituting Bi 3 þ with Ca 2 þ . The resulting materials exhibit a large positive Seebeck coefficient of B þ 330 lV K À1 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 B4.74 lW cm À1 K À2 at 923 K. Moreover, BiCuSeO shows very low thermal conductivity in the temperature range of 300 (B0.9 W m À1 K À1 ) to 923 K (B0.45 W m À1 K À1 ). Such low thermal conductivity values are most likely a result of the weak chemical bonds (Young's modulus, EB76.5 GPa) 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 923 K for Bi 0.925 Ca 0.075 CuSeO.

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Section: Structural and Thermoelectric Propertiesmentioning

confidence: 97%

Section: Experimental Procedures Synthesismentioning

confidence: 99%

Section: Structural and Thermoelectric Propertiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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High thermoelectric performance of oxyselenides: intrinsically low thermal conductivity of Ca-doped BiCuSeO

et al. 2013

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Multipoint Defect Synergy Realizing the Excellent Thermoelectric Performance of n‐Type Polycrystalline SnSe via Re Doping

Qiu

Chen

et al. 2019

Adv Funct Materials

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SnSe has attracted much attention due to the excellent thermoelectric (TE) properties of both p-and n-type single crystals. However, the TE performance of polycrystalline SnSe is still low, especially in n-type materials, because SnSe is an intrinsic p-type semiconductor. In this work, a three-step doping process is employed on polycrystalline SnSe to make it n-type and enhance its TE properties. It is found that the Sn 0.97 Re 0.03 Se 0.93 Cl 0.02 sample achieves a peak ZT value of ≈1.5 at 798 K, which is the highest ZT reported, to date, in n-type polycrystalline SnSe. This is attributed to the synergistic effects of a series of point defects: × × V V , Cl , ,Re ,Re Se .. Se . Sn ,, Sn 0 . In those defects, the V Se .. compensates for the intrinsic Sn vacancies in SnSe, the Cl Se .acts as a donor, the V Sn ,, acts as an acceptor, all of which contribute to optimizing the carrier concentration. Rhenium (Re) doping surprisingly plays dual-roles, in that it both significantly enhances the electrical transport properties and largely reduces the thermal conductivity by introducing the point defects, × × Re , Re Sn 0 . The method paves the way for obtaining high-performance TE properties in SnSe crystals using multipoint-defect synergy via a step-by-step multielement doping methodology.

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High‐Performance Thermoelectricity in Nanostructured Earth‐Abundant Copper Sulfides Bulk Materials

Liu

Feng

et al. 2016

Advanced Energy Materials

122

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In-and Cd-doped Cu 9 S 5 and reported that the electrical conductivity was reduced and the thermal power was improved when In and Cd were added to Cu 9 S 5 . However, they did not report the thermal conductivity and ZT value. [ 30 ] In our previous work, we reported that the ZT value of pristine Cu 9 S 5 reached 0.3 at 673 K and the ZT for the optimized sintering temperature sample could be further enhanced to 0.5 because of the existence of a second Cu 1.96 S phase and a considerable number of pores. [ 18 ] Dennler et al. [ 31 ] systematically studied the thermal stability and electrical stability of CuS, Cu 9 S 5, and Cu 2 S. The results showed that the CuS is not stable at temperatures beyond 240 °C either in air or N 2 . Experiments also showed that Cu 2 S is not electrically stable because both cracks and copper whiskers were observed in a Cu 2 S sample after long-time current stress tests (24 A cm −2 /24 h). In contrast, CuS and Cu 9 S 5 samples did not show any degradation in the electrical stability test, even when current densities were increased to as high as 48 A cm −2 . However, the Seebeck coeffi cient, electrical resistivity, crystal structure, and stoichiometry remained constant. [ 31 ] This indicates that only Cu 9 S 5 is both thermally and electrically stable.High-performance TE materials should simultaneously own large Seebeck coeffi cients, high electrical conductivity, and low thermal conductivity, but these three parameters are interrelated with each other. It is diffi cult to improve all the parameters at the same time, for instance, an improvement of electrical conductivity will normally lead to the deterioration in the Secbeck coeffi cient and thermal conductivity. [ 4 ] The main challenges for enhancing TE properties of Cu 9 S 5 -based materials are to improve the Seebeck coeffi cient via carrier concentration optimization. In this work, Na x Cu 9 S 5 ( x = 0, 0.025, 0.05, 0.15, 0.25) nanopowders with an average size of 3 nm were prepared by mechanical alloying (MA). The nanopowders were then sintered to bulk materials by spark plasma sintering (SPS) technology. Metallic Na was doped to Cu 9 S 5 to reduce carrier concentration and improve the Seebeck coeffi cient. Besides, nanopores and nanograins were observed unexpectedly in the Na-doped bulk samples, leading to a signifi cantly reduced thermal conductivity. Overall, a peak ZT value of 1.1 was achieved at 773 K in the composition of Na 0.05 Cu 9 S 5 . Figure 1 a,b shows the transmission electron microscope (TEM) and high-resolution transmission electron microscope (HRTEM) images (inset of Figure 1 b) of Na 0.05 Cu 9 S 5 powders obtained by MA method. Under the low magnifi cation mode, it can be seen that Na 0.05 Cu 9 S 5 powders disperse homogeneously on the microgrid support membrane, show a particle size smaller than 5 nm and an average size of 3 nm. This extremely small particle size obtained directly by MA method is quite astonishing, since the typical particle size of MAed powders is around several hundred nanometer to several micr...

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Remarkable Enhancement in Thermoelectric Performance of BiCuSeO by Cu Deficiencies

Cited by 44 publications

References 1 publication

High thermoelectric performance of oxyselenides: intrinsically low thermal conductivity of Ca-doped BiCuSeO

High thermoelectric performance of oxyselenides: intrinsically low thermal conductivity of Ca-doped BiCuSeO

Multipoint Defect Synergy Realizing the Excellent Thermoelectric Performance of n‐Type Polycrystalline SnSe via Re Doping

High‐Performance Thermoelectricity in Nanostructured Earth‐Abundant Copper Sulfides Bulk Materials

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