Effects of noble metal addition on microstructure and thermoelectric properties of NaxCo2O4

Ito, Mikio; Furumoto, Daisuke

doi:10.1016/j.jallcom.2006.11.032

Cited by 34 publications

(26 citation statements)

References 13 publications

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“…Using thermoelectric materials may provide a possible approach to make better use of energy sources and waste heat. 1,2 Development and commercial application of these materials, however, are limited, because most thermoelectric materials are inefficient and expensive. Numerous studies have been carried out to improve the thermoelectric properties of thermoelectric materials.…”

Section: Introductionmentioning

confidence: 99%

Thermoelectric Properties of (Na1−y M y )1.4Co2O4 (M = Sr, Li)

Liu

Jiang

et al. 2011

Journal of Elec Materi

136

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Oxide thermoelectric materials (Na 1Ày M y ) 1.4 Co 2 O 4 (M = Sr, Li; y = 0 to 0.4) were prepared by a sol-gel method. The influence of doping on the thermoelectric properties was investigated, and the phase composition was characterized by x-ray diffraction. Experimental results showed that the main crystalline phase of the undoped and Sr/Li-doped samples was c-Na 1.4 Co 2 O 4 . The thermoelectric properties of Na 1.4 Co 2 O 4 can be improved slightly by doping with Sr. Doping with Li improves the thermoelectric properties of Na 1.4 Co 2 O 4 . For a doping fraction of y = 0.1, the electrical conductivity of (Na 1Ày Li y ) 1.4 Co 2 O 4 at 288 K achieves its maximum value of 301.19 (X mm) À1 . The Seebeck coefficient and power factor of (Na 1Ày Li y ) 1.4 Co 2 O 4 at 288 K achieve their maximum values of 172.28 lV K À1 and 7.44 mW m À1 K À2 at a doping fraction of y = 0.4.

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Section: Introductionmentioning

confidence: 99%

Thermoelectric Properties of (Na1−y M y )1.4Co2O4 (M = Sr, Li)

Liu

Jiang

et al. 2011

Journal of Elec Materi

136

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“…The sharp peaks seen in Fig. 3 suggest that the obtained samples are predominantly of c-phase NaCo 2 O 4 (Cheng et al 2006;Nakatsugava and Nagasawa 2004;Park and Lee 2008;Ito and Furumoto 2008;Seetawan et al 2006). The X-ray results also exhibit that there are relatively small amounts of Co 3 O 4 present in the samples which is probably due to sodium evaporation during the calcination process at 850°C (Ma et al 2010).…”

Section: Resultsmentioning

confidence: 84%

“…They are nontoxic, nonpolluting, and can operate at high temperatures for long periods due to their excellent thermal and chemical stabilities. These merits make layered cobalt oxide thermoelectric materials potential candidates for high-temperature applications (Li et al 2011;Ito and Furumoto 2008;Park and Lee 2008). Among the known four types of Na x Co 2 O 4 crystal structures, c-Na x Co 2 O 4 (1 B x B 1.4) phase shows a large Seebeck coefficient and a good thermoelectric performance at around x = 1, and therefore great attention has been paid to the c-phase of sodium cobalt oxide (Maensiri and Nuansing 2006;Ito and Furumoto 2008).…”

Section: Introductionmentioning

confidence: 99%

The effect of synthesis technique on thermoelectric properties of nanocrystalline NaCo2O4 ceramics

2014

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Sodium cobalt oxide (NaCo 2 O 4 ) nanocrystalline thermoelectric ceramic powders were synthesized using conventional polymerized complex sol-gel and electrospinning techniques and then consolidated into bulk ceramics. We have investigated the differences in the microstructure and thermoelectric properties of the samples prepared using electrospinning and sol-gel methods. The crystal structures of the powders and nanofibers were characterized using X-ray diffraction and scanning electron microscopy before and after calcination at different temperatures. Nanofibers prepared by electrospinning have a diameter of approximately 300 nm, while the diameter of the grains of sol-gel powders ranges from 1 to 5 lm. Thermoelectric properties of the bulk ceramics were measured by physical properties measurement system in the temperature range of 15-300 K. The calculated values of dimensionless figure of merit at 300 K are 6 9 10 -7 and 4 9 10 -5 for sintered powders from sol-gel and nanofibers, respectively. While electrospinning production technique increase thermoelectric power approximately 15 % and it fold electrical conductivity average 20 times, it decreased thermal conductivity by 90 %.

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“…Silver doping increases electrical conductivity and thermopower and decreases thermal conductivity [165,166]. If Ag is doped as second phase, it can increase electrical conductivity and thermopower, but also increase thermal conductivity, so its effect on figure of merit is canceled out [167]. The effects of tansitional metallic elements on the properties of Na xCoO 2 are diversed.…”

Section: P-type Thermoelectric Oxidesmentioning

confidence: 99%

“…This maximum power factor has been observed at an optimal value, |S| & 0. 167 [210] and SrNbTiO 3 at 1,000 K [211]. In other words, the calculated optimal S can be used as a guidance to optimize the power factor of thermoelectric materials.…”

Section: Optimization Of Power Factormentioning

confidence: 99%

Waste Thermal Energy Harvesting (I): Thermoelectric Effect

Kong

Hng

et al. 2014

Waste Energy Harvesting

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Waste thermal energy (heat) is the second type of energy to be discussed. Usually, it is generated in a process by way of fuel combustion or chemical reaction, and then ''dumped'' into the environment even though it could still be reused for some useful and economic purpose. The essential quality of heat is not the amount but rather its ''value.'' The strategy of how to recover this heat depends in part on the temperature of the waste heat gases and the economics involved.Waste thermal energy is one of the largest sources of inexpensive, clean, and fuel-free energy available. The vast amount of heat that is discharged into the atmosphere everyday is one of the best sources of clean, fuel-free, and inexpensive energy. According to the US Department of Energy (DOE), up to 50 % of all fuels burned in the US goes unused into the atmosphere as waste heat is released to the atmosphere. Research indicates that the energy currently wasted by the industrial facilities in the U.S. could produce as much as 20 % of the total US electrical output with the associated 20 % reduction in greenhouse gas emissions. Various sources that can be classified as waste thermal energy (heat) with their properties are listed in Tables 4.1 , 4.2, 4.3, and 4.4 [1].Among the large quantities of waste heat that have been directly discharged into the Earth's environment, much of it is at temperatures which are too low to recover by using the conventional electrical power generators. Thermoelectric power generation, also known as thermoelectricity, has been demonstrated as a promising technology in the direct conversion of low-grade thermal energy, such as waste heat energy into electrical power. Probably, the earliest application is the utilization of waste heat from a kerosene lamp to provide thermoelectric energy to power a wireless device. Thermoelectric generators have also been used to provide small amounts electricity to remote regions, for instance, Northern Sweden, as an L. B. Kong et al., Waste Energy Harvesting, Lecture Notes in Energy 24,

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Effects of noble metal addition on microstructure and thermoelectric properties of NaxCo2O4

Cited by 34 publications

References 13 publications

Thermoelectric Properties of (Na1−y M y )1.4Co2O4 (M = Sr, Li)

Thermoelectric Properties of (Na1−y M y )1.4Co2O4 (M = Sr, Li)

The effect of synthesis technique on thermoelectric properties of nanocrystalline NaCo2O4 ceramics

Waste Thermal Energy Harvesting (I): Thermoelectric Effect

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