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Ca_3Co_2O_6 for high temperature side of thermoelectric FGM

机译：Ca_3Co_2O_6用于热电FGM的高温侧

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In modern age, much thermal energy is emitted from ceramic and/or steel industries. Their temperature range is between 500 K and 1300 K. Thermoelectric materials are promising to utilize the waste heat, because of no CO_2 emission and long life due to no moving parts.rnThe thermoelectric properties of every thermoelectric material have temperature dependence and high performance appears at a specific temperature range. If the proper materials are placed and joined along the temperature gradient to form an FGM, the performance should be higher than a monolithic material.rnThe performance of a thermoelectric material is expressed by the dimensionless figure of merit ZT=a~2ρ~(-1)k~(-1)T, where a is the Seebeck coefficient, ρ is the electrical resistivity, k is the thermal conductivity, and T is absolute temperature.rnThermoelectric oxides are suitable for high temperature materials because of chemical stability. Na_xCoO_2 shows relatively high ZT value in thermoelectric oxide at the temperature range below 800 K. Ca_3Co_4O_9 shows ZT ～1 at 1000 K. Recently, it is reported that Ca_3Co_2O_6 that is formed by decomposition of Ca_3Co_4O_9 at 1173 K has high performance at 1300 K. The properties and fabrication condition of high density Ca_3Co_2O_6 are, however, not reported in detail. In order to improve the thermoelectric properties and to shift the temperature range for Ca_3Co_2O_6, we investigated the effects of element substitution.rnIn this experiment, the sintered Ca_3Co_(2-x)M_xO_6 (x=0 or 0.2, M= Mn, Mo or V) were prepared by solid-state reaction or hot pressing. Relative density of Ca_3Co_2O_6 by hot-pressing (HP) was over 94% which is larger than one of Ca_3Co_2O_6 by solid-state reaction (SSR). The resistivity of Mo- or V-substituted Ca_3Co_2O_6 (HP-Mo or HP-V) were lower than one of non-substituted Ca_3Co_2O_6 (HP). The resistivity of Mo-substituted Ca_3Co_2O_6 (HP-Mo) showed the lowest value of 4.3×10~(-2) Ωcm in all specimens at 1181 K. The power factor a~2ρ~(-1) of Ca_3Co_2O_6 (HP-Mo) was 64.2 Wm~(-1)K~(-2), which is the largest of all specimens at 1178 K, and this value is approximately 1.3 times higher than 48.8 Wm~(-1)K~(-2) for Ca_3Co_2O_6 (HP).
机译：在现代时代，陶瓷和/或钢铁工业会散发大量的热能。它们的温度范围在500 K和1300 K之间。热电材料有望散发废热，因为它不会排放CO_2，并且由于没有活动部件而具有长寿命。rn每种热电材料的热电性能都与温度有关，并且在一个特定的温度范围。如果放置合适的材料并沿温度梯度接合以形成FGM，则其性能应高于整体材料。rn热电材料的性能由品质因数ZT = a〜2ρ〜（-1）表示）k〜（-1）T，其中a是塞贝克系数，ρ是电阻率，k是导热系数，T是绝对温度。rn热电氧化物由于化学稳定性而适用于高温材料。在800 K以下的温度范围内，Na_xCoO_2在热电氧化物中显示出相对较高的ZT值.Ca_3Co_4O_9在1000 K下显示ZT 〜1。最近，据报道，由Ca_3Co_4O_9在1173 K处分解而形成的Ca_3Co_2O_6在1300 K下具有较高的性能。然而，没有详细报道高密度Ca_3Co_2O_6的性质和制造条件。为了改善Ca_3Co_2O_6的热电性能并改变温度范围，我们研究了元素置换的影响.rn在本实验中，烧结的Ca_3Co_（2-x）M_xO_6（x = 0或0.2，M = Mn，Mo或V）通过固相反应或热压制备。通过热压（HP）得到的Ca_3Co_2O_6的相对密度超过94％，比通过固态反应（SSR）得到的Ca_3Co_2O_6的相对密度大。 Mo-或V-取代的Ca_3Co_2O_6（HP-Mo或HP-V）的电阻率低于未取代的Ca_3Co_2O_6（HP）之一。 Mo-取代的Ca_3Co_2O_6（HP-Mo）的电阻率在1181 K时最低，为4.3×10〜（-2）Ωcm.Ca_3Co_2O_6（HP-Mo）的功率因数a〜2ρ〜（-1） ）为64.2 Wm〜（-1）K〜（-2），在1178 K时是所有标本中最大的，这个值大约是48.8 Wm〜（-1）K〜（-2）的1.3倍。 Ca_3Co_2O_6（HP）。

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