Development of Al 2 O 3 -ZnO/Ca 3 Co 4 O 9 Module for Thermoelectric Power Generation
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1166-N03-23
Development of Al2O3-ZnO/Ca3Co4O9 module for thermoelectric power generation Paolo Mele1,2, Kaname Matsumoto1,2, Takeshi Azuma1, Keita Kamesawa1, Saburo Tanaka1, Jun-ichiro Kurosaki1 and Koji Miyazaki1,2 1
Department of Materials Science and Engineering, Kyushu Institute of Technology (KIT), 1-1, Sensui-cho, Tobata-ku, Kitakyushu 804-8550, Japan. 2 Fukuoka Industry, Science and Technology Foundation (IST), System LSI Division, 3-8-33, Momochihama, Sawara-ku, Fukuoka 814-0001, Japan ABSTRACT Pure and Al2O3 (2%, 5%, 8%) doped sintered ZnO (n-type) and pure sintered Ca3Co4O9 (p-type) pellets were prepared by conventional solid state synthesis starting from the oxides. The sintered pellets were cut by a diamond saw in a pillar shape (15 mm×5 mm×5 mm) for physical properties measurements. The best doped sample was 2 % Al2O3 ZnO showing Seebeck coefficient S = -180 mV/K and electrical conductivity σ = 8 S/cm at 400°C, while thermal conductivity κ = 1.8 W/m×K at 600°C. Typical values for Ca3Co4O9 were S = 82.5 mV/K and σ = 125 S/cm at 800°C, while κ = 1.01 W/m×K at 600°C. Several modules fabricated by elements cut from sintered pellets were tested and the best performance was obtained in the module formed by six 2 % Al2O3-ZnO/ Ca3Co4O9 couples, that generated an output power P = 3.7×10-5 W at 500°C (when ∆T = 260°C). INTRODUCTION These days, many difficult problems appear worldwide: energy problems, environmental problems, and so on. In order to overcome these difficulties, development of new industrial technologies is necessary. These new technologies will play very important roles in many kinds of fields, helping address present and future sustainable energy needs. New materials will play an important role in the current challenge to develop alternative energy technologies to reduce our dependence on fossil fuels and reduce greenhouse gas emissions [1]. An important class of materials is thermoelectrics, that can convert waste heat into electrical energy. One of the most fascinating challenges of material science is to develop new high-performance and low-cost thermoelectric materials for practical applications [2,3]. Then the science and technology of thermoelectric materials is expected to be fundamental in the future [1-3]. The performance of thermoelectric materials is expressed by the thermoelectric figure of merit ZT = (σS2T)/κ, where σ, S, T and κ are the electrical conductivity, Seebeck coefficient, absolute temperature and thermal conductivity, respectively. According to the expression, larger values of σ and S and smaller values of κ are essential for material with higher figure of merit. Recently, extremely high values of ZT were obtained in multilayered nanostructured Bi2Te3/Sb2Te3 thin films [4], with ZT = 2.4 at 300K and in nanostructured BiSbTe bulk alloys with ZT = 1.4 at 100°C [5]. Despite to their outstanding ZT values, these materials contain rare elements [6], are widely unstable at high temperatures (for example, Bi2Te3 decomposes at 857 K [7] and its maximum operating temperature is j
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