Koya Arai

Preparation and Thermoelectric Properties of TE Module by a Spark Plasma Sintering Method

NaCo2O4 and 0.5at%-Sb doped Mg2Si have excellent thermoelectric properties. We tried to fabricate a thermoelectric module composed of these materials and using Ni plates as electrodes. The fine powder of NaCo2O4 was prepared by metal-citric acid complex decomposition. 0.5at%-Sb doped Mg2Si bulk was ground to powder and sieved to a powder particle size of 75 micrometers or less. These powders were sintered using spark plasma sintering (SPS) to obtain a body of NaCo2O4 and 0.5at%-Sb doped Mg2Si. These thermoelectric materials were connected to the Ni plates by using the SPS method. The whole process took a very short time (less than 2 min) and could be done at low temperature (below 873 K). The open-circuit voltagevalues were 82.7 mV, and the maxima, maximum output current and maximum output power, for the single module were 212.4 mA and 6.65 mW at ΔT = 470 K.

Fabrication of thermoelectric modules with Mg2Si and SrRuO3 by the spark plasma sintering method

Thermoelectric (TE) modules with a π structure were fabricated by the spark plasma sintering method. The modules were composed of SrRuO3 for the p-type semiconductor, Mg2Si for the n-type semiconductor, and Ni for the electrodes. The SrRuO3 powder was synthesized using the metal-citric-acid complex decomposition method. Mg2Si bulk prepared by meltquenching was ground into powder and sieved to a particle size of 75 μm or less. To obtain the sintered body of SrRuO3, the powder was sintered using spark plasma sintering (SPS). For SPS, the precursor powder was placed in a graphite die and kept at that temperature under a uni-axial pressure of 50 MPa and in vacuum conditions (less than 7 Pa). After sintering by SPS, the ceramic sample was annealed at 1573K in air because the SrRuO3 was slightly reduced during the SPS process in the graphite die. These TE sintered bodies were cut and polished. The dimensions of the samples used for fabrication of the p-type parts of the TE modules were 4.50×9.50×7.45 mm3 and those for the n-type parts were 5.50×11.45×7.45 mm3. Pressed Ni powder was put between these TE materials and the Ni electrodes in order to connect them together, and electrical power was passed through the electrodes from the SPS equipment. The output power under temperature differences ΔT ranging from 100 to 500 K was measured. The open-circuit voltage, maximum output current and maximum output power increased with increasing temperature difference ΔT. The open-circuit voltage of the single module was 91.0 mV, and the maximum output current and maximum output power were 5000 mA and 110 mW at ΔT=500 K, respectively.Thermoelectric (TE) modules with a π structure were fabricated by the spark plasma sintering method. The modules were composed of SrRuO3 for the p-type semiconductor, Mg2Si for the n-type semiconductor, and Ni for the electrodes. The SrRuO3 powder was synthesized using the metal-citric-acid complex decomposition method. Mg2Si bulk prepared by meltquenching was ground into powder and sieved to a particle size of 75 μm or less. To obtain the sintered body of SrRuO3, the powder was sintered using spark plasma sintering (SPS). For SPS, the precursor powder was placed in a graphite die and kept at that temperature under a uni-axial pressure of 50 MPa and in vacuum conditions (less than 7 Pa). After sintering by SPS, the ceramic sample was annealed at 1573K in air because the SrRuO3 was slightly reduced during the SPS process in the graphite die. These TE sintered bodies were cut and polished. The dimensions of the samples used for fabrication of the p-type parts of the TE modules were 4.50×9.50×7.45 mm3 and th...