Considering heat recovery at the family-type water-cooled refrigerator, the temperature change between the exhaust heat and coolant can generate thermoelectric power using double cylinder module. Maximization of thermoelectric power was evaluated under several technical requirements by designing the optimum dimensions. Heat balance and thermal transfer via metallic electrodes and tubes between inner hot water and outer cold water were mathematically estimated under parallel flow. Heat transfer at the outer tube affects more critically than that at the inner on the electric power. The thinner thermoelectric module with the larger surface area can generate more power under some certain limitations on tube size (minimum length and practical thickness) and mass flow rate of thermal fluids (limited heat from the refrigerator). An example of optimal dimensions is proposed by taking higher flow rate of coolant, where a larger amount of hot water can be stored in the tube to supply to the kitchen and bathroom.

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Although the binary Al-Ir cubic quasicrystalline approximant (QCA) has been expected to be a narrow gap semiconductor， it does not realize due to large amount of aluminum sites vacancies leading to excess hole doping. We suggest that a high-pressure synthesis (HPS) is effective to reduce vacancies. In this work, effects of HPS on structural and thermoelectric properties were investigated for an Al-Ir QCA. We found that the Seebeck coefficient of a sample made by HPS has a larger value compared to that sintered by using conventional spark plasma sintering (SPS). Further， the lattice constant and the analyzed aluminum composition increased as high pressure applied due to increasing the number of Al atoms in the Ir-12 icosahedral cluster. These results indicate that HPS suppressed vacancies in the cluster leading to a 2 times higher value of zT.

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Si is a promising candidate for environmentally friendly thermoelectric (TE) material because of its non-toxicity and abundance. However, the lattice thermal conductivity of Si is extremely high, leading to low dimensionless figure of merit ZT. In a previous study, Xie et al. succeeded in reducing lattice thermal conductivity and improving ZT (0.39 at 1073 K) by forming dense dislocations in CoSi₂/Si composite. These dislocations were automatically introduced into Si matrix by sintering melt-spun powders. The formation mechanism of the dislocations is considered to be related to the eutectic reaction between CoSi₂ and Si. In this study, we applied the same process to Cr-Si system, which has similar eutectic temperature and eutectic composition to Co-Si system, intending to get insight into the formation mechanism of the dislocations. P-doped n-type Si and CrSi₂ nanocomposites were synthesized by melt spinning followed by spark plasma sintering. Transmission electron microscope observation showed that there were dislocations in Si matrix that seems to be formed by the same mechanism with CoSi₂/Si. Owing to the reduced lattice thermal conductivity, the maximum ZT reached 0.37 at 1073 K. This result indicates that a eutectic reaction plays an important role in the formation of the dislocations.

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