Yasuhiro Toyama1, Hirofumi Hazama2, Ryoji Asahi2 and Tsunehiro Takeuchi1,3
1Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Nagoya 464-8603
In order to make variation in thermoelectric properties of Si2Ti-type Al32Mn34Si34, which possesses a large magnitude of Seebeck coefficient exceeding 300 μV/K, we partially substituted Fe and Cr for Mn, and succeeded in decreasing the number of valence electrons by the latter. The large, positive Seebeck coefficient up to 330 μV/K was observed for Al32CrxMn34-xSi34 (1 −≤ x −≤ 2.5), which consists almost solely of the phase of Si2Ti-type structure. The increase of hole concentration with increasing Cr concentration was confirmed by the fact that the electrical resistivity was decreased with Cr concentration. The positive sign and the decrease of Seebeck coefficient with increasing Cr concentration also lend a support on this scenario. The largest ZT-value with the positive sign of Seebeck coefficient (p-type behavior) was obtained at Al32Cr2.5Mn31.5Si34, and the resulting ZT-value was twice as large as the largest ZT-value of the ternary compound Al33Mn34Si33 that possesses a p-type behavior.
thermoelectric material, Seebeck coefficient, electrical conductivity, thermal conductivity, dimensionless figure of merit
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