Effects of Codoping with Ga and P on Thermoelectric Properties of Ba₈Al₁₆Si₃₀ Clathrate System

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• 作者：Hiroaki Anno ; Takahiro Ueda ; Kazuya Okamoto
• 关键词：Silicon clathrate ; codoping ; carrier concentration ; thermoelectric properties ; elastic properties
• 刊名：Journal of Electronic Materials
• 出版年：2017
• 出版时间：March 2017
• 年：2017
• 卷：46
• 期：3
• 页码：1730-1739
• 全文大小：
• 刊物类别：Chemistry and Materials Science
• 刊物主题：Optical and Electronic Materials; Characterization and Evaluation of Materials; Electronics and Microelectronics, Instrumentation; Solid State Physics;
• 出版者：Springer US
• ISSN：1543-186X
• 卷排序：46

文摘

We have investigated the effects of Codoping With Ga and P on the thermoelectric properties of the Ba₈Al₁₆Si₃₀ clathrate system, attempting to optimize the carrier concentration. The elastic properties, which are important for design of thermoelectric devices, were investigated by ultrasonic testing. Ga/P-codoped specimens with nominal compositions Ba₈Al₁₆Ga_xSi_30−2xP_x (x = 1.0, 1.5, 2.0) were prepared by arc melting and spark plasma sintering and their Seebeck coefficient, electrical conductivity, and thermal conductivity were measured. Analytical studies revealed that the total content of Al and Ga, expressed as atoms per formula unit, increased to 15.65 at nominal x = 2.0, exceeding the maximum content (y = 15.16) of Al for the Ba₈Al_ySi_46−y clathrate system. Ultrasonic tests determined the Young’s modulus, shear modulus, bulk modulus, and Poisson’s ratio to be 102.55 GPa, 40.14 GPa, 76.85 GPa, and 0.2775, respectively, for Ba₈Al₁₆Ga_xSi_30−2xP_x (x = 2.0). The Hall carrier concentration decreased from ∼1.0 × 1021 cm−3 for Ba₈Al_ySi_46−y to ∼6.3 × 1020 cm−3 for Ba₈Al₁₆Ga_xSi_30−2xP_x (x = 2.0), suggesting that Ga/P codoping may be useful for tuning the carrier concentration. The value of the Seebeck coefficient at ∼320 K increased from −46 μV K−1 for Ba₈Al_ySi_46−y to −67 μV K−1 for Ba₈Al₁₆Ga_xSi_30−2xP_x (x = 2.0). The dimensionless thermoelectric figure␣of merit ZT at 900 K improved from ∼0.4 for Ba₈Al_ySi_46−y to ∼0.47 for Ba₈Al₁₆Ga_xSi_30−2xP_x (x = 2.0).