Crystallographic, Thermoelectric, and Mechanical Properties of Polycrystalline Type-I Ba8Al16Si30-Based Clathrates
Crystallographic, Thermoelectric, and Mechanical Properties of Polycrystalline Type-I Ba8Al16Si30-Based Clathrates
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Ba8Al16Si30 基多晶 I 型包合物的晶体学、热电和机械性能
DOI：
10.1007/s10853-012-6977-y
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发表时间：
2012
影响因子：
4.5
通讯作者：
Yuko Nagami
中科院分区：
文献类型：
--
作者：
Hiroaki Anno;Masahiro Hokazono;Ritsuko Shirataki;Yuko Nagami
采用电弧熔炼和放电等离子烧结相结合的方法制备了Ba 8Al 16 Si 30基I型笼形结构多晶样品，研究了其晶体学、热电性能和力学性能。样品的主相是I型笼形物，其实际Al/Si比为~15/31，强烈表明样品中不存在骨架缺陷或以非常低的浓度存在。样品的霍尔载流子浓度约为1 × 1021 cm −3，低于Ba 8Al 16 Si 30系统迄今为止报道的数值。样品的其他重要材料参数如下：态密度有效质量m * = 2.3m0，霍尔迁移率μ= 7.4 cm 2 V − 1 s −1，晶格热导率κL= 1.2 W m− 1 K −1。对于n = 9.7 × 1020 cm −3的样品，热电优值ZT达到约0.4（900 K）。使用实验确定的材料参数值进行的模拟表明，如果载流子浓度优化为约3 × 1020 cm −3，则ZT达到>0.5的值。杨氏模量、剪切模量和体积模量估计分别约为98、39和117 GPa，泊松比从纵向和横向声速vL= 6038 m/s和vT = 3503 m/s分别为0.25，对于ZT = 0.4的样品。热膨胀系数（CTE）的范围约为8 × 10− 6 K − 1至10 × 10− 6 K −1（330-690 K），小于Ba 8 Ga 16 Ge 30和Sr 8 Ga 16 Ge 30笼形化合物的数值。
Crystallographic, thermoelectric, and mechanical properties of polycrystalline Ba8Al16Si30-based samples with type-I clathrate structure prepared by combining arc melting and spark plasma sintering methods were investigated. The major phase of the samples was a type-I clathrate with an actual Al/Si ratio of ~15/31, strongly suggesting that framework deficiency was absent or was present in very low concentration in the samples. The Hall carrier concentrationnof the samples was approximately 1 × 1021cm−3, which is lower than the values reported so far for the Ba8Al16Si30system. Other important material parameters of the samples were as follows: the density-of-states effective massm* = 2.3m0, Hall mobilityμ= 7.4 cm2V−1s−1, and the lattice thermal conductivityκL= 1.2 W m−1K−1. The thermoelectric figure of meritZTreached approximately 0.4 (900 K) for a sample withn= 9.7 × 1020cm−3. Simulation using the experimentally determined values of material parameters showed thatZTreached values >0.5 if the carrier concentration is optimized at about 3 × 1020cm−3. Young’s, shear, and bulk moduli were estimated to be approximately 98, 39, and 117 GPa, respectively, and Poisson’s ratio was found to be 0.25 from the longitudinal and transverse velocities of sound,vL= 6038 m/s andvT= 3503 m/s, respectively, for a sample withZT= 0.4. The coefficient of thermal expansion (CTE) ranged from approximately 8 × 10−6K−1to 10 × 10−6K−1(330–690 K), which is smaller than the values reported for Ba8Ga16Ge30and Sr8Ga16Ge30clathrates.