Mg掺杂n型Sn基Ⅷ型单晶笼合物的结构及电传输特性

本文采用Sn自熔剂法，制备Mg掺杂Sn基单晶笼合物Ba₈Ga_16-XMg_XSn₃₀ （0 ≤ X ≤ 1.5），并对其结构及电传输性能进行研究. 结果表明所制备化合物为具有空间群I43 m的Ⅷ型单晶笼合物，随Mg掺杂量的增加，对应化合物的熔点略有升高，晶格常数减小，掺杂样品中填充原子Ba的实际含量低于理想值8.0，其在十二面体空洞中的占有率约为0.93（Mg的名义含量X=1.5时）. 所有样品均表现为n型传导，Mg的掺入对材料的能带结构有一定影响，Mg掺杂后，样品的载流子浓度降低，Seebeck系数的绝对值、电阻率增加，Mg的名义含量X=1.5时，样品的功率因子在430 K附近取得最大值1.26×10^-3 W·m^-1·K^-2. 关键词： Ⅷ型笼合物 n型传导 单晶

Structural and electrical transport properties of Mg-doped n-type Sn-based type Ⅷ single crystalline clathrate

Mg-doped Sn-based single crystalline samples Ba₈Ga_16-XMg_XSn₃₀(0 ≤ X ≤ 1.5) were grown from Sn flux to characterize their structural and electrical transport properties. Research results show that the prepared compounds are well indexed by the type-Ⅷ clathrate structure with a space group I43 m. With the increase in Mg content, the melting point of the corresponding compounds increases. On the contrary, the lattice constant decreases. The actual content of filling atomic Ba in doped samples is below the ideal value of 8.0, the occupancy of Ba in the dodecahedron is about 0.93 for the sample with X=1.5. All the samples show n-type conduction. The Mg atoms have an effect on the band structure of the materials, and the carrier concentrations in the doped samples are reduced. However, the absolute values of Seebeck coefficient and the resistivity of doped compounds increase, respectively. By calculation, the sample of X=1.5 obtains the maximum value of power factor 1.26×10^-3 W·m^-1·K^-2 near 430 K.
Keywords： Ⅷ-type clathrate n-type conduction single crystalline