Ce掺杂的Ba-Al-Ge基Ⅰ型笼状物的高压制备与结构和热电性能研究

Structure and thermoelectric properties of Ce-doped Ba-Al-Ge type-Ⅰ clathrate prepared at high pressure

采用高压高温的方法合成了Ce元素掺杂的Ba-Al-Ge基Ⅰ型笼状物热电材料。虽然X射线衍射图谱只发现微量杂相的存在,但通过扫描电子显微镜能谱分析表明样品有3种相衬度,分别为灰色相衬度、白色相衬度和黑色相衬度。这些相分别被命名为α、β和γ相,其中:α相为基体相,β相为富Ce的弥散相,γ相为Al、Ni与Ge组成的一种化合物相。β相随Ce掺杂量的增加而增多,样品的热电性能也随之提高。Ce的化学计量比为1.2的样品Ce1.2Ba7.0Ni0.44Al13.8Ge31.76在900 K时的ZT值可达0.26,较化学计量比为0.5的样品Ce0.5Ba7.7Ni0.62Al13.8Ge31.58的ZT增加了一倍多。Ce的加入明显地提高了热电性能。

Ce-doped Ba-A1-Ge-based type-I clathrate thermoelectric materials were synthetized through high pressure synthesis technique.Albeit the X-ray powder diffraction reveals the dominant phase of type-I clathrate, energy dispersive spectrometry detects three different contrasts in the background with gray, white and black colors, corresponding to alpha, beta, and gamma phases, respectively.Alpha-phase is the matrix phase, beta-phase is the Ce-rich phase homogeneously dispersed, and gamma-phase is composed of Al, Ni and Ge. The content of beta-phase increases with Ce concentration. The thermoelectric performance is significantly enhanced by increased beta phase.The ZT value of 0.26 is acieved at 900 K for Cel.2B7.0Ni0.44l13.8Ge31.76, two times higher than the sample of Ce0.5Ba7.7Ni0.62Al13.8G%1.58 with lower Ce doping content, suggesting Ce doping significantly improved the thermoelectric performance.