Liu Zihang, Shuai Jing, Geng Huiyuan, Mao Jun, Feng Yan, Zhao Xu, Meng Xianfu, He Ran, Cai Wei, Sui Jiehe
State Key Laboratory of Solidification Processing, Northwestern Polytechnical University , Xi'an 710072, China.
ACS Appl Mater Interfaces. 2015 Oct 21;7(41):23047-55. doi: 10.1021/acsami.5b06492. Epub 2015 Oct 12.
Microstructure has a critical influence on the mechanical and functional properties. For thermoelectric materials, deep understanding of the relationship of microstructure and thermoelectric properties will enable the rational optimization of the ZT value and efficiency. Herein, taking AgSbSe2 as an example, we first report a different role of alkaline-earth metal ions (Mg(2+) and Ba(2+)) doping in the microstructure and thermoelectric properties of p-type AgSbSe2. For Mg doping, it monotonously increases the carrier concentration and then reduces the electrical resistivity, leading to a substantially enhanced power factor in comparison to those of other dopant elements (Bi(3+), Pb(2+), Zn(2+), Na(+), and Cd(2+)) in the AgSbSe2 system. Meanwhile, the lattice thermal conductivity is gradually suppressed by point defects scattering. In contrast, the electrical resistivity first decreases and then slightly rises with the increased Ba-doping concentrations due to the presence of BaSe3 nanoprecipitates, exhibiting a different variation tendency compared with the corresponding Mg-doped samples. More significantly, the total thermal conductivity is obviously reduced with the increased Ba-doping concentrations partially because of the strong scattering of medium and long wavelength phonons via the nanoprecipitates, consistent with the theoretical calculation and analysis. Collectively, ZT value ∼1 at 673 K and calculated leg efficiency ∼8.5% with Tc = 300 K and Th = 673 K are obtained for both AgSb0.98Mg0.02Se2 and AgSb0.98Ba0.02Se2 samples.
微观结构对材料的力学性能和功能特性有着至关重要的影响。对于热电材料而言，深入理解微观结构与热电性能之间的关系，将有助于合理优化ZT值和效率。在此，以AgSbSe₂为例，我们首次报道了碱土金属离子（Mg²⁺和Ba²⁺）掺杂在p型AgSbSe₂的微观结构和热电性能中所起的不同作用。对于Mg掺杂，它单调地增加载流子浓度，进而降低电阻率，与AgSbSe₂体系中的其他掺杂元素（Bi³⁺、Pb²⁺、Zn²⁺、Na⁺和Cd²⁺）相比，显著提高了功率因子。同时，晶格热导率因点缺陷散射而逐渐受到抑制。相比之下，由于BaSe₃纳米沉淀的存在，随着Ba掺杂浓度的增加，电阻率先降低后略有上升，与相应的Mg掺杂样品呈现出不同的变化趋势。更显著的是，随着Ba掺杂浓度的增加，总热导率明显降低，部分原因是纳米沉淀对中长波声子的强烈散射，这与理论计算和分析结果一致。总体而言，AgSb₀.₉₈Mg₀.₀₂Se₂和AgSb₀.₉₈Ba₀.₀₂Se₂样品在673 K时的ZT值约为1，在Tc = 300 K和Th = 673 K时计算得到的腿效率约为8.5%。
