Unravelling the interplay between defects, dopant species, and thermoelectric properties in p-type Mg2X (X=Si, Ge, Sn)

热电材料可以将废热或处理热直接转化为可用的电能。因此，它们是提高各种工业过程的能源效率，从而减少化石燃料消耗的绝佳机会。在500 K至800 K的温度范围内，大部分可重复使用的热量是可用的，n型硅化镁基固溶体Mg2X （X = Si, Ge, Sn）是最有前途的热电材料之一。然而，对于相应的p型固溶体，实验发现其热电性能远不如理论预期。晶体结构缺陷在Mg2X中普遍存在，我们对现有实验数据和最新理论研究的分析表明，这些缺陷在很大程度上控制了p型Mg2X的热电性能。因此，提出的工作的目的是阐明缺陷对p型Mg2X热电性能的影响。我们将采用材料/合成参数的控制变化和微观结构分析来建立实验可获得参数与缺陷浓度之间的相关性。根据随附的输运测量，应量化缺陷对热电性能的影响。包括缺陷影响在内的热电性能的半解析建模将为进一步改进实验材料提供指导。

Thermoelectric materials can convert waste or process heat directly into usable electrical energy. They are therefore a fascinating opportunity to increase the energy efficiency of various industrial processes and thus reduce fossil fuel consumption. For the temperature range of 500 K to 800 K - where a large fraction of the reusable heat is available - n-type magnesium silicide based solid solutions Mg2X (X = Si, Ge, Sn) are among the most promising thermoelectric materials. However, for the corresponding p-type solid solutions the thermoelectric properties are experimentally found to be far inferior and fail to meet the theoretical expectations. Crystal structure defects are ubiquitous in Mg2X and our analysis of the available experimental data and recent theoretical studies indicates that these defects control the thermoelectric properties of p-type Mg2X to a large degree. The aim of the proposed work is therefore to elucidate the effect of defects on the thermoelectric properties of p-type Mg2X. We will employ controlled variation of material/synthesis parameter and microstructural analysis to establish correlations between experimentally accessible parameters and defect concentration. From accompanying transport measurements the effect of defects on the thermoelectric properties shall be quantified. Semi-analytical modelling of the thermoelectric properties including the effect of defects will guide the way for further experimental material improvement.