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过程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。对于500 K至800 K的温度范围（其中大部分可再利用的热量是可用的），基于n型硅化镁的固溶体Mg 2X（X = Si、Ge、Sn）是最有前途的热电材料之一。然而，对于相应的p型固溶体的热电性能实验发现是远远逊色，未能达到理论预期。Mg 2X中普遍存在晶体结构缺陷，我们对现有实验数据和最近理论研究的分析表明，这些缺陷在很大程度上控制着p型Mg 2X的热电性能。因此，所提出的工作的目的是阐明缺陷对p型Mg 2X的热电性能的影响。我们将采用受控变化的材料/合成参数和微观结构分析，以建立实验可访问的参数和缺陷浓度之间的相关性。应根据随附的运输测量，量化缺陷对热电性能的影响。半分析模型的热电性能，包括缺陷的影响，将指导进一步的实验材料的改进。

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.