Yukun Liu Selected for 2023 Microscopy & Microanalysis Student Scholar Award

Yukun Liu, a doctoral student in the VPD Group in Material Science & Engineering, has been selected for the 2023 Microscopy & Microanalysis Student Scholar Award for his work titled "Probing the 'Order' in Complexity: Entropy-Engineered Thermoelectric Materials." This work is focused on understanding how entropy engineering can be applied to the design of thermoelectric materials. Thermoelectric materials have the unique ability to directly and reversibly convert heat into electricity. In essence, achieving high thermoelectric performance requires a delicate balance between a high Seebeck coefficient, electrical conductivity, and low thermal conductivity, as all these transport properties are interconnected.

Entropy engineering, a recent concept, offers the potential to strike this balance by introducing short-range disorder in ionic mass, size, and bond state while maintaining long-range atomic order. However, the introduction of additional atomic species can lead to various mixing reactions, potentially resulting in structural and chemical heterogeneity. The lack of understanding in these aspects can lead to erroneous interpretations of the impact of entropy engineering on transport properties.

To establish a robust structure-property relationship, this work employs a combination of conventional S/TEM, 4D-STEM, and in-situ heating TEM analysis to uncover the composition and temperature-driven evolution of microstructure. The study reveals the existence of polar domain structures in the low-entropy multicomponent system PbGeSnTe₃. These polar domains form as a result of centrosymmetry breaking during the cooling process. Through the implementation of entropy engineering, the centrosymmetric phase is successfully stabilized at room temperature, suppressing the formation of polar domain structures. Simultaneously, the increase in crystal symmetry enhances the density-of-state effective mass, leading to an improvement in the Seebeck coefficient. The identified atomic short-range disorder effectively reduces lattice thermal conductivity, while electrical conductivity is maintained due to the preservation of long-range order. These improvements collectively contribute to high thermoelectric performance, showcasing the promising application of entropy engineering in thermoelectric materials.

For more details, please refer to the following link: 10.1021/jacs.3c01693.