The correlation between off-centering cation and the lattice thermal conductivity
Department of Chemistry, Northwestern University
Thermoelectric materials have been considered as a novel clean energy technique, due to their ability to directly convert heat into electricity. The performance of the thermoelectric material depends on its electronic transport behavior and thermal conductivity. In this talk, I will focus on the thermal conductivity and discuss the impact of the off-centering cation to the thermal conductivity of perovskite CsSnBr3？xIx and chalcopyrite Cu1-xInxFeS2. First, we find a strong correlation between lattice dynamics and the ultralow thermal conductivity for CsSnBr3？xIx. The crystallography data and theoretical calculations suggest the Cs atom deviates from its ideal cuboctahedral geometry and behaves as a heavy atom rattling oscillator. This off-center tendency of Cs produces a highly dynamic and disordered structure in CsSnBr3？xIx, which gives rise to the ultralow lattice thermal. Besides, for the Cu1-xInxFeS2, we find that In is not fully ionized to +3 when on the Cu sublattice and exists mainly in the +1 oxidation state. The 5s2 lone pair of electrons of In+ makes this atom incompatible with the tetrahedral geometry of the crystallographic site. This causes strong local bond distortions and off-center behavior in the Cu1-xInxFeS2, thus, leads to the low lattice thermal conductivity. These cases demonstrate a new avenue to suppress the lattice thermal conductivity via the concept of off-centering atoms.
Brief CV of Dr. Hongyao Xie:
Dr. Hongyao Xie received his Ph.D. in Material Science and Engineering in 2018 under the supervision of Prof. Xinfeng Tang at Wuhan University of Technology. Currently, he worked in Prof. Kanatzidis’ group at Northwestern University as a postdoctoral fellow. His research involves studying the correlation between lattice dynamics and thermal transport properties and exploring new metal chalcogenides for use as thermoelectric materials.
Contact: Shujuan Cui (崔书娟）
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