The Mechanism of Deformation and Failure of In₄Se₃ Based Thermoelectric Materials

Abstract

The layered In 4 Se 3 based material is recognized as a state-of-the-art n-type thermoelectric material for the middle temperature range of 500 to 900 K. Despite excellent thermoelectric properties, its inferior mechanical properties restrict its commercial possibilities. In this work, we use quantum mechanics (density functional theory) to investigate the ideal strength and failure mechanisms of ideal and Se deficient In 4 Se 3 under pure shear and biaxial shear loads. We found that the lowest ideal shear strength of ideal In 4 Se 3 is 1.25 GPa along the (100)/<001> slip system. Slippage between the In/Se layer dominates its deformation and failure. With Se vacancies, the ideal strength of In 4 Se 2.75 drops to 1.00 GPa, while the failure mechanism remains almost the same as that of ideal In 4 Se 3 . Moreover, under biaxial shear loads (as in nanoindentation experiments), the ideal strength of In 4 Se 3 increases to 1.50 GPa, with compression now accounting for the failure. Even so, In 4 Se 3 shows poorer mechanical properties under biaxial shear loads. These insights into the deformation and failure mechanism of In 4 Se 3 compounds should help suggest designing modifications to improve mechanical properties.

Effects of stresses on the thermoelectric properties of In4Se3

“…The interlayers are bonded by van der Waals forces, and the In4 atom exists between these quasi-one-dimensional chains to enhance the interlayer bonding. 26…”

“…Three distinct In atoms covalently bond to three separate Se atoms, forming a quasione-dimensional chain structure. The interlayers are bonded by van der Waals forces, and the In4 atom exists between these quasi-one-dimensional chains to enhance the interlayer bonding 26.…”

Deformation and Failure Mechanisms of Element-Substituted Thermoelectric Type-I and Type-VIII Clathrates

“…Thermoelectric (TE) semiconductors realize direct conversion between heat and electricity based on carrier and phonon transport, which is considered to have potential applications in waste heat utilization and microrefrigeration. , The conversion efficiency of TE semiconductors is typically expressed as a dimensionless figure of merit, ZT = α 2 σ T /κ, where α is the Seebeck coefficient, σ is the electric conductivity, and κ is the thermal conductivity . Under Slack’s guidance “phonon-glass, electron crystal”, diversified TE semiconductor systems have been developed, including covalent compounds (TiNiSn and InSb), ionic compounds (PbTe, PbSe, Mg 2 Si, PbS, α-MgAgSb, CuInTe 2 , La 3 Te 4 , CaZn 2 Sb 2 , CaMg 2 Sb 2 , BiCuSeO, and Mg 3 Sb 2 ), van der Waals compounds (Bi 2 Te 3 , SnSe, α-Ag 2 S, and In 4 Se 3 ), and clathrates (skutterudite CoSb 3 , type-I Ba 8 Au 6 Ge 40 , type-VIII Ba 8 Ga 16 Sn 30 , and tI -Na 2 ZnSn 5 ). With the improvement of the TE conversion efficiency and the progress of device miniaturization technology, the importance of TE semiconductors has become increasingly prominent.…”

Structural failure of layered thermoelectric In4Se3-δ semiconductors is dominated by shear slippage

“…We have applied density functional theory to determine that the (001)/<100> is the easiest slip system of In 4 Se 3 under shear stress among these slip systems ((001)/<100>, (100)/<010>, (010)/<001>, (110)/<100> and (-110)/<110>) [34].…”