Water-Free SbOx ALD Process for Coating Bi2Te3 Particles

Abstract

We developed a water-free atomic layer deposition (ALD) process to homogeneously deposit SbOx using SbCl5 and Sb-Ethoxide as precursors, and report it here for the first time. The coating is applied on Bi2Te3 particles synthesized via the solvothermal route to enhance the thermoelectric properties (i.e., Seebeck coefficient, thermal and electrical conductivity) via interface engineering. The amorphous character of the coating was shown by the missing reflexes on the X-ray diffractograms (XRD). A shift from the oxidation state +III to +V of the Sb species was observed using X-ray photoelectron spectroscopy (XPS), indicating increased thickness of the SbOx coating layer. Additionally, a peak shift of the Sb 3d5/2 + O 1s peak indicated increased n-type doping of the material. Electrical measurements of spark plasma-sintered bulk samples confirmed the doping effect on the basis of decreased specific resistivity with increasing SbOx layer thickness. The Seebeck coefficient was improved for the coated sample with 500 cycles of SbOx, while the total thermal conductivity was reduced, resulting in enhancement of the zT. The results distinctly show that surface engineering via powder ALD is an effective tool for improving key properties of thermoelectric materials like electrical conductivity and the Seebeck coefficient.

Unlocking the Potential of Porous Bi2Te3-Based Thermoelectrics Using Precise Interface Engineering through Atomic Layer Deposition

“…We also reported that the formation of the heterointerfaces in Bi 2 Te 3 -based alloys through ALD could reduce the resistivity by the interfacial doping, 35,36 and κ L by enhancement of phonon scattering at the heterointerfaces. 23,31,37 Consequently, the combination of the porous BST with interface engineering using ALD may yield synergistic effects in terms of decreased resistivity and κ L and enhanced mechanical strength.…”

“…ALD, which is a thin-film growth technique based on a self-limiting mechanism, enables the conformal coating of heterogeneous thin films over thermoelectric powders. Thus, the introduction of the ALD technique allows for the creation of a core–shell structure consisting of a thermoelectric core and a heterointerface. − In particular, the use of the ALD approach for fabricating Bi 2 Te 3 -based alloys has been reported to result in grain refinement, , indicating the possibility of improving the mechanical strength of the materials. Furthermore, the heterointerfaces formed through ALD can further enhance mechanical strength by inhibiting the propagation of cracks and dislocations.…”