Doped-PbTe Thermoelectric Inks with Viscoelasticity for 3D Printing of Systemically Optimized Power-Generating Tube

Thermoelectric (TE) technology offers a promising means of improving fossil energy efficiency by generating electricity from waste heat from industrial or automobile exhaust gases. In these applications, thermoelectric modules must be designed in terms of system integration for efficient heat transfer, system simplification and low processing costs. Despite recent advances in material efficiency, the structural designs of TE legs and modules are subject to limited design flexibility within conventional planar structures. For real-world TE power generation applications, the modular structure sometimes needs to be customized for integration with thermal systems or may require geometric or heat-source-structure adjustments. For example, tubular thermoelectric generators (TEGs) have been extensively studied in academia and industry to improve fuel energy efficiency by recovering automotive or industrial waste heat. One significant problem in these applications is the unavoidable temperature drop at the interface between the conventional planar TEG and the exhaust gas pipe due to non-adaptable thermal contact, which significantly reduces the output power. Therefore, post-processing is required by pressing the TEG into the pipe with high force; however, this renders a heavy system. These limitations of modular structures stem from the fundamental challenges of processing the bulk-scale materials used to fabricate TEGs, such as top-down dicing, metallization, and soldering. This is because precise engineering of the structure for customization of TE legs and modules is not possible.<br/>Three-dimensional (3D) printing technology offers an innovative way to address these challenges through cost-effective direct molding and computer-aided design of 3D bulk-scale TE legs and modules with optimized structures. In this presentation, we report a 3D printing method of PbTe thermoelectric materials for fabrication of systemically optimized high-performance power generation TE tubes. The electronic doping-induced surface charges in PbTe particles were shown to significantly improve the viscoelasticities of inks without additives, thereby enabling 3D printing of PbTe for precise shape and dimension engineering with figures of merit of 1.4 for p-type and 1.2 for n-type materials. The performance of power-generating TE tube fabricated from 3D printed p-type and n-type PbTe tubes has been demonstrated experimentally and computationally as an effective strategy for designing system-adaptive, high-performance thermoelectric generators.