3D Printing of Functionally Graded Thermoelectric Materials for Improving Performance

Functionally graded materials (FGMs) are noted for their heterogeneous characteristics, with spatial variations in composition, particularly in terms of dopant concentrations and structural configurations. These materials are carefully engineered to meet specific properties and functionalities for a variety of applications. Recently, 3D printing has emerged as a promising technique for creating FGMs with complex geometries and precise material distributions. Despite this, 3D printing's use in FGMs has largely been confined to structural materials, with less frequent application in energy and electronic sectors. Thermoelectric power generation, which converts waste heat into electrical energy, holds significant promise; however, the performance of thermoelectric materials is highly temperature-dependent, limiting their broader use. In this study, we present a sequential 3D printing method to fabricate n-type Bi₂Te₃-based thermoelectric materials with gradients in both electronic dopants and structural voids. By formulating Na-doped thermoelectric colloid inks with suitable viscoelastic properties for 3D printing, we achieved the fabrication of materials with intricate architectures and 150 µm precision. These materials exhibited atomic-level doping and macroscopic void gradients. The thermoelectric peak temperatures of the printed materials varied from room temperature to 450 K, depending on the doping levels. Designed to operate over a wide temperature range, these graded thermoelectric materials, fabricated via 3D printing, demonstrated enhanced power-generating performance compared to homogeneous materials. This method offers a fast and cost-efficient approach to producing functionally graded thermoelectric materials, making it well-suited for applications in energy and electronic devices.