Bi₂Te₃ Nanowire Array/Epoxy Composites for Thermoelectric Power Generators and Microcoolers

The thermal conductivity of a nanowire array composite is controlled by the matrix thermal conductivity and volume fraction, thus the effective thermoelectric figure-of-merit (ZT) of the composite will be reduced relative to that of the thermoelectric nanowire material alone. In this report, we demonstrate a process for fabricating nanowire array /epoxy composite with high structural integrity and low effective thermal conductivity required for thermoelectric power generation applications. Using galvanostatic electrodeposition into sacrificial porous anodic alumina (PAA) templates of 50 micron thickness, we synthesized dense (∼75% volume fraction) self-supporting nanowire arrays of textured Bi₂Te₃. X-ray diffraction and transmission electron microscopy analysis showed that the nanowires have <11.0> texture, the orientation that yields the highest ZT in single crystals. The nanowire array was infiltrated with SU-8 epoxy resin, a low thermal conductivity material (0.2 W/m-K) with a thermal conductivity that is about an order of magnitude lower than that of PAA (1.7 W/m-K). Scanning electron micrographs of fractured composites confirm nearly complete infiltration of SU-8 epoxy in nanowire array with good adhesion and high structural integrity.