Monolithic Bi1.5Sb0.5Te3 ternary alloys with a periodic 3D nanostructure for enhancing thermoelectric performance

Abstract

The selective reduction of thermal conductivity while preserving the Seebeck coefficient and electrical conductivity is regarded as a key strategy for achieving the high dimensionless figure-of-merit (ZT) of thermoelectric materials. Here, we newly propose a periodic three-dimensional (3D) nanostructure that has an ability to significantly reduce thermal conductivity, resulting in an improved ZT value of thermoelectric materials near room temperature. A 3D nanostructured thermoelectric monolith is developed by electrochemical deposition of a Bi–Sb–Te ternary alloy into a highly ordered, interstitial porous network in an epoxy template predefined by advanced lithography. The resultant inch-scale, bicontinuous nanocomposite monolith released from a substrate can be easily transferred to a customized reliable platform for evaluating thermoelectric properties. The measured thermal conductivity is only ∼0.89 W mK⁻¹ at 350 K due to greatly increased phonon boundary scattering without any degradation in the Seebeck coefficient and electrical conductivity, leading to an enhanced ZT value (∼0.56) which is ∼50% higher than that of an ordinary film with the same elemental composition. The 3D nanostructure developed here will provide new design opportunities for nanostructured thermoelectric materials, potentially usable in flexible thermoelectric coolers and wearable energy harvesting systems.