[Paper Review] Magnetic control of flexible thermoelectric devices based on macroscopic 3D interconnected nanowire networks

Flavio Abreu Araujo, Tristan da Câmara Santa Clara Gomes+1 more|arXiv (Cornell University)|Jan 1, 2019

Advanced Thermoelectric Materials and Devices40 references28 citations

TL;DR

This paper demonstrates magnetic field control of Peltier cooling in flexible, macroscopic 3D interconnected Co/Cu nanowire networks, achieving a spin-dependent Peltier coefficient of −2.8 mV and a power factor of ~7.5 mW/K²·m at room temperature, exceeding state-of-the-art thermoelectric materials. The approach enables scalable, shapeable thermoelectric coolers leveraging spin caloritronics.

ABSTRACT

Spin-related effects in thermoelectricity can be used to design more efficient refrigerators and offer novel promising applications for the harvesting of thermal energy. The key challenge is to design structural and compositional magnetic material systems with sufficiently high efficiency and power output for transforming thermal energy into electric energy and vice versa. Here, the fabrication of large-area 3D interconnected Co/Cu nanowire networks is demonstrated, thereby enabling the controlled Peltier cooling of macroscopic electronic components with an external magnetic field. The flexible, macroscopic devices overcome inherent limitations of nanoscale magnetic structures due to insufficient power generation capability that limits the heat management applications. From properly designed experiments, large spin-dependent Seebeck and Peltier coefficients of −9.4μV/K and −2.8mV at room temperature, respectively. The resulting power factor of Co/Cu nanowire networks at room temperature (∼7.5mW/K2m) is larger than those of state of the art thermoelectric materials, such as BiTe alloys and the magneto-power factor ratio reaches about 100\\% over a wide temperature range. Validation of magnetic control of heat flow achieved by taking advantage of the spin-dependent thermoelectric properties of flexible macroscopic nanowire networks lay the groundwork to design shapeable thermoelectric coolers exploiting the spin degree of freedom.

Motivation & Objective

• To develop flexible, macroscopic thermoelectric devices with magnetic field control of heat flow.
• To overcome limitations of nanoscale magnetic structures, such as low power output and poor scalability.
• To enable accurate measurement of spin-dependent thermoelectric parameters in large-area 3D nanowire networks.
• To demonstrate practical magnetic control of Peltier cooling in macroscopic electronic components.
• To validate spin caloritronics in interconnected, shapeable nanowire networks for energy harvesting and thermal management.

Proposed method

• Fabricated large-area 3D interconnected Co/Cu nanowire networks via pulsed electrochemical deposition into 3D nano-porous polymer templates.
• Used a two-step ion-irradiation process to create symmetric, crossed 3D nanoporous templates with controlled pore size and porosity.
• Employed a dual experimental setup to simultaneously measure magneto-resistance, Seebeck coefficient, and Peltier/Joule heating at the NW network/metal electrode junction.
• Applied magnetic fields up to 8 kOe to modulate spin-dependent transport and isolate Peltier effects from Joule heating.
• Used a two-current model and linear fitting to separate Joule (quadratic I²) and Peltier (linear I) contributions to temperature changes.
• Performed temperature measurements at zero-field and saturated magnetic field states to extract magneto-Peltier and magneto-Joule effects.

Experimental results

Research questions

• RQ1 Can magnetic fields be used to control Peltier cooling in macroscopic, flexible thermoelectric devices?
• RQ2 What are the spin-dependent Seebeck and Peltier coefficients in 3D interconnected Co/Cu nanowire networks?
• RQ3 Can the power factor and magneto-power factor ratio in such networks exceed those of state-of-the-art thermoelectric materials?
• RQ4 How can the Peltier effect be isolated from dominant Joule heating in nanoscale magnetic thermoelectric systems?
• RQ5 Can shapeable, large-area thermoelectric coolers be realized using spin caloritronics in 3D nanowire networks?

Key findings

• The Co/Cu nanowire network achieved a power factor of ~7.5 mW/K²·m at room temperature, exceeding that of BiTe alloys and other state-of-the-art thermoelectric materials.
• The spin-dependent Seebeck coefficient was measured as −9.4 µV/K, and the Peltier coefficient as −2.8 mV at room temperature.
• The magneto-power factor ratio reached approximately 100% over a wide temperature range, indicating strong spin-dependent thermoelectric response.
• Magnetic field control of Peltier cooling was experimentally demonstrated in macroscopic electronic components using the flexible nanowire network.
• The Peltier effect was successfully isolated from Joule heating by fitting temperature changes to linear (Peltier) and quadratic (Joule) current dependencies.
• The system exhibited a 25% relative change in resistance and thermopower at 8 kOe, confirming strong spin-dependent transport in the 3D network.