Lead-free room-temperature ferroelectric thermal conductivity switch using anisotropies in thermal conductivities

TL;DR

This paper demonstrates a lead-free, room-temperature thermal conductivity switch based on ferroelectric domains in barium titanate, utilizing anisotropic thermal conductivities for reversible control with an electric field.

Contribution

It introduces a novel, environmentally friendly thermal switch operating near room temperature, leveraging anisotropic thermal conductivities in ferroelectric barium titanate.

Findings

Achieved a switching ratio of 1.6 ± 0.3 at room temperature.

Confirmed anisotropic thermal conductivities via experiments.

Predicted and demonstrated reversible thermal switching using electric fields.

Abstract

Materials with on-demand control of thermal conductivity are the prerequisites to build thermal conductivity switches, where the thermal conductivity can be turned ON and OFF. However, the ideal switch, while required to develop novel approaches to solid-state refrigeration, energy harvesting, and even phononic circuits, is still missing. It should consist of an active material only, be environment friendly, and operate near room temperature with a reversible, fast, and large switching ratio. Here, we first predict by ab initio electronic structure calculations that ferroelectric domains in barium titanate exhibit anisotropic thermal conductivities. We confirm this prediction by combining frequency-domain thermoreflectance and scanning thermal microscopy measurements on a single crystal of barium titanate. We then use this gained knowledge to propose a lead-free thermal conductivity switch without inactive material, operating reversibly with an electric field. At room temperature, we find a switching ratio of 1.6 $\pm$ 0.3, exceeding the performances of state-of-the-art materials suggested for thermal conductivity switches.