Session: 17-15-01: Society-Wide Micro/Nano Poster Forum

Paper Number: 99692

99692 - Rapid Macroscale Thermal Switching Based on Domain Wall Engineering in Pmn-Pt Single Crystals 

On-demand temperature control is desirable in several solid-state applications, from nanoscale thermoelectric devices to macroscale thermal control systems employed in space. This has been achieved by switching the thermal conductivity (k) of a material between a high (k_high) and low thermal conductivity (k_low) state. Several thermal switches have been demonstrated with different switching ratios (k_high/k_low), switching times between the 2 states (from a few secs to several minutes) and switching stimuli/mechanism (electrical, thermal, optical, magnetic, mechanical, and electrochemical) under various operating temperatures. An ideal thermal switch offers a rapid switching at RT with a high thermal conductivity contrast that can be conveniently triggered based on the application. Most of the thermal switches reported so far are thin films that restricts their applicability. A few macro-scale solid-state thermal switches have been reported but are either restricted to cryo- temperatures or have complicated switching mechanism with long switching times. Here, we experimentally demonstrate a bulk thermal switching action in [001]-oriented PbMg_1/3Nb_2/3O₃-PbTiO₃ (PMN-PT) single crystals. Being a relaxor ferroelectric material, PMN-PT based switches are conveniently and rapidly switched from an Unpoled state (k_high) to a poled state (k_low) using electric field (poling). This approach takes advantage of the variation in ferroelectric domain wall (DW) density between the 2 states. The DW’s, much like grain boundaries, scatter phonons that results in different thermal conductivity between the unpoled and poled state. In this study, we investigated the switching behavior for several PMN-PT single crystals under direct current (DCP) and alternating current (ACP) poling along [001] direction for 2 different compositions, PMN-(27-30) PT (low-PT) and PMN-(30-33) PT (high-PT). The thermal conductivity has been measured along the [100] direction using photothermal reflectivity (PTR) measurements. Temperature gradient measurement using Infrared thermography (IR) gives the thermal conductivity along the other 2 directions. The IR camera results were first validated with PTR measurements along the [100] direction. The thermal conductivity results have also been correlated with a dielectric property (d₃₃) to gain insight on the dependence of DW density on piezoelectric property enhancement. Our results show a rise in thermal conductivity under poled state for both ACP and DCP under different poling conditions compared to unpoled state with a max. contrast of ~ 15% for low-PT. Anisotropic thermal conductivity measurements show that the poling direction gives the maximum thermal conductivity contrast. Our results also show that the enhancement in piezoelectric properties is mostly independent of the DW density. The bulk PMN-PT based thermal switch offers rapid (~ ms) and repeatable (ex-situ and in-situ measurements) contrast with convenient electric field trigger.

Presenting Author: Ankit Negi North Carolina State University

Presenting Author Biography: Ankit Negi is pursuing a PhD in Mechanical Engineering at NC State University. He received his Bachelor's degree from Institute of Technology, Nirma University. His research interests include understanding thermal transport in ferroelectric and 2D hybrid organic-inorganic perovskite.

Authors:

Ankit Negi North Carolina State University
Hwang Pill Kim North Carolina State University
Zilong Hua Idaho National Lab
Yong Zhu North Carolina State University
Xiaoning Jiang North Carolina State University
Jun Liu North Carolina State University