Ferroelectric Domain Wall Engineering Enabled Thermal Modulation in PMN-PT Single Crystals.

Acting like thermal resistances, ferroelectric domain walls can be manipulated to realize dynamic modulation of thermal conductivity (k), which is essential for developing novel phononic circuits. Despite the interest, little attention has been paid to achieve room-temperature thermal modulation in bulk materials due to challenges in obtaining a high thermal conductivity switch ratio (k high /k low ), particularly in commercially viable materials. Here, we demonstrate room-temperature thermal modulation in 2.5 mm-thick Pb(Mg 1/3 Nb 2/3 )O 3 -xPbTiO 3 (PMN-xPT) single crystals. With the use of advanced poling conditions, assisted by the systematic study on composition and orientation dependence of PMN-xPT, we observed a range of thermal conductivity switch ratios with a maximum ≈1.27. Simultaneous measurements of piezoelectric coefficient (d 33 ) to characterize the poling state, domain wall density using polarized light microscopy (PLM) and birefringence change using quantitative PLM reveal that compared to the unpoled state, the domain wall density at intermediate poling states (0< d 33 < d 33,max ) is lower due to the enlargement in domain size. At optimized poling conditions (d 33,max ), the domain sizes show increased inhomogeneity that leads to enhancement in the domain wall density. This work highlights the potential of commercially available PMN-xPT single crystals among other relaxor-ferroelectrics for achieving temperature control in solid-state devices. This article is protected by copyright. All rights reserved.