Electric field dependent thermal conductivity on relaxor ferroelectric PMN-PT

Polarization caloritronics is an emerging field dedicated to investigating thermal fluctuations within the polarization of ferroelectrics, which Bauer et al. [1] labels "ferrons." Wooten et al. [2] measure the electric field dependencies of the thermal conductivity (k), diffusivity (D) and longitudinal acoustic sound velocity (v_LA) of ferroelectric Pb(Zr,Ti)O₃ (PZT), identify ferrons in this material to include acoustic phonons and explain the results quantitatively and without adjustable parameters in terms of the piezoelectric coefficients (d₃₃ and d₃₁), which strain-mixes optical and acoustic modes, and the Grüneisen parameter (γ). Here, we measure k, v_LA and d₃₁ of a ferroelectric relaxor, Pb[Mg_1/3Nb_2/3]O₃ - PbTiO₃ (PMN-PT) and confirm the validity of the theory, again without adjustable parameters. The effects of field E on PMN-PT are of opposite polarity and an order of magnitude larger than on PZT. Furthermore, k-measurements revealed a significant alteration in behavior as the electric field was cycled more than ten times through the field-induced crystallographic phase transitions of PMN-PT: the effects changed sign again. An experimental investigation of d₃₁ values for both a pristine and a cycled sample shows that it is this parameter that changes, and that the theory holds.



[1] Phys. Rev. Lett. 126, 187603 (2021)

[2] Sci. Adv. 9, eadd7194 (2023)

Funding: NSF CBET 213 3718