Phase-field modeling of the influence of domain structures on the electrocaloric effects in PbTiO3 thin films

Abstract

A phase-field model has been developed to study the influence of epitaxial strains and domain structures on the electrocaloric effects (ECEs) in PbTiO 3 (PTO) thin films. The simulated domain-switching dynamics obtained from the proposed model was tallied with the existing experimental results. In the case of single-domain PTO thin film, the ECE gradually increased with the increasing epitaxial strain, whereas, in the case of polydomain PTO thin film, the influence of epitaxial strain on ECE can be divided into three regions of stable domain structures, i.e., c-domains, a/c-domains, and a-domains regions. It is worth noting that the maximum ECE occurred under a tensile epitaxial strain in the a/c-domains region, which was the consequence of the competition between the enhancement of ECE and the reduction of c-domains volume fraction, both caused by the increasing tensile epitaxial strain. Although the change of temperature arising from the ECE may not be large enough to be viable for practical applications, it does illustrate the important influence of domain structures on the ECEs of thin films, which has not gained much attention of most researchers whose focus is still on single-domain thin films.

Understanding the Role of Ferroelastic Domains on the Pyroelectric and Electrocaloric Effects in Ferroelectric Thin Films

“…It was suggested that these extrinsic contributions, which were often ignored in prior calculations, can have an appreciable impact on PEE and ECE and both the effects are maximized at the phase and domain‐structure boundaries (e.g., between c and c / a , and between c / a and a 1 / a 2 ). Later, phase‐field studies predicted that the ECE can be maximized under a tensile strain in the c / a phase as a consequence of the competition between the enhancement of ECE and the reduction of c ‐domain fraction. A systematic experimental study across the entire strain‐induced phase space is therefore necessary to understand the true magnitude and nature of the electrothermal response in polydomain ferroelectrics where domain interconversion under both changes in temperature and electric field can result in sizable electrothermal responses.…”

Giant Negative Electrocaloric Effects of Hf0.5Zr0.5O2 Thin Films

“…Therefore, this mechanism can hardly explain the negative ECE in the present work. Li et al and Lee et al have suggested that a negative ECE can be microscopically induced within a domain whose polarization is non‐collinear with the applied electric field. The negative ECE value estimated in this work, however, is a result of a macroscopic effect, where most of the Hf 0.5 Zr 0.5 O 2 film switched in the direction of the applied electric field .…”

Understanding electrocaloric cooling of ferroelectrics guided by phase‐field modeling

“…Lee et al 86 . investigated the effects of epitaxial mismatch strain on the ECE of monodomain and multidomain PTO TFs when the electric field is applied in the x 3 direction at RT with a phase‐field model.…”

“…Compressive strain reduces the domain transition temperature while increasing tensile strain will enhance it, but it is still much higher than RT. In addition, as shown in Figure 8, an electric field is applied in the direction of x 3 in PTO ferroelectric nanotubes (NTs) with equiaxed misfit strain near the RT, 4 and the results resemble those in TFs, 6,60,83,85,86,110 the compression misfit strain favors out-of-plane polarization, while the tensile strain favors in-plane polarization. When there is no electric field, the polarization in PTO NTs is in-plane.…”