Influence of Finite Size on the Electrocaloric Response in PbTiO₃ Ceramics Near Room Temperature Using Landau Theory

Abstract

We investigate the influence of grain size on the electrocaloric properties of ferroelectric systems using Landau theory. We study how the phase transformation temperature and electrocaloric property can be tuned by changing the grain size close to the critical size. Our results show that the electrocaloric coefficient at room temperature can be greatly enhanced by controlling the grain size. In particular, we calculate the adiabatic temperature change, ΔT to be %2 K with an electric field difference ΔE ¼ 50 kV cm À1 at room temperature in a model for PbTiO 3 ceramics. The results provide an approach to improving the electrocaloric properties at room temperature in experiments by engineering the grain size.

Understanding electrocaloric cooling of ferroelectrics guided by phase‐field modeling

“…found that when the grain size of BTO core–shell ceramics decreased to a critical size of 20 nm, the internal tetragonal core turn to cubic phase. Liu et al 94 . displayed that when the grain size of PTO ceramics was reduced to a critical size of 8.8 nm, its spontaneous polarization was suppressed to zero near RT.…”

“…Fang et al 97 found that when the grain size of BTO core-shell ceramics decreased to a critical size of 20 nm, the internal tetragonal core turn to cubic phase. Liu et al 94 displayed that when the grain size of PTO ceramics was reduced to a critical size of 8.8 nm, its spontaneous polarization was suppressed to zero near RT. Dai et al 100 also found that, at RT, BTO nanoshells with cylindrical cores exhibit an EC coefficient peak with a size-driven phase transition near the critical nanoshell thickness.…”

“…The significant effects of grain size on the ECE of ferroelectric nanomaterials have been proven by thermodynamic theory and phase-field models. Through simulation and calculation of PTO 94,95 and BTO 96 nanoceramics, BTO nanocore-shell structure 97,98 and spherical single-domain BTO NPs with semiconductor shells and dielectric polymer nanocomposites, 99 one can see that the reduced grain size will reduce the temperature of the maximal ECE and widen the ΔT peak, while the ΔT max decreases to some extent. Based on the phase-field simulation, Li et al 78 indicated that the size reduction can enhance the RT EC ATC of PTO NPs with vortex structure.…”

Statistical Mechanical Model of the Giant Electrocaloric Effect in Ferroelectric Polymers

“…This macroscopic thermodynamic approach is widely applied in the experiments of measuring the ECE without furnishing any microscopic properties of the materials studied. The second approach is the Landau phenomenological approach, which incorporates the correction of Curie temperature by crystal size and creates a quantitative connection between macroscopic material properties and the ECE. − However, the Landau approach precludes the investigation of micromechanisms. Pirc et al introduced a microscopic dipole model to estimate the upper bound value of ECE temperature, but this model is not directly applicable to systems under finite values of E or for understanding material responses to changing external electric fields.…”