Influence of 90° charged domain walls on the electrocaloric effect in PbTiO_3 ferroelectric thin films

摘要

The electrocaloric (EC) effect in PbTiO_3 ferroelectric thin films (FETFs) with an array of partially compensated head-to-head (HH) and tail-to-tail (TT) 90° charged domain walls (CDWs) has been studied by using a phase field method. The calculation results indicate that the magnitude of the adiabatic temperature change ΔT increases with the diminution of the charge density (ρ*), in which ρ* is provided by charged defects or band bending. In particular, a negative EC effect caused by the direction difference between the applied electric field and the dipole is found near the HH and TT domain walls when ρ* ＞ 2.0. The EC strength |ΔT|/|ΔE| is 0.020 K cm kV~(-1) with the positive ΔT=2.03K at the external dimensionless electric field E*_b = 0.08 (ΔE= 104 kV cm~(-1)). These results indicate that the CDWs can provide an efficient way to adjust the EC effect of FETFs for refrigeration applications at room temperature.