The influence of vortex domain switching on the electrocaloric (EC) property of a PbTiO 3 nanoparticle is studied using the phase field method combined with thermodynamics analysis. The calculation results reveal that both a very large negative adiabatic temperature change (DT ¼ À6.34 K) and a positive adiabatic temperature change (DT ¼ 4.16 K) appear in the PbTiO 3 nanoparticle when the vortex domain switches from the clockwise state to the counterclockwise state under a curled electric field. The obtained results will be of help in understanding the EC property in ferroelectrics with multidomain structure.

Electrocaloric effects of Bi 4 Ti 3 O 12 (BIT) ferroelectric nanoparticles with vortex domain structures in a curled electric field are investigated using a phase field method. A large adiabatic temperature change (DT = 16.6 K) is observed in the BIT nanoparticles with the change in vorticity vector of the curled field DQ = 0.15 mV Å 22 at 620 uC. This large DT is attributed to a large change in the toroidal moment which is associated with vortex domain structures in the nanoparticles under the curled electric field. These results indicate that ferroelectric nanostructures with vortex domain structures can be exploited for use in solid state refrigeration.

Hollow microspheres constructed by single-crystalline Bi4Ti3O12 (BIT) nanoplates were synthesized through a hydrothermal process. The characterization results show that the BIT nanoplates are single crystalline with a lateral size of about 200-500 nm and a thickness of 30-50 nm. Local piezoresponse force measurement indicated an enhanced piezoelectric coefficient d * 33 (58 pm/V) of BIT nanoplates than that of the BIT bulk single crystal. The possible reasons for such a large piezoelectric coefficient were analyzed by surface effects and nanodomain structures.

No abstract

No abstract