Influence of thermal strains on the electrocaloric and dielectric properties of ferroelectric nanoshells

The electrocaloric effect and dielectric tunability of BaTiO3 ferroelectric nanoshells on Si and MgO cores are investigated using the modified Landau-Ginzburg-Devonshire theory, in which the surface tension and thermal strain are taken into account. The numerical results exhibit a peak of electrocaloric coefficient near the critical nanoshell thickness accompanied with the size-driven phase transition. In addition to the enhanced adiabatic temperature difference, the compressive thermal strain also significantly improves the dielectric tunability. More importantly, the ferroelectric nanoshell displays pronounced electrocaloric effect: Delta T(T-m)=2.09 K for the nanoshell on Si core and Delta T(T-m)=2.33 K on MgO core, respectively. Essentially, the ferroelectric nanoshell provides an effective means to acquire good electrocaloric effect and high dielectric tunability by adjusting the wall thickness, core radius, annealing temperature, and various core materials, which may effectively contribute to the stress level in the ferroelectric nanoshell.