The electrocaloric and elastocaloric properties at the 180° domain wall in the tetragonal BaTiO3 are studied using the Landau–Ginzburg–Devonshire model as a function of the domain wall rotation angle α. The Ising-Bloch character is predicted at the 180° domain wall in tetragonal BaTiO3 under the flexoelectric effect. The electric field-induced adiabatic temperature change (ΔTE) which is induced by the Bloch-type polarization component depends on α, and a giant positive ΔTE appears at α  =  (π  +  12n)/24 where n is an integer. The asymmetry of ΔTE is found around the Bloch-type domain wall. The Bloch-type polarization component has a little contribution to the stress-induced adiabatic temperature change. This calculation indicates a contribution of helix polarization at the domain wall on the caloric effects (CEs) in the ferroelectric materials.

The low storage density of ferroelectric thin film memory currently limits the further application of ferroelectric memory. Topologies based on controllable ferroelectric domain structures offer opportunities to develop microelectronic devices such as high-density memories. This study uses ferroelectric topology domains in a ferroelectric field-effect transistor (FeFET) structure for memory. The electrical behavior of FeFET and its flip properties under strain and electric fields are investigated using a phase-field model combined with the device equations of field-effect transistors. When the dimensionless electric field changes from −0.10 to 0.10, the memory window drops from 2.49 V to 0.6 V and the on-state current drops from 2.511 mA to 1.951 mA; the off-state current grows from 1.532 mA to 1.877 mA. External tensile stress increases the memory window and off-state current, while compressive stress decreases it. This study shows that a ferroelectric topology can be used as memory and could significantly increase the storage density of ferroelectric memory.

A phase field method was used to investigate the influence of charge accumulation at the grain boundary on the electrical behavior of a ferroelectric field-effect transistor containing a polycrystalline gate. Both the domain structure and the electrical behavior of the ferroelectric field-effect transistor were found to depend on the coefficient χ, which represents the charge accumulation at the grain boundary. With increasing χ, both the width of the memory window of the capacitance–voltage curves and the on-state source–drain current decreased, while the off-state source–drain current increased. This can be explained in terms of the weakening polarization effect in the grain interior owing to the presence of a built-in electric field caused by the accumulated charge at the grain boundary.