Abstract
Interfaces in oxide heterostructures act as critical regions to induce emergent and novel types of functionality in thin films. Herein, we demonstrate the creation of bulk ferroelectric heterostructures (BFHs) in monolithic ferroelectrics by nanoscale elemental partitioning, unlocking functionalities beyond the reach of conventional ferroelectrics and thin-film devices. The unique percolating, compositionally modulated networks act as built-in heterointerfaces that generate coupled ferroelectric-electrostatic-elastic fields, which stabilize charged domain walls and imprint predefined domain configurations throughout the bulk. In exemplar BiFeO
3
-BaTiO
3
ceramics, the BFH approach raises the Curie temperature to 824°C (increment Δ
T
C
> 350°C) and yields superior high-temperature piezoelectric responses (
d
33
> 400 picocoulombs per newton,
k
33
> 0.4), surpassing those of existing high-temperature piezoelectrics. Domain-engineered BFHs further unlock programmable control of domain switching, enabling the strongest yet tunable internal bias fields (>8 megavolts per meter) in bulk materials and record-high reversible shear electrostrains (up to 0.98%) at supercoercive field levels. The BFH design concept provides a transformative platform for next-generation ferroelectric and electromechanical transduction devices with extended temperature, high-power, and high-stress capability. It also establishes a universal framework for programmable control across ferroic families, including ferroelastic, ferromagnetic, and multiferroic materials in polycrystalline, single-crystal, and thin-film forms.