Charged dislocations in ceramics have been frequently discussed since they modulate composition, strain, and charge over broad length scales, thus providing an extra degree of freedom to tailor electronic properties beyond limits inherent in bulk doping.[1] Recently, we demonstrated that dislocations imprinted in barium titanate bulk crystals enhanced the piezoelectric coefficient.[2-4] Despite the excitement surrounding the controlled creation of dislocations, such as dislocation density, particularly through mechanical deformation, significant challenges persist in harnessing their full potential—a potential that, while well-established in semiconductors and metals, remains poorly understood in ferroic oxides.

Here, we introduce a new paradigm in the design of functional oxides using irreversible, plastic deformation of single crystals, and demonstrate its large potential on the prototypical ferroelectric material barium titanate. By controlled plastic deformation we selected dislocations with special dislocation density. Through a dislocation density-based approach, dielectric permittivity, converse piezoelectric coefficient, and alternating current conductivity are engineered via varying the dislocation density by one order of magnitude.[5] Our findings were supported by detailed transmission electron microscopy, in situ optical microscopy, angle-dependent nuclear magnetic resonance, and detailed electrical characterization as well as extensive phase-field simulations.[5] Our results demonstrate the potential of plastic deformation and dislocation engineering for the manipulation of functional properties of ferroelectric materials.