Control of polarization in bulk ferroelectrics by mechanical dislocation imprint

Abstract

Defects are essential to engineering the properties of functional materials ranging from semiconductors and superconductors to ferroics. Whereas point defects have been widely exploited, dislocations are commonly viewed as problematic for functional materials and not as a microstructural tool. We developed a method for mechanically imprinting dislocation networks that favorably skew the domain structure in bulk ferroelectrics and thereby tame the large switching polarization and make it available for functional harvesting. The resulting microstructure yields a strong mechanical restoring force to revert electric field–induced domain wall displacement on the macroscopic level and high pinning force on the local level. This induces a giant increase of the dielectric and electromechanical response at intermediate electric fields in barium titanate [electric field–dependent permittivity (ε33) ≈ 5800 and large-signal piezoelectric coefficient (d33*) ≈ 1890 picometers/volt]. Dislocation-based anisotropy delivers a different suite of tools with which to tailor functional materials.

Room‐temperature dislocation plasticity in SrTiO3 tuned by defect chemistry

“…Dislocations in ceramics have the potential to impact both functional and mechanical properties. On the one hand, dislocations in various oxides have demonstrated potential to tune electrical conductivity, thermal conductivity, 3–5 dielectric and piezoelectric properties 6 . On the other hand, dislocations can be introduced into ceramics to improve plasticity 7–10 and fracture toughness 11–13 .…”

“…On the one hand, dislocations in various oxides have demonstrated potential to tune electrical conductivity, thermal conductivity, [3][4][5] dielectric and piezoelectric properties. 6 On the other hand, dislocations can be introduced into ceramics to improve plasticity [7][8][9][10] and fracture toughness. [11][12][13] These new endeavors modify the conventional belief that ceramics are brittle, exhibiting little or no dislocation-mediated plasticity at room temperature.…”

Multiple property enhancement in bismuth ferrite‐based ferroelectrics by balancing nanodomain and relaxor state

“…[19][20][21] For example, a giant increase of dielectric and electromechanical response can be obtained in barium titanate single crystal by mechanical dislocation imprint. 19 Totally different conduction mechanism can be realized in BNT-based ceramics via A-site nonstoichiometry. 20 Enhanced electromechanical transducer efficiency has been achieved in lead zirconate titanate (PZT)-based ceramics by Mn doping.…”

“…The reason for defect engineering is that defect can effectively manipulate electrical properties in ferro/piezoelectrics. [19][20][21] For example, a giant increase of dielectric and electromechanical response can be obtained in barium titanate single crystal by mechanical dislocation imprint. 19 Totally different conduction mechanism can be realized in BNT-based ceramics via A-site nonstoichiometry.…”

Understanding Nanoscale Plasticity by Quantitative In Situ Conductive Nanoindentation

“…Interestingly, the disordered surface dislocations altered the electrical properties than controlled bulk deformation in SrTiO 3 . Very recently, Höfling et al [ 235 ] introduced a network of dislocations using uniaxial compression into BaTiO 3 , which enhanced the dielectric and piezoelectric properties ( ε 33 ≈ 5800 and d 33 ≈ 1890 pm V −1 ). These studies provide evidence that dislocation‐based anisotropy could be utilized as a tool for altering the functional properties of oxides.…”