Dislocation Density-Mediated Functionality in Single-Crystal BaTiO₃.

Area of Science:

• Materials Science
• Solid State Physics
• Ceramics Engineering

Background:

• Dislocations in metals primarily carry strain, but in oxide ceramics, they possess both strain fields and local charges.
• Oxide ceramics are crucial in technologies like semiconductors and ferroics, yet controlling their functionality via dislocation density remains a challenge.
• Existing models like Taylor hardening law, applicable to metals, do not fully capture the behavior of dislocations in functional ceramics.

Purpose of the Study:

• To develop a strategy for imprinting specific dislocations and controlling dislocation density in barium titanate (BaTiO3) single crystals.
• To investigate the relationship between engineered dislocation density and the functional properties of BaTiO3.
• To provide a mechanistic understanding of how plastic strain engineering influences the electrical properties of bulk ferroelectrics.

Main Methods:

• High-temperature uniaxial compression was used to introduce dislocations with {100}<100> slip systems into BaTiO3 single crystals.
• Dislocation density was systematically varied by tenfold.
• Dielectric permittivity, converse piezoelectric coefficient, and AC conductivity were measured as a function of dislocation density.
• Phase-field simulations and domain wall potential energy analyses were employed for mechanistic rationalization.

Main Results:

• A tenfold change in dislocation density was achieved in BaTiO3 single crystals.
• Dielectric permittivity, converse piezoelectric coefficient, and AC conductivity exhibited a peak at medium dislocation densities.
• The study established a correlation between dislocation density and key electrical properties.

Conclusions:

• Plastic strain engineering via controlled dislocation density offers a new method to tune the electrical properties of ferroelectric ceramics.
• The findings suggest a pathway for advancing dislocation technology in functional ceramics.
• This work provides a dislocation density-based design strategy for bulk ferroelectrics.