Observation of Domain Motion in Single-Crystal Barium Titanate under Combined Electromechanical Loading Conditions

The nonlinear electromechanical behavior of ferroelectric materials is governed by the motion of domains. Since many common ferroelectric materials, such as barium titanate and PZT, are also ferroelastic, the domain motion is highly affected by stress as well as electric field. Experiments are performed on (001) and (100) oriented single crystals of barium titanate under combined electromechanical loading conditions. The crystal is subjected to a constant compressive stress (dead load) and an oscillating electric field along the [001] direction. Global deformation and polarization are measured as a function of electric field at different values of compressive stress. The use of semi-transparent electrodes and transmitted illumination allows in situ, real-time microscopic observations of domain patterns using a long working-distance, polarizing microscope. The combined electromechanical loading results in a cycle of stress and electric field induced 90° domain switching. This is an electrostrictive behavior with measured strains of up to 0.9%.