Characterization of flexoelectric effect of unpolarized BST under impact loading
Key Laboratory of Transient Physical Mechanics and Energy Conversion Materials of Liaoning Province, Shenyang Ligong University, No. 6, Nanping Middle Road, Hunnan District, 110159, Shenyang, China
Accepted: 7 January 2023
Published online: 6 February 2023
The depolarization of piezoelectric materials is inevitable due to thermal–mechanical coupling fields; however, the electrical response of unpolarized materials remains unknown. In order to clarify the flexoelectric response characteristics of barium strontium titanate (BaXSr1−XTiO3, BST) with different ratios under dynamic loading and calibrate the electrical response in sensing field, this paper conducts experimental research and theory study on the electromechanical response characteristics of unpolarized BST with different loading velocities, thicknesses and ratios. Split Hopkinson pressure bar integrating with electrical signal acquisition system is used to characterize the dynamic stress, strain, strain rate and polarization voltage. Then, the shock polarization theory based on one-dimensional wave equation and flexoelectric theory has been proposed to solve the strain gradient and flexoelectric coefficient. The results show that the maximum stress of unpolarized BST increases with increasing impact velocities and decreasing thickness; the maximum stress of Ba0.75Sr0.25TiO3 and Ba0.25Sr0.75TiO3 is similar under same impact velocity, but the maximum strain of Ba0.25Sr0.75TiO3 is larger; peak polarization voltage increases with strain rate, and the polarization voltage of Ba0.75Sr0.25TiO3 is larger than that of Ba0.25Sr0.75TiO3. Some factors that affect the electromechanical response of BST have also been theoretical studied. It can be concluded that higher electrical response of BST can be obtained for BST with smaller thickness, larger loading velocity and smaller sound velocity; flexoelectric coefficient of Ba0.75Sr0.25TiO3 is larger than Ba0.25Sr0.75TiO3, generally.
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