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Electric-field-induced crack growth under cyclic electric field was reported for BaTiO 3 single crystals with different poling directions. Pre-existing cracks were introduced by Vicker's indent on the polished surfaces of the single crystals, and crack propagation was observed in-situ under cyclic electric field using a polarized optical microscope. For [001]-oriented BaTiO 3 Êsingle crystal, the applied cyclic electric field is perpendicular to the poling direction. Electric field-induced fatigue crack tends to propagate perpendicular to the applied electric field or in 45° directions, but not in the direction parallel to the cyclic electric field, before the global domain switching takes place. At the same time, cracks that initiated from the electrode/crystal interface grow rapidly along the domain boundary. For [100]-oriented BaTiO 3 Êsingle crystal, the applied electric field is parallel to the poling direction. The cracks induced by Vickers indentation remains stationary under a cyclic electric field below the coercive field, but start to extend when the cyclic field causes global domain switching. The crack slightly propagates along its original crack direction, and then arrests. When the electric field increases further, the indented cracks remain unchanged while cracks emanating from the electrode propagate rapidly within the single crystal.
Acknowledgements
The financial support by the National Natural Science Foundation of China and National Basic Research Program of China through Grant No. 2004CB619304 is greatly acknowledged.