Indentation-induced cracking and 90° domain switching pattern in barium titanate ferroelectric single crystals under different poling

We report different domain switching patterns and indenting crack orientations under Vickers indentation for BaTiO3 single crystals poled in different directions. For BaTiO3 single crystal cut and poled in [001] direction, the short indenting cracks emanate not only from the diagonals of the indentation, but also from (110) directions due to the structure mismatch along the boundaries between two adjacent domain switching zones of equivalent spreading. For single crystal cut along [100] and poled in [001] direction, we found that much shorter cracks are induced if one diagonal of the indent is put 45degrees (termed 45degrees indent), instead of 0degrees (termed 0degrees indent), away from the poling direction. It shows that 45degrees indents favor the formation of 90degrees a-c domain switching just around the indents. Driven by the structure mismatch, cracks prefer to emanate along the boundary of two adjacent domain switching zones, or from the boundary dividing the domain switch zone and non-switching zone. (C) 2002 Elsevier Science B.V. All rights reserved.