中文摘要：

通过偏振光显微镜对连续应力和恒电场作用下的BaTiO_3单晶中的裂纹扩展和畴变过程进行原位观察.结果表明.在连续应力的作用下,裂尖处应力集中导致出现畴变带,裂纹与畴变带垂直相交,畴带和裂纹一起向前移动,畴变在先,裂纹扩展在后;在恒电场作用下,畴变引起的不协调应变导致电致裂纹扩展,畴变始终发生在裂纹扩展之前.裂纹向前扩展时不断的切过前方的畴带,直到不再有畴变发生时裂纹停止扩展.

英文摘要：

Domain switching and crack propagation in BaTiO_3 single crystal under external field were in-situ observed by polarized light microscopy（PLM）.It was found that under mechanical field, domain-switching bands appear around the crack tip to relax stress and domain switching occurred before crack propagation.Under electric field,the internal stress induced by domain switching results in crack propagation.