Anisotropy of Indentation Cracks Propagation of PZT-5H Ferroelectric Ceramics in Air and Water under Sustained Load

The propagation process and the anisotropy of the indentation cracks of poled PZT-5H ferroelectric ceramics in air and water under sustained load were investigated using Vickers indentation equipment. It is found that the length of the indentation cracks increased with increasing time to keep indentation load in air and water, thus, sub-critical crack growth or stress corrosion cracking (SCC) under sustained load occurred. For the cracks parallel to the poling direction, the threshold stress intensity factor for cracks arrest, K-ISCC, is larger, whereas the crack propagation rate, da/dt, is smaller than those for the cracks perpendicular to the poling direction. The anisotropy of susceptibility to SCC is related to the anisotropy of fracture toughness. The larger the fracture toughness is, the more susceptibility to SCC is, that is, the smaller the K-ISCC is, the larger the da/dt is.