Fracture toughness anisotropy by indentation and SEVNB on tetragonal PZT polycrystals

The fracture toughness of several poled and unpoled well characterized PZT materials was studied by indentation and bending techniques to determine the materials intrinsic fracture toughness anisotropy. Indenter loads were applied both in perpendicular and parallel directions to the polarization axis. Hardness, Hv, Hk, Youngʹs Modulus, E, and fracture toughness, K1c, measured using the indentation technique showed anisotropy in poled samples. The observed anisotropy was partly related with reorientation of ferroelectric domains. Values of K1c were determined using the single edge V-notch beam (SEVNB) technique to determine the influence of experimental artifacts associated with the indentation method. A significantly lower anisotropy in fracture toughness was observed.