Characterization of PZN single crystals [ferroelectric properties and fracture behavior]

PZN single crystals poled in the [100] crystallographic direction display electro-mechanical coupling coefficients around 90 %, and electric field induced strain as high as 1 %. Obtaining these very high strain levels involves driving the material through a rhombohedral to tetragonal phase change, during which the material tends to develop cracks. Driving the material with a negative electric field reverses the polarization direction due to the relatively low coercive field, but also results in cracking. This paper presents results of various measurements of fracture behavior including observations of electric field induced damage evolution in the crystals, interactions of the electric field with indentation induced flaws, and Vickers indentation measurements of fracture toughness as a function of crack orientation relative to the crystal structure