Effect of poling direction on R-curve behavior in lead zirconate titanate

R-curves of lead zirconate titanate (PZT) have been measured with compact tension (CT) specimens for different poling conditions and grain sizes. Depending on poling direction the plateau value of the R-curves ranged from 1.13 to 1.54 MPa.m(1/2) for a grain size of 6.4 mu m and from 1.14 to 1.30 MPa.m(1/2) for a grain size of 5.2 mu m. Poling in the thickness direction yielded the material with the highest fracture toughness while the direction parallel to the loading direction led to the lowest fracture toughness.