FRACTURE MECHANISMS IN FERROELECTRIC-FERROELASTIC LEAD ZIRCONATE TITANATE [ZR-TI=0.54-0.46] CERAMICS

Fracture toughness, KIC, of a single‐phase commercial lead zirconate titanate (PZT) ceramic (Zr/Ti=0.54/0.46) of tetragonal structure (c/a=1.019) was measured using the single edge notched beam method above and below the Curie temperature. Domain switching (poling) under electrical and mechanical loading was examined using X‐ray diffraction. Surface grinding, electrical poling, and mechanical poling caused crystallographic texture. Similar texture, indicative of domain switching, was also observed on fracture surfaces of some saples fractured at room temperature. At room temperature, the highest KIC measured was 1.85 MPa·m1/2, while above the Curie temperature it was about 1.0 MPa·m1/2. Cracks emanating from Vickers indents in poled samples were different in the poling and the transverse directions. The difference in crack sizes is explained on the basis of domain switching during crack growth. These results indicate that ferroelastic domain switching (twinning) is a viable toughening mechanism in the PZT materials tested. Copyright © 1990, Wiley Blackwell. All rights reserved