Crack Initiation at Electrode Edges in PZN-4.5%PT Single Crystals

Fringing electric fields emanating from an electrode edge in electromechanically coupled materials can potentially lead to cracking from a strain incompatibility of the active and inactive regions. Partial electrodes and specimen geometry are studied in single crystal PZN-4.5%PT to characterize the fracture behavior near an electrode edge. Crack growth was characterized by varying the specimen thickness (t ¹ /4 0.7 and 2 mm) and electrode coverage (50-95%). An applied electric field of 3 MV/m was required to initiate cracks in the 0.7-mm specimens, while an electric field of 2 MV/m was required to initiate cracks in the 2 mm thick specimens. Linear elastic finite element modeling was used to determine the field quantities near the electrode edge and evaluate the internal energy density.