Anisotropy of stress corrosion cracking of a PZT piezoelectric ceramics

Anisotropy of stress corrosion cracking (SCC) of a lead zirconate titanate piezoelectric ceramics in water and formamide has been investigated at constant load test using a single-edge notched tensile specimen. The results showed that SCC could occur in the two solutions, and the normalized threshold stress intensity factor of SCC, KISCC, revealed anisotropy. The KaISCC for poling direction parallel to the crack plane, KISCC, was greater than that perpendicular to the crack plane, KbISCC, similar to the anisotropy of fracture toughness KIC, however, the anisotropy factor of the KISCC, which was KaISCC/KbISCC=1.8 (in formamide) and 2.1 (in water), was larger than that of KIC, which is KaIC/KbIC=1.4. The stress-induced 90° domain switching decreases the efficient stress intensity factor and then causes the anisotropy of apparent KIC and KISCC, besides, the resistance of SCC exists also anisotropy.