The effect of poling treatment and crystal structure of PZT on fracture toughness and fatigue resistance

초록

Empirical measurements of fracture toughness and fatigue strength were conducted for piezoelectric Pb(Zr<inf>x</inf>, Ti<inf>1-x</inf>)O<inf>3</inf> of various compositions such as tetragonal, MPB, and rhombohedral. Before the poling treatment the rhombohedral showed the highest fracture toughness, while the tetragonal revealed the lowest fracture toughness. After poling treatment, the fracture toughness measured by the pre-cracked SENB method decreased in all three compositions. The most remarkable decrease was observed in the tetragonal composition. However, when the indentation strength method was used the highest fracture toughness was observed in the tetragonal. The stress intensity factor relief due to microcracks around the indentation marks and the anisotropic internal stresses caused by domain alignment during the poling treatment were proposed as explanations for the conflicting results. Fatigue resistance was lowered by the compressive stress introduced during the poling treatment. The highest fatigue resistance was observed in the rhombohedral composition of low tetragonality, which exhibited low internal stress.