Temperature dependence of the fatigue and mechanical properties of lead zirconate titanate piezoelectric ceramics

This paper presents research results on the temperature dependence of the fatigue and mechanical properties of piezoelectric ceramics. The material being examined is a lead zirconate titanate piezoelectric ceramic, PZT. The fatigue strength apparently increases with increasing sample temperature. The mean endurance limit at 10⁵ cycles for the sample tested at 573 K is twice as high as that at 293 K. Similarly, the bending strength of the PZT increases with increasing sample temperature. A maximum bending strength is obtained at a sample temperature between 573 K and 773 K. The increment in the bending strength is attributed to the distorted lattice structure, in which a tetragonal lattice system is being changed to a cubic structure at 573 K, the Curie temperature. On the other hand, the reduction in the bending strength at temperatures greater than 773 K is caused by a reduction in the concentration of oxygen defects and high thermal energy, leading to dislocation movement. A wavy fracture surface with a mixture of transgranular and intergranular fractures is obtained in the samples fractured at temperatures between 573 K and 773 K due to the distorted lattice structure. In contrast, a flat face with transgranular fracture appears in tests at the room temperature and the high temperature (over 773 K). Details of the fracture mechanism are further discussed.