Effect of electrical fatigue on the electromechanical behavior and microstructure of strontium modified lead zirconate titanate ceramics

The fatigue behavior of strontium doped lead zirconate titanate (PSZT) ceramics is investigated. Different compositions near the antiferroelectric–ferroelectric (AF–F) phase boundary are synthesized by tape casting and sintering route. The influence of electric field-induced AF to F phase transition on piezoelectric and strain behaviors is studied. Very high maximum polarization (∼41 μC/cm2) and ultrahigh strain (0.8%) are seen for some of the PSZT compositions near the morphotropic phase boundary. The samples are subjected to low frequency (30 Hz) electric field up to 107 cycles. Although the maximum polarizations of most of the PSZT ceramics showed fatigue-free behavior (less than 10% degradation), the strains in most of them showed degradation as high as over 50%. Electron microscopy of the fractured surface of the electrically cycled samples showed some intergranular fracture below the electroded surface. Results indicated that diffusion of silver electrode into the PSZT ceramics is responsible for the electro-coloration and degradation in strain response with fatigue cycles. Thermal annealing and removal of the damaged layer under the electrode showed the complete recovery of the strain to its original as-sintered value. X-ray diffraction technique is used before and after the fatigue cycles to investigate the influence of electrical cycles on the changes at the crystal structure level, which are also related to the fatigue-induced changes to electromechanical properties of PSZT ceramics.