Addition of a Sr, K, Nb (SKN) combination to PZT(53/47) for high strain applications

A lead zirconate titanate composition incorporating the dopants Sr, K, and Nb (SKN) in the specific ratio 4:1:3 has been studied. In principle, the SKN should act as a donor dopant but since its addition reduced the grain size from 11.4 mu m (for 1% SKN) to 1.5 mu m (for 5% SKN), the overall effect was found to be more complicated. It was observed that the addition of SKN reduced the Curie temperature, by 16 degrees C/mol (%) and broadened the dielectric peak. X-ray measurements further suggested that the ceramic was a mixture of rhombohedral and tetragonal phases and that the room temperature c/a ratio of the tetragonal phase decreased with SKN addition. The piezoelectric coefficient d(33), determined from high field unipolar drives, gave an optimum value of 779 pm/V for the 0.02 SKN compositions, which also exhibited a relatively high Curie temperature of 356 degrees C. Competing effects of enhanced domain wall mobility from donor doping and reduced mobility due to smaller grain size may explain the observed compositional variation in the measured material properties. Materials based on this composition are attractive for high performance piezoelectric actuator applications such as fuel injection.