INFLUENCE OF LOWER-VALENT A-SITE MODIFICATIONS ON THE STRUCTURE-PROPERTY RELATIONS OF LEAD-ZIRCONATE-TITANATE

Studies of the structure-property relationships have been performed fo r lead zirconate titanate as a function of concentration of a lower-va lent A-site substitution. Investigations focused on the system (Pb1-yK y)(Zr0.65Ti0.35)O-3-y/2 for 0 < y < 0.20. These studies revealed modes t changes in the dielectric response with increasing K1+ concentration . However, no evidence of relaxer ferroelectric characteristics was fo und. Transmission electron microscopy (TEM) studies were also performe d. These investigations revealed strong changes in the ferroelectric d omain structures with moderate increases in K1+ concentration. For K c ontent >4%, fine ferroelectric domains were found, which possessed a s trong degree of wavy character. Increasing K1+ concentration resulted in further decreases in domain size. Sawyer-Tower polarization studies then demonstrated a strong reduction in the switchable polarization w ith increasing K1+ concentration, indicating that the polarization bec omes pinned. Hot-stage TEM investigations were then performed, These s tudies revealed evidence for a pinning of the polarization into fine w avy domains at temperatures significantly below that of the ferroelect ric transformation. These results are then compared to recent investig ations of the influence of La3+ on the same base composition. We belie ve that the differences between lower- (K1+) and higher- (La3+) valent A-site modifications can be explained on the basis of the influence o f quenched (which become mobile on heating in the ferroelectric phase) versus randomly quenched (above the ferroelectric transformation) def ect complexes on the evolution of polar order. (C) 1996 American Insti tute of Physics.