Structure-property relationship investigations of higher and lower valent modified lead zirconate titanate ceramics

Investigations of the structure-property relations of lead zirconate titanate (PZT) modified by various higher and lower valent substituents on the A- and B-sites were systematically performed by dielectric spectroscopy, polarization switching, X-ray diffraction, and electron microscopy methods. These investigations have shown a strong dependence of the structure-property relations on substituents concentration, substituent mobility, and substituent-defect distribution, irrespective of the charge compensation mechanism. Lower valent substituent-defect complexes which were mobile until temperatures below the phase transition were found to preferentially locate near domain boundaries, resulting in domain wall pinning. No evidence of relaxor behavior was observed, rather long-range ferroelectric order was preserved and "wavy" domain morphologies were found. However, for higher valent substituents which were essentially quenched from temperatures above that of the ferroelectric phase transformation, relaxor behavior and polar nanodomains were found.;Ionic radii effects were also found to influence the structure-property relations of both ferroelectrics and antiferroelectrics. Smaller A-site "donors" had a stronger tendency to occupy B-sites than larger ones, resulting in increased domain wall pinning, and ferroelectric stability with decreasing radii. In the antiferroelectric phase, larger A-site and smaller B-site substituents stabilized the rhombohedral ferroelectric phase. Valence considerations were found to significantly enhance the changes in antiferroelectric-ferroelectric stability.;The studies on the dynamic behaviors of higher valent modified PZT revealed the presence of strong nonlinearities and induced relaxor characteristics under moderate AC drive for lower La-content compositions. TEM investigations demonstrated a breakdown of ferroelectric domains with increasing AC drive, resulting in anomalous AC field effects.