The properties of lead zirconate titanate (PZT) ceramics are determined by
the microstructure and chemical homogeneity of Zr, Ti, and dopants within t
he grains as well as the presence of secondary grain boundary phases. Stoic
hiometric 53/47 PZT and compositions with 3 mol% PbO excess were prepared b
y the mixed-oxide process, and were densified by pressureless sintering in
oxygen, The influence of PbO content and different La concentrations on the
densification behavior was analyzed by dilatometric measurements. Quantita
tive image analysis showed a different relative density and grain size depe
ndence for samples containing >0.5 mol% additives compared to samples with
<0.5 mol% La. On the basis of a model experiment and by using different ana
lytical methods (microprobe analysis, HRTEM, STEM, and Anger spectroscopy)
three types of inhomogeneities could be detected in conventionally prepared
PZT ceramics: the existence of Ti and La enrichment in the core of PZT gra
ins, and PbO-rich secondary phases in triple junctions as well as in grain
boundary films, The results of the microstructural characterization and the
analysis of the densification behavior were finally combined to deduce a s
intering model based on a Pb-vacancy concentration gradient within the PZT
grains.