Effect of temperature on grain size, phase composition, and electrical properties in the relaxor-ferroelectric-system Pb(Ni1/3Nb2/3)O-3-Pb(Zr,Ti)O-3

Relaxor ferroelectrics near the morphotropic phase boundary were
prepared by pressureless sintering at various temperatures in order to
study the influence of grain size on phase composition and electrical
properties. Investigations of the microstructure indicate an increase
in grain size from 0.5 to 3.7 mu m when the sintering temperature is
increased from 1050 to 1290 degrees C. The corresponding phase
composition is changed from predominantly rhombohedral for small grain
sizes to more than 80% tetragonal for larger grain sizes. Low-voltage
measurements of poled and unpoled samples correlate well with the x-ray
diffraction results. An increase of the permittivity after poling is
found for samples with a high tetragonal phase content, while samples
with a predominantly rhombohedral composition show a slight decrease.
The remanent polarization as well as uni- and bipolar strain increase
with increasing sintering temperature by a factor larger than 2,
whereas the coercive field E-C remains nearly constant for all
sintering conditions.