  Interactions between grain boundaries and domain walls were extensively
studied in ferroelectric films and bicrystals. This knowledge, however, has not
been transferred to polycrystalline ceramics, in which the grain size
represents a powerful tool to tailor the dielectric and electromechanical
response. Here, we relate changes in dielectric and electromechanical
properties of a bulk polycrystalline Pb(Zr0.7Ti0.3)O3 to domain wall
interactions with grain boundaries. Samples with grain sizes in the range of
3.9 - 10.4 micrometers were prepared and their microstructure, crystal
structure, and dielectric/electromechanical properties were investigated. A
decreasing grain size was accompanied by a reduction in large-signal
electromechanical properties and an increase in small-signal dielectric
permittivity. High-energy diffraction analysis revealed increasing microstrains
upon decreasing the grain size, while piezoresponse force microscopy indicated
an increased local coercive voltage near grain boundaries. The changes in
properties were thus related to strained material volume close to the grain
boundaries exhibiting reduced domain wall dynamics.
