  The most characteristic functional property of antiferroelectric materials is
the possibility to induce a phase transition from a non-polar to a polar phase
by an electric field. Here, we investigate the effect of this field-induced
phase transition on the birefringence change of $PbZr_{0.95}Ti_{0.05}O_{3}$. We
use a transparent polycrystalline $PbZr_{0.95}Ti_{0.05}O_{3}$ film grown on
$PbTiO_{3}/HfO_{2}/SiO_{2}$ with interdigitated electrodes to directly
investigate changes in birefringence in a simple transmission geometry. In
spite of the polycrystalline nature of the film and its moderate thickness, the
field-induced transition produces a sizeable effect observable under a
polarized microscope. The film in its polar phase is found to behave like a
homogeneous birefringent medium. The time evolution of this field-induced
birefringence provides information about irreversibilities in the
antiferroelectric switching process and its slow dynamics. The change in
birefringence has two main contributions, one that responds briskly (~ 0.5 s),
and a slower one that rises and saturates over a period of as long as 30
minutes. Possible origins for this long saturation and relaxation times are
discussed.
