  In the archetypal antiferroelectric PbZrO3, antiparallel electric dipoles
cancel each other, resulting in zero spontaneous polarisation at the
macroscopic level. Yet in actual hysteresis loops, the cancellation is rarely
perfect and some remnant polarization is often observed, suggesting the
metastability of polar phases in this material. In this work, using
aberration-corrected scanning transmission electron microscopy methods on a
PbZrO3 single crystal, we uncover the coexistence of the common
antiferroelectric phase and a ferrielectric phase featuring an electric dipole
pattern of "up down up". This dipole arrangement, predicted by Aramberri et al.
(2021) to be the ground state of PbZrO3 at 0K, appears at room temperature in
the form of translational boundaries that aggregate to form wider stripe
domains of the polar phase embedded within the antiferroelectric matrix.
