Rotational intersite displacement of disordered lead atoms in a relaxor ferroelectric during piezoelectric lattice straining and ferroelectric domain switching

We report results of the time-resolved x-ray structure analysis of a relaxor ferroelectric single crystal under an alternating electric field. The time dependence of the lattice strain, atomic displacements, and ferroelectric domain volumes in a $0.955\mathrm{Pb}(\mathrm{Z}{\mathrm{n}}_{1/3}\mathrm{N}{\mathrm{b}}_{2/3}){\mathrm{O}}_{3}\ensuremath{-}0.045\mathrm{PbTi}{\mathrm{O}}_{3}$ (PZN-4.5PT) single crystal during piezoelectric lattice straining and ferroelectric domain switching is revealed. The lattice strain induced by an electric field is consistent with that expected from the piezoelectric constants. The crystal mosaicity is momentarily increased by a nucleation of nanosized ferroelectric domains when the polarization switching starts. The nucleated ferroelectric domains grow with the time constant of $\ensuremath{\tau}=14\phantom{\rule{0.16em}{0ex}}\ensuremath{\mu}\mathrm{s}$. An intersite displacement of the disordered Pb atoms observed in those site occupancies suggests that a rotational intersite displacement of Pb atoms is easily induced by an electric field and causes continuous rotation of the spontaneous polarization. The rotational intersite displacement of Pb atoms is essential for the large piezoelectric lattice strain and fatigue-free ferroelectric domain switching.