Sub-lattice polarization states in anti-ferroelectrics and their relaxation process

We report studies of quasi-remanent polarization states in Pb0.99Nb0.02 [(Zr0.57Sn0.43) 0.94Ti0.06] 0.98O3 (PNZST) anti-ferroelectric ceramics and investigation of their relaxation effects using unique insitu electrically activated time-resolved Synchrotron X-ray powder diffraction (SXPD) and 119Sn Mössbauer Spectroscopy (MS). The SXPD patterns are consistent with a phase transition from quasi-tetragonal perovskite in 0V relaxed anti-ferroelectric state to rhombohedral distortion in ferroelectric state under saturating applied voltages of 2kV. The observed quasi-remanent polarization relaxation processes are due to the fact that tetragonal to rhombohedral distortion does not occur at the applied voltage required to access the quasi-remanent polarization states, and the tetragonal symmetry restored after the removal of the applied electric field is preserved. Since these quasi-remanent polarization states were seen as possibly suitable for memory applications, the implications of this study are that anti-ferroelectrics are more feasible for multi-state dynamic random access memories (DRAM), while their application to non-volatile memories requires development of more sophisticated "read-out" protocols, possibly involving dc electrical biasing.