Electric-field-induced, antiferroelectric-ferroelectric (AFE-FE) phase transitions are common for AFE materials. To date, the strain and preferred orientation evolution as well as the role of the intermediate FE state during the successive AFE-FE-AFE phase transitions has not been clear. To this end, we have herein studied a typical AFE Pb0.97La0.02(Zr0.56Sn0.33Ti0.11)O3 (PLZST) material using in-situ neutron diffraction. It is striking that the AFE-FE phase transition is not fully reversible: in the electric-field-induced FE state, the induced strain exhibits an elliptical distribution, which in turn leads to significant preferred orientation in the final AFE state after withdrawal of the applied electric-field. The ω-dependent neutron diffraction patterns show clear evidence of the induced strain distribution and associated preferred orientation arising from the AFE-FE phase transition. The current work also provides an explanation for several temperature and electric-field dependent dielectric anomalies as well as unrecovered strain change which appear in AFE materials after exposure to sufficiently high electric fields.
Modern ab initio calculations have become increasingly accurate
for predicting the symmetry of crystal structures; however, the standard
methods usually only determine the 0 K static configuration and therefore
misrepresent structures where dynamics play a key role. In this work,
we demonstrate a clear experimental example of this phenomenon in
the AlPO4-5 molecular sieve where the average high-symmetry P6cc structure emerges from local dynamics
involving corner-sharing tetrahedra. Quasielastic and inelastic neutron
scattering experiments were conducted to clarify the thermally activated
motions between 1.5 and 300 K. Through comparison with ab
initio molecular dynamics, we explain why the theoretically
predicted structure is not observed in diffraction experiments. Instead,
the results indicate this material is an inorganic analogue of a plastic
crystal where thermal dynamics dictate the average symmetry.
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