To meet the increasing demand for environment-friendly, high-performance energy devices, sodium niobate (NaNbO3) is considered one of the most promising lead-free antiferroelectric (AFE) oxide perovskites for green energy storage applications. However, as disclosed by recent experimental reports, under an external electric field, the room-temperature AFE P phase of NaNbO3 has been demonstrated to undergo an irreversible phase transition to the ferroelectric (FE) Q phase. This puzzle challenges our current atomic-scale understanding of this field-induced AFE-to-FE transition, and thus hinders the widespread use of NaNbO3 in lead-free AFE energy storage devices. To unravel this puzzle, we perform first-principles density-functional theory calculations to establish phase stability maps of the NaNbO3 polymorphs determined from group-subgroup relations. For the first time, we identify two new key intermediates (P′ and Q′) via the symmetry-adapted phonon mode analysis based on high-symmetry cubic phase and minimum energy pathway transition state searches, that facilitate de novo phase transition pathways for the switching of polarization with significantly lowered energy barriers. By means of a phenomenological Landau-Devonshire model, we predict and explain why these new intermediates can rationalize the persistent lack of a double polarization-electric field hysteresis for NaNbO3 under an applied field. This sets the design platform for future precise engineering of NaNbO3 at the atomic-scale for lead-free AFE energy storage applications.
Bibliographical noteFunding Information:
We gratefully acknowledge support from the National Research Foundation of Korea under the Material Convergence Innovation Technology Development Program (2020M3D1A2102913) and the Ministry of Science and ICT under the Creative Materials Discovery Program (2018M3D1A1058536). Computational resources have been kindly provided by the KISTI Supercomputing Center (KSC-2021-CRE-0450) and the Australian National Computational Infrastructure (NCI).
© 2022 The Royal Society of Chemistry.
All Science Journal Classification (ASJC) codes
- Materials Chemistry