Department of Computer Science and Electrical Engineering, Graduate School of Science and Technology, Kumamoto University, 2-39-1, Kurokami, Chuo-ku, Kumamoto, 860-8555, Japan.
International Research Organization for Advanced Science & Technology (IROAST), Kumamoto University, 2-39-1, Kurokami, Chuo-ku, Kumamoto, 860-8555, Japan.
Sci Rep. 2023 Apr 25;13(1):6771. doi: 10.1038/s41598-023-33975-6.
Sodium niobate (NaNbO) is a potential material for lead-free dielectric ceramic capacitors for energy storage applications because of its antipolar ordering. In principle, a reversible phase transition between antiferroelectric (AFE) and ferroelectric (FE) phases can be induced by an application of electric field (E) and provides a large recoverable energy density. However, an irreversible phase transition from the AFE to the FE phase usually takes place and an AFE-derived polarization feature, a double polarization (P)-E hysteresis loop, does not appear. In this study, we investigate the impact of chemically induced hydrostatic pressure (p) on the phase stability and polarization characteristics of NaNbO-based ceramics. We reveal that the cell volume of Ca-modified NaNbO [(CaNaV)NbO], where V is A-site vacancy, decreases with increasing x by a positive p. Structural analysis using micro-X-ray diffraction measurements shows that a reversible AFE-FE phase transition leads to a double P-E hysteresis loop for the sample with x = 0.10. DFT calculations support that a positive p stabilizes the AFE phase even after the electrical poling and provides the reversible phase transition. Our study demonstrates that an application of positive p is effective in delivering the double P-E loop in the NaNbO system for energy storage applications.
铌酸钠（NaNbO）是一种用于储能应用的无铅介电陶瓷电容器的潜在材料，因为它具有反铁电（AFE）有序。原则上，通过施加电场（E）可以诱导反铁电（AFE）和铁电（FE）相之间的可逆相转变，并提供大的可恢复能量密度。然而，通常会发生从 AFE 到 FE 相的不可逆相转变，并且不会出现 AFE 衍生的极化特征，即双极化（P）-E 滞后环。在这项研究中，我们研究了化学诱导的静压（p）对基于 NaNbO 的陶瓷的相稳定性和极化特性的影响。我们揭示了 A 位空位 V 的 Ca 改性 NaNbO [（CaNaV）NbO] 的晶胞体积随 x 的增加呈正 p 减小。使用微 X 射线衍射测量进行的结构分析表明，对于 x = 0.10 的样品，可逆的 AFE-FE 相转变导致双 P-E 滞后环。DFT 计算支持正 p 即使在电极化后也能稳定 AFE 相，并提供可逆相转变。我们的研究表明，施加正 p 可有效在 NaNbO 系统中提供用于储能应用的双 P-E 环。
