Morphotropic phase boundary (MPB) composition 0.94Na0.5Bi0.5TiO3–0.06BaTiO3 (NBT–6BT) has received industrial acceptance in certain aspects such as ultrasonic cleaners to replace those of lead-based systems. While detailed structure–property analysis on NBT–6BT is mostly confined to room temperature and above, less attention is paid with regard to their structure and property understanding below room temperature. In this work, utilizing the complementarity of Raman spectroscopy, x-ray diffraction, and neutron powder diffraction, we unravel low temperature polar-structural behavior of the MPB composition. While x-ray diffraction shows the persistence of a cubic like global structure in the temperature interval from 300 to 100 K, neutron diffraction reveals a structural crossover from long period modulated to non-modulated P4bm + R3c phase coexistence at ∼150 K. We show that the tendency of growing ferroelectric ordering with reducing temperature is responsible for the structural crossover. Concurrence of weak anomaly in dielectric loss (tan δ) at the same temperature seems to be correlated to the structural crossover.

中文翻译：

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Na0.5Bi0.5TiO3–BaTiO3的同形相界在低温下从长周期调制到非调制类立方相的结构交叉

变相相界 (MPB) 成分 0.94Na0.5Bi0.5TiO3–0.06BaTiO3 (NBT–6BT) 在某些方面已获得工业认可，例如超声波清洗器以取代铅基系统。虽然对 NBT-6BT 的详细结构-性能分析主要限于室温及以上，但很少有人关注它们在室温以下的结构和性能理解。在这项工作中，我们利用拉曼光谱、X 射线衍射和中子粉末衍射的互补性，揭示了 MPB 组合物的低温极性结构行为。虽然 X 射线衍射显示在 300 到 100 K 的温度区间内存在立方体状的全局结构，中子衍射揭示了从长周期调制到非调制 P4bm + R3c 相共存的结构交叉，在~150 K。我们表明，随着温度降低，铁电有序性增长的趋势是结构交叉的原因。相同温度下介电损耗（tanδ）的弱异常的并发似乎与结构交叉有关。