Ferroelectric Mesocrystals of Bismuth Sodium Titanate: Formation Mechanism, Nanostructure, and Application to Piezoelectric Materials

Abstract

Ferroelectric mesocrystals of Bi0.5Na0.5TiO3 (BNT) with [100]-crystal-axis orientation were successfully prepared using a topotactic structural transformation process from a layered titanate H1.07Ti1.73O4·nH2O (HTO). The formation reactions of BNT mesocrystals in HTO-Bi2O3-Na2CO3 and HTO-TiO2-Bi2O3-Na2CO3 reaction systems and their nanostructures were studied by XRD, FE-SEM, TEM, SAED, and EDS, and the reaction mechanisms were given. The BNT mesocrystals are formed by a topotactic structural transformation mechanism in the HTO-Bi2O3-Na2CO3 reaction system and by a combination mechanism of the topotactic structural transformation and epitaxial crystal growth in the HTO-TiO2-Bi2O3-Na2CO3 reaction system, respectively. The BNT mesocrystals prepared by these methods are constructed from [100]-oriented BNT nanocrystals. Furthermore, these reaction systems were successfully applied to the fabrication of [100]-oriented BNT ferroelectric ceramic materials. A BNT ceramic material with a high degree of orientation, high relative density, and small grain size was achieved.

Optimization of preparation conditions of highly textured piezoelectric (Bi_0.5K_0.5)TiO₃ ceramics

“…The development of ©100ª-orientation in (Bi 0.5 Na 0.5 )TiO 3 ceramics prepared using HTOBi 2 O 3 Na 2 CO 3 reaction system has been explained by an in situ topotactic transformation reaction and an epitaxial growth mechanism. 37) Likewise, the formation of oriented BKT ceramics is expected to proceed by a topotactic transformation reaction of plate-like HTO particles with Bi and K matrix components into BKT nanoparticles and then to plate-like BKT particles by the epitaxial growth mechanism followed by the growth of the oriented plate-like BKT particles. Temperature programs during calcination/sintering have been reported to affect the epitaxial crystal growth reaction in the textured Bibased ceramics fabricated using HTO template particles.…”

“…The formation of such small particles by the collapse of large plate-like particles with increasing the calcination/sintering temperature was reported for a HTO Bi 2 O 3 Na 2 CO 3 reaction system. 37) The SEM image of the With optimizing the preparation conditions such as the mixing procedure of the matrix and template particles with a binder solution, the temperature programs for binder removal and sintering, and the sintering conditions, the single perovskite-phase and highly textured BKT ceramics were successfully fabricated. That is, the suppression of the sintering-associated-samples' bending via weighted sintering resulted in a higher degree of texturing (F 100 = 92%).…”

Mesostructured crystals: Growth processes and features

“…The apparent piezoelectric constant d33 value estimated from a unipolar strain−electric field curve is larger than that reported for the non-oriented Bi0.5Na0.5TiO3. This result suggests that the oriented architecture with a small grain size is promising for high-performance piezoelectric materials [129].…”

Mesocrystals and Their Related Structures as intermediates between single crystals and polycrystals

“…This result suggests that the oriented architecture with small grain size is promising for the high-performance piezoelectric materials. 137) …”