Synchrotron XRD: Enlightening the processing-properties correlation in (Bi0.5Na0.5)0.96Ba0.04TiO3 (BNBT4) ceramics

High-resolution X-ray diffraction is applied to investigate macro and micro crystal structure changes across different synthesis routes in BNBT4 piezoceramics. Synthetic powders were obtained by conventional sol-gel auto combustion and mixed oxides methods; then samples were sintered by combining hot uniaxial pressing and subsequent recrystallization. The crystal structure of the ceramic obtained by sol-gel is rhombohedral (R3c) and the one obtained from mixed oxides is monoclinic (Cc). In the sol-gel case, a poling process produces an intense 001 texture parallel to the polarizing electric field. Poling the mixed oxides ceramics quickly transforms the structure from monoclinic to rhombohedral while texture and anisotropic micro-strains develop further as the poling increases. A correlation between detected structural transformations and variations in selected physical properties is suggested. The anisotropy of the critical temperatures for dielectric and electromechanical depolarization is lower for mixed oxides ceramics than for sol-gel ceramics.

Automated summary

This study investigates the crystal structure changes of BNBT4 piezoceramics synthesized through different routes using high-resolution X-ray diffraction. It is found that the ceramic obtained from sol-gel method has a rhombohedral structure, while the one obtained from mixed oxides method has a monoclinic structure. Poling process can produce texture in the sol-gel ceramic, and poling the mixed oxides ceramic can quickly transform the structure from monoclinic to rhombohedral, with further development of texture and anisotropic micro-strains. The anisotropy of critical temperatures for dielectric and electromechanical depolarization is lower in the mixed oxides ceramics compared to the sol-gel ceramics.