Bi-fluctuation in Na_0.5Bi_0.5TiO₃ ferroelectric ceramics with abnormal relaxor behaviour

ABSTRACT

The existence of Bi-fluctuation dispersing in Na_0.5Bi_0.5TiO₃ (NBT) relaxor ferroelectric is hinted in other recent studies. However, this fluctuation has not been directly observed yet. We introduce the Bi-rich nano-regions with different sizes in a series of NBT ceramics by the slight excess of Bi³⁺ content. The crystal symmetries of the Bi-rich nano-regions and the NBT matrix are rhombohedral. The lattice parameters of the nano-regions are larger than those of the matrix in NBT ceramics, which were confirmed by the X-ray diffraction Rietveld refinement, TEM techniques and first-principles calculation. Also, the disorder-induced nano-regions appearing as Bi-fluctuation are associated with the complex phase transitions and the high-frequency relaxor behaviour of NBT suggested by the dielectric measurements and Raman spectra.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research has been funded by National Natural Science Foundation of China (NSFC, Grant Nos. 51472063, 51772065 and 51621091).