Abstract
Structure, phase transition, and dielectric relaxor behavior have been investigated in morphotropic phase boundary compositions of (1−x)(Bi0.5Na0.5)TiO3-xBaTiO3 ceramics for x=0.06, 0.07, and 0.075. In-situ structural thermal stability has been analyzed by using high-resolution synchrotron X-ray diffraction as a function of temperature. A transition sequence of rhombohedral+tetragonal−tetragonal−cubic phases is observed upon heating. The “rhombohedral+tetragonal” indicates a coexistence of rhombohedral R3c and tetragonal P4bm phases. The two-phase coexistence extends from room temperature to 200°C. Zero-field dielectric permittivity reveals a frequency dispersion at low temperature region (T<Tm) and polar nanoregions below Burns temperature (TB). The two-phase coexistence plays a vital role for frequency dispersion below Tm. Dielectric spectra of pre-poled samples reveal a field-induced ferroelectric−relaxor phase transition at depolarization temperature Td.
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