The Global and Local Symmetries of Nanostructured Ferroelectric Relaxor 0.94(Bi0.5Na0.5)TiO3 0.06BaTiO3

Abstract

Novel submicrometer-grained 0.94(Bi0.5Na0.5)TiO3 ¿ 0.06 BaTiO3 ceramic, prepared from nanopowder by a combination of hot-pressing and recrystallization, is investigated by high-resolution synchrotron x-ray diffraction and x-ray absorption near-edge spectroscopy (XANES). The simplest and best-fitting Rietveld refinement of the performed wide-Q diffraction experiment corresponds to a three-phase system formed by a ferroelectric rhombohedral R3c phase, a globally cubic P-3mm phase and a small amount of nanosized (~12 nm) quasi-cubic phase. The globally cubic phase and the nanosized one built up a complex, nanostructured, configuration that accounts for the reported dielectric relaxor behavior. XANES reveals that the departures from centro-symmetry at the unit cell scale for the precursor powder and for the sintered ceramic are practically the same.