The Global and Local Symmetries of Nanostructured Ferroelectric Relaxor 0.94(Bi_0.5Na_0.5)TiO₃ – 0.06BaTiO₃

Abstract

Novel submicrometer-grained 0.94(Bi_0.5Na_0.5)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 Pmm 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.

Acknowledgments

Authors wish to thank Prof. Jürgen Rodel, Institute of Materials Science, Technische Universität Darmstadt, Germany, for his advice. Portions of this research were carried out at the Stanford Synchrotron Radiation Lightsource, a national user facility operated by Stanford University on behalf of the U.S. Department of Energy, Office of Basic Energy Sciences. Authors express their gratitude to Elisa Mercadelli and Carmen Galassi, from the Institute of Science and Technology for Ceramics, Faenza, Italy, for the preparation of the starting BNBT nanopowders. LP and AG wish to thank Mr. José Luis Millán (FINNOVA 2010 grantee) for his technical assistance in the quantitative microstructural characterization.

Additional information

Funding

Support from CONACYT-CNPQ project 174391 is recognized. Spanish CSIC project #201060E069 is acknowledged.