caa a22 4500 46792743X CHVBK 20180406152933.0 cr unu---uuuuu 170328e20060501xx s 000 0 eng 10.1134/S0020168506050165 doi (NATIONALLICENCE)springer-10.1134/S0020168506050165 Structure and dielectric properties of the Aurivillius phase Bi2.25Ca0.5Na0.25Nb2O9 [Elektronische Daten] [V. Vlasenko, A. Shuvaev, D. Drannikov, I. Pirog, I. Zarubin] A new layered perovskite-like bismuth-oxide compound with the Bi2.25Ca0.5Na0.25Nb2O9 stoichiometry (Aurivillius phase) has been synthesized in polycrystalline form. As shown by powder x-ray diffraction, Bi2.25Ca0.5Na0.25Nb2O9 has an orthorhombic structure (sp. gr. A21 am, no. 36) with unit-cell parameters a = 5.4845 Å, b = 5.4549 Å, and c = 24.9195 Å. Rietveld analysis has been used to determine the atomic positional parameters in its unit cell and the position of the niobium ions. Nb5+ has been shown to be displaced from the center position in the oxygen octahedra by ∼0.15 Å. The Nb K-edge extended x-ray absorption fine structure (EXAFS) spectrum of the new compound has been measured in the range 295 to 960 K. The 295-K EXAFS data have been used to evaluate the Nb-O bond lengths in the octahedra and the corresponding Debye-Waller factors. The bond lengths thus determined agree well with those inferred from powder x-ray data. With increasing temperature, the short Nb-O bonds become longer, while the long bonds become shorter. The dielectric properties of the new compound have been studied between room temperature and 1200 K at frequencies from 1 to 50 kHz. Bi2.25Ca0.5Na0.25Nb2O9 is shown to be a ferroelectric with a Curie temperature of 972 K. Pleiades Publishing, Inc., 2006 Vlasenko V. Research Institute of Physics, Rostov State University, pr. Stachki 194, 344090, Rostov-on-Don, Russia aut Shuvaev A. Research Institute of Physics, Rostov State University, pr. Stachki 194, 344090, Rostov-on-Don, Russia aut Drannikov D. Research Institute of Physics, Rostov State University, pr. Stachki 194, 344090, Rostov-on-Don, Russia aut Pirog I. Research Institute of Physics, Rostov State University, pr. Stachki 194, 344090, Rostov-on-Don, Russia aut Zarubin I. Research Institute of Physics, Rostov State University, pr. Stachki 194, 344090, Rostov-on-Don, Russia aut Inorganic Materials Nauka/Interperiodica 42/5(2006-05-01), 537-542 0020-1685 42:5<537 2006 42 10789 https://doi.org/10.1134/S0020168506050165 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1134/S0020168506050165 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Vlasenko V. Research Institute of Physics, Rostov State University, pr. Stachki 194, 344090, Rostov-on-Don, Russia aut NATIONALLICENCE 700 1- Shuvaev A. Research Institute of Physics, Rostov State University, pr. Stachki 194, 344090, Rostov-on-Don, Russia aut NATIONALLICENCE 700 1- Drannikov D. Research Institute of Physics, Rostov State University, pr. Stachki 194, 344090, Rostov-on-Don, Russia aut NATIONALLICENCE 700 1- Pirog I. Research Institute of Physics, Rostov State University, pr. Stachki 194, 344090, Rostov-on-Don, Russia aut NATIONALLICENCE 700 1- Zarubin I. Research Institute of Physics, Rostov State University, pr. Stachki 194, 344090, Rostov-on-Don, Russia aut NATIONALLICENCE 773 0- Inorganic Materials Nauka/Interperiodica 42/5(2006-05-01), 537-542 0020-1685 42:5<537 2006 42 10789 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer