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Phase Formation, Crystal Chemistry, and Properties in the Magnetic Dielectric System Bi2O3-Fe2O3-Nb2O5



M W. Lufaso, Terrell A. Vanderah, I M. Pazos, Igor Levin, Juan C. Nino, Virgil Provenzano, Peter K. Schenck, Robert S. Roth


Subsolidus phase relations have been determined for the Bi2O3-Fe2O3-Nb2O5 system in air (900-1075 C). Three new ternary phases were observed Bi3Fe0.5Nb1.5O9 with an Aurivillius-type structure, and two phases with approximate stoichiometries Bi17Fe2Nb31O106 and Bi17Fe3Nb30O105 that appear to be structurally related to Bi8Nb18O57. The fourth ternary phase found in this system is pyrochlore. X-ray powder diffraction data confirmed that all Bi-Fe-Nb-O pyrochlores form with displacively disordered A2O networks. A structural refinement of the pyrochlore 0.4400:0.2700:0.2900 Bi2O3:Fe2O3:Nb2O5 using neutron powder diffraction data is reported. Bi-Fe-Nb-O pyrochlores exhibited overall paramagnetic behavior with large negative Curie-Weiss temperature intercepts, slight superparamagnetic effects, and depressed observed moments compared to high-spin, spin-only values. The single-phase pyrochlore with composition Bi1.657Fe1.092Nb1.150O7 exhibited low-temperature dielectric relaxation similar to that observed for Bi1.5Zn0.92Nb1.5O6.92; at 1 MHz and 200 K the relative permittivity was 125. Bi-Fe-Nb-O pyrochlores were readily obtained as single crystals and also as textured thin films used pulsed laser deposition.
Journal of Solid State Chemistry


Bi2O3-Fe2O3-Nb2O5, phase diagram, phase equilibria


Lufaso, M. , Vanderah, T. , Pazos, I. , Levin, I. , Nino, J. , Provenzano, V. , Schenck, P. and Roth, R. (2006), Phase Formation, Crystal Chemistry, and Properties in the Magnetic Dielectric System Bi<sub>2</sub>O<sub>3-</sub>Fe<sub>2</sub>O<sub>3-</sub>Nb<sub>2</sub>O<sub>5</sub>, Journal of Solid State Chemistry (Accessed May 30, 2023)
Created June 21, 2006, Updated October 12, 2021