Characterization of ternary compounds in the BaO:Fe{sub 2}O{sub 3}:TiO{sub 2} system: Ba{sub 6}Fe{sub 45}Ti{sub 17}O{sub 106} and BaFe{sub 11}Ti{sub 3}O{sub 23}

Journal Article · Mon Mar 01 00:00:00 EST 1999 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1006/jssc.1999.8075· OSTI ID:338442

Vanderah, T A; Wong-Ng, W; Toby, B H; Shull, R D; Roth, R S ^[1]; Browning, V M ^[2]; Geyer, R G ^[3]

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1. National Inst. of Standards and Technology, Gaithersburg, MD (United States). Materials Science and Engineering Lab.
2. Naval Research Lab., Washington, DC (United States)
3. National Inst. of Standards and Technology, Boulder, CO (United States)

Single crystals of Ba{sub 6}Fe{sub 45}Ti{sub 17}O{sub 106} and BaFe{sub 11}Ti{sub 3}O{sub 23} were obtained as major and minor coproducts, respectively, by slow-cooling an off-stoichiometric BaO:Fe{sub 2}O{sub 3}:TiO{sub 2} melt. The former compound exhibits variable stoichiometry, Ba{sub 6}Fe{sub 48{minus}x}Ti{sub 14+x}O{sub 106}, with the Fe:Ti ratio dependent upon the partial pressure of oxygen. The value of x corresponds to the equivalents of reduction that occur to maintain electroneutrality as the Ti-content increases. When prepared in air, this phase occurs at x = 3 with the stoichiometry Ba{sub 6}Fe{sub 45}Ti{sub 17}O{sub 106}, while in 100% oxygen the x-value approaches zero with the resulting stoichiometry Ba{sub 6}Fe{sub 48}Ti{sub 14}O{sub 106} (all Fe{sup 3+} and Ti{sup 4+}). The structures of Ba{sub 6}Fe{sub 45}Ti{sub 17}O{sub 106} and BaFe{sub 11}Ti{sub 3}O{sub 23} were solved using single-crystal X-ray diffraction methods. Ba{sub 6}Fe{sub 45}Ti{sub 17}O{sub 106} was prepared in polycrystalline form, and further structural details, including accurate Fe/Ti occupancy factors, were determined by a combined refinement using neutron and synchrotron powder diffraction data. (Ba{sub 6}Fe{sub 45}Ti{sub 17}O{sub 106}: Space group C2/m (No 12); a = 19.390(1) {angstrom}, b = 20.260(1) {angstrom}, c = 10.076(1) {angstrom}, {beta} = 105.27(1){degree}; V = 3818.5(3) {angstrom}{sup 3}; Z = 2; {rho}{sub calc} = 5.08 g/cm{sup 3}. Ba{sub 6}Fe{sub 11}Ti{sub 3}O{sub 23}: Space group C2/c (No 15); a = 19.56(1) {angstrom}, b = 8.6614(7) {angstrom}, c = 10.120(1) {angstrom}, {beta} = 105.62(1){degree}; V = 1651.1(3) {angstrom}{sup 3}; Z = 4; {rho}{sub calc} = 5.08 g/cm{sup 3}.) The magnetic behavior of Ba{sub 6}Fe{sub 45}Ti{sub 17}O{sub 106} above room temperature up to 1073 K was found to obey the Curie-Weiss law, which indicated a small effective magnetic moment (34 {mu}{sub B} per mole Ba{sub 6}Fe{sub 45}Ti{sub 17}O{sub 106}) and a large negative temperature intercept ({minus}806 K). Electrical resistivity measurements between room temperature and 120 K revealed nonmetallic behavior with an activation energy on the order of 0.17 eV. At 347 MHz under ambient conditions, Ba{sub 6}Fe{sub 45}Ti{sub 17}O{sub 106} exhibited a relative permittivity of 24 and a dielectric loss tangent of 0.10.

• OSTI ID: 338442
• Journal Information: Journal of Solid State Chemistry, Vol. 143, Issue 2; Other Information: PBD: Mar 1999
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CRYSTAL STRUCTURE
MAGNETIC PROPERTIES
ELECTRICAL PROPERTIES
BARIUM OXIDES
IRON OXIDES
TITANIUM OXIDES
STOICHIOMETRY
X-RAY DIFFRACTION
LATTICE PARAMETERS
EXPERIMENTAL DATA