Skip to main content

NOTICE: Due to a lapse in annual appropriations, most of this website is not being updated. Learn more.

Form submissions will still be accepted but will not receive responses at this time. Sections of this site for programs using non-appropriated funds (such as NVLAP) or those that are excepted from the shutdown (such as CHIPS and NVD) will continue to be updated.

U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Subsolidus Phase Equilibria and Properties in the Magnetic Dielectric System Bi2O3:Mn2O3+x:Nb2O5

Published

Author(s)

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

Abstract

Subsolidus phase relations have been determined for the Bi-Mn-Nb-O system in air (750-900 C). Phases containing Mn2+, Mn3+, and Mn4+ were all observed. Ternary compound formation was limited to pyrochlore, which formed a substantial solid solution region at Bi-deficient stoichiometries. X-ray powder diffraction data confirmed that all Bi-Mn-Nb-O pyrochlores form with displacively disordered A2O networks. A structural refinement of the pyrochlore 0.4000:0.3000:0.3000 Bi2O3:Mn2O3 x:Nb2O5 using neutron powder diffraction data is reported with A and O atoms displaced (0.36 and 0.33 , respectively) from ideal positions to 96g sites, and with Mn2+ on A-sites and Mn3+ on B-sites (Bi1.6Mn2+0.4(Mn3+0.8Nb1.2)O7, Fdm (#227), a = 10.478(1) ). The displacive disorder is crystallographically analogous to that reported for Bi1.5Zn0.92Nb1.5O6.92. EELS spectra for this pyrochlore were consistent with an Mn oxidation between 2+ and 3+. Bi-Mn-Nb-O pyrochlores exhibited overall paramagnetic behavior with negative Curie-Weiss temperature intercepts, slight superparamagnetic effects, and depressed observed moments. At 300 K and 1 MHz the relative dielectric permittivity of Bi1.600Mn1.200Nb1.200O7 was 128 with tan d = 0.05; however, at lower frequencies the sample was conductive which is consistent with the presence of mixed-valent Mn. Bi-Mn-Nb-O pyrochlores were readily obtained as single crystals and also as textured thin films used pulsed laser deposition.
Citation
Journal of Solid State Chemistry
Volume
179
Issue
11

Keywords

Bi-Mn-Nb-O, bismuth manganese niobates, dielectric properties, displacive disorder, phase diagram, phase equilibria, pyrochlore

Citation

Vanderah, T. , Lufaso, M. , Adler, A. , Levin, I. , Nino, J. , Provenzano, V. , Schenck, P. and Roth, R. (2006), Subsolidus Phase Equilibria and Properties in the Magnetic Dielectric System Bi<sub>2</sub>O<sub>3</sub>:Mn<sub>2</sub>O<sub>3+x</sub>:Nb<sub>2</sub>O<sub>5</sub>, Journal of Solid State Chemistry (Accessed October 11, 2025)

Issues

If you have any questions about this publication or are having problems accessing it, please contact [email protected].

Created July 20, 2006, Updated February 19, 2017
Was this page helpful?