Polymorphism, structural characterisation and electrical properties of Na2Nb4O11
Masó, Nahum, Woodward, David I., Várez, Alejandro and West, Anthony R.. (2011) Polymorphism, structural characterisation and electrical properties of Na2Nb4O11. Journal of Materials Chemistry, Vol.21 (No.32). pp. 12096-12102. ISSN 0959-9428Full text not available from this repository.
Official URL: http://dx.doi.org/10.1039/c1jm11848j
Structural characterisation of Na(2)Nb(4)O(11) powder has been carried out by Rietveld refinement of neutron powder diffraction data in the temperature range 10-573 K and measurements of second harmonic generation in the range 75 to 450 K. The space group changes from R (3) over barc to C2/c on cooling through a phase transition at similar to 380 K. The origin of the phase transition in Na(2)Nb(4)O(11) is mainly related to distortion of some Nb(1)O(7) pentagonal bipyramids within the equatorial plane whereas other Nb(2) O(7) pentagonal bipyramids become almost regular. Although Na(2)Nb(4)O(11) ceramics show a maximum permittivity of similar to 150 at similar to 380 K and frequency-independent permittivity below this temperature, the room temperature polymorph is not ferroelectric. Comparison of the high and room temperature structures shows clear evidence of antiparallel atomic displacements in the room temperature structure and, therefore, a tendency towards low temperature antiferroelectric behaviour. A comparison is also made with the structurally-related ferroelectric Ag(2)Nb(4)O(11).
|Item Type:||Journal Article|
|Subjects:||Q Science > QC Physics
Q Science > QD Chemistry
T Technology > TP Chemical technology
|Divisions:||Faculty of Science > Physics|
|Library of Congress Subject Headings (LCSH):||Polymorphism (Crystallography), Powders -- Electric properties, Ferroelectricity, Rietveld method|
|Journal or Publication Title:||Journal of Materials Chemistry|
|Publisher:||Royal Society of Chemistry|
|Page Range:||pp. 12096-12102|
|Funder:||Engineering and Physical Sciences Research Council (EPSRC)|
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