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$Bi_{4}LnNb_{3}O_{15}$ (Ln = La, Pr, Nd) and $Bi_{4}LaTa_{3}O_{15}$: New intergrowth Aurivillius related phases

Mandal, Tapas Kumar and Augustine, Saji and Gopalakrishnan, J and Boullay, Ph (2005) $Bi_{4}LnNb_{3}O_{15}$ (Ln = La, Pr, Nd) and $Bi_{4}LaTa_{3}O_{15}$: New intergrowth Aurivillius related phases. In: Materials Research Bulletin, 40 (6). pp. 920-927.

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Abstract

We describe the synthesis and characterization of new intergrowth Aurivillius related phases, $Bi_{4}LnNb_{3}O_{15}$ (Ln = La, Pr, Nd) and $Bi_{4}LaTa_{3}O_{15}$. Both powder X-ray diffraction and electron microscopy investigations show that the compounds adopt orthorhombic structures with the cell parameters a similar to 5.5 angstrom, b ~ 5.5 angstrom and c ~ 20.9 angstrom, suggesting an ordered intergrowth structure that consists of n = 1 $[Bi_{2}NbO_{6}]^{-}$ and n = 2 $[Bi_{2}LnNb_{2}O_{9}]^{+}$ Aurivillius fragments which are stacked alternately along the c-axis. The oxides do not show a second harmonic generation (SHG) response toward 1064 nm laser radiation; they do notshow a ferroelectric-paraelectric transition either between 30 and 900 centigrade in dielectric measurements, indicating a centrosymmetric structure.Optical absorption studies show that the intergrowth phases possess considerably smaller band gaps than the parent $Nb_{2}O_{5}$ and $Ta_{2}O_{5}$.

Item Type: Journal Article
Additional Information: Copyright for this article belongs to Elsevier.
Keywords: A. oxides;A. layered compounds;C. X-ray diffraction;C. electron diffraction;C. electron microscopy;D. optical properties
Department/Centre: Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited: 10 Aug 2005
Last Modified: 19 Sep 2010 04:19
URI: http://eprints.iisc.ernet.in/id/eprint/3498

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