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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
Title:
$Bi_{4}LnNb_{3}O_{15}$ (Ln = La, Pr, Nd) and $Bi_{4}LaTa_{3}O_{15}$: New intergrowth Aurivillius related phases
Archive:
Eprints@iisc
Author(s):
Mandal, Tapas Kumar
Augustine, Saji
Gopalakrishnan, J
Boullay, Ph
Augustine, Saji
Gopalakrishnan, J
Boullay, Ph
Date:
2005-06-01
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 $Ta_{2}O_{5}$.
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Solid State & Structural Chemistry Unit
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Type:
Journal Article
Format:
pdf http://eprints.iisc.ernet.in/archive/00003498/01/A110.pdf
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