Research Article
Structural, Optical, and Compactness Characteristics of
Nanocrystalline CaNb
2
O
6
Synthesized through an Autoigniting
Combustion Method
K. C. Mathai,
1
S. Vidya,
2
Annamma John,
2
Sam Solomon,
3
and J. K. Thomas
2
1
Department of Physics, St. Aloysius College, Edathua, Kerala 689573, India
2
Electronic Materials Research Laboratory, Department of Physics, Mar Ivanios College, iruvananthapuram, Kerala 695 015, India
3
Department of Physics, St. John’s College, Anchal, Kollam District, Kerala 691306, India
Correspondence should be addressed to J. K. omas; jkthomasemrl@yahoo.com
Received 31 May 2013; Revised 5 October 2013; Accepted 5 October 2013; Published 9 January 2014
Academic Editor: R. N. P. Choudhary
Copyright © 2014 K. C. Mathai et al. is is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Nanoparticles of calcium metaniobate compound are prepared by an autoigniting combustion technique and its structural, optical,
and dielectric properties are investigated. e X-ray diffraction, Fourier-transform Raman, and infrared studies reveal that calcium
metaniobate possesses phase pure orthorhombic columbite structure with space group of Pbcn. e average particle size of the
as-prepared nanoparticles obtained from both the Scherrer formula and transmission electron microscopy is ∼37 nm. e optical
band gap calculated from Tauc’s Plot is 3.25eV. Photoluminescence studies reveal that Calcium metaniobate can be used as an
idealphotoluminarmaterial. e powders are pelletised and sintered at an optimized temperature of 1350
∘
C in a short duration of
two hours, yielding a high density. e morphology of the sintered pellet is further examined using scanning electron microscopy.
e dielectric constant and loss factor values measured at 5MHz for a well-sintered Calcium metaniobate pellet are found to be
27.6 and 5.3 × 10
−4
respectively, at room temperature.
1. Introduction
Calcium metaniobate (CaNb
2
O
6
) crystallizes with orthor-
hombic columbite structure in the space group of Pbcn(60)
and is a strong source of coherent light which can be
useful in applications of holography [1]. CaNb
2
O
6
crystal
possesses a low-symmetry crystal structure and the Ca and
Nb cations are at the centre of the octahedra surrounded
by six oxygen atoms in the CaNb
2
O
6
columbite structure.
e CaO
6
and NbO
6
octahedra form independent zigzag
chains by sharing edges and the chains are connected by
sharing corners in the order of CaO
6
chain-NbO
6
chain-
NbO
6
chain [2, 3]. CaNb
2
O
6
has good mechanical, dielectric,
and thermal properties like thermal conductivity, specific
heat, and thermal coefficient of expansion making it suitable
for laser crystal host, substrates for electronic circuits, and
so forth [1, 3]. e photocatalytic activity of CaNb
2
O
6
is
studied by a number of researchers and Cho et al. reported its
enhanced photocatalytic activity for producing H
2
from pure
water under UV irradiation [4–7]. CaNb
2
O
6
also exhibits
strong blue luminescence emission under UV light irradia-
tion at 300 K. CaNb
2
O
6
also possesses interesting properties,
namely, piezoelectricity, pyroelectricity, and electrooptic and
nonlinear optical activity [8–11]. e compacted calcium-
metaniobate (CaNb
2
O
6
) is a good dielectric material for
microwave dielectric applications [12–14]. CaNb
2
O
6
, a sub-
component of the complex perovskite family A(B
1/3
B
2/3
)O
3
prepared by the conventional route, has been studied for
its microwave dielectric properties [15–17]. Generally, the
relative band positions, optical band gaps, and so forth, in
niobate compounds, are affected by the characteristic of their
crystal structure, octahedral distortion, and the ionic size
of cations [7]. e various synthesis techniques employed
for the preparation of CaNb
2
O
6
are conventional solid state
route, hydrothermal synthesis, solvothermal process, and sol-
gel technique [6, 7, 17, 18].
Hindawi Publishing Corporation
Advances in Condensed Matter Physics
Volume 2014, Article ID 735878, 6 pages
http://dx.doi.org/10.1155/2014/735878