Materials Science and Engineering B 143 (2007) 90–93
Short communication
Combustion synthesis and luminescent properties of
Dy
3+
-doped La
2
Sn
2
O
7
nanocrystals
Shu Mei Wang, Zhi Liang Xiu, Meng Kai L¨ u
∗
, Ai Yu Zhang,
Yuan Yuan Zhou, Zhong Sen Yang
State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
Received 12 April 2007; received in revised form 20 July 2007; accepted 21 July 2007
Abstract
A new combustion method for preparation of Dy
3+
-doped La
2
Sn
2
O
7
nanocrystals is presented. The morphologies of the as-synthesized nanocrys-
tals are characterized by X-ray diffraction (XRD) and transmission electron micrograph (TEM). The pyrochlore structure nanocrystals less than
50 nm with a hexagonal morphology are synthesized for the first time. The luminescent properties of these nanocrystals have been investigated by
fluorescence measurements at room temperature. The results indicate that the energy transfers from the La
2
Sn
2
O
7
host to dysprosium ions.
© 2007 Published by Elsevier B.V.
Keywords: Combustion; Nanocrystal; Luminescent properties; Fluorescence; Luminescent centers
1. Introduction
In the past few years, various routes have been explored
to synthesize pyrochlore-type oxides (A
2
B
2
O
7
) because of
their wide applications in ionic/electric conductors [1,2], cata-
lysts [3,4], hosts of fluoresce center [5] and radioactive waste
management [6]. In particular, rare-earth pyrochlore oxides
are of refractory materials with very high melting points
(>2000
◦
C) for high-temperature applications [7], moreover for
the environment-related automobile exhaust gas and combus-
tion gas control [8]. All the methods, including the conventional
solid-state reaction [9–12] and several improved methods, such
as sol–gel and hydrothermal [8,13–17], use many starting and
intermediate chemical components, or have many heat treat-
ment steps, or are very long in time. To our knowledge, there are
no reports that describe a simple La
2
Sn
2
O
7
synthesis method,
which claims at short reaction time, low calcination temperature,
simplicity, mass production and high level of repeatability.
Combustion synthesis which leads to a nearly instanta-
neous reaction, is an efficient, quick and straightforward
method for the preparation of oxide materials, such as alumi-
nates [18–21], chromites [22–25], ferrites [26,27], manganites
[25,28], titanates [29,30], etc. A key feature of this technique
∗
Corresponding author.
E-mail address: mklu@icm.sdu.edu.cn (M.K. L¨ u).
is that the heat required to drive the synthesis is provided for
the main part by an exothermal reaction occurring among the
reagents, thus greatly reducing the amount of heat that has
to be supplied by an external source [31]. It offers several
attractive advantages such as: simplicity of process, surprisingly
short calcination time, availability of mass production and good
repeatability with low cost.
It is necessary for the conventional combustion method to
consist of the reagent of nitrate, which restricts its wide applica-
tion. In this paper, we have successfully synthesized phase-pure
La
2
Sn
2
O
7
with a pyrochlore structure by a new universal
combustion method for the first time. Simultaneously, the Dy
3+
-
doped La
2
Sn
2
O
7
nanocrystals have been obtained by the same
method to investigate their effect on the La
2
Sn
2
O
7
properties.
2. Experiment
The undoped and Dy
3+
-doped La
2
Sn
2
O
7
nanocrystals were
prepared by a new combustion method. All chemicals used in
this study were analytic reagent. A calculated amount of stannic
chloride pentahydrate (SnCl
4
·5H
2
O), lanthanum oxide (La
2
O
3
),
nitric acid (HNO
3
) and dysprosium nitrate (Dy(NO
3
)
3
) were
mixed in distilled water to form the symmetrical solution. The
mole ratio of La
2
Sn
2
O
7
:Dy
3+
is 1:0.015. The solution was then
added to a sufficient aqueous ammonia solution drop-wise under
continuous stirring. The as-synthesized white precipitates were
0921-5107/$ – see front matter © 2007 Published by Elsevier B.V.
doi:10.1016/j.mseb.2007.07.070