Materials Chemistry and Physics 97 (2006) 247–251
Hydrothermal synthesis and characterization of ZnGa
2
O
4
phosphors
Limiao Chen
∗
, Younian Liu, Zhouguang Lu, Kelong Huang
College of Chemistry & Chemical Engineering, Central South University, Changsha 410083, PR China
Received 22 January 2005; received in revised form 21 July 2005; accepted 9 August 2005
Abstract
ZnGa
2
O
4
crystals in the shapes of polyhedron-like, rod-like, and irregular particle have been successfully synthesized using different
gallium sources, namely, GaO(OH), Ga
2
(SO
4
)
3
·16H
2
O, and Ga
2
O
3
, by a hydrothermal method and characterized by X-ray diffraction,
transition electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectrometer (EDX), ultraviolet–visible
(UV–vis) absorption spectroscopy, and fluorescence spectrophotometer. From the experimental results, it was revealed that the gallium source
played an important role in the formation of the products with different morphologies and sizes. The absorption and corresponding emission
peaks of ZnGa
2
O
4
obtained from Ga
2
O
3
and Ga
2
(SO
4
)
3
·16H
2
O shifted to a higher energy when compare to these peaks of ZnGa
2
O
4
obtained
from GaO(OH), respectively. These phenomena were attributed to the quantum-size effect in the nanosized ZnGa
2
O
4
.
© 2005 Elsevier B.V. All rights reserved.
Keywords: ZnGa
2
O
4
; Hydrothermal synthesis; Photoluminescence
1. Introduction
ZnGa
2
O
4
is a good low-voltage phosphor material used
in a new type of vacuum flat cathode-ray tube used in
field emission displays [1]. This ultraviolet-transparent and
electroconductive material is expected to be utilized for
ultraviolet-photo-electronic devices with CdGa
2
O
4
[2] and
MgIn
2
O
4
[3]. Synthesis of ZnGa
2
O
4
spinel powders have
been previously accomplished by traditional solid-state reac-
tions between zinc oxide and gallium oxide [2–4] and by pul-
verizing ZnGa
2
O
4
single crystals synthesized above 1000
◦
C
by the flux method [5,6]. As we know, different material
preparation methods have some important effects on material
microstructure and physical properties. In the recent decade,
there is a strong trend toward the application of solution
routes for direct synthesis of crystalline ceramic particles
at low temperature [7,8]. Hydrothermal method is one of
the most promising solution chemical methods. The particles
size and their distribution, phase homogeneity, and morphol-
ogy could be well controlled [9–11]. Nanosized ZnGa
2
O
4
spinel powders have been synthesized from zinc powder and
∗
Corresponding author. Tel.: +86 7318879850; fax: +86 7318879616.
E-mail address: chenlimiao@mail.csu.edu.cn (L. Chen).
GaCl
3
chlorohydric acid solution under hydrothermal condi-
tions at 150
◦
C [12]. Hirano et al. also synthesized nanosized
ZnGa
2
O
4
spinel powders from gallium and zinc salts under
hydrothermal conditions at 150–240
◦
C [13–15] and under
atmospheric conditions below 90
◦
C [16]. However, there
are no reports on the preparation of ZnGa
2
O
4
spinel pow-
ders with different morphologies by the hydrothermal method
using GaO(OH) and Ga
2
O
3
as reactants.
In this paper, ZnGa
2
O
4
spinel powders with different
shapes were synthesized by the hydrothermal method from
zinc salt and different gallium sources, namely, GaO(OH),
Ga
2
O
3
, and Ga
2
(SO
4
)
3
·16H
2
O. The optical properties of the
obtained nanoparticles were also investigated.
2. Experimental procedure
The ZnGa
2
O
4
nanocrystalline samples were pre-
pared by the hydrothermal method using GaO(OH),
Ga
2
(SO
4
)
3
·16H
2
O, and Ga
2
O
3
as reactants. GaO(OH) pow-
ders were synthesized by the precipitation method [17]. All
reagents were analytical grade pure and purchased from
Shanghai Chemical Co. Ltd. In a typical procedure, a suitable
mount of powder gallium source (including 0.002 mol Ga
3+
)
0254-0584/$ – see front matter © 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.matchemphys.2005.08.024