Solvothermal synthesis of fusiform hexagonal prism SrCO3 microrods via ethylene glycol solution

Article abstract of DOI:10.1016/j.materresbull.2006.10.026

Fusiform hexagonal prism SrCO₃ microrods were prepared by a simple solvothermal route at 120 °C, and characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and Fourier transform infrared (FT-IR) spectroscopy. By controlling the content of ethylene glycol (EG), it was found that ethylene glycol (EG) played an important role in the formation of such SrCO₃ microrods. Finally, effects of other solvents on the products, including 1,2-propanediol and glycerin, were also investigated.

Full text of DOI:10.1016/j.materresbull.2006.10.026

Materials Research Bulletin 42 (2007) 1550–1555
www.elsevier.com/locate/matresbu
Solvothermal synthesis of fusiform hexagonal prism SrCO3
microrods via ethylene glycol solution
*
Liange Shi, Fanglin Du
Key Laboratory for Nanostructured Materials, Qingdao University of Science and Technology,
Qingdao 266042, PR China
Received 27 July 2006; received in revised form 24 September 2006; accepted 25 October 2006
Available online 4 December 2006
Abstract
Fusiform hexagonal prism SrCO3 microrods were prepared by a simple solvothermal route at 120 8C, and characterized by X-
ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and Fourier transform infrared (FT-IR)
spectroscopy. By controlling the content of ethylene glycol (EG), it was found that ethylene glycol (EG) played an important role in
the formation of such SrCO3 microrods. Finally, effects of other solvents on the products, including 1,2-propanediol and glycerin,
were also investigated.
# 2006 Elsevier Ltd. All rights reserved.
Keywords: A. Inorganic compounds; B. Chemical synthesis; C. Electron microscopy; C. X-ray diffraction; D. Microstructure
1. Introduction
In recent years, strontium carbonate has attracted much attention due to its potential applications in the inorganic
chemical field. Usually, strontium carbonate is used to produce paints, dryer, pigments, fireworks and so on. In
addition, it is also used to prepare color television picture tubes and computer displays due to the X-ray shielding
capability, the high rigidity and the good ductility. Although many methods [1–7] have been developed to prepare
SrCO3 particles, solvothermal synthesis of SrCO3 using ethylene glycol (EG) as the solvent has not been studied up to
now.
Solvothermal route has recently been the focus of attention because of its unique reaction environment [8–13].
Using organic solvents as the solvothermal medium can effectively prevent agglomeration and control the
morphology development of crystals. Moreover, ethylene glycol (EG) was proved to be a great solvothermal medium
[14,15].
2ꢀ
In this study, a simple solvothermal route was developed to prepare SrCO3 microstructures using urea as CO3
source, strontium nitrate as Sr2+ source and ethylene glycol (EG) as the solvent. Fusiform hexagonal prism SrCO3
microrods with uniform shape and excellent monodispersity were successfully obtained. The whole procedure was
* Corresponding author. Tel.: +86 532 84022870; fax: +86 532 84022870.
E-mail address: dufanglin@qust.edu.cn (F. Du).
0025-5408/$ – see front matter # 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.materresbull.2006.10.026

L. Shi, F. Du / Materials Research Bulletin 42 (2007) 1550–1555
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easily manipulated and free of surfactant. Moreover, the use of urea was distinct from those chemicals (NaCO3, etc.)
2ꢀ
used as CO3 source in the former SrCO3 studies.
2. Experimental
All the reagents used in our experiments are of analytical grade. In a typical procedure, 0.96 g urea, 0.423 g
strontium nitrate and 60 mL ethylene glycol (EG) were added into 20 mL distilled water, and then the mixed solution
was transferred into the autoclave. After 5 min agitated ultrasonic, the autoclave was sealed and maintained at 120 8C
for 24 h. Finally, white precipitates were collected and washed with distilled water and anhydrous ethanol for several
times, then dried in a vacuum at 80 8C for 1 h.
˚
XRD analysis was carried out on a D/max-500 diffractometer with Cu Ka radiation (l = 1.5418 A). FE-SEM
images were taken on a JSM-6700F field-emission scanning electron microscopy with an accelerating voltage of
16 kV. FT-IR spectrum was performed on a Nicolet Fourier transform infrared (FT-IR) spectroscopy.
3. Results and discussion
Fig. 1 shows a typical XRD pattern of fusiform hexagonal prism SrCO3 microrods. The diffraction peaks in
˚
˚
˚
this pattern can be indexed to strontianite structure (a = 5.107 A, b = 8.418 A, c = 6.029 A). It is in accordance
with the JCPDS card for SrCO3 (JCPDS 05-0418). The formation of SrCO3 was further confirmed from FT-IR
analysis (Fig. 2). The absence of EG peaks in the FT-IR spectrum indicates that EG is not included in the SrCO3
crystals.
SEM images of fusiform hexagonal prism SrCO3 microrods are shown in Fig. 3. The general morphology (Fig. 3A)
of SrCO3 microrods shows the as-synthesized microrods with the mean length of 13 mm have uniform fusiform shape
and excellent monodispersity, and the mean diameter shrinks from above 1 mm in the middle of microrods to about
900 nm at the end. Interestingly, the special planes and tips of SrCO3 microrods were observed. The image of an
individual microrod (Fig. 3B) reveals that there are six smooth prismatic side planes of each microrod. The amplified
tip in Fig. 3B shows that there are special tips at the top of each microrod.
The solvent EG played an important role in the formation of fusiform hexagonal prism SrCO3 microrods. When
30 mL EG was added under otherwise identical conditions, fusiform hexagonal prism SrCO3 microrods with the loose
surface (inset) were obtained (Fig. 4A). The mean length of the as-synthesized microrods is about 11 mm, and the
mean diameter shrinks from about 1 mm in the middle of microrods to about 700 nm at the end. However, without EG
(0 mL), aggregates composed of the ill-defined irregular-shaped particles with a small size were obtained (Fig. 4B).
The reaction equations of SrCO3 formation could be written as follows:
COðNH2Þ2 þ 3H2O ! CO2 " þ 2NH3ꢁH2O
(1)
(2)
2ꢀ
Sr2þ þ CO3 ! SrCO3 #
Fig. 1. XRD pattern of SrCO3 microrods.

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Fig. 2. FT-IR spectrum, top: SrCO3 microrods, bottom: pure SrCO3 (AR).
Fig. 3. SEM images of SrCO3 microrods.

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Fig. 4. SEM images of the products prepared in the presence of (A) 30 mL and (B) 0 mL EG.
Under solvothermal conditions, urea was hydrolyzed into CO2 and NH3ꢁH2O (Eq. (1)), and then Sr2+ cations and
CO32ꢀ anions collided in the solvothermal solution to form SrCO3 nuclei (Eq. (2)). It is supposed that the selective
absorption of EG molecules on the specified planes of SrCO3 nuclei resulted in the different growth rate of different
planes to form fusiform hexagonal prism SrCO3 microrods. When EG was decreased to 30 mL, the absorption on the
specified planes of SrCO3 nuclei became weak, so that fusiform hexagonal prism SrCO3 microrods with the loose
surface were formed. Furthermore, without EG as the solvent, aggregations composed of the ill-defined irregular-
shaped particles were obtained.
It is interesting that when 1,2-propanediol (60 mL) was employed as the solvent, hexagonal prism microrods
with the length of 8–16 mm and the mean diameter of above 1 mm were obtained (Fig. 5A); if glycerin (60 mL)
was used as the solvent, the as-synthesized products were primarily composed of hexahedral ellipsoids
(Fig. 5B). Compared with the products prepared in the presence of EG (60 mL), morphologies of these products
obviously changed, but there was a common ground between them, namely six smooth side planes. The morphology
difference led by different solvents may be due to the fact that these solvents (ethylene glycol, 1,2-propanediol
and glycerin) have the different molecular structure. The detailed reasons will be further explored in our future
works.

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Fig. 5. SEM images of the products prepared in the presence of 60 mL (A) 1,2-propanediol and (B) glycerin.
4. Conclusions
In summary, fusiform hexagonal prism SrCO3 microrods were prepared via solvothermal route. These
SrCO3 microrods have special planes and tips. This convenient method may be applicable to prepare other metal
carbonates.
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