· 35 ·
陈文刚 等：经热处理的蛇纹石粉体对金属磨损特性的影响
第 36 卷第 1 期
硅 酸 盐 学 报
第 36 卷第 1 期
2008 年 1 月
Vol. 36，No. 1
January，2008
JOURNAL OF THE CHINESE CERAMIC SOCIETY
水热法制备负热膨胀性 ZrW2O8 粉体
孙秀娟，杨 娟，刘芹芹，程晓农
(江苏大学材料科学与工程学院，江苏 镇江 212013)
摘 要：用水热法并经 570 ℃热处理 6 h 制备了 ZrW2O8 粉体，对水热法制备的前驱体进行了热重–差热分析。用 X 射线粉末衍射、扫描电子显微镜
对 ZrW2O8 粉体的微观结构及形貌进行表征，结果表明：ZrW2O8 粉体为单一 α-ZrW2O8 相，粉体颗粒为规则的长方体棒状，尺寸约为 1.2 μm×1.2 μm×10
μm。原位 X 射线粉末衍射分析表明：所得 ZrW2O8 粉体具有很好的负热膨胀特性，从室温到 500 ℃，其热膨胀系数为–6.30×10–6 ℃–1；在 150～175 ℃
温度范围内发生了 α-ZrW2O8 向 β-ZrW2O8 相的转变。
关键词：负热膨胀；钨酸锆粉体；水热法
中图分类号：TQ174；O614
文献标识码：A
文章编号：0454–5648(2008)01–35–05
SYNTHESIS OF NEGATIVE THERMAL EXPANSION ZrW2O8 POWDER
USING THE HYDROTHERMAL METHOD
SUN Xiujuan，YANG Juan，LIU Qinqin，CHENG Xiaonong
(School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013, Jiangsu, China)
Abstract: ZrW2O8 powder was synthesized using hydrothermal method and heat treated at 570 ℃ for 6 h, and the negative thermal
expansion property was analyzed. The precursor prepared by hydrothermal method was analyzed by thermogravimetric and differential scanning calorimeter. The microstructure and morphology of the ZrW2O8 powder were characterized by powder X-ray diffraction
and scanning electron microscopy respectively. The results show that the powder is single phases of α-ZrW2O8 with a regular rectangular particle shape and an average size of 1.2 μm×1.2 μm×10 μm. The results of in situ X-ray diffraction analysis indicate that the
thermal expansion coefficient of ZrW2O8 is –6.30×10–6 ℃–1 from room temperature to 500 ℃. The temperature transition of α to β
phase is between 150 ℃ and 175 ℃.
Key words: negative thermal expansion; zirconium tungstate; hydrothermal method
Cubic ZrW2O8 exhibits large isotropic negative thermal expansion over its entire stability range from 0.3 K to
1 050 K. The thermal expansion coefficient is –8.9×10–6
K–1.[1–3] However, ZrW2O8 is thermodynamically stable
only between 1 105 ℃ and 1 257 ℃; ZrW2O8 will decompose into zirconium oxide (ZrO2) and tungsten oxide
(WO3) at 777–1 105 ℃ and is metastable below 777
℃.[4–5] Obviously, it is difficult to obtain high-quality
ZrW2O8 crystal. In recent years, several methods have
been adopted to prepare ZrW2O8, such as solid state reaction,[5–6] the co-precipitation method,[7–8] the sol–gel
route,[9–10] and single crystal growth.[11] The solid state
reaction method is widely used due to the simplicity of its
theory and process. However, this method involves high
temperature (above 1 105 ℃) sintering and it is difficult
to obtain pure powder because of the volatilization of
WO3. The hydrothermal method has some advantages
compared with other methods; it can be used to directly
obtain fine and uniformly crystallized powder with narrow size distribution without high temperature sintering.
The hydrothermal method has become one of the important technique to synthesize powders.[12] In this paper,
收稿日期：2007–04–11。
Received date: 2007–04–11.
修改稿收到日期：2007–06–23。
基金项目：国 家 自 然 科 学 基 金 (50372027)； 江 苏 省 自 然 科 学 基 金
(BK2003404)；江苏高校自然科学重大基础研究(06KJA43010)
资助项目。
Approved date: 2007–06–23.
First author: SUN Xiujuan (1981–), female, postgraduate student for doctor
degree.
E-mail: zihesun@163.com
第一作者：孙秀娟(1981—)，女，博士研究生。
Correspondent author: CHENG Xiaonong (1958–), male, professor.
通讯作者：程晓农(1958—)，男，教授，博士研究生导师。
E-mail: xncheng@ujs.edu.cn
· 36 ·
硅
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zirconium oxynitrate (ZrO(NO3)2·5H2O) and ammonium
metatungstate (N5H37W6O24·H2O) were used as raw materials to prepare ZrW2O8 powder using the hydrothermal
method,[13] and the negative thermal expansion property
was analyzed. The results were compared with those obtained by solid state reaction. The possibility of preparing
ZrW2O8 film by the hydrothermal method was also analyzed.
1 Experimental procedure
1.1 Preparation of samples
1.1.1
ZrW2O8 powder prepared by hydrothermal
method
ZrO(NO3)2·5H2O and N5H37W6O24·H2O were
used as raw materials. Solutions of Zr (50 mL, 0.2 mol/L)
and W (50 mL, 0.4 mol/L) were mixed according to the
molar ratio of n(Zr):n(W)=1:2 with constant stirring over
a period of about 2.5 h. After that, 35 mL of 6 mol/L HCl
solution was added and was stirred continually for 3 h.
This slurry was transferred to a Teflon-lined Parr bomb,
and heated at 180 ℃ for 15 h. Then the product was filtered, washed with distilled water, and dried at 60 ℃.
The resulting precursor was heated at 570 ℃ for 6 h to
obtain ZrW2O8 powder.
1.1.2 ZrW2O8 powder prepared by solid state reaction
ZrO2 and WO3 were used as raw materials. Raw
materials were weighed according to the molar ratio of
n(Zr):n(W)=1:2. ZrO2 and WO3 were thoroughly ground
together in an agate mortar and pestle for 20 min, and the
mixture was heated at 600 ℃ for 4 h and rapidly cooled
down to room temperature in the air. Then, the mixture
was heated at 800 ℃ for 8 h and cooled slowly in the
furnace. The mixture was ground for 40 min, then heated
at 900 ℃ for 12 h and cooled slowly. Finally the mixture
was ground for another 40 min and pressed in a steel die
to form pellets. These pellets were heated in air at 1 180
℃ for 3 h and rapid quenched in ice water to avoid decomposition.
1.2 Characterization
The precursor of ZrW2O8 was studied by thermogravimetric and differential scanning calorimeter
(TG–DSC) using a Germany Netzsch–STA449 C instrument. The powder structure was characterized by
X-ray diffraction (XRD), using Cu Kα (λ=0.154 18 nm)
radiation with 40 kV/200 mA (model D/max2500, Rigaku). XRD data were collected with a scan speed of
5°/min by continuum scanning method. In situ X-ray
diffraction measurements were used to characterize the
XRD patterns of samples with a scan speed of 2°/min
at room temperature, 100, 125, 150, 175, 200, 300, 400,
500, 600 ℃ and 700 ℃. The lattice constants were
calculated by powder X software.[14] The morphology of
the samples was examined with Philips XL–30ESEM
(25 kV) and JXA 840A (20 kV) scanning electron microscopes (SEM).
盐
学
报
2008 年
2 Results and discussion
2.1 TG–DSC results of the precursor
The TG–DSC curves of the precursor are shown in
Fig.1. A well-defined mass loss of 7% centered from
room temperature to 250 ℃ can be observed in the TG
curve, reflecting a DSC curve with an endothermic peak.
This may be attributed to the dehydration and volatilization of chloride ions. And there is almost no change in
mass loss between 250 ℃ and 1 300 ℃. There is a broad
exothermic peak between 550 ℃ and 660 ℃. This may
be caused by the formation of ZrW2O8, which is consistent with Ref. [13]. The TG–DSC results indicate that
ZrW2O8 powder may be crystallized at low temperature
(550–660 ℃), which was not the same as the phase diagram of the ZrO2–WO3 system.[4] The difference might
be caused by the special high temperature and high pressure environment provided by the hydrothermal method.
In this case, solvent is in the critical or supercritical state;
the reaction activity for the precusor is increased and the
reaction temperature may be reduced.
Fig.1
TG–DSC curves of the precursor
2.2 XRD results
Curve 1 in Fig.2 shows the XRD pattern of the precursor prepared by the hydrothermal method. It is in good
agreement with that of ZrW2O7(OH)2(H2O)2 (JCPDS
28–1500). Based on the result of TG–DSC, the precursor
was heated at 570 ℃ for 6 h and the XRD pattern of the
resulting powder is shown in curve 2 in Fig.2, which
can be indexed to pure α-ZrW2O8 (JCPDS 50–1868). The
sharp peaks indicate the good crystallinity of the resulting
powder. Curve 3 in Fig.2 shows the XRD pattern of
ZrW2O8 powder prepared by solid state reaction at 1 180
℃; the pattern is the same as the curve 2. These XRD
patterns confirm the formation of cubic ZrW2O8 by either
synthesis method; however, the hydrothermal method
第 36 卷第 1 期
Fig.2
孙秀娟 等：水热法制备负热膨胀性 ZrW2O8 粉体
XRD patterns at room temperature of powders prepared
by different methods
1—Precursor by hydrothermal method; 2—ZrW2O8 powder prepared
by hydrothermal method and heat treated at 570 ℃ for 6 h; 3—Powder
prepared by solid state reaction and heat treated 1 180 ℃ for 3 h
can effectively decrease the reaction temperature, and
obtain the well crystallized pure powder.
2.3 SEM analysis results
Figure 3(a) shows the SEM photograph of the ZrW2O8
powder synthesized by the hydrothermal method. The
particles are homogeneously dispersed, with a regular
rectangular shape and an average dimension of 1.2μm×1.2
Fig.3
SEM images of ZrW2O8 powders prepared by different
methods
· 37 ·
μm×10 μm. Figure 3(b) shows the SEM photograph of
the ZrW2O8 powder synthesized by solid state reaction.
The particles have different shapes, such as irregular
polyhedron and regular rectangular shapes. Comparing
the two photographs, the morphologies are obviously
different; particles in the powder prepared by the hydrothermal method have an obvious orientation that can be
proved by the relative intensity change of the (210) and
(211) diffraction peaks as shown in Fig.2. Generally,
powder prepared by solid state reaction usually has irregular shapes, whereas particles in the powder prepared
by the hydrothermal method exhibit a regular rectangular
morphology, perhaps due to the reaction in strong acid
mediator. In the process of crystal growth, different crystal faces have different capacities for anion adsorption,
causing the different crystal faces to have different
growth speeds. The process is the same as the effect of
organic ligand binding on the growth of CdSe nanoparticles.[15] The specific mechanism is still undergoing further study.
2.4 Negative thermal expansion property
Figure 4 shows the XRD patterns at different temperatures of ZrW2O8 powder prepared by the hydrothermal method and heat treated at 570 ℃ for 6 h. In Fig.4,
the peaks slightly shift to above 2θ with increasing temperature, which is obvious in the inset of Fig.4. Because
of the cubic structure of ZrW2O8, when the diffraction
angle increases, the value of d decreases, and the lattice
constants decrease too. This indicates that the lattice constants decrease and the cell volume of ZrW2O8 is shrinking when the temperature increases. Powder prepared by
solid state reaction also exhibits a similar phenomenon.
Figure 5 shows XRD patterns at 700 ℃ of ZrW2O8
powders prepared by different methods. Powder prepared
Fig.4 XRD patterns at different temperatures of ZrW2O8
powder prepared by the hydrothermal method and
heat-treated at 570 ℃ for 6 h
· 38 ·
Fig.5
硅
酸
XRD patterns at 700 ℃ of ZrW2O8 powders prepared
by different methods
by the hydrothermal method and heat treated at 570 ℃ for
6 h do not decompose, whereas powder prepared by solid
state reaction and heat treated 1 180 ℃ for 3 h has already
decomposed, with the main diffraction peaks of WO3. This
indicates that powder prepared by the hydrothermal
method are much more stable. This result mainly relies on
the low temperature, high pressure and solution situation
of the hydrothermal method, which are preferable to obtain
perfact crystals with few defects and good orientation.
Combining all the data of XRD, the lattice constants
were calculated by powder X software. Figure 6 shows
the relation between lattice constants and temperature.
The lattice constants decrease with increasing temperature. After linear fitting, the thermal expansion coefficient
of powder prepared by the hydrothermal method is
–6.30×10–6 ℃–1, and –6.31×10–6 ℃ –1 for powder prepared by solid state reaction. Although the morphologies
are different, the thermal expansion coefficients are almost the same.
盐
学
报
2008 年
Figure 7 shows the XRD patterns at 125, 150 ℃ and
175 ℃ of ZrW2O8 powder prepared by the hydrothermal
method and heat treated at 570 ℃ for 6 h. Compared
with the pattern obtained at 125 ℃, there is no change in
the pattern at 150 ℃. However, in the pattern obtained at
of 175 ℃, several diffraction peaks such as the (111),
(310), (322), and (331) peaks that exist at low temperature disappeared, and the (221) diffraction peak weakened. This indicates that a structural phase transition from
an acentric phase to a centric phase took place in this
temperature range. The low-temperature phase (P213)
transited to the high temperature phase (Pa 3 ). ZrW2O8
underwent an α to β structure phase transition between
150 ℃ and 175 ℃ , which is considered to be order-disorder type. The same result observed for powder
prepared by solid state reaction and heat treated 1 180 ℃
for 3 h. The thermal expansion coefficients are
–9.89×10–6 ℃–1 and –4.49×10–6 ℃–1 for α and β structure phases in the powder prepared by the hydrothermal
method shown in Fig.6. Moreover, the thermal expansion
coefficients are –11.58×10–6 ℃–1 and –3.77×10–6 ℃–1 for
α and β structure phases in the powder prepared by solid
state reaction, respectively. Comparing the data, the absolute value of negative thermal expansion coefficient of the α structure phase is larger than that of the β
structure phase.
Fig.7 XRD patterns at 125, 150 ℃ and 175 ℃ of ZrW2O8
powder prepared by the hydrothermal method and
heat-treated at 570 ℃ for 6 h
Fig.6
Relation between lattice constants of ZrW2O8 powder
prepared by the hydrothermal method and heat-treated
at 570 ℃ for 6 h and temperature
2.5 Preparing ZrW2O8 film
Reports on ZrW2O8 film preparation are limited to
physical methods, and the preparation conditions are rigorous. In this paper, the hydrothermal method was used
to prepare ZrW2O8 film. Glass was used as a substrate
after being washed and dried. The experiment was almost
the same as for the preparation of powder. Before the
slurry was transferred to a Teflon-lined Parr bomb, the
substrates were put on the bottom of the bomb. After the
孙秀娟 等：水热法制备负热膨胀性 ZrW2O8 粉体
第 36 卷第 1 期
reaction, the substrates were removed, washed for 5 min,
and dried at 80 ℃. Finally the substrates were heated at
480 ℃ for 1 min.
Figure 8 shows the XRD pattern of ZrW2O8 film. Under the test conditions, two main diffraction peaks, (210)
and (211) appeared. The results indicate that the hydrothermal method may have been useful in preparing
ZrW2O8 film.
· 39 ·
[2] MARY T A, EVANS J S O, VOGT T, et al. Negative thermal expansion
from 0.3–1.50 Kelvin in ZrW2O8 [J]. Science, 1996, 272(5): 90–92.
[3] EVANS J S O, DAVID W I F, SLEIGHT A W. Structural investigation
of the negative-thermal-expansion material ZrW2O8 [J]. Acta Cryst B,
1999, 55(3): 333–340.
[4] CHANG L L Y, SCROGER M G, PHILIPS B. Condensed phase relations in the systems ZrO2–WO2–WO3 and HfO2–WO2–WO3 [J]. J Am
Ceram Soc, 1967, 50(2): 211–215.
[5] CHENG Xiaonong, SUN Xiujuan, YANG Juan, et al. Synthesis of
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350–353.
[6] SUN Xiujuan, YANG Juan, LIU Qinqin, et al. Effect of preparation
method on particle size and negative thermal expansion property of
negative thermal expansion ZrW2O8 powders [J]. J Inorg Chem (in
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[7] YAN Xuehua, CHENG Xiaonong, ZHANG Meifen. Effect of different
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Fig.8
XRD pattern of ZrW2O8 film
Int J Inorg Mater, 2000, 2(4): 333–337.
[9] LIND C, WILKINSON A P. Seeding and the non-hydrolytic Sol–Gel
3 Conclusions
synthesis of ZrW2O8 and ZrMo2O8 [J]. J Sol–Gel Sci Technol, 2002,
25(1): 51–56.
(1) The hydrothermal method was adopted to synthesize ZrW2O8 at relatively low temperature. α-ZrW2O8
powder can be obtained after heat-treatment at 570 ℃.
The resulting powder has a regular rectangular shape.
(2) The ZrW2O8 powder prepared by the hydrothermal
method and heat-treatment at 570 ℃ has good negative
thermal expansion property. The thermal expansion coefficient is –6.30×10–6 ℃–1 from room temperature to 500
℃, and an α to β structure phase transition occurs between 150 ℃ and 175 ℃.
[10] WILKINSON A P, LIND C, PATTANAIK S. A new polymorph of
ZrW2O8 prepared using nonhydrolytic sol–gel chemistry [J]. Chem
Mater, 1999, 11(1): 101–108.
[11]
KOWACH G R. Growth of single crystals of ZrW2O8 [J]. J Cryst
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[12] SHI Erwei, XIA Changtai, WANG Buguo, et al. Development and
application of hydrothermal method [J]. J Inorg Mater (in Chinese),
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[13] XING Xianran, XING Qifeng, YU Ranbo, et al. Hydrothermal synthesis of ZrW2O8 nanorods [J]. Physica B, 2006, 371(1): 81–84.
[14] DONG C. Powder X: Windows–95–based program for powder X-ray
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