Synthesis of nanocrystalline zirconium nitride powders by reduction-nitridation of zirconium oxide

Article abstract of DOI:10.1111/j.1551-2916.2004.00696.x

Nanocrystalline ZrN powder was synthesized by reduction-nitridation of nanosized ZrO₂ powder in ammonia gas with magnesium as the reducing agent. The effects of nitridation temperature, holding time, and Mg:ZrO₂ mole ratio on the powder properties were investigated. Cubic phase ZrN powder with a 30-100-nm particle size was synthesized at 1000°C for 6 h, under a Mg:ZrO₂ mole ratio of 10:1.

Full text of DOI:10.1111/j.1551-2916.2004.00696.x

J. Am. Ceram. Soc., 87 [4] 696–98 (2004)
journal
Synthesis of Nanocrystalline Zirconium Nitride Powders by
Reduction–Nitridation of Zirconium Oxide
,
†
Bo Fu and Lian Gao*
State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics,
Chinese Academy of Sciences, Shanghai 200050, People’s Republic of China
Nanocrystalline ZrN powder was synthesized by reduction–
II. Experimental Procedure
nitridation of nanosized ZrO powder in ammonia gas with
magnesium as the reducing agent. The effects of nitridation
2
(
1) Synthesis of Nanocrystalline ZrN Powders
Zirconium oxychloride (ZrOCl ⅐8H O, 99.5% pure), the start-
2
2
temperature, holding time, and Mg:ZrO mole ratio on the
2
ing material to prepare nanosized ZrO powder, was dissolved in
2
powder properties were investigated. Cubic phase ZrN powder
with a 30–100-nm particle size was synthesized at 1000°C for
distilled water and slowly added into an ammonia solution with
continuous stirring. When the titration process was finished, the
precipitate suspension was settled for 12 h, filtered, and washed
6
h, under a Mg:ZrO mole ratio of 10:1.
2
with distilled water and ethanol successively. ZrO powder with an
2
average particle size around 20 nm was obtained after the
precipitate was dried at 120°C and calcined at 450°C for 1 h. The
I. Introduction
ZrO nanosized powder was ground with Mg powder (grade, 100
2
IRCONIUM NITRIDE (ZrN) is a refractory material with many
mesh) at different Mg:ZrO2 mole ratios (10:1 without special
notification) for 2 h in an agate mortar using an agate pestle, then
put into a quartz tube furnace, and subjected to nitridation in
flowing NH3 gas at a flow rate of 1 L/min. The nitridation
temperature ranged from 800° to 1000°C; nitridation time varied
from 2 to 6 h. The nitridation product was washed with 1.5M
Z
outstanding properties such as high hardness, abrasive resis-
1
tance, and good electrical conductivity. Because of these proper-
ties, it has a number of technological applications, such as hard
coatings for cutting tools, diffusion barriers in integrated circuits,
2
,3
and the Josephson junction in electronics. ZrN is traditionally
synthesized by heating zirconium or zirconium chloride in the
presence of nitrogen or ammonia at elevated temperature. How-
ever, the stoichiometry of zirconium nitride cannot be properly
controlled, and the incorporation of residual metal in the final
HNO and ethanol to remove the byproducts and then dried at
3
8
5°C for 12 h to obtain nanosized ZrN powder.
4
,5
product is unavoidable. Alternative approaches have also been
6
(2) Characterization of the Nanocrystalline ZrN Powder
reported, such as reactive ball milling (RBM) and benzene–
7
The morphology and size of ZrN particles were observed by
transmission electron microscopy (TEM; Model 2010CX, JEOL,
Tokyo, Japan). The powder-phase composition was identified by
X-ray diffraction (XRD; Model D/MAX-RB, Rigaku Co., Tokyo,
Japan), using CuK␣ (␭ ϭ 1.5418 Å), over the scan range of
thermal method. Although ZrN can be prepared through high-
energy ball milling of elemental Zr powder in nitrogen for a
prolonged period of 20–50 h, the high energy consumption and the
contamination from the wear of milling media make it not a
cost-effective method and the ZrN powders prepared are usually of
poor quality. For the benzene–thermal route, the requirement of
high-purity starting materials, the possible danger in manipulation
with high-temperature organic solvents, and the low production
efficiency also limit it from industrial mass production.
2
0°–80°.
In this paper, we report a reduction–nitridation method for the
synthesis of nanocrystalline ZrN powders, using nanosized ZrO2
powder as the starting material and elemental Mg as reductant. An
instantaneous reaction between ZrO and Mg will release a mass
2
reaction heat, which allows the nitridation process to be finished in
a lower heating temperature and a shorter time. The byproducts
(
MgO and Mg N ) can be washed off by acid. So high-purity ZrN
3 2
powder can be obtained conveniently.
T. M. Besmann—contributing editor
Manuscript No. 10545. Received September 19, 2003; approved November 17,
2
003.
Member, American Ceramic Society.
*
†
Fig. 1. X-ray diffraction patterns of the nanopowders nitrided at different
Author to whom correspondence should be addressed. e-mail:
liangaoc@online.sh.cn.
temperatures in NH for 6 h at (a) 800°, (b) 900°, and (c) 1000°C.
3
6
96

April 2004
Communications of the American Ceramic Society
697
Fig. 2. X-ray diffraction patterns of the nanopowders nitrided at 1000°C
Fig. 3. X-ray diffraction patterns of the nanopowders nitrided at 1000°C
in NH for 2 h using a Mg:ZrO ratio of (a) 3:1 and (b) 10:1.
3 2
in NH for holding times of (a) 2, (b) 4, and (c) 6 h, respectively.
3
powders nitridated at 800°–1000°C for 6 h. Weak but distinct
peaks assigned to zirconium nitride appear in the XRD pattern of
the 800°C sample, together with very strong ZrO2 peaks. This
indicates that ZrN began to form at this temperature. With an
increase in the nitridation temperature, the intensities of ZrN peaks
III. Results and Discussion
(
1) Reduction–Nitridation Reaction
First, the effect of temperature on the composition of the final
product was investigated. Figure 1 shows the XRD patterns of the
Fig. 4. TEM micrographs of ZrN nanopowders nitrided at (a) 900°C for 6 h and (b) 1000°C for 6 h.

6
98
Communications of the American Ceramic Society
Vol. 87, No. 4
increase, while the ZrO peak intensities decrease. At 900°C, a
high-purity ZrN powder was produced. The diffraction peaks of
nm, except a few abnormal large particles. These large particles
are 80–100 nm and might be derived from the large aggregates in
2
ZrN dominate the XRD pattern of this sample, and the ZrO peaks
the ZrO starting powder. Figure 4(b) shows a micrograph of the
2
2
become hardly visible. Only ZrN is detected in the sample nitrided
sample synthesized at 1000°C. The absolute majority of ZrN
particles in this sample are 30–50 nm in size; only very few
particles show a larger size of 100 nm. Therefore, the increase in
synthesizing temperature has led to a significant growth of ZrN
particles.
at 1000°C, indicating the complete conversion of ZrO to ZrN at
2
this temperature.
The holding time is another important factor influencing the
composition of the final product. Figure 2 shows the X-ray
diffraction patterns of the powders produced at 1000°C for various
periods of time. A considerable amount of ZrO still remains in the
2
sample nitrided at 1000°C for 2 h, as indicated by the distinctive
ZrO peaks in the XRD pattern. The ZrO content continuously
decreases with prolonged nitridation time. When the holding time
IV. Conclusions
2
2
A simple method for the synthesis of nanosized crystalline ZrN
powder has been developed. In this process, ZrN powder was
produced by the reduction–nitridation of ZrO2 powder in NH3
increases to 6 h, ZrO peaks completely disappear and only ZrN
2
peaks are detected in it by XRD.
Besides the nitridation temperature and holding time, the mole
ratio of Mg to ZrO2 also influences the reduction–nitridation
flow gas with Mg as the reductant. Nitridation temperature,
holding time, and Mg:ZrO ratio significantly influenced the purity
2
of the ZrN powder. Cubic phase ZrN powder with an average
particle size of 40 nm was successfully obtained at 1000°C for 6 h,
using a Mg:ZrO ratio of 10:1.
reaction. Theoretically, a Mg:ZrO ratio of 2:1 is high enough to
2
ensure the complete reduction of ZrO2 by Mg. However, our
experiment implied that a higher ratio was more suitable. Figure 3
shows the X-ray diffraction patterns of the powders produced at
2
1
000°C for 2 h using Mg:ZrO ratios of 3:1 and 10:1. The 10:1
2
References
sample shows a much higher ZrN content than the 3:1 sample, as
indicated by the higher relative peak intensity of ZrN to ZrO in
the XRD pattern of the former sample.
Based on the above results, the optimum condition for the
formation of nanocrystalline ZrN powder was found to be 1000°C
for 6 h at a Mg:ZrO ratio of 10:1. If the temperature was lower
than 1000°C, or the holding time shorter than 6 h, the purity of the
ZrN powder was low; therein residual ZrO unavoidably occurred
in the powder.
1
L. E. Toth, “General Properties, Preparation, and Characterization”; pp. 1–8 in
Transition Metal Carbides and Nitrides, Vol. 7, Refractory Materials Series. Edited
by J. L. Margrave. Academic Press, New York, 1971.
M. Wittmer, “High-Temperature Contact Structures for Silicon Semiconductor
Devices,” Appl. Phys. Lett., 37 [6] 540–42 (1980).
K. Schwarz, A. R. Williams, J. J. Cuomo, J. H. E. Harper, and H. T. G. Hentzell,
Zirconium Nitride—A New Material for Josephson Junctions,” Phys. Rev. B:
Condens. Matter Mater. Phys., 32 [12] 8312–16 (1985).
2
2
3
2
“
2
4
S. T. Oyama, “Preparation and Catalytic Properties of Transition Metal Carbides
and Nitrides,” Catal. Today, 15 [2] 179–200 (1992).
Y. Mamonttov, A. L. Suris, and S. N. Shorin, “Thermodynamic Analysis of the
5
Formation of ZrN from ZrCl
1975).
M. Sherif El-Eskanadarany and A. H. Ashour, “Mechanically Induced Gas–Solid
4
,” Sov. Powder Metall. Met. Ceram., 14 [12] 955–56
(
2) Morphology Observation of Nano ZrN Powders by TEM
Figure 4 shows the TEM micrographs of samples that were
(
6
Reaction for the Synthesis of Nanocrystalline ZrN Powder and Their Subsequent
synthesized at different temperatures for 6 h. The average particle
sizes are 25 and 40 nm for the samples synthesized at 900° and
1
Consolidation,” J. Alloys Compd., 313, 224–34 (2000).
7
Y. Gu, F. Guo, Y. T. Qian, H. G. Zheng, and Z. P. Yang, “A Benzene-Thermal
000°C, respectively. From Fig. 4(a), it can be seen that most of
Synthesis of Powdered Cubic Zirconium Nitride,” Mater. Res. Bull., 57, 1679–82
the ZrN particles in the powders synthesized at 900°C are 10–30
(2003).
Ⅺ