Preparation and Formation Mechanism of ZrW 2 O 8 by Sol–Gel Process
ZrW 2 O 8 is known as a material that shows negative thermal expansion. Amorphous ZrW 2 O 8 with a particle size of 50–300 nm was prepared by a sol–gel process at a lower temperature of 723 K for 12 h. X‐ray diffraction analysis showed that the amorphous ZrW 2 O 8 started to crystallize at 833 K and...
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| Published in | Journal of the American Ceramic Society Vol. 91; no. 11; pp. 3542 - 3545 |
|---|---|
| Main Authors | , , , , |
| Format | Journal Article |
| Language | English |
| Published |
01.11.2008
|
| Online Access | Get full text |
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| Summary: | ZrW
2
O
8
is known as a material that shows negative thermal expansion. Amorphous ZrW
2
O
8
with a particle size of 50–300 nm was prepared by a sol–gel process at a lower temperature of 723 K for 12 h. X‐ray diffraction analysis showed that the amorphous ZrW
2
O
8
started to crystallize at 833 K and remained kinetically stable up to 953 K. We investigated the formation mechanism in a sol–gel process of ZrW
2
O
8
by Fourier transform‐infrared spectroscopy, thermogravimetry‐differential thermal analysis, and X‐ray diffraction analysis. The precursor solution changed into an amorphous precursor sol at room temperature, and this changed into a crystalline precursor gel between 351 and 358 K. The precursor ZrW
2
O
7
(OH)
2
(H
2
O)
2
was obtained by drying this gel at 343 K. These results indicate that the crystallization of the amorphous precursor depends on the heat‐treatment temperatures under low pH conditions because the residual −OH or −OR groups are removed by polycondensation reactions. |
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| ISSN: | 0002-7820 1551-2916 |
| DOI: | 10.1111/j.1551-2916.2008.02726.x |