Structural evolution in a hydrothermal reaction between Nb2O5 and NaOH solution: From Nb2O5 grains to microporous Na2Nb2O6 center dot(2)/3H2O fibers and NaNbO3 cubes

Zhu, Huaiyong, Zheng, Zhanfeng, Gao, Xueping, Huang, Yining, Yan, Zhimin, Zou, Jin, Yin, Hongming, Zou, Qingdi, Kable, Scott H., Zhao, Jincai, Xi, Yunfei, Martens, Wayde N. and Frost, Ray L. (2006) Structural evolution in a hydrothermal reaction between Nb2O5 and NaOH solution: From Nb2O5 grains to microporous Na2Nb2O6 center dot(2)/3H2O fibers and NaNbO3 cubes. Journal of the American Chemical Society, 128 7: 2373-2384. doi:10.1021/ja056301w


Author Zhu, Huaiyong
Zheng, Zhanfeng
Gao, Xueping
Huang, Yining
Yan, Zhimin
Zou, Jin
Yin, Hongming
Zou, Qingdi
Kable, Scott H.
Zhao, Jincai
Xi, Yunfei
Martens, Wayde N.
Frost, Ray L.
Title Structural evolution in a hydrothermal reaction between Nb2O5 and NaOH solution: From Nb2O5 grains to microporous Na2Nb2O6 center dot(2)/3H2O fibers and NaNbO3 cubes
Journal name Journal of the American Chemical Society   Check publisher's open access policy
ISSN 0002-7863
Publication date 2006-02-22
Sub-type Article (original research)
DOI 10.1021/ja056301w
Volume 128
Issue 7
Start page 2373
End page 2384
Total pages 12
Editor Charlotte Steigers Sauer
Place of publication Washington, D.C.
Publisher American Chemical Society
Collection year 2006
Language eng
Subject C1
780102 Physical sciences
680399 Other
671699 Manufactured products not elsewhere classified
291499 Materials Engineering not elsewhere classified
291804 Nanotechnology
03 Chemical Sciences
06 Biological Sciences
09 Engineering
Abstract Niobium pentoxide reacts actively with concentrate NaOH solution under hydrothermal conditions at as low as 120 degrees C. The reaction ruptures the corner-sharing of NbO7 decahedra and NbO6 octahedra in the reactant Nb2O5, yielding various niobates, and the structure and composition of the niobates depend on the reaction temperature and time. The morphological evolution of the solid products in the reaction at 180 degrees C is monitored via SEM: the fine Nb2O5 powder aggregates first to irregular bars, and then niobate fibers with an aspect ratio of hundreds form. The fibers are microporous molecular sieve with a monoclinic lattice, Na2Nb2O6 center dot(2)/3H2O. The fibers are a metastable intermediate of this reaction, and they completely convert to the final product NaNbO3 Cubes in the prolonged reaction of 1 h. This study demonstrates that by carefully optimizing the reaction condition, we can selectively fabricate niobate structures of high purity, including the delicate microporous fibers, through a direct reaction between concentrated NaOH solution and Nb2O5. This synthesis route is simple and suitable for the large-scale production of the fibers. The reaction first yields poorly crystallized niobates consisting of edge-sharing NbO6 octahedra, and then the microporous fibers crystallize and grow by assembling NbO6 octahedra or clusters of NbO6 octahedra and NaO6 units. Thus, the selection of the fibril or cubic product is achieved by control of reaction kinetics. Finally, niobates with different structures exhibit remarkable differences in light absorption and photoluminescence properties. Therefore, this study is of importance for developing new functional materials by the wet-chemistry process.
Keyword Chemistry, Multidisciplinary
Octahedral Molecular-sieves
Na0.5k0.5nbo3 Thin-films
Sodium Niobate
Solid-solutions
Electrochemical Performance
Potassium Hexaniobate
Room-temperature
Mas Nmr
Nanotubes
K4nb6o17
Q-Index Code C1

 
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Created: Wed, 15 Aug 2007, 09:16:18 EST