Synthesis, Decomposition and Crystallization Characteristics of Peroxo-Citrato-Niobium: An Aqueous Niobium Precursor
详细信息 查看全文
- 作者：Y. Narendar and Gary L. Messing
- 刊名：Chemistry of Materials
- 出版年：1997
- 出版时间：February 1997
- 年：1997
- 卷：9
- 期：2
- 页码：580 - 587
- 全文大小：320K
- 年卷期：v.9,no.2(February 1997)
- ISSN：1520-5002
文摘
The synthesis of peroxo-citrato-niobium, a novel aqueousprecursor of niobium, isreported. Niobium oxalate was decomposed with acidifiedH2O2 to form a peroxo-niobiumcomplex, which was reacted with citric acid at pH ~ 7.5 to form thestable peroxo-citrato-niobium complex. IR and Raman spectroscopy indicate that theperoxo-citrato-niobiumcomplex consists of tridentate bridging citrato and bidentate peroxoligands. The aqueouscomplex is binuclear with peroxo groups chelated to niobium and theprecipitated complexis polynuclear with bridging type peroxo groups. Due to kineticlimitations duringcrystallization, the formation of seven-coordinated niobium inperoxo-citrato-niobiumenergetically favors the formation of niobium oxides withseven-coordinated niobium, viz.TT-Nb2O5 andT-Nb2O5. Consequently, nanocrystallinemetastable TT-Nb2O5, with aparticle size of ~25 nm, crystallizes from theperoxo-citrato-niobium complex at 580 
C.On further heating, TT-Nb2O5 transformsto T-Nb2O5 at 800 C,M-Nb2O5 at 1000 C,and H-Nb2O5 at 1200 C. The nanometricparticle size is retained after heating to 1200 Cand H-Nb2O5 has an average crystallite sizeof 53 nm.
C.On further heating, TT-Nb2O5 transformsto T-Nb2O5 at 800 C,M-Nb2O5 at 1000 C,and H-Nb2O5 at 1200 C. The nanometricparticle size is retained after heating to 1200 Cand H-Nb2O5 has an average crystallite sizeof 53 nm.