Synthesis of transparent mixed vanadia/niobia gels and their decomposition to a new metastable VNb9O25 phase

被引：12

作者：

Mayer-Uhma, T. ^{[1
]}

Langbein, H. ^{[1
]}

机构：

[1] Tech Univ Dresden, Dept Chem, D-01069 Dresden, Germany

来源：

THERMOCHIMICA ACTA | 2006年 / 447卷 / 02期

关键词：

sol-gel synthesis; V2O5/Nb2O5 complex oxides; thermal analysis; XRD;

D O I：

10.1016/j.tca.2006.06.003

中图分类号：

O414.1 [热力学];

学科分类号：

摘要：

Controlled hydrolysis and condensation of a mixture of vanadyl-tris-n-propoxide, VO(OPr)(3), and niobium pentaethoxide, [Nb(OEt)(5)](2), at 5 degrees C in propanol yields clear and transparent gets in which the ratio of V:Nb is 1: 1, 1:4.5 or 1:9. Oxalic acid and low temperatures are used to slow down the rate of condensation processes. At 800 degrees C, the thermal decomposition of a gel with the composition 1:9 forms a thermodynamically metastable, new phase of the composition VNb9O25. At lower temperatures, metastable solid solutions with TT-Nb2O5 structure (600 degrees C) and M-Nb2O5 structure (700 degrees C) are formed from the amorphous xerogel. The new VNb9O25 phase is structurally related to M-Nb2O5. The solid solution with M-Nb2O5 structure acts structure directing, leading preferentially to a monoclinic low-temperature form of VNb9O25. The full transformation of this metastable phase to the well known tetragonal VNb9O25 requires a annealing temperature of about 1000 degrees C. (C) 2006 Elsevier B.V. All rights reserved.

引用

页码：178 / 183

页数：6

共 30 条

[1]

ALQUIER C, 1986, J NON CRYSTAL SOL, V79, P319

[2] SYNTHESIS AND CHARACTERIZATION OF THE NEW MIXED-OXIDE NBVO5 [J].

AMARILLA, JM ;

CASAL, B ;

RUIZHITZKY, E .

MATERIALS LETTERS, 1989, 8 (3-4) :132-136

[3]

AMINI MM, 1990, MATER RES SOC SYMP P, V180, P675, DOI 10.1557/PROC-180-675

[4] Electrical conductivity of the ceramic compounds VNb9O25 and VTa9O25 [J].

Amountza, A ;

Riza, F ;

Kasselouri, V .

MATERIALS LETTERS, 2003, 57 (15) :2298-2304

[5] SYNTHESIS AND THERMAL EVOLUTION OF STRUCTURE IN ALKOXIDE-DERIVED NIOBIUM PENTOXIDE GELS [J].

BANSAL, NP .

JOURNAL OF MATERIALS SCIENCE, 1994, 29 (17) :4481-4486

[6] Mixed-oxide catalysts involving V, Nb and Si obtained by a non-hydrolytic sol-gel route: preparation and catalytic behaviour in oxydative dehydrogenation of propane [J].

Barbieri, F ;

Cauzzi, D ;

De Smet, F ;

Devillers, M ;

Moggi, P ;

Predieri, G ;

Ruiz, P .

CATALYSIS TODAY, 2000, 61 (1-4) :353-360

[7] VM9O25(M = NB, TA), A COMBINATION OF TETRAHEDRAL VO4 AND OCTAHEDRAL MO6 UNITS [J].

CASAIS, MT ;

GUTIERREZPUEBLA, E ;

MONGE, MA ;

RASINES, I ;

RUIZVALERO, C .

JOURNAL OF SOLID STATE CHEMISTRY, 1993, 102 (01) :261-266

[8] Synthesis of alkoxide-derived V-Nb catalysts prepared by sol-gel route [J].

Catauro, M ;

Pagliuca, C ;

Lisi, L ;

Ruoppolo, G .

THERMOCHIMICA ACTA, 2002, 381 (01) :65-72

[9]

GOLDSCHMIDT HJ, 1960, METALLURGICA, P212

[10] CONTRIBUTIONS TO THE INVESTIGATION OF INORGANIC NONSTOICHIOMETRIC COMPOUNDS .18. NEW RESULTS CONCERNING THE STRUCTURE AND STABILITY OF M-NB2O5 [J].

HEURUNG, G ;

GRUEHN, R .

ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE, 1982, 491 (08) :101-112

← 1 2 3 →