Die Modifikationen des Niobpentoxids

Schäfer, Harald; Gruehn, R.; Schulte, Friedrich

doi:10.1002/ange.19660780104

Cited by 142 publications

(25 citation statements)

References 36 publications

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“…8(b). We did not observe the superstructure in the mono-Nb12029 which was described as 'Ox-I' by Sch/ifer, Gruehn & Schulte (1966) and Browne, Hutchison & Anderson (1972), but there is no doubt that its structure also consists of a regular arrangement of the linear chains of the pairs of the point defects similar to the superstructure of ortho-NblzOz9 mentioned before.…”

Section: Faulted Slabssupporting

confidence: 49%

Ordering of the point defects in nonstoichiometric crystals of Nb₁₂O₂₉

Iijima¹

1975

Acta Cryst Sect A

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Section: Faulted Slabssupporting

confidence: 49%

Ordering of the point defects in nonstoichiometric crystals of Nb₁₂O₂₉

Iijima¹

1975

Acta Cryst Sect A

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“…Based on data from the literature (SCHAFER et al 1964 and1966 The fact that during the chemical transport of a V,O,/Nb,O, sample in the molar ratio of 8:92 a phase with the composition Vl,osNb8,94025 was obtained as the transport product and that no Nb,O, was detectable besides that (SCHADOW, OPPERMANN et al) surely can be put down to the fact that in this case the low quantities of Nb,O, transported first were bonded by the quartz of the ampoule walls at the applied high transport temperatures, so that they can escaped detection. There points to it, too, that even the crystals precipitated from the gaseous phase at 873 K had firmly grown on the ampoule walls.…”

Section: Performing Of Experiments and Resultsmentioning

confidence: 99%

Investigations on the Quasi‐binary Subsystem VNb₉O₂₅Nb₂O₅

Schadow¹,

Oppermann²,

Grossmann³

1992

Cryst. Res. Technol.

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By X-ray phase analysis in connection with chemical transport reactions it was proved that two boundary phases coexist in the pseudo-binary subsystem VNb,O,, -Nb,O,. The maximum solubility of V,O, in solid N b , 0 5 which was spectrometrically determined in corresponding chemically transported samples of the system is 0.37% (n/n). The examination of the pseudo-binary system V,O, -Nb,O, (SCHADOW, OPPERMANN et al.) did not allow any safe statements concerning the phases occurring in the subsystem VNb,O,,-Nb,O, and their solubility limits, since there was not achieved an exact phase separation in this range of composition by chemical transport reactions under the conditions applied at that time. Therefore, a detailed investigation was carried out in the subregion VNb,O,, -Nb,O, of the system V,O, -Nb,O,, previously produced VNb,O,, having been used as starting material. Moreover, the temperatures during the chemical transport were lowered considerably in order to achieve a better phase separation. These additional investigations were necessary also because WARINC and ROTH had referred to a phase containing 6 . . . 7 % (n/n) V,O, which is not characterized in more detail in this system. ExperimentalThe VNb,O,, used as starting material for the investigation of the system was produced by annealing a mixture of V,O, and Nb,O, in the corresponding molar ratio. First, the wellhomogenized mixture was pre-annealed in a closed quartz ampoule for 250 h at 873 K, then it was homogenized and subsequently annealed for another 300 h at 1273 K. The following X-ray examination showed that the product of reaction was phase-pure VNb9025. The phase separation in the subsystem VNb,O,,-Nb,O, was carried out with the aid of chemical transport reactions in such a way as described in detail for the investigation of the binary system V,O, -Nb,O, (SCHADOW, OPPERMAUN et al.). Only the transport temperatures were kept much lower (973 + 873 K). An equimolar mixture NbCl,/CI, was used as the means of transport. The quantity of the means of transport was such that a pressure of 200 kPa was obtained at the mean transport temperature.For the spectrophotometric analysis of the chemically transported products the respective samples were triturated and melted in platinum crucible with sodium carbonate. After that, the melting cake was leached with water, the obtained niobium-hydroxide precipitate was filtered off and in the filtrate the vanadium was determined as yellow vanadium(I1) phosphotungstic acid.

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“…The oxide hydrate is filtered, washed, and calcined at 800 -1100 C. The temperature and treatment time determine which of the various crystalline modifications is formed. Nearly all the phase changes are irreversible [23][24][25].…”

Section: Chlorinationmentioning

confidence: 99%

Niobium and Niobium Compounds

Albrecht

Cymorek

Eckert

2011

Ullmann's Encyclopedia of Industrial Chemistry

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The article contains sections titled: 1. Introduction 2. Properties 2.1. Physical Properties 2.2. Chemical Properties 3. Occurrence 4. Processing of Niobium Ores 4.1. Winning of Pyrochlore Concentrates 4.2. Treatment of Pyrochlore Concentrates 4.3. Production of Niobium Oxide from Columbites and Tantalites 4.3.1. Extraction Processes 4.3.2. Chlorination 5. Niobium Compounds 5.1. Oxides 5.2. Halides 5.3. Carbides and Hard Materials 6. Niobium Metal 6.1. Reduction of Niobium Pentoxide 6.2. Reduction of Halides 6.3. Refining 6.4. Uses 7. Ferroniobium 7.1. Production 7.2. Uses of Ferroniobium 8. Analysis 9. Economic Aspects

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Die Modifikationen des Niobpentoxids

Cited by 142 publications

References 36 publications

Ordering of the point defects in nonstoichiometric crystals of Nb₁₂O₂₉

Ordering of the point defects in nonstoichiometric crystals of Nb₁₂O₂₉

Investigations on the Quasi‐binary Subsystem VNb₉O₂₅Nb₂O₅

Niobium and Niobium Compounds

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Die Modifikationen des Niobpentoxids

Cited by 142 publications

References 36 publications

Ordering of the point defects in nonstoichiometric crystals of Nb12O29

Ordering of the point defects in nonstoichiometric crystals of Nb12O29

Investigations on the Quasi‐binary Subsystem VNb9O25Nb2O5

Niobium and Niobium Compounds

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Ordering of the point defects in nonstoichiometric crystals of Nb₁₂O₂₉

Ordering of the point defects in nonstoichiometric crystals of Nb₁₂O₂₉

Investigations on the Quasi‐binary Subsystem VNb₉O₂₅Nb₂O₅