Chemistry of Tantalum and Niobium Fluoride

Electronic, optical, mechanical and medical appliances are just a few examples of modern applications that use tantalum and niobium. In Chemistry of Tantalum and Niobium Fluoride Compounds, the author draws on thirty years' experience to produce the first ever monograph to systemize and summarize the data available on tantalum and niobium fluoride compounds. This comprehensive reference source offers a rich variety of study methodology and is invaluable to researchers examining the chemistry of fluorides, as well as teachers and students in chemistry and metallurgy. * Collects the latest research on the chemistry of complex fluorides and oxyfluorides of Tantalum and Niobium. * Covers both theory and application of Tantalum and Niobium Fluoride Chemistry * Is suitable for tantalum and niobium producers, researchers studying the chemistry of fluorides, as well as teachers and students in chemistry and metallurgy

Preface

vii

1. Introduction

1

(10)

1.1. General information on the applications of tantalum and niobium

1

(3)

1.2. Tantalum and niobium raw materials

4

(1)

1.3. Refining processes

5

(3)

1.4. Material science aspects

8

(3)

2. Synthesis of tantalum and niobium fluoride compounds

11

(48)

2.1. Aqueous solutions

12

(11)

2.2. Non-aqueous solutions

23

(1)

2.3. Interactions with TaF5 and NbF5

24

(2)

2.4. Synthesis of oxyfluoride compounds using NbO2F and TaO2F

26

(12)

2.4.1. Interactions in NbO2F - M2CO3 systems

26

(6)

2.4.2. Interactions in TaO2F - M2CO3 systems

32

(2)

2.4.3. Interaction mechanism in systems containing carbonates

34

(4)

2.5. Hydrofluoride synthesis of niobium and tantalum compounds

38

(21)

2.5.1. Synthesis of fluorotantalates

41

(8)

2.5.2. Synthesis of oxyfluoroniobates

49

(7)

2.5.3. Hydrofluoride synthesis: performance and capability

56

(3)

3. Crystal chemistry of tantalum and niobium fluoride compounds

59

(66)

3.1. Island-type structure compounds

60

(22)

3.2. Compounds with chain-type structures

82

(10)

3.3. Compounds with layered-type structures

92

(9)

3.4. Compounds with framework-type structures

101

(8)

3.5. Compounds with coordination-type structures

109

(7)

3.6. Crystal chemical classification

116

(9)

4. Tantalum and niobium complexes in fluoride solutions

125

(10)

4.1. Niobium-containing solutions

125

(5)

4.2. Tantalum -containing solutions

130

(5)

5. Tantalum and niobium complexes in fluoride melts

135

(60)

5.1. Preliminary notes

135

(2)

5.2. Melting diagrams

137

(11)

5.2.1. Niobium-containing systems

137

(7)

5.2.2. Tantalum-containing systems

144

(4)

5.3. Physicochemical properties

148

(20)

5.3.1. General observations

148

(2)

5.3.2. Physicochemical properties of fluoride melts containing niobium

150

(1)

5.3.3. Physicochemical properties of fluoride melts containing tantalum

151

(17)

5.4. Vibration spectroscopy of fluoride melts

168

(23)

5.4.1. Experimental techniques

168

(5)

5.4.2. Brief review of molten fluoride systems

173

(3)

5.4.3. Tantalum-containing fluoride melts

176

(9)

5.4.4. Niobium-containing fluoride melts

185

(6)

5.5. Main conclusions

191

(4)

6. Thermal properties and decomposition of tantalum- and niobium- containing fluoride compounds

195

(22)

6.1. Impact of temperature on solid fluoride complexes

195

(5)

6.2. Melting processes

200

(2)

6.3. Thermal decomposition of oxyfluoroniobates

202

(3)

6.4. Gaseous components

205

(10)

6.5. Main conclusions

215

(2)

7. Ferroelectric properties of niobium and tantalum fluoride compounds

217

(36)

7.1. General notes

217

(3)

7.2. Compounds derived from lithium metatantalate

220

(3)

7.3. Spontaneous polarization and non-linear optical effect in niobium and tantalum fluoride compounds

223

(11)

7.3.1 General notes

223

(1)

7.3.2. Order-disorder mechanism

224

(8)

7.3.3. Displacement mechanism

232

(2)

7.4. Piezoelectric, pyroelectric and related properties in M5Nb3OF18 compounds

234

(19)

7.4.1. General notes

234

(2)

7.4.2. Preparation and thermal stability

236

(1)

7.4.3. Crystal structure and powder X-ray diffraction

237

(1)

7.4.4. Microcalorimetry

237

(2)

7.4.5. Thermal dependence of birefringence

239

(1)

7.4.6. Raman spectra

240

(3)

7.4.7. Dielectric measurements

243

(2)

7.4.8. Piezoelectric resonance and electromechanical properties

245

(3)

7.4.9. Pyroelectric measurements

248

(3)

7.4.10. Conclusions

251

(2)

8. Fluorine chemistry in the processing of tantalum and niobium

253

(86)

8.1. General notes

253

(3)

8.2. Raw material decomposition

256

(11)

8.2.1. Digestion using hydrofluoric and sulfuric acid

256

(7)

8.2.2. Decomposition by molten ammonium hydrofluoride

263

(4)

8.3. Liquid-liquid extraction

267

(25)

8.3.1. General notes

267

(7)

8.3.2. Mechanism of tantalum and niobium extraction

274

(2)

8.3.3. Extraction schemes

276

(3)

8.3.4. Frequently used extractants

279

(3)

8.3.5. Process performance

282

(2)

8.3.6. Extraction of tantalum and niobium with 2-octanol - definition of the process parameters

284

(8)

8.4. Preparation of tantalum and niobium oxides

292

(24)

8.4.1. General notes

292

(1)

8.4.2. Precipitation of hydroxides by ammonia solution

293

(6)

8.4.3. Washing and of hydroxides

299

(1)

8.4.4. Thermal treatment of hydroxides

300

(3)

8.4.5. Other methods for precipitation of tantalum and niobium oxide precursors

303

(6)

8.4.6. Plasma chemical decomposition of fluoride solutions

309

(7)

8.5. K - salt production

316

(4)

8.6 The production of tantalum and niobium metals by reduction of fluoride melts

320

(21)

8.6.1. General notes

320

(1)

8.6.2. Electrolysis of melts

320

(6)

8.6.3. Reduction of tantalum and niobium with sodium

326

(13)

9. Main principals of the chemistry of tantalum and niobium fluoride compounds

339

(2)

Appendix (X - ray powder diffraction data of some important tantalum and niobium fluoride compounds)

341

(14)

Niobium-containing compounds

341

(7)

Tantalum-containing compounds

348

(7)

References

355

(28)

Subject index

383

(6)

Formula index

389

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Chemistry of Tantalum and Niobium Fluoride Compounds

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