PERGAMON MATERIALS SERIES

Multinuclear Solid-State NMR of Inorganic Materials

by

Kenneth J.D. MacKenzie School of Chemical and Physical Sciences,

Victoria University of Wellington, and New Zealand Institute for Industrial Research and Development

Mark E. Smith Department of Physics, University of Warwick, UK

2002

PERGAMON An Imprint of Elsevier Science

Amsterdam - Boston - London - New York - Oxford - Paris San Diego - San Francisco - Singapore - Sydney - Tokyo

Contents

Preface v

CHAPTER 1 INTRODUCTION 1.1. Methodology of Materials Characterisation by NMR 3 1.2. Historical Aspects of NMR Spectroscopy 6 1.3. Brief Description of the NMR Experiment 7

1.3.1 General Principles 7 1.3.2 Overcoming NMR Spectral Broadening in Solids by MAS 10 1.3.3 Other NMR Experiments used with Solids 11

1.3.3.1 Decoupling 12 1.3.3.2 Cross-Polarisation (CP) 12 1.3.3.3 Spin-Echo Experiments 12 1.3.3.4 Two-Dimensional Experiments 12

1.3.4 Nuclei Suitable for NMR Spectroscopy 13 1.4. Further Reading 17 References 18

CHAPTER 2 PHYSICAL BACKGROUND 2.1. Fundamental Interaction with External Magnetic Fields 23

2.1.1 A Quantum Mechanical Description of the Zeeman Interaction 25 2.1.2 Bulk Magnetisation 26 2.1.3 The Rotating Frame and the Application of RF Pulses 29 2.1.4 Observation of the NMR Signal 34

2.2. Internal Interactions 35 2.2.1 The Dipolar Interaction 37 2.2.2 Scalar Coupling 40 2.2.3 Paramagnetic Coupling 43 2.2.4 Chemical Shielding 44 2.2.5 Knight Shift 48 2.2.6 Quadrupole Interaction 50 2.2.7 Nature of Interactions 57

x Contents

2.3. One Dimensional Methods for Improving Resolution 58 2.3.1 Magic Angle Spinning and First-Order Effects 59

2.3.1.1 Physical Principles 59 2.3.1.2 Formation of Spinning Sidebands 61

2.3.2 Magic Angle Spinning and Higher-Order Effects 63 2.3.2.1 MAS of Second-Order Quadrupole Effects 64 2.3.2.2 Residual Coupling Effects due to Quadrupolar Nuclei inMASSpectra 71 2.3.2.3 Nonequivalent Homonuclear Spins 74

2.3.3 Variable Angle Spinning 74 2.3.4 Double Angle Spinning 75 2.3.5 Multiple Quantum Transitions 77 2.3.6 Ultrasonically-Induced Narrowing 78

2.4. Dipolar Decoupling 78 2.4.1 Heteronuclear Dipolar Decoupling 78 2.4.2 Homonuclear Dipolar Decoupling 79

2.5. Spin-locking 83 2.6. Cross-Polarisation 85 2.7. Two-Dimensional Methods 90

2.7.1 Dynamic Angle Spinning 92 2.7.2 2D MQMAS 93

2.8. NMR Relaxation 98 2.8.1 Introduction to Relaxation 98 2.8.2 Mechanism for Relaxation Processes 101

References 105

CHAPTER 3 EXPERIMENTAL APPROACHES 3.1. Basic Experimental Principles of FT NMR 111 3.2. Instrumentation 112

3.2.1 Overview of a Pulsed FT NMR Spectrometer 112 3.2.2 Magnets 113 3.2.3 Shimming 115 3.2.4 Transmitters 116 3.2.5 Probes 120 3.2.6 Connection of the Probe 122 3.2.7 Signal Detection 124 3.2.8 Additional Equipment 127

Contents XI

3.3. Practical Acquisition of NMR Spectra 127 3.3.1 Processing the FID to Produce a Spectrum 128

3.3.1.1 Window Functions 128 3.3.1.2 Shifting of the Time Origin and Linear Back

Prediction 129 3.3.1.3 ZeroFilling 129 3.3.1.4 Phase Correction 130 3.3.1.5 Baseline Correction 130

3.3.2 Complications in Recording Spectra 130 3.4. Static Broad Line Experiments 133

3.4.1 Pulsed Echo Experiments 133 3.4.2 Stepped Experiments 136

3.5. One-Dimensional High Resolution Techniques 138 3.5.1 Magic Angle Spinning (MAS) 138 3.5.2 Extraction of Parameters from MAS NMR Spectra 143 3.5.3 Suppression of Spinning Sidebands 143 3.5.4 Special Considerations for MAS of Quadrupolar Nuclei 144 3.5.5 Magic Angle Spinning Observation of Satellite Transitions 149 3.5.6 Double Angle Rotation of Quadrupolar Nuclei 150 3.5.7 Practical Implementation of CRAMPS 152

3.6. Two-Dimensional Experiments 153 3.6.1 NutationNMR 153 3.6.2 Off-Resonance Nutation 154 3.6.3 Order-Resolved Sideband Spectra 155 3.6.4 Dynamic Angle Spinning (DAS) 156 3.6.5 Two-Dimensional Sequences Developed from Solution NMR 157 3.6.6 Multiple Quantum Experiments in Dipolar Coupled Systems 160 3.6.7 Multiple Quantum NMR Experiments of Non-Integer 161

Spin Quadrupolar Nuclei 3.6.8 2D XY Correlation Methods 168 3.6.9 Correlation of Tensor Information - Separated Local 170

Field Experiments 3.7. Summary of Approaches for Examining Quadrupole Nuclei 172 3.8. Multiple Resonance 172

3.8.1 Cross-Polarisation (CP) 173 3.8.2 SEDOR, REDOR and TEDOR 178 3.8.3 TRAPDOR and REAPDOR 182

3.9. Techniques for Determining Relaxation Times and Motional 183 Parameters 3.9.1 MeasurementofTi 183

Xll Contents

3.9.2 Other Spin-Lattice Relaxation Times (T lp T1D) 184 3.9.3 Transverse Relaxation Times (T2) 185 3.9.4 Molecular Motion 186 3.9.5 Diffusion Measurements 187

3.10. NMR Under Varying Physical Conditions 187 3.10.1 Variable Temperature NMR 187 3.10.2 High Pressure Experiments 189

References 190

CHAPTER 4 29SI NMR

4.1. General Considerations 201 4.1.1 Broadening Effects in 29Si Spectra 201 4.1.2 Relaxation Effects in 29Si Spectra 202 4.1.3 Effect of Structure on 29Si Spectra 204

4.2. Si-0 Compounds 205 4.2.1 Relationships between 29Si NMR Spectra and 205

Structure/Bonding 4.2.2 Four-Coordinated Si-O-Compounds 205 4.2.3 Tetrahedral 29Si Chemical Shifts in Silicates 205 4.2.4 29Si Chemical Shifts in Aluminosilicates 206 4.2.5 Effects of Other Nearest Neighbours on the 29Si Shift 208

4.3. Order-Disorder Effects in Minerals 208 4.4. Identification of Silicate Minerals 212 4.5. Thermal Decomposition of Silicate Minerals 214 4.6. Relationships between 29Si Chemical Shift (d) and Structure 217

4.6.1 Relationships between 8 and the Si-O Bond Length 218 4.6.2 Relationships between 8 and the Si-O-Si Bond Angle 219 4.6.3 More Complex Relationships between 8 and the Structure 223

4.7. Five and Six-Coordinated Si-0 Compounds 225 4.8. Cross-Polarisation (CPMAS) Experiments 227

4.8.1 Cross-Polarisation between'H and 29Si 227 4.8.2 Cross-Polarisation between l9F and 29Si 229 4.8.3 Other Cross-Polarisation Experiments with 29Si 229

4.9. Glasses, Gels and Other Amorphous Materials 230 4.9.1 Silicate Glasses 231 4.9.2 Deconvolution of 29Si NMR Spectra 235 4.9.3 Connectivities in Glass 236 4.9.4 Chalcogenide Glasses 238

Contents Xll l

4.9.5 Gels 240 4.9.6 Other Amorphous Materials 242

4.10. Si-N and Si-N-0 Compounds 244 4.11. Si-Al-O-N Compounds 247

4.11.1 /3-Sialon, Si6_zAlzOzN8_z 247 4.11.2 O-Sialon, Si2_xAlx01+xN2.x 250 4.11.3 X-Sialon, nominally Si12Al I8039N8 251 4.11.4 Polytypoid Sialons, (Si,Al)m(OJSf)m+] 253 4.11.5 a-Sialons, MxSii2.(m+n)Alm+nOnN16_n 253

4.12. Other Metal Silicon Nitrides and Oxynitrides 253 4.13. Si-C, Si-C-O and Si-C-N Compounds 255

4.13.1 Silicon Oxycarbide Species 256 4.13.2 Silicon Carbonitride Species 257

4.14. Other Materials 257 4.14.1 Biologically Compatible Glasses 257 4.14.2 Cements 257 4.14.3 Inorganic Polymers 259

References 260

CHAPTER 5 27AL NMR

5.1. General Considerations 271 5.2. Chemical Shifts in 27A1 Spectra 272

5.2.1 27A1 Chemical Shifts in Al-O Environments 273 5.2.2 27A1 Chemical Shifts in Aluminosilicates 274 5.2.3 Relationships between 27A1 Chemical Shift (8jso) and Structure 279

5.3. Five-Coordinated Al-0 281 5.3.1 A1(V) in Well-Defined (Crystalline) Environments 281 5.3.2 A1(V) in Non-Crystalline Environments 283 5.3.3 A1(V) in Zeolites 287

5.4. Aluminium Oxides 291 5.5. Amorphous Aluminium Compounds 294

5.5.1 Aluminate Gels 294 5.5.2 Glasses 299 5.5.3 Other Amorphous Systems 303

5.6. Aluminophosphates 304 5.7. Aluminium Borate and Molybdate 307

5.7.1 Aluminium Borate 307 5.7.2 Aluminium Molybdate 307

XIV Contents

5.8. Aluminium Fluorides 308 5.9. Thermal Decomposition Reactions 310

5.10. Cements 313 5.11. Nitride and Oxynitride Compounds 316 5.12. Sialon Compounds 317

5.12.1 Polytypoid Sialons 317 5.12.2 ß-Sialons 318 5.12.3 O-Sialons 320 5.12.4 X-Sialons 321 5.12.5 a-Sialons 322 5.12.6 Sialon Glasses 323

References 324

CHAPTER 6 l 7 0 NMR 6.1. Introduction 333 6.2. Background 334

6.2.1 Enrichment Schemes 334 6.2.2 Experimental NMR Methodology 337 6.2.3 Relationships between NMR Parameters and Structure 346

6.3. Binary Oxides 349 6.3.1 Crystalline Materials 349 6.3.2 Sol-Gel Produced Samples 352

6.4. Crystalline Ternary Ionic Systems 355 6.5. Silicates and Germanates 359

6.5.1 Crystalline Materials 359 6.5.1.1 Silica and Germania 359 6.5.1.2 Ternary Silicates 361 6.5.1.3 Silicates and Germanates of Zirconium and Titanium 365

6.5.2 Amorphous Materials 366 6.5.2.1 Silica and Germania 366 6.5.2.2 Metal Silicate and Germanate Glasses 367 6.5.2.3 Gel-Based Silicates 369

6.6. Aluminium- and Gallium-Containing Systems 372 6.6.1 Alumina and Aluminates 372 6.6.2 Crystalline Alumino- and Gallosilicates 375 6.6.3 Amorphous Aluminosilicates 379

6.7. Boron-Containing Systems 381 6.7.1 Borates 381

Contents xv

6.7.2 Ternary and Quaternary Systems 382 6.8. Other Systems 384 6.9. Hydrogen-Containing Samples 386

6.9.1 Crystalline Hydroxides and Other Hydrogen-Containing 386 Materials

6.9.2 Hydrous Gels and Glasses 387 6.10. High Temperature Ceramic Superconductors 388 References 390

CHAPTER 7 NMR OF OTHER COMMONLY STUDIED NUCLEI

7.1. 23NaNMR 399 7.1.1 General Considerations 399 7.1.2 23Na NMR Spectra of Sodium Compounds 399 7.1.3 Relationships between the 23Na Chemical Shift and 403

Structural Parameters 7.1.4 23Na NMR of Crystalline Materials 406 7.1.5 23Na NMR Studies of Thermal Reactions 412 7.1.6 23Na NMR of Glasses 413

7.1.6.1 Silicate and Aluminosilicate Glasses 413 7.1.6.2 Sodium Borosilicate Glasses 414 7.1.6.3 Sodium Borate, Germanate and Tellurite 415 Glasses and Melts 7.1.6.4 Phosphate Glasses 415 7.1.6.5 Miscellaneous Glass Studies 416

7.1.7 23NaNMRofZeolites 418 7.2. "BNMR 420

7.2.1 General Considerations 420 7.2.2 "B NMR of Crystalline Compounds 421 7.2.3 ' 'B NMR of Glasses 424 7.2.4 ' 'B NMR of Zeolites 431

7.3. 31PNMR 432 7.3.1 Relationships between 31P NMR Parameters and Structure 438 7.3.2 31P NMR of Glasses 441

7.3.2.1 Binary Phosphate Glasses 441 7.3.2.2 Phosphosilicate Glasses 443 7.3.2.3 Alkali Borophosphate Glasses 445 7.3.2.4 Borosilicophosphate Glasses 445 7.3.2.5 Phosphoaluminosilicate Glasses 446 7.3.2.6 Alkali Phosphoaluminoborosilicate Glasses 447

XV) Contents

7.3.2.7 Phosphorus Chalcogenide Glasses 7.3.3 31P NMR of AlP04Molecular Sieves 7.3.4 31P NMR of Biomaterials

References

447 448 450 452

CHAPTER 8 NMR OF LOW--Y NUCLIDES 8.1. General Considerations

8.1.1 Problems Associated with Low-y Nuclei 8.2. NMR of Spin-'/2 Nuclei

"9Y NMR 107Ag and 109Ag NMR

8.2.1 8.2.2 8.2.3 ' " W N M R

8.3. Quadrupolar Nuclei 8.3.1 14NNMR

25Mg NMR 33S NMR 35C1 and 37C1 NMR 39K NMR 43Ca NMR 47Ti and 49Ti NMR 67Zn NMR 91Zr NMR

95Mo and 97Mo NMR 1 3 5Baand1 3 7BaNMR Other Miscellaneous Low-y Nuclei

8.3.2 8.3.3 8.3.4 8.3.5 8.3.6 8.3.7 8.3.8 8.3.9 8.3.10 8.3.11 8.3.12

References

461 461 462 462 469 473 475 475 479 488 491 495 502 505 511 514 516 522 525 526

CHAPTER 9 N M R OF OTHER SPIN-1/;, NUCLEI

9.1. Introduction 9.2. Abundant High-y Nuclei

9.2.1 'HNMR 9.2.1.1 Background to Proton Studies in Inorganic Materials 9.2.1.2 Studies of Stoichiometric Protons in

Crystalline Materials 9.2.1.3 Non-Stoichiometric Proton Environments in

Crystalline and Glassy Materials

535 536 536 536

539

542

Contents xvn

9.2.1.4 'H NMR ofHydrous Glasses 545 9.2.1.5 Biomineral-Related Materials 550

9.2.2 19F NMR 550 9.2.2.1 Introduction 550 9.2.2.2 Simple Inorganic Fluorides 551 9.2.2.3 More Complex Fluorides 554 9.2.2.4 Applications to Fluoroapatite Studies 555 9.2.2.5 Fluorine in Aluminosilicate Minerals and

Related Materials 556 9.2.2.6 Surface Interaction of Fluorine with Silica- and

9.3.

Alumina-Based Materials 9.2.2.7 Fluorine in Alumino- and Gallophosphates 9.2.2.8 Fluorine in Oxygen-Containing Glasses 9.2.2.9 Fluoride Glasses 9.2.2.10 Fluorine in Other Materials 9.2.2.11 Fluorine as a Source of Cross-Polarisation 9.2.2.12 Summary of 19F Shift Trends and Other

NMR Properties Dilute or Medium-7 Nuclei 9.3.1

9.3.2

9.3.3 9.3.4 9.3.5

9.3.6

13C NMR 9.3.1.1 13C NMR of Elemental Carbon 9.3.1.2 Silicon Carbide 9.3.1.3 Other Binary Carbides 9.3.1.4 Ternary and Quaternary Carbides 9.3.1.5 Carbonates

15NNMR 9.3.2.1 Nitrides 9.3.2.2 Silicon Aluminium Oxynitride Ceramics and Glasses 9.3.2.3 Nitride Ceramics from Polymerie Precursors 9.3.2.4 Nitrates and Nitrites 77Se NMR l u Cdand 1 1 3 CdNMR "5Sn, 117Snand119SnNMR 9.3.5.1 Crystalline Oxygen-Containing Materials 9.3.5.2 Oxide Solid Solutions and Glasses 9.3.5.3 Non-oxide Materials 123Teand 125TeNMR 9.3.6.1 Crystalline Tellurides 9.3.6.2 Crystalline Tellurites and Tellurates 9.3.6.3 Glassy Tellurium-Containing Materials

557 559 559 560 562 562

562 563 563 563 568 570 572 572 574 575 576 579 582 583 587 591 591 594 595 598 598 599 601

xvin Contents

9.3.7 l29XeNMR 601 9.3.8 195Pt NMR 603 9.3.9 199Hg NMR 604 9.3.10 203T1 and 205T1 NMR 604 9.3.11 207PbNMR 607

9.3.11.1 Correlations between 207Pb Chemical Shifts and Structure 607

9.3.11.2 207Pb NMR of Crystalline Lead Compounds 609 9.3.11.3 2ü7Pb NMR of Lead-Containing Glasses 613 9.3.11.4 2ü7Pb in Sol-Gel Prepared Ceramics 615

References 616

CHAPTER 10 NMR OF OTHER QUADRUPOLAR NUCLEI 10.1. 6Liand7LiNMR 629

10.1.1 General Considerations 629 10.1.2 6 JLi NMR of Crystalline Solids 630 10.1.3 Relation between 6Li Chemical Shifts and Structure 634 10.1.4 67Li NMR of Fast Lithium Ion Conductors 636 10.1.5 6 JLi NMR of Glasses 638

10.2. 9BeNMR 639 10.3. 5 IVNMR 642

10.3.1 General Considerations 642 10.3.2 51V NMR of Vanadium Oxides and the Vanadates 642 10.3.3 51VNMRofZeolitesandCatalysts 646

10.4. 63Cu and 65Cu NMR 649 10.4.1 63Cu NMR of Superconductors and Superfast lonic Conductors

650 10.5. 6 9Gaand7 1GaNMR 653

10.5.1 General Considerations 653 10.5.2 6 9 7 lGa NMR of Crystalline Compounds 655 10.5.3 6971Ga NMR of Other Compounds 657

10.6. 87Rb NMR 658 10.6.1 General Considerations 658 10.6.2 87Rb NMR of Crystalline Compounds 658 10.6.3 87Rb NMR of Rubidium Fullerides 661

10.7. 93Nb NMR 662 10.8. l 33CsNMR 665

10.8.1 General Considerations 665

Contents xix

10.8.2 133Cs NMR of Crystalline Caesium Compounds 666 10.8.3 l33Cs NMR of Minerals and Zeolites 669 10.8.4 133Cs NMR of Füllendes, Superionic Conductors 673

and Semiconductors 10.9. 139LaNMR 674 References 678

CHAPTER 11 SOLID STATE NMR OF METALS AND ALLOYS 11.1. Introduction 687 11.2. Experimental Approaches 689 11.3. Metallic Elements 691 11.4. Intermetallic Alloys 693 11.5. Phase Transformations, Ordering and Defect Sites 696 11.6. Phase Composition and Precipitation 698 11.7. Atomic Motion 700 References 701

SUBJECT INDEX MINERAL INDEX

703