NMR techniques in materials physics: a review

Abstract

Nuclear magnetic resonance (NMR) has progressed rapidly over the last decade as a result of improved experimental technology and development of novel approaches. In this review a brief introduction to NMR interactions and relaxation processes is given to allow an appreciation of the experimental developments. The underlying physical principles of the latest NMR methodology for probing solid materials are stressed. Techniques covered include pulse Fourier transform with emphasis on the difficulties of recording broad resonances and strategies for overcoming them. Selective experiments such as polarization transfer are included. The major impetus given to NMR spectroscopy by improved resolution through line-narrowing methods is detailed. Advanced methods such as multiple quantum and two-and three-dimensional spectroscopy are also discussed. NMR as a probe of microscopic dynamic behaviour through relaxation and direct diffusion measurements over a wide temperature range is examined. Recent developments in magnetic resonance imaging that now offer the possibility of non-destructive investigation of materials are presented. Dr M E Smithhas been interested in solid state NMR for over a decade. He learnt the art from Professor R Dupree, graduating with a PhD from the University of Warwick in 1988 and has subsequently held appointments with Bruker Analytische Messtechnik and CSIRO Division of Materials Science in Melbourne as a physicist specializing in solid state NMR. He was appointed lecturer in the Physics Department at the University of Kent in 1992 and is now Reader in Solid State NMR, where his main research interest is to develop NMR into an accepted technique for materials characterization.

Beryllium-9 NMR Study of Solid Bis(2,4-pentanedionato-O,O‘)beryllium and Theoretical Studies of 9Be Electric Field Gradient and Chemical Shielding Tensors. First Evidence for Anisotropic Beryllium Shielding

“…Cross polarization (CP) was not employed because of the observed pronounced distortion of the central transition line shape caused by this technique. Barrie has reported similar problems in the 27 Al NMR spectra of Al(acac) 3 . 20 MAS samples were spun at a rate of 5.0 kHz to suppress the first-order quadrupolar interaction and chemical shielding anisotropy.…”

“…Quadrupolar parameters determined in the solid state have the additional advantage that the "solvent effects" are well-defined; the surrounding molecules have long-range crystallographic order. For comparison, consider Co(acac) 3 . In the solid state, a single-crystal 59 Co NMR study 18 yielded the values C Q ) 5.53 ( 0.10 MHz and η ) 0.219 ( 0.005.…”

“…In the solid state, a single-crystal 59 Co NMR study 18 yielded the values C Q ) 5.53 ( 0.10 MHz and η ) 0.219 ( 0.005. In acetonitrile solution, C Q ) 4.8 MHz at 298.8 K, 16 while in acetone and diglyme, C Q ) 4.5 MHz, and in benzene, C Q ) 4.2 MHz at 298 K. 16,40 For Al(acac) 3 , 27 Al NMR studies in the solid state 19 revealed values of C Q ) 3.03 ( 0.01 MHz and η ) 0.15 ( 0.01, while in toluene solution, the quadrupole coupling constant has been reported as 0.49 MHz. 21 These data clearly demonstrate the marked dependence of C Q on solvation.…”

“…1,2 In the solid state, the observation of the spectra of halfinteger spin quadrupolar nuclei is a rapidly growing area of research partly as a result of the potential applications to the materials and biological sciences, where quadrupolar nuclei such as 27 Al, 17 O, 11 B, and 23 Na, for example, are of interest. 3,4 Recent advances in experimental solid-state NMR methodology for halfinteger spin quadrupolar nuclei have been summarized by Smith and van Eck. 5 An important advantage of using NMR to study solids is its ability to characterize not only the isotropic values of the various NMR interactions but also the individual tensor components, which, in principle, should provide more insight into the nature of the interaction as well as the local molecular and electronic structures.…”

Analyse spectrale paramétrique et non-paramétrique du signal de précession libre en RMN

“…Sous ces deux aspects, la RMN est une méthode d'analyse extrêmement performante utilisée pour les investigations dans le coeur de la matière. La signature de ces investigations est appelée signal de précession libre ou Free Induction Decay (FID) [1][2][3][4]. Pour des expériences classiques de RMN, le signal FID est analysé par des méthodes non paramétriques : FFT (Fast Fourier Transform), Périodogramme, Corrélogramme, etc., et par des méthodes paramétriques : AR (Auto-Regressive modelling), ARMA (AutoRegressive with Moving Average) [5].…”