Local structure in perovskite relaxor ferroelectrics: high-resolution 93Nb 3QMAS NMR

Zhou, Donghua H.; Hoatson, Gina L.; Vold, Robert L.

doi:10.1016/j.jmr.2003.12.015

Cited by 15 publications

(24 citation statements)

References 30 publications

(44 reference statements)

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“…(12) and (13). Explicit expressions for the site frequencies of the central transition in terms of C Q , g, and Euler angles relating PAS to lab fixed axes can be found the literature [50,51,16,52]. EXPRESS uses formulae presented in Ref.…”

Section: Second Order Quadrupole Effectsmentioning

confidence: 99%

Effects of jump dynamics on solid state nuclear magnetic resonance line shapes and spin relaxation times

Vold

Hoatson

2009

Journal of Magnetic Resonance

163

222

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Section: Second Order Quadrupole Effectsmentioning

confidence: 99%

Effects of jump dynamics on solid state nuclear magnetic resonance line shapes and spin relaxation times

Vold

Hoatson

2009

Journal of Magnetic Resonance

163

222

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“…It has also been established in this study that the best computational method(s) of analysis for the niobium phosphates, with niobium(V) oxides and mixed oxides frequently underpinning metal supports and combined metal-oxide catalyst systems. [2,4,10,11] Solid-state niobate chemistry also plays a crucial role in the piezoelectric phases formed by Pb(Mg 1/3 Nb 2/3 )O 3 (PMN) [12,13] and by the solid solutions (1Àx)Pb(Mg 1/3 Nb 2/3 )O 3 ·xPbTiO 3 (PMN/ PT) [14][15][16] and (1Àx)Pb(Mg 1/3 Nb 2/3 )O 3 ·xPb(Sc 1/2 Nb 1/2 )O 3 (PMN/PSN) [17][18][19] comprising the perovskite relaxor ferroelectric families of materials. Furthermore, significant advances in glass fabrication and utility have been associated with the incorporation of Nb V into disordered oxide networks.…”

Section: Introductionmentioning

confidence: 99%

A ⁹³Nb Solid‐State NMR and Density Functional Theory Study of Four‐ and Six‐Coordinate Niobate Systems

Hanna¹,

Pike²,

Charpentier³

et al. 2010

Chemistry A European J

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A variable B(0) field static (broadline) NMR study of a large suite of niobate materials has enabled the elucidation of high-precision measurement of (93)Nb NMR interaction parameters such as the isotropic chemical shift (delta(iso)), quadrupole coupling constant and asymmetry parameter (C(Q) and eta(Q)), chemical shift span/anisotropy and skew/asymmetry (Omega/Deltadelta and kappa/eta(delta)) and Euler angles (alpha, beta, gamma) describing the relative orientation of the quadrupolar and chemical shift tensorial frames. These measurements have been augmented with ab initio DFT calculations by using WIEN2k and NMR-CASTEP codes, which corroborate these reported values. Unlike previous assertions made about the inability to detect CSA (chemical shift anisotropy) contributions from Nb(V) in most oxo environments, this study emphasises that a thorough variable B(0) approach coupled with the VOCS (variable offset cumulative spectroscopy) technique for the acquisition of undistorted broad (-1/2<-->+1/2) central transition resonances facilitates the unambiguous observation of both quadrupolar and CSA contributions within these (93)Nb broadline data. These measurements reveal that the (93)Nb electric field gradient tensor is a particularly sensitive measure of the immediate and extended environments of the Nb(V) positions, with C(Q) values in the 0 to >80 MHz range being measured; similarly, the delta(iso) (covering an approximately 250 ppm range) and Omega values (covering a 0 to approximately 800 ppm range) characteristic of these niobate systems are also sensitive to structural disposition. However, their systematic rationalisation in terms of the Nb-O bond angles and distances defining the immediate Nb(V) oxo environment is complicated by longer-range influences that usually involve other heavy elements comprising the structure. It has also been established in this study that the best computational method(s) of analysis for the (93)Nb NMR interaction parameters generated here are the all-electron WIEN2k and the gauge included projector augmented wave (GIPAW) NMR-CASTEP DFT approaches, which account for the short- and long-range symmetries, periodicities and interaction-potential characteristics for all elements (and particularly the heavy elements) in comparison with Gaussian 03 methods, which focus on terminated portions of the total structure.

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“…Nuclear magnetic resonance (NMR) can be an important probe of local structure, and NMR has increasingly been used to study complex ferroelectric alloys. 3,4,5 First-principles calculations of NMR properites are likely to play an important role in helping to interpret complex measured spectra. A material's characteristic NMR spectra is determined by the coupling of the nuclear magnetic dipole and electric quadrupole moments with the local magnetic field and with the electric field gradients (EFG), respectively.…”

Section: Introductionmentioning

confidence: 99%

High sensitivity of O17 NMR to p-d hybridization in transition metal perovskites: First principles calculations of large anisotropic chemical shielding

Pechkis

Krakauer

2009

The Journal of Chemical Physics

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A first principles embedded cluster approach is used to calculate O chemical shielding tensors, σ, in prototypical transition metal oxide ABO3 perovskite crystals. Our principal findings are 1) a large anisotropy ofσ between deshielded σx ≃ σy and shielded σz components (z along the Ti-O bond); 2) a nearly linear variation, across all the systems studied, of the isotropic σiso and uniaxial σax components, as a function of the B-O-B bond asymmetry. We show that the anisotropy and linear variation arise from large paramagnetic contributions to σx and σy due to virtual transitions between O(2p) and unoccupied B(nd) states. The calculated isotropic δiso and uniaxial δax chemical shifts are in good agreement with recent BaTiO3 and SrTiO3 single crystal 17 O NMR measurements. In PbTiO3 and PbZrO3, calculated δiso are also in good agreement with NMR powder spectrum measurements. In PbZrO3, δiso calculations of the five chemically distinct sites indicate a correction of the experimental assignments. The strong dependence ofσ on covalent O(2p)-B(nd) interactions seen in our calculations indicates that 17 O NMR spectroscopy, coupled with first principles calculations, can be an especially useful tool to study the local structure in complex perovskite alloys.

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Local structure in perovskite relaxor ferroelectrics: high-resolution 93Nb 3QMAS NMR

Cited by 15 publications

References 30 publications

Effects of jump dynamics on solid state nuclear magnetic resonance line shapes and spin relaxation times

Effects of jump dynamics on solid state nuclear magnetic resonance line shapes and spin relaxation times

A ⁹³Nb Solid‐State NMR and Density Functional Theory Study of Four‐ and Six‐Coordinate Niobate Systems

High sensitivity of O17 NMR to p-d hybridization in transition metal perovskites: First principles calculations of large anisotropic chemical shielding

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Local structure in perovskite relaxor ferroelectrics: high-resolution 93Nb 3QMAS NMR

Cited by 15 publications

References 30 publications

Effects of jump dynamics on solid state nuclear magnetic resonance line shapes and spin relaxation times

Effects of jump dynamics on solid state nuclear magnetic resonance line shapes and spin relaxation times

A 93Nb Solid‐State NMR and Density Functional Theory Study of Four‐ and Six‐Coordinate Niobate Systems

High sensitivity of O17 NMR to p-d hybridization in transition metal perovskites: First principles calculations of large anisotropic chemical shielding

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A ⁹³Nb Solid‐State NMR and Density Functional Theory Study of Four‐ and Six‐Coordinate Niobate Systems