23Na multiple-quantum MAS NMR of the perovskites NaNbO3and NaTaO3

Ashbrook, Sharon E.; Pollès, Laurent Le; Gautier, Régis; Pickard, Chris J.; Walton, Richard I.

doi:10.1039/b604520k

Cited by 85 publications

(84 citation statements)

References 39 publications

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“…Na 0:5 K 0:5 NbO 3 is one of the important lead-free piezoelectric materials with perovskite structure. Studies on various aspects of phase transitions in Na 0:5 K 0:5 NbO 3 have been reported using a variety of experimental techniques, including X-ray absorption fine structure (Shuvaeva et al, 2001), transmission electron spectroscopy (Chen & Feng, 1988), electron paramagnetic resonance (Avogadro et al, 1974), nuclear magnetic resonance (D'Ariano et al, 1982;Ashbrook et al, 2006) and Raman spectroscopy (Mishra et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Mode-crystallography analysis of the crystal structures and the low- and high-temperature phase transitions in Na_0.5K_0.5NbO₃

et al. 2015

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Na 0.5 K 0.5 NbO 3 has been synthesized by the conventional solid-state reaction process. The crystal structures and phase transitions, at low and high temperature, determined from the Rietveld refinements of X-ray and neutron powder diffraction data are reported. The structure evolution of Na 0.5 K 0.5 NbO 3 in the temperature range from 2 to 875 K shows the presence of three phase transitions. The first one, at $135 K, is discontinuous from the rhombohedral R3c (No. 161) space group to the room-temperature orthorhombic Amm2 (No. 38) space group; the second is discontinuous from the orthorhombic to the tetragonal P4mm space group (No. 99) at $465 K, and the third is continuous from the tetragonal to the cubic Pm3m space group (No. 221) at $700 K. The obtained phase-transition sequence is R3c ! Amm2 ! P4mm ! Pm3m. No previous studies at low temperature have been carried out on the material with composition Na 0.5 K 0.5 NbO 3 . In the course of the determination of the three experimentally found phases, a novel method of refinement is presented. This is a step forward in the use of the symmetry-adapted modes as degrees of freedom in the refinement process: the parameterization of a direction in the internal space of the, in this case, sole irreducible representation, GM 4 À , responsible for the symmetry breaking from the parent cubic space group to the polar distorted low-symmetry phases. Eventually, this procedure enables the calculation of the spontaneous polarization.

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Section: Introductionmentioning

confidence: 99%

Mode-crystallography analysis of the crystal structures and the low- and high-temperature phase transitions in Na_0.5K_0.5NbO₃

et al. 2015

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“…This method, which uses pseudopotentials and plane wave basis sets to describe the system, [30] has gained popularity recently for the calculation of SSNMR parameters. [13,[31][32][33][34][35][36][37][38] …”

Section: Introductionmentioning

confidence: 99%

Alkaline Earth Chloride Hydrates: Chlorine Quadrupolar and Chemical Shift Tensors by Solid‐State NMR Spectroscopy and Plane Wave Pseudopotential Calculations

Bryce

Bultz

2007

Chemistry A European J

114

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A series of alkaline earth chloride hydrates has been studied by solid-state (35/37)Cl NMR spectroscopy in order to characterize the chlorine electric field gradient (EFG) and chemical shift (CS) tensors and to relate these observables to the structure around the chloride ions. Chlorine-35/37 NMR spectra of solid powdered samples of pseudopolymorphs (hydrates) of magnesium chloride (MgCl(2).6H(2)O), calcium chloride (CaCl(2).2H(2)O), strontium chloride (SrCl(2), SrCl(2).2H(2)O, and SrCl(2).6H(2)O), and barium chloride (BaCl(2).2H(2)O) have been acquired under stationary and magic-angle spinning conditions in magnetic fields of 11.75 and 21.1 T. Powder X-ray diffraction was used as an additional tool to confirm the purity and identity of the samples. Chlorine-35 quadrupolar coupling constants (C(Q)) range from essentially zero in cubic anhydrous SrCl(2) to 4.26+/-0.03 MHz in calcium chloride dihydrate. CS tensor spans, Omega, are between 40 and 72 ppm, for example, Omega= 45+/-20 ppm for SrCl(2).6H(2)O. Plane wave-pseudopotential density functional theory, as implemented in the CASTEP program, was employed to model the extended solid lattices of these materials for the calculation of their chlorine EFG and nuclear magnetic shielding tensors, and allowed for the assignment of the two-site chlorine NMR spectra of barium chloride dihydrate. This work builds upon our current understanding of the relationship between chlorine NMR interaction tensors and the local molecular and electronic structure, and highlights the particular sensitivity of quadrupolar nucleus solid-state NMR spectroscopy to the differences between various pseudopolymorphic structures in the case of strontium chloride.

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“…Since it has been demonstrated that projector augmented wave (PAW) based density functional theory (DFT) calculations yield reasonable values of electric field gradient components in solids26, several combined experimental-theoretical studies of perovskites have been published. There are, for example, DFT-assisted assignments of crystal structures based on electric field gradients for NaNbO 3 272829, PbZr 1- x Ti x O 3 30 or La x Y 1- x ScO 3 31. Besides being a suitable method to assist the interpretation of NMR spectra, DFT calculations are also a well-suited tool to explore the relationship between electric field gradients and structural features in order to reveal general structure-property relations.…”

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Reconciling Local Structure Disorder and the Relaxor State in (Bi1/2Na1/2)TiO3-BaTiO3

Groszewicz

Gröting

Breitzke

et al. 2016

Sci Rep

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Lead-based relaxor ferroelectrics are key functional materials indispensable for the production of multilayer ceramic capacitors and piezoelectric transducers. Currently there are strong efforts to develop novel environmentally benign lead-free relaxor materials. The structural origins of the relaxor state and the role of composition modifications in these lead-free materials are still not well understood. In the present contribution, the solid-solution (100-x)(Bi1/2Na1/2)TiO3-xBaTiO3 (BNT-xBT), a prototypic lead-free relaxor is studied by the combination of solid-state nuclear magnetic resonance (NMR) spectroscopy, dielectric measurements and ab-initio density functional theory (DFT). For the first time it is shown that the peculiar composition dependence of the EFG distribution width (ΔQISwidth) correlates strongly to the dispersion in dielectric permittivity, a fingerprint of the relaxor state. Significant disorder is found in the local structure of BNT-xBT, as indicated by the analysis of the electric field gradient (EFG) in 23Na 3QMAS NMR spectra. Aided by DFT calculations, this disorder is attributed to a continuous unimodal distribution of octahedral tilting. These results contrast strongly to the previously proposed coexistence of two octahedral tilt systems in BNT-xBT. Based on these results, we propose that considerable octahedral tilt disorder may be a general feature of these oxides and essential for their relaxor properties.

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²³Na multiple-quantum MAS NMR of the perovskites NaNbO₃and NaTaO₃

Cited by 85 publications

References 39 publications

Mode-crystallography analysis of the crystal structures and the low- and high-temperature phase transitions in Na_0.5K_0.5NbO₃

Mode-crystallography analysis of the crystal structures and the low- and high-temperature phase transitions in Na_0.5K_0.5NbO₃

Alkaline Earth Chloride Hydrates: Chlorine Quadrupolar and Chemical Shift Tensors by Solid‐State NMR Spectroscopy and Plane Wave Pseudopotential Calculations

Reconciling Local Structure Disorder and the Relaxor State in (Bi1/2Na1/2)TiO3-BaTiO3

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23Na multiple-quantum MAS NMR of the perovskites NaNbO3and NaTaO3

Cited by 85 publications

References 39 publications

Mode-crystallography analysis of the crystal structures and the low- and high-temperature phase transitions in Na0.5K0.5NbO3

Mode-crystallography analysis of the crystal structures and the low- and high-temperature phase transitions in Na0.5K0.5NbO3

Alkaline Earth Chloride Hydrates: Chlorine Quadrupolar and Chemical Shift Tensors by Solid‐State NMR Spectroscopy and Plane Wave Pseudopotential Calculations

Reconciling Local Structure Disorder and the Relaxor State in (Bi1/2Na1/2)TiO3-BaTiO3

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²³Na multiple-quantum MAS NMR of the perovskites NaNbO₃and NaTaO₃

Mode-crystallography analysis of the crystal structures and the low- and high-temperature phase transitions in Na_0.5K_0.5NbO₃

Mode-crystallography analysis of the crystal structures and the low- and high-temperature phase transitions in Na_0.5K_0.5NbO₃