Zone-center soft mode behavior in the cubic phase of NaNbO3

Gervais, F.; Servoin, J. L.; Baumard, Jean‐François; Dénoyer, F.

doi:10.1016/0038-1098(82)90390-8

Cited by 20 publications

(7 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The crystal structure at any pressure (at zero temperature) is obtained by minimization of the enthalpy. Our experimental crystal structure and reported Raman [16][17][18][19][20] and infrared 26 data have been us ed to refine the interatomic potentials. Using these potentials, we have studied the double wells and computed the zero pressure free energies including the complete vibrational contributions 43 , to understand the relative stability of the ferroelectric R3c and antiferroelectric Pbcm phases.…”

Section: Ez(k)z(k')-brc V(r)=+a Exp{}-4rr(k)+r(k') R πεmentioning

confidence: 99%

“…Experimental studies of NaNbO 3 using a wide variety of techniques including x-ray and neutron diffraction [8][9][10][11][12][13][14][15] , Raman and infrared spectroscopy [16][17][18][19][20][21] , XAFS 22 , transmission electron microscopy (TEM) 23 , electron paramagnetic resonance (EPR) 24 , nuclear magnetic resonance (NMR) 25 , etc. have been reported and the crystal structure [8][9][10][11][12][13][14][15] , phonon spectrum [16][17][18][19][20][21]26 , dielectric and piezoelectric behavior 4,6,2 6-30 , temperature and pressure driven phase transitions and critical behavior of the order parameter 24,25 studied. First principles calculations of the structural and dynamical properties, epitaxial strain and anomalous LO-TO splittings of NaNbO 3 have also been reported.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Competing antiferroelectric and ferroelectric interactions inNaNbO3: Neutron diffraction and theoretical studies

et al. 2007

View full text Add to dashboard Cite

Neutron diffraction studies using powder samples have been used to understand the complex sequence of low temperature phase transitions of NaNbO3 in the temperature range from 12 K-350 K. Detailed Rietveld analysis of the diffraction data reveal that the antiferroelectric to ferroelectric phase transition occurs on cooling around 73 K while the reverse ferroelectric to antiferroelectric transition occurs on heating at 245 K. However, the former transformation is not complete till down to 12 K and there is unambiguous evidence for the presence of the ferroelectric R3c phase coexisting with an antiferroelectic phase (Pbcm) over a wide range of temperatures. The coexisting phases and reported anomalous smearing of the dielectric response akin to dipole glasses and relaxors observed in the same temperature range are consistent with competing ferroelectric and antiferroelectric interactions in NaNbO 3 . We have carried out theoretical lattice dynamical calculations which reveal that the free energies of the antiferroelectric Pbcm and ferroelectric R3c phases are nearly identical over a wide range of temperature. The small energy difference between the two phases is of interest as it explains the observed coexistence of these phases over a wide range of temperature. The computed double well depths and energy barriers from paraelectric Pm 3m to antiferroelectric Pbcm and ferroelectric R3c phases in NaNbO 3 are also quite similar, although the ferroelectric R3c phase has a slightly lower energy.

show abstract

Section: Ez(k)z(k')-brc V(r)=+a Exp{}-4rr(k)+r(k') R πεmentioning

confidence: 99%

mentioning

confidence: 99%

Competing antiferroelectric and ferroelectric interactions inNaNbO3: Neutron diffraction and theoretical studies

et al. 2007

View full text Add to dashboard Cite

show abstract

“…The temperature dependence of the zone-centre polar lattice vibrations, including a soft mode, in the cubic phase of NN single crystal was studied by infrared (IR) reflectivity spectroscopy [27]. The lowest-frequency transverse optic (TO) mode displayed a soft-mode behaviour in the cubic paraelectric phase between 106 and 91 cm −1 on cooling down from 1250 to 915 K. In addition, on cooling towards the U-T2 transition, Gervais et al [27] have observed the progressive passage from the underdamped soft-mode regime with a resolved central peak to the highly overdamped soft-mode regime with unresolved central peak. These features imply that a simple picture of the U-T2 phase transition associated with the condensation of a soft mode at the M-point of the BZ is incomplete.…”

Section: Literature Reviewmentioning

confidence: 99%

Modulated phases in NaNbO₃: Raman scattering, synchrotron x-ray diffraction, and dielectric investigations

Yuzyuk¹,

Simon²,

Gagarina³

et al. 2005

J. Phys.: Condens. Matter

108

View full text Add to dashboard Cite

Raman spectra of sodium niobate (NaNbO 3 ) were obtained in all phases and revealed a significant disorder in the high-temperature U, T2 and T1 phases and a complicated folding of the Brillouin zone at the transitions into modulated S, R, P and N phases associated with the competitive zone-boundary soft modes (in-phase and out-of phase octahedral tilts) along the M-T-R line. An extensive Raman study combined with x-ray diffraction (XRD) and dielectric measurements confirmed the presence of the incommensurate (INC) phase in sodium niobate. XRD experiments revealed the invar effect in the temperature interval 410-460 K corresponding to the INC phase associated with rotations of the NbO 6 octahedra modulated along the b-direction. Our experiments suggest that the phase P consists of three phases: monoclinic (P m ) between 250 and 410 K, INC between 410 and 460 K, and orthorhombic (P o ) between 460 and 633 K. At the low-temperature transition to the ferroelectric rhombohedral N phase all folded modes originating from the M-and T-points of the Brillouin zone abruptly disappear, Raman spectra in the N phase become much simpler and all peaks were assigned.

show abstract

“…NaNbO 3 has a perovskite-like structure with antiferroelectric phase at room temperature, and it undergoes a transition to a ferroelectric phase at a temperature of 170 K [1].…”

Section: Introductionmentioning

confidence: 99%

Colossal dielectric constant of NaNbO₃doped BaTiO₃ceramics

Cao

Ismail

et al. 2016

Materials Science-Poland

View full text Add to dashboard Cite

BaTiO 3 ceramics doped with 0.40 mol% NaNbO 3 were prepared using a traditional approach by sintering at temperature of 1250°C to 1290°C. The prepared ceramics was characterized by very good dielectric properties, such as high dielectric constant (1.5 × 10 5 ), low dielectric loss (0.1), and good dielectric temperature stability in the −40°C to 100°C range for the sample sintered below 1270°C. The dielectric characteristics obtained with XPS confirmed that Ti 4+ ions remain in the state without any change. The huge increase in dielectric constant in NaNbO 3 doped BaTiO 3 samples occurs when large amount of Ba 2+ ions are excited to a high energy bound state of Ba 2+ − e or Ba + to create electron hopping conduction. For samples with the content of NaNbO 3 higher than 0.40 mol%, or sintering temperature higher than 1280°C, compensation effect is dominated by cation vacancies with sharply decreasing dielectric constant and increased dielectric loss. The polaron effect is used to explain the relevant mechanism of giant dielectric constant appearing in the ferroelectric phase.

show abstract

Zone-center soft mode behavior in the cubic phase of NaNbO3

Cited by 20 publications

References 18 publications

Competing antiferroelectric and ferroelectric interactions inNaNbO3: Neutron diffraction and theoretical studies

Competing antiferroelectric and ferroelectric interactions inNaNbO3: Neutron diffraction and theoretical studies

Modulated phases in NaNbO₃: Raman scattering, synchrotron x-ray diffraction, and dielectric investigations

Colossal dielectric constant of NaNbO₃doped BaTiO₃ceramics

Contact Info

Product

Resources

About

Zone-center soft mode behavior in the cubic phase of NaNbO3

Cited by 20 publications

References 18 publications

Competing antiferroelectric and ferroelectric interactions inNaNbO3: Neutron diffraction and theoretical studies

Competing antiferroelectric and ferroelectric interactions inNaNbO3: Neutron diffraction and theoretical studies

Modulated phases in NaNbO3: Raman scattering, synchrotron x-ray diffraction, and dielectric investigations

Colossal dielectric constant of NaNbO3doped BaTiO3ceramics

Contact Info

Product

Resources

About

Modulated phases in NaNbO₃: Raman scattering, synchrotron x-ray diffraction, and dielectric investigations

Colossal dielectric constant of NaNbO₃doped BaTiO₃ceramics