Formation of ferroelectric phases in KNbO3 and other niobates with perovskite structure

Ivliev, M. P.; Raevskaya, S. I.; Raevski, I. P.; Shuvaeva, V. A.; Pirog, I. V.

doi:10.1134/s1063783407040294

Cited by 19 publications

(13 citation statements)

References 28 publications

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“…Similar ideas have been expressed by Ivliev et al 25 from their dielectric and EXAFS measurements on KNbO 3 and NaNbO 3 . In the absence of octahedral tilting in KNbO 3 , ordering of Nb displacements gives rise to a sequence of well-defined phase transitions accompanied by reduction in the average symmetry.…”

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confidence: 55%

Structural changes underlying the diffuse dielectric response inAgNbO3

et al. 2009

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Structural differences in the so-called M polymorphs of AgNbO 3 were analyzed using combined highresolution x-ray diffraction, neutron total scattering, electron diffraction, and x-ray absorption fine-structure measurements. These polymorphs all crystallize with Pbcm symmetry and lattice parameters ͱ2a c ϫ ͱ 2a c ϫ 4a c ͑where a c Ϸ 4 Å corresponds to the lattice parameter of an ideal cubic perovskite͒ which are determined by a complex octahedral tilt system ͑a − b − c − ͒ / ͑a − b − c + ͒ involving a sequence of two in-phase and two antiphase rotations around the c axis. Our results revealed that, similar to KNbO 3 , the Nb cations in AgNbO 3 exhibit local off-center displacements correlated along Nb-Nb-Nb chains. The displacements appear to be present even in the high-temperature AgNbO 3 polymorphs where the Nb cations, on average, reside on the ideal fixedcoordinate sites. The onset of the ͑a − b − c − ͒ / ͑a − b − c + ͒ tilting in the M polymorphs lifts the symmetry restrictions on the Nb positions and promotes ordering of the local Nb displacements into a long-range antipolarlike array. This ordering preserves the average Pbcm symmetry but is manifested in electron diffuse scattering and corroborated by other local-structure sensitive techniques. Structural states previously identified as the M 3 and M 2 phases represent different stages of displacive ordering rather than distinct thermodynamic phases. Rietveld refinements indicated intimate coupling between the displacive behavior on the oxygen, Nb, and Ag sublattices. The Pbcm symmetry of the octahedral framework precludes a complete ordering of Nb displacements so that some positional disorder is retained. This partial disorder likely gives a source to the dielectric relaxation which, according to previous spectroscopic studies, is the origin of the diffuse dielectric response exhibited by M-type AgNbO 3 at Ϸ250°C.

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confidence: 55%

Structural changes underlying the diffuse dielectric response inAgNbO3

et al. 2009

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“…The polarization (P) vs. electric field (E) hysteresis loops for (1-x)KNN-xCMgFO where x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5 composites are shown in Figure 3. The maximum polarization, remanence and coercive field for KNN have been found to be 10.378 μC/cm 2, 7.268 μC/cm 2 and 10.094 kV/cm, respectively, which may be attributed to B-site off center shift of Nb cation from the centers of the oxygen octahedra [26][27][28][29]. The ferroelectric nature of KNN is also reflected in the PE loops of the composites.…”

Section: Ferroelectric Analysismentioning

confidence: 99%

Multiferroic and magnetodielectric properties of (1-x)KNN-xCMgFO ceramic-based composites

Kaur

Singh

et al. 2020

Journal of Asian Ceramic Societies

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The multiferroic composite ceramics of (1-x)[K 0.5 Na 0.5 NbO 3 ]-x[Co(Mg 0.05 Fe 1.95 )O 4 ]; x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5 and 1.0 have been synthesized by solid-state route. The effect of stoichiometric proportions on their structural, morphological, ferroelectric, dielectric, magnetic and magnetodielectric properties has been explored in detail. The dual phase formation in the XRD pattern has revealed the presence of orthorhombic and spinel cubic structures of KNN and CMgFO, respectively. SEM investigations indicated the cuboidal shaped grains of KNN, while agglomeration has been observed for CMgFO. All the composites have found to exhibit ferromagnetic ordering, where M s continuously increases with increasing CMgFO concentration (~9 to 41 emu/g for x = 0.1 to x = 0.5); however, ferroelectric nature of composites decreases with increasing CMgFO concentration. The dielectric constant decreases, while loss increases with increasing ferrite concentration, except for x = 0.5. The decrease in dielectric constant with magnetic field is an evidence of magnetodielectric (MD) effect, with MD values of −3.5%, −3.6%, −4.5%, −10.3% and −5.2% for x = 0.1, 0.2, 0.3, 0.4 and 0.5, respectively. The maximum value of MD ~ −10% for x = 0.4 composite, indicated the appreciable ME coupling effect between ferroelectric and ferromagnetic phases, in present research work.

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“…DFT+ U calculations , revealed the doping induced midgap states to be of predominantly Mn 3d character, as was also concluded from enhancement of the Mn 3d states detected by resonant photoelectron spectroscopy, identifying Jahn–Teller (JT) active Mn 3+ (d 4 ) to be responsible for reduction of the observed band gap. Nb 5+ (d 0 ), on the other hand, acted as a charge compensator, also capable of stabilizing ferroelectric ground states similar to ferroelectric niobates. − The Mn–Nb dopant pair dipole was argued to effectively couple to the BaTiO 3 lattice, thereby retaining the electric polarization to a large extent. Domain switching was observed through piezoresponse force microscopy (PFM) measurements on epitaxial thin films of Mn–Nb co-doped BaTiO 3 (hereafter termed BTMNO) grown by pulsed later deposition, validating good ferroelectric response in films, a key step toward BaTiO 3 -based PV , device fabrication.…”

Section: Introductionmentioning

confidence: 90%

Structure and Electronic Effects from Mn and Nb Co-doping for Low Band Gap BaTiO₃ Ferroelectrics

et al. 2021

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We have investigated the doping-induced local structural and electronic effects in the recently developed low band gap room temperature ferroelectric Mn–Nb co-doped BaTiO3. Experimental and theoretical Raman spectroscopies are utilized to quantify the Ti off-centering, identified to be the intrinsic origin of ferroelectricity in these systems. Mn and Nb exhibit contrasting doping behaviors that have remarkable effects on BaTiO3 functionality. Jahn–Teller distorted Mn3+ is primarily associated with lowering of the bulk band gap, while charge-compensating Nb5+ off-centers within the O6 octahedra, creating a polar mode that stabilizes the ferroelectric ground state. The charge neutral aliovalent Mn3+–Nb5+ pair effectively couples to the inherent ferroelectric instability of the BaTiO3 lattice, restoring some spontaneous polarization lost by doping Mn3+ (d4) ions at Ti4+ (d0) sites.

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Formation of ferroelectric phases in KNbO3 and other niobates with perovskite structure

Cited by 19 publications

References 28 publications

Structural changes underlying the diffuse dielectric response inAgNbO3

Structural changes underlying the diffuse dielectric response inAgNbO3

Multiferroic and magnetodielectric properties of (1-x)KNN-xCMgFO ceramic-based composites

Structure and Electronic Effects from Mn and Nb Co-doping for Low Band Gap BaTiO₃ Ferroelectrics

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Formation of ferroelectric phases in KNbO3 and other niobates with perovskite structure

Cited by 19 publications

References 28 publications

Structural changes underlying the diffuse dielectric response inAgNbO3

Structural changes underlying the diffuse dielectric response inAgNbO3

Multiferroic and magnetodielectric properties of (1-x)KNN-xCMgFO ceramic-based composites

Structure and Electronic Effects from Mn and Nb Co-doping for Low Band Gap BaTiO3 Ferroelectrics

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Structure and Electronic Effects from Mn and Nb Co-doping for Low Band Gap BaTiO₃ Ferroelectrics