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Bianchi, U.; Dec, J.; Kleemann, W.; Jg, Bednorz

doi:10.1103/physrevb.51.8737

Cited by 173 publications

(81 citation statements)

References 34 publications

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“…[45][46][47][48] Within the polaron model, such trend towards zero-activation energy polarons is in full agreement Taking into account the real part which is several thousands in the same temperature range, the resulting dielectric losses are about 0.1%. The operating frequency f and the temperature where the loss maximum occur can be plotted on an Arrhenius scale thus leading to activation energy of about 100 meV.…”

Section: Polaron Contribution To the Dielectric Permittivity Of Perovsupporting

confidence: 50%

Free charge localization and effective dielectric permittivity in oxides

Maglione

2016

J. Adv. Dielect.

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This review will deal with several types of free charge localization in oxides and their consequences on the effective dielectric spectra of such materials. The first one is the polaronic localization at the unit cell scale on residual impurities in ferroelectric networks. The second one is the collective localization of free charge at macroscopic interfaces like surfaces, electrodes and grain boundaries in ceramics. Polarons have been observed in many oxide perovskites mostly when cations having several stable electronic configurations are present. In manganites, the density of such polarons is so high as to drive a net lattice of interacting polarons. On the other hand, in ferroelectric materials like BaTiO 3 and LiNbO 3 , the density of polarons is usually very small but they can influence strongly the macroscopic conductivity. The contribution of such polarons to the dielectric spectra of ferroelectric materials is described. Even residual impurities as for example Iron can induce well-defined anomalies at very low temperatures. This is mostly resulting from the interaction between localized polarons and the highly polarizable ferroelectric network in which they are embedded. The case of such residual polarons in SrTiO 3 will be described in more detail, emphasizing the quantum polaron state at liquid helium temperatures. Recently, several nonferroelectric oxides have been shown to display giant effective dielectric permittivity. It is first shown that the frequency/temperature behavior of such parameters is very similar in very different compounds (donor-doped BaTiO 3 , CaCu 3 Ti 4 O 12 , LuFe 2 O 4 , Li-doped NiO, etc.). This similarity calls for a common origin of the giant dielectric permittivity in these compounds. A space charge localization at macroscopic interfaces can be the key for such extremely high dielectric permittivity.

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Section: Polaron Contribution To the Dielectric Permittivity Of Perovsupporting

confidence: 50%

Free charge localization and effective dielectric permittivity in oxides

Maglione

2016

J. Adv. Dielect.

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“…7 For example, compositional substitution creates structural disorder and subsequent local dipolar interactions, such as Ca-induced polar nanoregions in Ca 2+ -substituted SrTiO 3 , which prompts a relaxor behavior in the material. 31,32 However, there was no reported evidence of an average structural transition in the Ca 2+ -substituted material. The long-range, average structure of SSTO was determined through Rietveld refinement of diffraction data collected on the NOMAD (400 K, 300 K, 200 K, and 100 K) and POWGEN (300 K and 100 K) instruments at SNS.…”

Section: Resultsmentioning

confidence: 90%

Average and local structure of the Pb-free ferroelectric perovskites(Sr,Sn)TiO3and(Ba,Ca,Sn)
Laurita
¹
,
Page
²
,
Suzuki
³

et al. 2015
Phys. Rev. B
30
3
22
0
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Average and local structure of the Pb-free ferroelectric perovskites (Sr,Sn)TiO3 and (Ba,Ca,Sn)TiO3 The characteristic structural off-centering of Pb 2+ in oxides, associated with its 6s 2 lone pair, allows it to play a dominant role in polar materials, and makes it a somewhat ubiquitous component of ferroelectrics. In this work, we examine the compounds Sr0.9Sn0.1TiO3 and Ba0.79Ca0.16Sn0.05TiO3 using neutron total scattering techniques with data acquired at different temperatures. In these compounds, previously reported as ferroelectrics, Sn 2+ appears to display some of the characteristics of Pb 2+ . We compare the local and long-range structures of the Sn 2+ -substituted compositions to the unsubstituted parent compounds SrTiO3 and BaTiO3. We find that even at these small substitution levels, the Sn 2+ lone pairs drive the local ordering behavior, with the local structure of both compounds more similar to the structure of PbTiO3 rather than the parent compounds.

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“…The hard polar modes TO 2 and TO 4 in doped incipient ferroelectrics such as STO and KTaO 3 have been used to characterize the PNRs. 23,24,28 The intensity of the TO 2 mode in Sr 0.993 Ca 0.007 TiO 3 ͑T m ϳ 18 K͒ has been related to the space and time autocorrelation ͗P 2 ͘ of the fluctuating impurity-induced polarization P͑r , t͒. 28 The intensity of the TO 2 mode in Pr-doped STO persisted on heating up to 773 K, which is ϳ280 K above the temperature of the dielectric anomaly ͑T m ϳ 500 K͒, without any appreciable change.…”

Section: B Raman Scattering: Temperature Dependencementioning

confidence: 99%

“…For example, for 0.67 mol % Bi-doped STO, the mode frequency has been reported to change from 103 cm −1 at 300 K to 86 cm −1 at 260 K-i.e., a shift of 17 cm −1 on changing the temperature by merely 40 K. 27 The softening behavior of the TO 1 mode in Bi-doped STO, though reduced on increasing the Bi concentration, survives even for 13.3 mol % of Bi doping and continues well below T m . 27 Thus, unlike for the lightly Ca-doped STO ͑Sr 0.993 Ca 0.007 TiO 3 , T m ϳ 18 K͒, 28 where it has been shown that the TO 1 mode hardens below T m and splits into three components, thereby lowering the symmetry of the system from tetragonal to orthorhombic, 16 ened below their respective T m 's of Pr-and Bi-doped STO ͑x = 0.025, 0.05͒. As a result, a symmetry change across T m is less likely in the latter systems.…”

Section: B Raman Scattering: Temperature Dependencementioning

confidence: 99%

High-temperature relaxor ferroelectric behavior in Pr-dopedSrTiO3

et al. 2007

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Temperature-dependent Raman scattering, dielectric, and powder x-ray diffraction studies have been carried out on Pr-doped SrTiO 3 ceramic samples. Activation of TO 2 and TO 4 polar modes indicated increasing degree of polar distortion by Pr doping. Dielectric measurements revealed that the system exhibits dielectric relaxation peaks at ϳ500 K. The softening tendency of the polar TO 1 soft mode decreases with increasing Pr doping. X-ray diffraction results show no evidence of symmetry breaking across the dielectric peak temperatures. The system exhibits features of high-temperature relaxor ferroelectrics.

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Cluster and domain-state dynamics of ferroelectricSr1−xCa<

Cited by 173 publications

References 34 publications

Free charge localization and effective dielectric permittivity in oxides

Free charge localization and effective dielectric permittivity in oxides

Average and local structure of the Pb-free ferroelectric perovskites(Sr,Sn)TiO3and(Ba,Ca,Sn)
Laurita
¹
,
Page
²
,
Suzuki
³

et al. 2015
Phys. Rev. B
30
3
22
0
View full text Add to dashboard Cite

High-temperature relaxor ferroelectric behavior in Pr-dopedSrTiO3

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Cluster and domain-state dynamics of ferroelectricSr1−xCa<

Cited by 173 publications

References 34 publications

Free charge localization and effective dielectric permittivity in oxides

Free charge localization and effective dielectric permittivity in oxides

Average and local structure of the Pb-free ferroelectric perovskites(Sr,Sn)TiO3and(Ba,Ca,Sn)Laurita1, Page2, Suzuki3 et al. 2015Phys. Rev. B303220View full textAdd to dashboardCite

High-temperature relaxor ferroelectric behavior in Pr-dopedSrTiO3

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Average and local structure of the Pb-free ferroelectric perovskites(Sr,Sn)TiO3and(Ba,Ca,Sn)
Laurita
¹
,
Page
²
,
Suzuki
³

et al. 2015
Phys. Rev. B
30
3
22
0
View full text Add to dashboard Cite