Dielectric and thermal properties of Pb2Nb2O7 at low temperature

Siegwarth, J. D.; Lawless, W. N.; Morrow, A. J.

doi:10.1063/1.323263

Cited by 19 publications

(10 citation statements)

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“…Our interpretation of the literature is different from that of Siegwarth et al [84], shown in Fig. 8: This is not relaxation of defects, but a relaxor ferroelectric transition.…”

Section: B Pyrochlore Reanalysis Literature Sectioncontrasting

confidence: 94%

“…These have been interpreted as magnetically driven, but we suspect that they are typical of most pyrochlores and independent of magnetism. Siegwarth and Lawless [84] report a very small pyrochlore polarization of 6 nC cm −2 for Pb-niobate. They published details of the equipment, in 1971, with such sensitive capabilities [104].…”

Section: B Pyrochlore Reanalysis Literature Sectionmentioning

confidence: 98%

“…This controversy regarding pyrochlore Pb 2 Nb 2 O 7 , with Hulm, Pepinsky, and others reporting [82,83,85,86] a phase transition (ferroelectric) at T = 14.0−15.4 K but Siegwarth et al [84] and Lawless [87] argued strongly that this was some sort of defect relaxation continues 50 years as moot until the present day.…”

Section: B Pyrochlore Reanalysis Literature Sectionmentioning

confidence: 99%

“…9. Our Vogel-Fulcher fits to the original data of Siegwarth et al [84], first using a free fit model (solid line) generating an attempt frequency f 0 that is unrealistic, hence a constrained model with f 0 = 1 × 10 13 also shown (dashed lines). The lack of data points causes the parameters f 0 and E a in the fit to be highly correlated and not independent.…”

Section: B Pyrochlore Reanalysis Literature Sectionmentioning

confidence: 99%

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Quantum critical points in ferroelectric relaxors: Stuffed tungsten bronze K3Li2Ta5O
Smith
¹
,
Gardner
²
,
Morrison
³

et al. 2018
Phys. Rev. Materials
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0
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We have synthesized ceramic specimens of the tetragonal tungsten bronze K 3 Li 2 Ta 5 O 15 (KLT) and characterized its phase transition via x-ray diffraction, dielectric permittivity, resonant ultrasonic spectroscopy, and heat capacity measurements. The space group of KLT is reported as both P 4/mbm and Cmmm with the orthorhombic distortion occurring when there are higher partial pressures of volatile K and Li used inside the closed crucibles for the solid state synthesis. The data show strong relaxor behavior, with the temperature at which the two dielectric relative permittivity peaks decreasing, with 104 T m1 69 K and 69 T m2 46 K as probe frequency f is reduced from 1 MHz to 316 Hz. F tests show that the data satisfies a Vogel-Fulcher model better than Arrhenius with an extrapolated freezing temperature for ε and ε of T f 1 = +15.8 and −11.8 K and T f 2 = −5.0 and −15.0 K for f → 0 (tending to dc). This difference between T f from real and imaginary values, albeit counterintuitive, is mandatory, according to the theory of Tagantsev. Therefore, by tuning frequency, the transition could be shifted to absolute zero, suggesting KLT has a relaxor-type quantum critical point. In addition, we have reanalyzed the conflicting literature for Pb 2 Nb 2 O 7 pyrochlore which suggests that this also has a relaxor-type quantum critical point since the freezing temperature from the Vogel-Fulcher fitting is below absolute zero. Since the transition temperature evidenced in the dielectric data at approximately 100 kHz shifts below 0 K for very low frequencies, this transition would not be seen with heat capacity data collected in the zero-frequency (dc) limit. Both of these materials show promise for possible new relaxor-type quantum critical points with nonperovskite based structures. DOI: 10.1103/PhysRevMaterials.2.084409 I. THE SEARCH FOR NEW QUANTUM CRITICAL POINT (QCP) FERROELECTRICS INCLUDING RELAXOR QCPSQuantum critical point (QCP) studies of ferroelectrics have been limited to a few crystal structures, emphasizing perovskite oxides. The drive to find new QCPs with ferroelectrics (FEs) are of interest due to the likelihood that they will exhibit novel electrical and thermal properties over wide ranges in temperature and tuning parameters, similar to what is seen in more widely studied magnetic counterparts. However, as the dynamical exponent is 1 for displacive FE rather than 3 for itinerant ferromagnets, the understanding and modeling of their properties are likely to be more complex, since real systems can exceed the upper and lower critical dimensionality [1]. For a QCP to occur, the transition should be driven by quantum fluctuations rather than classical fluctuations, and such quantum fluctuations tend to dominate in a region just above 0 K. Interest in ferroelectric quantum critical points has grown rapidly in the past several years, with emphasis upon perovskites [1,2] and several other materials, including hexaferrites [3][4][5][6] and organic or molecular crystals [7][8][9][10]. However, the QCPs studied thus ...

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“…Our interpretation of the literature is different from that of Siegwarth et al [84], shown in Fig. 8: This is not relaxation of defects, but a relaxor ferroelectric transition.…”

Section: B Pyrochlore Reanalysis Literature Sectioncontrasting

confidence: 94%

Section: B Pyrochlore Reanalysis Literature Sectionmentioning

confidence: 98%

Section: B Pyrochlore Reanalysis Literature Sectionmentioning

confidence: 99%

Section: B Pyrochlore Reanalysis Literature Sectionmentioning

confidence: 99%

See 2 more Smart Citations

Quantum critical points in ferroelectric relaxors: Stuffed tungsten bronze K3Li2Ta5O
Smith
¹
,
Gardner
²
,
Morrison
³

et al. 2018
Phys. Rev. Materials
2
0
2
0
View full text Add to dashboard Cite

show abstract

“…Many years ago a presumably ferroelectric transition was reported at T c = 15.4 K [19,20]. However, subsequent work showed that this temperature marked a relaxation onset [21]. This was before the era of relaxor ferroelectrics, and so these authors assumed that this is not a structural phase transition but merely the relaxation of a point defect.…”

Section: Hexaferritesmentioning

confidence: 99%

Ferroelectric Relaxor Quantum Crystals

Scott

2018

Crystals

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Abstract:A discussion is given of ferroelectrics (FEs) that have their Curie temperatures T c very near absolute zero. These have differences in their dynamics in comparison with higher-temperature systems, since domain wall motion occurs via quantum mechanical tunneling and not by thermally activated diffusion. Emphasis in the present paper is on FEs that have relaxor characteristics. In such systems, the temperature at which the isothermal electric susceptibility ε(T,f ) peaks is a strong function of frequency, and it decreases with decreasing frequency. This is due to glassy viscosity and is symbolic of non-equilibrium dynamics, usually described by a Vogel-Fulcher equation. It permits an extra dimension with which to examine the transitions. The second half of this paper reviews domain wall instabilities and asks about their presence in QCP ferroelectrics, which has not yet been reported and may be unobservable due to the absence of thermal diffusion of walls near T = 0; in this respect, we note that diffusion does exist in ferroelectric relaxors, even at T = 0, by virtue of their glassy, viscous dynamics.

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High Permittivity Materials

Ubic

Subodh

Sebastian

2017

Microwave Materials and Applications 2V Set

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Dielectric and thermal properties of Pb2Nb2O7 at low temperature

Cited by 19 publications

References 10 publications

Quantum critical points in ferroelectric relaxors: Stuffed tungsten bronze K3Li2Ta5O
Smith
¹
,
Gardner
²
,
Morrison
³

et al. 2018
Phys. Rev. Materials
2
0
2
0
View full text Add to dashboard Cite

Quantum critical points in ferroelectric relaxors: Stuffed tungsten bronze K3Li2Ta5O
Smith
¹
,
Gardner
²
,
Morrison
³

et al. 2018
Phys. Rev. Materials
2
0
2
0
View full text Add to dashboard Cite

Ferroelectric Relaxor Quantum Crystals

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Dielectric and thermal properties of Pb2Nb2O7 at low temperature

Cited by 19 publications

References 10 publications

Quantum critical points in ferroelectric relaxors: Stuffed tungsten bronze K3Li2Ta5OSmith1, Gardner2, Morrison3 et al. 2018Phys. Rev. Materials2020View full textAdd to dashboardCite

Quantum critical points in ferroelectric relaxors: Stuffed tungsten bronze K3Li2Ta5OSmith1, Gardner2, Morrison3 et al. 2018Phys. Rev. Materials2020View full textAdd to dashboardCite

Ferroelectric Relaxor Quantum Crystals

High Permittivity Materials

Contact Info

Product

Resources

About

Quantum critical points in ferroelectric relaxors: Stuffed tungsten bronze K3Li2Ta5O
Smith
¹
,
Gardner
²
,
Morrison
³

et al. 2018
Phys. Rev. Materials
2
0
2
0
View full text Add to dashboard Cite

Quantum critical points in ferroelectric relaxors: Stuffed tungsten bronze K3Li2Ta5O
Smith
¹
,
Gardner
²
,
Morrison
³

et al. 2018
Phys. Rev. Materials
2
0
2
0
View full text Add to dashboard Cite