87,336 results on '"FERROELECTRICITY"'
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2. OSCILLOGRAPH STUDY OF DIELECTRIC PROPERTIES OF BARIUM TITANATE
- Author
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Alexander de Bretteville
- Subjects
Materials science ,Analytical chemistry ,Field strength ,Dielectric ,Oscillograph ,Atmospheric temperature range ,Ferroelectricity ,chemistry.chemical_compound ,chemistry ,Barium titanate ,Materials Chemistry ,Ceramics and Composites ,Saturation (magnetic) ,Voltage - Abstract
A disk of barium titanate was fired to 1350°C. for six hours in an electric furnace. Silvered electrodes were then fired on the disk at 650°C. A cathode-ray oscillograph measurement was made of the dielectric properties in order to analyze the whole charging and discharging cycle. The material showed saturation of the dielectric flux density or charge with increase of field strength or voltage and is therefore a new type of ferroelectric material. The dielectric properties of such a nonlinear circuit element was studied over a temperature range from –175° to +140°C. at field strengths of 59, 134,234, 580, and 4300 volts per cm. Peaks in the dielectric constant were observed near –70°, +10°, and 120°C. As the field strength was increased, the two lower peaks increased in magnitude and all peaks shifted slightly to lower temperature.
- Published
- 1946
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3. Untersuchungen an Bariumtitanat-Einkristallen
- Author
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W. Merz, P. Scherrer, B. Matthias, and H. Blattner
- Subjects
Pharmacology ,Condensed matter physics ,Chemistry ,Cell Biology ,Dielectric ,Ferroelectricity ,Condensed Matter::Materials Science ,Cellular and Molecular Neuroscience ,Hysteresis ,Nuclear magnetic resonance ,Physics::Atomic and Molecular Clusters ,Temperature curve ,Molecular Medicine ,Molecular Biology - Abstract
It was possible to produce bariumtitanate monocrystals with ferroelectric qualities, which is shown in the temperature curve of the dielectric constant, in the resonance frequency, and also in hysteresis phenomena.
- Published
- 1947
- Full Text
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4. Comments on 'Theory of the Ferroelectric Effect and Clamped Dielectric Constant of Rochelle Salt'
- Author
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W. P. Mason
- Subjects
chemistry.chemical_classification ,Materials science ,chemistry ,Condensed matter physics ,General Physics and Astronomy ,Salt (chemistry) ,Dielectric ,Ferroelectricity - Published
- 1947
- Full Text
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5. Domain Structure and Dielectric Response of Barium Titanate Single Crystals
- Author
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A. von Hippel and B. Matthias
- Subjects
Diffraction ,Physics ,Condensed matter physics ,General Physics and Astronomy ,Dielectric ,Polarization (waves) ,Ferroelectricity ,Piezoelectricity ,Orientation (vector space) ,Condensed Matter::Materials Science ,chemistry.chemical_compound ,chemistry ,Barium titanate ,Curie temperature - Abstract
Single crystals of BaTi${\mathrm{O}}_{3}$ have been grown and investigated by means of the polarization microscope, x-ray diffraction, and their dielectric and piezoelectric response. It has become possible to see the domains in the ferroelectric state and to change their number, size, and orientation. Wall displacements and the alignment of such domains, for which well-known indirect evidence exists in the case of ferromagnetics, have been observed in both polarized and unpolarized light, and the influence of temperature and electric fields on the domain structure and orientation of the polar axis have been investigated. In addition to the Curie point near 120\ifmmode^\circ\else\textdegree\fi{}C, there exist two polymorphic transitions near 5\ifmmode^\circ\else\textdegree\fi{}C and -70\ifmmode^\circ\else\textdegree\fi{}C. A tentative explanation for the development of the ferroelectric state is given which brings the new ferroelectric group of the titanates into close relation to those of the tartrates and phosphates.
- Published
- 1948
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6. Electrostrictive Effect in Barium Titanate Ceramics
- Author
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Warren P. Mason
- Subjects
Materials science ,Condensed matter physics ,General Physics and Astronomy ,Resonance ,Join (topology) ,Coupling (probability) ,Ferroelectricity ,chemistry.chemical_compound ,Tetragonal crystal system ,Nuclear magnetic resonance ,chemistry ,Electric field ,Barium titanate ,Single crystal - Abstract
When a direct current bias is applied to a multicrystalline barium titanate ceramic, an alternating voltage can excite resonances in the ceramic. Four modes of motion have been excited---a longitudinal mode at right angles to the applied field, a radial mode of a circular plate at right angles to the applied field, a thickness longitudinal mode, and a thickness shear mode. The first three are excited when the a.c. field is applied in the same direction as the d.c. polarization, but the fourth is excited when the a.c. field is at right angles to the d.c. polarization. The amount of motion is larger than in magnetostrictive materials, and it appears that barium titanate may be an important electromechanical transducing element.All of these modes can be accounted for on the basis of a second-order electrostrictive effect. Two electrostrictive constants are involved and these have been evaluated as ${{Q}_{12},=\ensuremath{-}2.15\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}12}(\frac{{\mathrm{cm}}^{4}}{{(\mathrm{statcoulombs})}^{2}})}{{Q}_{11},=+6.9\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}12}(\frac{{\mathrm{cm}}^{4}}{{(\mathrm{statcoulombs})}^{2}}).}$Using these constants, the measured electromechanical coupling factors for the four modes are evaluated, and these compare well with the calculated values.A theoretical explanation of this effect is given which depends on the fact that when a given domain becomes ferro-electric it loses its cubic structure and becomes tetragonal. In this process it expands one percent along the tetragonal axis and contracts one-half percent along the other two axes. In the ceramic piece all directions for the tetragonal axis are equally probable, but an applied field can cause the domains in the direction of the field to grow at the expense of domains perpendicular to the field. This growth is accompanied by an increase in the thickness of the crystal and a decrease in radial dimensions. The measured ratio of 3 to 1, compared to the 2 to 1 ratio observed by x-rays for a single crystal, is accounted for by the nature of the ceramic material which does not join up for all grains. This does not prevent the ceramic from increasing in thickness but does cut down the radial contraction.Experimental measurements of the electrostrictive effect are given, and it is shown that the displacement is proportional to the square or products of the electric displacements in the ceramic.
- Published
- 1948
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7. Theoretical Model for Explaining the Ferroelectric Effect in Barium Titanate
- Author
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Bernd T. Matthias and Warren P. Mason
- Subjects
Materials science ,Condensed matter physics ,General Physics and Astronomy ,Dielectric ,Ferroelectricity ,Crystal ,Condensed Matter::Materials Science ,chemistry.chemical_compound ,Hysteresis ,chemistry ,Barium titanate ,Relaxation (physics) ,Single bond ,Single domain - Abstract
In order to explain the properties of a barium titanate single domain crystal, a previous theory of the ferroelectric effect in rochelle salt has been extended to the three-dimensional structure of barium titanate. This involves six equilibrium positions and results in significant differences from the single bond type of structure of rochelle salt. The theoretical features considered are a calculation of the spontaneous polarization as a function of temperature, the dielectric constants along the $a=y$ and $c=z$ axes as a function of temperature, the relaxation of the dielectric constant at high frequencies, and the hysteresis loops. All of these features are explained by the three-dimensional model considered here.
- Published
- 1948
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8. XCV. Symmetry changes in barium titanate at low temperatures and their relation to its ferroelectric properties
- Author
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P. Vousden and H.F. Kay
- Subjects
Tetragonal crystal system ,chemistry.chemical_compound ,Dipole ,Materials science ,Condensed matter physics ,chemistry ,Barium titanate ,Orthorhombic crystal system ,Interaction energy ,Crystal structure ,Polarization (waves) ,Ferroelectricity - Abstract
Summary The optical changes in BaTiO3 are described, and it is shown that they can be completely explained if the crystal symmetry changes from tetragonal to orthorhombic at -5°C, and then to rhombohedral at -90°C. These changes have been confirmed by X-ray investigations, and it is concluded that the three transitions are caused by the structure becoming successively spontaneously polarized along the [100] [110] and [111] cube directions. The relation of polarization to the cell structure is discussed and it is shown that the simple Lorentz equation is inapplicable if the titanium-oxygen interaction energy is large. An explanation of the three transitions is outlined on the basis of this interaction and some difficulties of electrical dipole cooperative effects in BaTiO3 are discussed.
- Published
- 1949
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9. Domain Structures and Phase Transitions in Barium Titanate
- Author
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Peter W. Forsbergh
- Subjects
Physics ,Phase transition ,chemistry.chemical_compound ,Tetragonal crystal system ,Condensed matter physics ,chemistry ,Lattice (order) ,Barium titanate ,General Physics and Astronomy ,Orthorhombic crystal system ,Crystal twinning ,Ferroelectricity ,Energy (signal processing) - Abstract
The arrangements of domains that arise in single crystals of barium titanate in the ferroelectric tetragonal phase have been studied in detail. The domains are the results of tetragonal (101) twinning, and appear by the formation of wedge-shaped laminar domains between two converging (101) twin planes. The distance of penetration of thin wedge-shaped laminae into the crystal follows changes in an applied electric field reversibly. Often thin laminae extend through the thickness of a crystal plate at an angle of 45\ifmmode^\circ\else\textdegree\fi{} to the surface. These laminae frequently advance in groups in the two perpendicular directions parallel to the edges of the rectangular plate. As a result of the intersections of these groups, the domain pattern becomes an array of laminated and unlaminated pyramids and tetrahedra, the birefringence properties of which give rise to net-like patterns of multicolored squares in polarized light. The evidence indicates that the squarenet pattern is an arrangement of twinning reducing as much as possible the total energy of lattice strains. These strains are probably due to an inhomogeneous distribution of impurities causing a bending effect, as in a bimetallic disk.A preliminary investigation of the phase transitions near 5\ifmmode^\circ\else\textdegree\fi{}C and -70\ifmmode^\circ\else\textdegree\fi{}C has been completed. Using clearly defined optical observations, we conclude that the crystal is orthorhombic $\mathrm{Cmm}$ between 5\ifmmode^\circ\else\textdegree\fi{}C and -70\ifmmode^\circ\else\textdegree\fi{}C, and trigonal $R3m$ below -70\ifmmode^\circ\else\textdegree\fi{}C, with the lattice stretched along the polar axis. The twinning is identified in terms of these lattices. It is maintained that the transitions near 5\ifmmode^\circ\else\textdegree\fi{}C and -70\ifmmode^\circ\else\textdegree\fi{}C can only be of the first order, in contrast with the $\ensuremath{\lambda}$-transition at 120\ifmmode^\circ\else\textdegree\fi{}C. While a statistical mechanical treatment of the properties of barium titanate would be exceedingly difficult, a definite qualitative thermodynamic correlation of its properties has been made. Due to the piezoelectric "inter-action," the free energy can be visualized in the ferroelectric states in terms of a simultaneous polarization and lattice deformation. The overall situation may be regarded as one in which a ferroelectric $\ensuremath{\lambda}$-transition from the (ordered) cubic phase can, in principle, take place along any direction of the highly symmetric cubic lattice, but subject to anisotropy effects which favor the [100] directions down to 5\ifmmode^\circ\else\textdegree\fi{}C, the [110] directions between 5\ifmmode^\circ\else\textdegree\fi{}C and -70\ifmmode^\circ\else\textdegree\fi{}C, and the [111] directions below -70\ifmmode^\circ\else\textdegree\fi{}C.
- Published
- 1949
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10. Ferroelectric zirconate ceramics
- Author
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Shepard Roberts
- Subjects
Materials science ,Ferroelectric ceramics ,Inorganic chemistry ,Oxide ,Monoxide ,Ferroelectricity ,Zirconate ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,visual_art ,visual_art.visual_art_medium ,Barium carbonate ,Ceramic ,Lead oxide - Abstract
A new class of ferroelectric ceramics was revealed in a study of mixtures of lead zirconate and up to 40 mol percent barium zirconate. These compositions were prepared from pure zirconium oxide, lead monoxide and barium carbonate mixed in the desired stoichiometric proportions and calcined in covered platinum crucibles at 1050°C. The calcined product was pulverized and compressed in the form of discs which were sintered at temperatures ranging from 1300°C to 1400°C. This was done in air with lead, oxide vapor in equilibrium with molten lead oxide.
- Published
- 1949
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11. On the ferroelectricity of KH2PO4 and KD2PO4 crystals
- Author
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Jean Pirenne
- Subjects
Physics ,Absorption spectroscopy ,Proton ,General Engineering ,Finite potential well ,Ionic bonding ,Dielectric ,Atomic physics ,Saturation (magnetic) ,Ferroelectricity ,Order of magnitude - Abstract
The ferro-electric properties of KH 2 PO 4 and KD 2 PO 4 crystals exhibit a most striking, yet unexplained, isotopic effect: the C u r i e point, for instance, is shifted by as much as 90° and other physical properties are surprisingly different in both crystals. The analysis of this situation leads to a new theory in which the protons are moving in a certain potential well, the spontaneous polarisatoin arising from the electrostatic dipole-dipole interaction; the isotopic effect has a simple quantum-mechanical origin. The case of a square well potential is studied in detail as offering a suitable discussion base. It already leads, in the inner-field approximation, to a quantitative agreement for the C u r i e point, saturation polarisation, paraelectric C u r i e constant and total extra heat of both crystals. The widh of the well is found to correspond to a separation of about 148 cm −1 between the two first proton levels. The values which have to be assigned to the L o r e n t z factor and to the ionic character of the protons are quite reasonable and the contribution of the ground to the polarisation appears to be of the same order of magnitude as that of the protons. Further experiments, and especially far infra-red absorption spectra, seam to be extremely desirable in order to improve the model.
- Published
- 1949
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12. Ferroelectricity in the Ilmenite Structure
- Author
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Bernd T. Matthias and J. P. Remeika
- Subjects
Materials science ,Condensed matter physics ,engineering ,General Physics and Astronomy ,engineering.material ,Ferroelectricity ,Ilmenite - Published
- 1949
- Full Text
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13. Dielectric Properties of Lead Zirconate and Barium-Lead Zirconate
- Author
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Smepard Roberts
- Subjects
Materials science ,Mineralogy ,chemistry.chemical_element ,Barium ,Dielectric ,Atmospheric temperature range ,Piezoelectricity ,Ferroelectricity ,Zirconate ,chemistry ,visual_art ,Materials Chemistry ,Ceramics and Composites ,visual_art.visual_art_medium ,Ceramic ,Composite material ,Lead (electronics) - Abstract
Methods are described for preparing lead zirconate and mixtures of lead and barium zirconate in ceramic form. These compositions are shown to constitute a new class of ferroelectric materials having dielectric constants as high as 11,000. Dielectric constants are measured at 1 mc. per second in a temperature range 25° to 350° C. Nonlinear dielectric properties and piezoelectric effects are demonstrated.
- Published
- 1950
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14. The Lorentz Correction in Barium Titanate
- Author
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John C. Slater
- Subjects
symbols.namesake ,Condensed matter physics ,Polarizability ,Lorentz transformation ,symbols ,General Physics and Astronomy ,Circular symmetry ,Dielectric ,Electric potential ,Ferroelectricity ,Local field ,Potential energy - Abstract
It is assumed, following Devonshire, that the ferroelectric behavior of BaTi${\mathrm{O}}_{3}$ arises because of the Lorentz correction, leading to a vanishing term in the denominator of the expression for dielectric constant. If the polarizability varies slowly with temperature, the temperature variation of dielectric constant follows. This temperature variation is assumed to come from that part of the polarization resulting from the displacement of the Ti ion, in a field whose potential energy has fourth-power as well as second-power terms in the displacement. The main object of this paper is to compute the Lorentz correction exactly, not assuming spherical symmetry, but taking account of the precise crystal structure. When this is done, it is found that the Ti ions, and those oxygen ions which are in the same line with them, the line being parallel to the electric field, exert very strong fields on each other, the resulting local field at the Ti ion being much greater than if computed on the assumption of spherical symmetry. This enhanced field makes it clear that even a relatively small ionic polarizability for the Ti ions will be enough to lead to ferroelectricity. The polarization of the Ti ions is however an essential feature of the theory; if they are not polarized, the Lorentz correction is profoundly modified, leading almost exactly to the value given by the approximate theory assuming spherical symmetry, and not resulting in ferroelectricity. Detailed formulas are given for comparison of the present theory with Devonshire's results, so that the present methods can be incorporated in his treatment of the effect of elastic strain energy on the stability of the various phases below the Curie point.
- Published
- 1950
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15. Ferroelectricity, Domain Structure, and Phase Transitions of Barium Titanate
- Author
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A. von Hippel
- Subjects
Physics ,Phase transition ,Condensed matter physics ,General Physics and Astronomy ,Field strength ,Dielectric ,Ferroelectricity ,Piezoelectricity ,chemistry.chemical_compound ,chemistry ,visual_art ,Barium titanate ,visual_art.visual_art_medium ,Ceramic ,High-κ dielectric - Abstract
A summarizing account is given of the research on barium titanate in progress at the Laboratory for Insulation Research at M. I. T. since 1943. The investigations have led to an understanding of the mechanism of ferroelectricity in the titanates and to discoveries such as the piezoelectric effect in the ceramics and the domain structure of the single crystals of BaTi${\mathrm{O}}_{3}$. The high dielectric constant, field strength and temperature sensitivity, and piezo-response of the barium titanate dielectrics make them useful for numerous technical applications.
- Published
- 1950
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16. Atomic Positions and Vibrations in the Ferroelectric BaTiO3Lattice
- Author
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W. Kaenzig
- Subjects
Vibration ,Materials science ,Ferromagnetism ,Condensed matter physics ,Lattice (order) ,General Physics and Astronomy ,Curie temperature ,Dielectric ,Atomic physics ,Ferroelectricity ,Ion - Published
- 1950
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17. Erratum: A Ferroelectric Curie Point in KTaO3at Very Low Temperatures
- Author
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E. A. Long, B. T. Matthias, and John K. Hulm
- Subjects
Materials science ,Condensed matter physics ,General Physics and Astronomy ,Curie temperature ,Ferroelectricity - Published
- 1950
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18. New Ferroelectric Tartrates
- Author
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B. T. Matthias and John K. Hulm
- Subjects
Materials science ,Condensed matter physics ,General Physics and Astronomy ,Ferroelectricity - Published
- 1951
- Full Text
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19. On the Ferroelectric Behaviors of Sodium Vanadate
- Author
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Shoichiro Nomura and Shozo Sawada
- Subjects
Materials science ,Sodium Vanadate ,Inorganic chemistry ,General Physics and Astronomy ,Ferroelectricity - Published
- 1951
- Full Text
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20. Dielectric Properties of Lead Zirconate
- Author
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Gen Shirane, Yutaka Takagi, and Etsuro Sawaguchi
- Subjects
Physics ,Permittivity ,Transition point ,Condensed matter physics ,General Physics and Astronomy ,Order (ring theory) ,Curie temperature ,Field strength ,Dielectric ,Critical field ,Ferroelectricity - Abstract
In order to distinguish whether it is really a ferroelectric or not, the dielectric response of PbZr${\mathrm{O}}_{3}$ ceramic to biasing dc field has been examined. In contrast to ordinary ferroelectrics, an effect is scarcely detected below the Curie point of 233\ifmmode^\circ\else\textdegree\fi{}C even up to a field strength of 20 kv/cm, except for a slight increase of permittivity at the vicinity of the transition point. In addition, the Curie temperature decreases with increasing biasing field attaining the value $\ensuremath{\Delta}{T}_{c}=\ensuremath{-}1.7$\ifmmode^\circ\else\textdegree\fi{}C for 20 kv/cm. The hysteresis loops of this ceramic have been studied. So long as the amplitude of the applied ac field is less than a critical field of about 23 kv/cm, the $D\ensuremath{-}E$ curves are almost always linear, except that a slight upward curvature becomes perceptible just at the temperature range wherein permittivity increases, and never show any hysteresis characteristics even just below the Curie point. But if the amplitude of the applied field is greater than this threshold value, anomalous hysteresis loops of very impressive form are observed in a narrow temperature range just below the Curie point. These experimental facts all seem to suggest that PbZr${\mathrm{O}}_{3}$ may be, not a ferroelectric, but an antiferroelectric. A preliminary pyroelectric test also seems to show that no net polarization grows spontaneously when the sample is cooled through its Curie point.
- Published
- 1951
- Full Text
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21. Ferroelectricity
- Author
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Matthias, Bernd T.
- Published
- 1951
22. Dielectric Properties of Sodium and Potassium Niobates
- Author
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Bernd T. Matthias and J. P. Remeika
- Subjects
Materials science ,Condensed matter physics ,Potassium ,Sodium ,General Physics and Astronomy ,chemistry.chemical_element ,Dielectric ,Atmospheric temperature range ,Ferroelectricity ,Dielectric spectroscopy ,Condensed Matter::Materials Science ,chemistry ,Saturation polarization ,Dissipation factor - Abstract
The following paper deals with evidence of ferroelectricity in KNb${\mathrm{O}}_{3}$ and NaNb${\mathrm{O}}_{3}$. Temperatures at which both materials undergo crystallographic changes and corresponding changes in dielectric constant and loss tangent are reported. Photographs of dielectric hysteresis loops and values of saturation polarization taken at various points over a temperature range are given for KNb${\mathrm{O}}_{3}$.
- Published
- 1951
- Full Text
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23. Theory of Antiferroelectric Crystals
- Author
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C. Kittel
- Subjects
Physics ,Condensed matter physics ,General Physics and Astronomy ,Order (ring theory) ,Dielectric ,Cubic crystal system ,Ferroelectricity ,Condensed Matter::Soft Condensed Matter ,Condensed Matter::Materials Science ,chemistry.chemical_compound ,chemistry ,Strontium titanate ,Antiferroelectricity ,Antiferromagnetism ,Curie temperature - Abstract
An antiferroelectric state is defined as one in which lines of ions in the crystal are spontaneously polarized, but with neighboring lines polarized in antiparallel directions. In simple cubic lattices the antiferroelectric state is likely to be more stable than the ferroelectric state. The dielectric constant above and below the antiferroelectric curie point is investigated for both first- and second-order transitions. In either case the dielectric constant need not be very high; but if the transition is second order, $\ensuremath{\epsilon}$ is continuous across the Curie point. The antiferroelectric state will not be piezoelectric. The thermal anomaly near the Curie point will be of the same nature and magnitude as in ferroelectrics. A susceptibility variation of the form $\frac{C}{(T+\ensuremath{\theta})}$ as found in strontium titanate is not indicative of antiferroelectricity, unlike the corresponding situation in antiferromagnetism.
- Published
- 1951
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24. On the Ferroelectric Curie Point of Tungsten Oxide
- Author
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R. Ando, Susumu S. Sawada, and Shoichiro Nomura
- Subjects
Materials science ,Condensed matter physics ,General Physics and Astronomy ,Curie temperature ,Tungsten oxide ,Ferroelectricity - Published
- 1951
- Full Text
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25. A study of the unit-cell dimensions and symmetry of certain ferroelectric compounds of niobium and tantalum at room temperature
- Author
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P. Vousden
- Subjects
Crystallography ,Materials science ,chemistry ,Tantalum ,Niobium ,General Earth and Planetary Sciences ,chemistry.chemical_element ,Unit (ring theory) ,Ferroelectricity ,Symmetry (physics) ,General Environmental Science - Published
- 1951
- Full Text
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26. An Electrostatically Induced Permanent Memory
- Author
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Charles F. Pulvari
- Subjects
Range (particle radiation) ,Materials science ,business.industry ,General Physics and Astronomy ,Nanotechnology ,Ferroelectricity ,chemistry.chemical_compound ,chemistry ,visual_art ,Barium titanate ,visual_art.visual_art_medium ,Optoelectronics ,Curie temperature ,Ceramic ,business - Abstract
The possibility of using a ferroelectric substance (barium titanate) as a medium for storing information is described. Preliminary experiments were performed to determine the necessary conditions for inscribing and erasing electrostatic preorientation in barium titanate ceramics at a temperature somewhat below the Curie point. The results suggest the possibility of a memory device that can be operated in the range of audio‐frequencies or higher.
- Published
- 1951
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27. FerroelectricityversusAntiferroelectricity in Barium Titanate
- Author
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M. H. Cohen
- Subjects
chemistry.chemical_compound ,Materials science ,chemistry ,Condensed matter physics ,Barium titanate ,General Physics and Astronomy ,Antiferroelectricity ,Ferroelectricity - Published
- 1951
- Full Text
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28. The structure of ferroelectric sodium niobate at room temperature
- Author
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P. Vousden
- Subjects
Materials science ,Sodium niobate ,business.industry ,General Earth and Planetary Sciences ,Optoelectronics ,business ,Ferroelectricity ,General Environmental Science - Published
- 1951
- Full Text
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29. STUDY OF PHASE TRANSITIONS IN PEROVSKITE-TYPE CRYSTALS
- Author
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PENNSYLVANIA STATE UNIV UNIVERSITY PARK X-RAY AND CRYSTAL ANALYSIS LAB, Shirane, GenN, Pepinsky, Ray, PENNSYLVANIA STATE UNIV UNIVERSITY PARK X-RAY AND CRYSTAL ANALYSIS LAB, Shirane, GenN, and Pepinsky, Ray
- Published
- 1952
30. Phase Transitions in Solid Solutions of PbZrO3and PbTiO3(II) X-ray Study
- Author
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Kazuo Suzuki, Akitsu Takeda, and Gen Shirane
- Subjects
Tetragonal crystal system ,Phase transition ,Materials science ,Condensed matter physics ,General Physics and Astronomy ,Crystal structure ,Dielectric ,Superstructure (condensed matter) ,Ferroelectricity ,Phase diagram ,Solid solution - Abstract
The phase diagram of the whole range of the PbZrO 3 -PbTiO 3 system was determined by the dielectric and dilatometric measurements. According to the reason shown in part I, this phase diagram can be divided into three regiors; paraelectric, ferroelectric and antiferroelectric phases. The crystal structure of this system was determined by the Debye photographs. In the antiferroelectric region solid solutions have a tetragonal modification of perovskite structure with c / a 1 without any superstructure.
- Published
- 1952
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31. Phase Transition of ND4D2PO4
- Author
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B.T. Matthias
- Subjects
Phase transition ,Condensed matter physics ,Ferromagnetism ,General Physics and Astronomy ,Allotropy ,Polarization (electrochemistry) ,Ferroelectricity ,Ammonium compounds - Published
- 1952
- Full Text
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32. Ferroelectricity and Antiferroelectricity of a Crystal Containing Rotatable Polar Molecules
- Author
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Yutaka Takagi
- Subjects
Crystal ,Condensed Matter::Materials Science ,Dipole ,Materials science ,Condensed matter physics ,Polarizability ,General Physics and Astronomy ,Antiferroelectricity ,Dielectric ,Cubic crystal system ,Ferroelectricity ,Ion - Abstract
We have investigated the dielectric properties of a CsCl type crystal made up by insertion of ions into the body center sites of a simple cubic array of rotatable polar molecules. Owing to the Lorentz field exerted by the dipoles themselves, a non-uniform distribution in orientation of the polar molecules is predicted below a certain critical temperature. The main results obtained are as follows: (1) It is shown that the crystal is antiferroelectric so long as the polarizability of the central ions is small, half of the dipoles being partially oriented parallel to and the other half antiparallel to one of the cube edges. On the other hand, if the polarizability of the ions is larger than a certain threshold value, the crystal is ferroelectric, all the dipoles being partially oriented parallel to each other. (2) The dielectric constant-temperature curves calculated for antiferroelectric cases show a variety of forms according to the polarizabilities of both components. For some specimens they are almost flat throughout the region around their own critical temperatures, while for other specimens they can show such sharp peaks that they are hardly discernible from those of ferroelectric crystals, which always show very sharp peaks tending to infinity. (3) Below their respective critical temperatures, the dielectric constant should decrease with increasing dc bias in a ferroelectric crystal, while in an antiferroelectric crystal it should increase slightly under the same condition. (4) If a sufficiently strong field is applied to an antiferroelectric crystal at just below its critical temperature, it will be forced to make a momentary transition to a ferroelectric one, the change being accompanied by an abrupt increase of polarization.It is suggested that most of the phenomenological predictions derived with this model may, qualitatively at least, be valid also for other models which have ions capable of displacement instead of freely rotatable dipoles, as is really the case with the well-known BaTi${\mathrm{O}}_{3}$ and the like.
- Published
- 1952
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33. Ferroelectric Transitions and Heterogenous Catalysis
- Author
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G. Parravano
- Subjects
Materials science ,General Physics and Astronomy ,Physical and Theoretical Chemistry ,Photochemistry ,Ferroelectricity ,Catalysis - Published
- 1952
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34. Remarks on Vousden's structure of ferroelectric sodium niobate
- Author
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R. Pepinsky
- Subjects
Materials science ,Sodium niobate ,business.industry ,General Earth and Planetary Sciences ,Optoelectronics ,business ,Ferroelectricity ,General Environmental Science - Published
- 1952
- Full Text
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35. Crystal Structure of the Ferroelectric Phase in PbZrO3Containing Ba or Ti
- Author
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Sadao Hoshino and Gen Shirane
- Subjects
Crystallography ,Materials science ,Phase (matter) ,General Physics and Astronomy ,Crystal structure ,Ferroelectricity - Published
- 1952
- Full Text
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36. A Ferroelectric Ammonium Metaphosphate
- Author
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K. Drenck, C. M. McCarty, E. Zemyan, and R. Pepinsky
- Subjects
chemistry.chemical_compound ,Materials science ,chemistry ,Metaphosphate ,Inorganic chemistry ,General Physics and Astronomy ,Ammonium ,Ferroelectricity - Published
- 1952
- Full Text
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37. Ferroelectricity in the Ilmenite Structure
- Author
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Harold C. Schweinler
- Subjects
Physics ,Condensed matter physics ,General Physics and Astronomy ,Crystal structure ,Polarization (waves) ,Ferroelectricity ,Crystal ,Condensed Matter::Materials Science ,chemistry.chemical_compound ,Dipole ,Nuclear magnetic resonance ,chemistry ,Polarizability ,Barium titanate ,Curie temperature - Abstract
The ferroelectricity of the ilmenite structure minerals lithium tantalate and lithium niobate is studied theoretically, using the method recently introduced by Slater for barium titanate. The metal ions are assumed to move in a potential which has small quartic terms as well as the usual quadratic terms, all satisfying the appropriate crystal symmetry requirements. This results in a slight dependence of the ionic-displacement polarizability of each metal ion on both the temperature and the polarization of the crystal. The local electric field strength is computed exactly for each ion by Ewald's method, and the internal field constants are given for a number of positions in a rhombohedral unit cell of axial angle $\ensuremath{\alpha}={56}^{\ensuremath{\circ}}$. The polarizabilities can be estimated from other crystal polarization data, leading to a spontaneous polarization below the upper Curie temperature ${T}_{0}$ of $2{({T}_{0}\ensuremath{-}T)}^{\frac{1}{2}}$ microcoulombs ${\mathrm{cm}}^{\ensuremath{-}2}$ (without electromechanical correction). Whereas in barium titanate all dipole moments are in the direction of the resultant polarization, it is found here that the lower crystal symmetry results in sizeable components of the oxygen dipole moments perpendicular to the total polarization, but these last components produce a large field in the direction of the polarization at other ionic positions.
- Published
- 1952
- Full Text
- View/download PDF
38. Twinning Structure in Crystals of Tungsten Trioxide
- Author
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R. G. Rhodes
- Subjects
Multidisciplinary ,Materials science ,Inorganic chemistry ,chemistry.chemical_element ,Tungsten ,Tungsten trioxide ,Ferroelectricity ,chemistry.chemical_compound ,Crystallography ,Tetragonal crystal system ,chemistry ,Phase (matter) ,Barium titanate ,Crystal twinning - Abstract
A MICROSCOPIC examination of crystals of tungsten trioxide (WO3) has revealed a type of twinning very similar to the domain patterns characteristic of the ferroelectric (tetragonal) phase of barium titanate (BaTiO3). This similarity is significant in view of the reported ferroelectric behaviour of tungsten trioxide1.
- Published
- 1952
- Full Text
- View/download PDF
39. Piezoelectricity, ferroelectricity, and crystal structure
- Author
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A. von Hippel
- Subjects
Physics ,Nuclear and High Energy Physics ,Dipole ,chemistry.chemical_compound ,Condensed matter physics ,chemistry ,Barium titanate ,Molecular symmetry ,Dielectric ,Crystal structure ,Ferroelectricity ,Piezoelectricity ,Wurtzite crystal structure - Abstract
By visualizing polar crystals as a network of permanent dipole moments, the piezo- and ferroelectric properties of dielectrics may be derived from the standpoint of molecular symmetry. This approach is used to clarify the relation between the sphalerite and wurtzite structures, the ferroelectric feedback effect in barium titanate, aspects of domain formation, and the interrelationship between ferro and piezoelectricity.
- Published
- 1952
- Full Text
- View/download PDF
40. Ferroelectrics and ferromagnetics as memory devices
- Author
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W. N. Papian
- Subjects
Physics ,Condensed Matter::Materials Science ,Ring (mathematics) ,Field (physics) ,Ferromagnetism ,Remanence ,Slab ,Electronic engineering ,Binary number ,Magnetic hysteresis ,Ferroelectricity - Abstract
Storage of binary information in the stationary field of a ferromagnetic ring or a ferroelectric slab promises a neat solution to one of the most vexing problems in the digital computer field, the problem of “remembering” and making available a very large number of binary “words” rapidly and efficiently. The flux remanence and non-linear characteristics of the “rectangular” hysteresis loop simplify the information-retention and the work-selection aspects of the problem tremendously.
- Published
- 1952
- Full Text
- View/download PDF
41. Industrial applications of magnetic amplifiers
- Author
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R. W. Moore
- Subjects
Materials science ,Electromagnet ,business.industry ,Voltage control ,Magnetic separation ,Electrical engineering ,Ferroelectricity ,law.invention ,Magnetic circuit ,law ,Remanence ,Optoelectronics ,business ,Saturation (magnetic) ,Magnetic amplifier - Abstract
Numerous outstanding advantages of “Magamps” are presented which help make possible more reliable, faster, simpler, and inherently more stable regulating systems. Several industrial applications exemplifying these characteristics are discussed.
- Published
- 1952
- Full Text
- View/download PDF
42. Ferroelectric storage elements for digital computers and switching systems
- Author
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J. R. Anderson
- Subjects
Materials science ,business.industry ,Square inch ,Electrical engineering ,Capacitance ,Ferroelectricity ,Ferroelectric capacitor ,law.invention ,Microsecond ,Capacitor ,Hysteresis ,law ,Optoelectronics ,business - Abstract
These ferroelectric storage devices, although still comparatively new, show great promise. They can store up to 2,500 bits of information per square inch in a surface only a few thousandths of an inch thick with pulses less than a microsecond long.
- Published
- 1952
- Full Text
- View/download PDF
43. Origin of ferroelectricity in barium titanate and other perovskite-type crystals
- Author
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Helen D. Megaw
- Subjects
chemistry.chemical_compound ,Crystallography ,Materials science ,chemistry ,Barium titanate ,General Earth and Planetary Sciences ,Ferroelectricity ,General Environmental Science ,Perovskite (structure) - Published
- 1952
- Full Text
- View/download PDF
44. STUDY OF PHASE TRANSITIONS IN PEROVSKITE-TYPE CRYSTALS
- Author
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GenN Shirane and Ray Pepinsky
- Subjects
Phase transition ,Crystallography ,Materials science ,X-ray crystallography ,Dielectric ,Crystal structure ,Hafnium compounds ,Ferroelectricity ,Perovskite (structure) - Published
- 1952
- Full Text
- View/download PDF
45. Ferroelectricity in Oxides of Fluorite Structure
- Author
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William R. Cook and Hans Jaffe
- Subjects
Crystallography ,Materials science ,General Physics and Astronomy ,Ferroelectricity ,Fluorite - Published
- 1952
- Full Text
- View/download PDF
46. The snapping dipoles of ferroelectrics as a memory element for digital computers
- Author
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Charles F. Pulvari
- Subjects
Dipole ,Materials science ,Amplitude ,business.industry ,Electrical engineering ,Optoelectronics ,Pulse duration ,Polarization (waves) ,business ,Ferroelectricity ,Ferroelectric capacitor - Abstract
A brief review is given of the memory properties of non-linear ferroelectric materials in terms of the direction of polarization.A sensitive pulse method has been developed for obtaining static remanent polarization data of ferroelectric materials. This method has been applied to study the effect of pulse duration and amplitude and decay of polarization on ferroelectric ceramic materials with fairly high crystalline orientation.These studies indicate that ferroelectric memory devices can be operated in the megacycle ranges.Attempts have been made to develop electrostatically induced memory devices using ferroelectric substances as a medium for storing information. As an illustration, a ferroelectric memory using a new type of switching matrix is presented having a selection ratio 50 or more.
- Published
- 1953
- Full Text
- View/download PDF
47. XIV. The properties ofKH2PO4below the Curie point
- Author
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D.M. Finlayson and H.M. Barkla
- Subjects
Range (particle radiation) ,Materials science ,Condensed matter physics ,Curie temperature ,Dielectric ,Coercivity ,Ferroelectricity ,Piezoelectricity - Abstract
The study of the dielectric, piezoelectric and elastic properties of KH2PO4 has been extended into the ferroelectric range of temperatures, and should permit further theoretical consideration of the behaviour of this group of crystals. In addition to the main transition, the treatment of which is still inadequate, there is another transition for which no complete explanation can yet be given; this second characteristic temperature marks the onset of a steep rise of coercive field with decreasing temperature. A qualitative domain theory is presented to account for the main features of the ferroelectric state in KH2PO4.
- Published
- 1953
- Full Text
- View/download PDF
48. X-ray analysis of the ferroelectric transition in KH2PO4
- Author
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R. Pepinsky and B. C. Frazer
- Subjects
Materials science ,Condensed matter physics ,General Earth and Planetary Sciences ,X ray analysis ,Ferroelectricity ,General Environmental Science - Published
- 1953
- Full Text
- View/download PDF
49. Ferroelectricity in Oxides of Face-Centered Cubic Structure
- Author
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William R. Cook and Hans Jaffe
- Subjects
Materials science ,Condensed matter physics ,Structure (category theory) ,General Physics and Astronomy ,Cubic crystal system ,Ferroelectricity - Published
- 1953
- Full Text
- View/download PDF
50. Domain Structure of Rochelle Salt and KH2PO4
- Author
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Toshito Mitsui and Jiro Furuichi
- Subjects
Physics ,Crystal ,Phase transition ,Domain wall (magnetism) ,Self-energy ,Condensed matter physics ,Domain (ring theory) ,General Physics and Astronomy ,Curie temperature ,Ferroelectricity ,Energy (signal processing) - Abstract
It has been verified by means of the polarization microscope that rochelle salt in the ferroelectric state consists of many domains. The domain structure in an annealed crystal is caused by the electrostatic self energy. When the electric field along the $X$ direction is increased and then decreased gradually, successive positions of the domain wall produce a hysteresis loop, which proves the existence of a restoring force on the wall. This restoring force causes lag of charging, and its variation with time produces a fatigue effect. The propagation velocity of a domain wall is about 0.2 cm/sec for 100 v/cm. A group of domains parallel to the $b$ axis has been created artificially. When a stress ${Y}_{z}$ is applied, a set of domains inverts its polarization direction. $Z$-cut specimens of K${\mathrm{H}}_{2}$P${\mathrm{O}}_{4}$ cooled below the Curie temperature divide into many regions which appear to be domains. The phase transition in K${\mathrm{H}}_{2}$P${\mathrm{O}}_{4}$ propagates from only one nucleus.Theoretically it has been concluded that the domain wall energy of rochelle salt is $1.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}{{P}_{0}}^{3}$ erg/${\mathrm{cm}}^{2}$ and the wall width $\ensuremath{\sim}2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}/{P}_{0}$ cm, where ${P}_{0}$ is the saturation polarization.
- Published
- 1953
- Full Text
- View/download PDF
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