Showing papers on "Ferroelectricity published in 1972"
TL;DR: In this article, the authors demonstrated that phase holograms in ferroelectric materials can be achieved by fast electrical control, using an external field slightly smaller than the coercive field to the crystal.
Abstract: We have demonstrated that fixation and erasure of phase holograms in ferroelectric materials can be achieved by fast electrical control. High ionic mobility that allows the change of the electronic pattern into a stable ionic one is obtained by applying, during 0.1 sec, an external field slightly smaller than the coercive field to the crystal. Erasure is accomplished in 3 sec by applying a field that causes saturation of the polarization. Investigation of this process was carried out in BaTio3 crystals doped with Fe.
208 citations
TL;DR: In this paper, the temperature characteristics of dielectric constants, spontaneous polarization, thermal expansion coefficients, indices of refraction, and optical rotatory power of Pb5Ge3O11 single crystals have been investigated in detail from room temperature up to above the Curie temperature, 177°C.
Abstract: The temperature characteristics of dielectric constants, spontaneous polarization, thermal‐expansion coefficients, indices of refraction, and optical rotatory power of Pb5Ge3O11 single crystals have been investigated in detail from room temperature up to above the Curie temperature, 177°C. From the results of these measurements, the following constants were obtained: linear thermal‐expansion coefficients (αa)F=7.75×10−6/deg°C and (αc)F=7.79×10−6/deg°C (ferroelectric phase), (αa)P=13.8×10−6/deg°C and (αc)P=13.4×10−6/deg°C (paraelectric phase); quadratic electro‐optic constants g33T=0.47×108 cm4 /C2, g13T=0.37×108 cm4 /C2; and electrogyration coefficient γ33 =8.7 cm2/C. An isomorphous compound Pb5(Ge2O7)(SiO4) was synthesized and was found to be ferroelectric with T c=60°C and Ps=1.7 μC/cm2 at room temperature. Ferroelectric properties and electrogyration coefficient were studied in the solid‐solution system Pb5(Ge2O7)(GeO4)1−x (SiO4)x.
161 citations
TL;DR: In this paper, the role of an α-alanine molecule in the lattice of triglycine sulphate (TGS) was examined in terms of the atomic motions normally required to reverse the polarity of the ferroelectric crystal.
Abstract: The recently reported permanent poling effects in triglycine sulphate (TGS) containing some α-alanine additive is further investigated by pyroeiectric and dielectric measurements. The probable role of an L-alanine molecule in the lattice of TGS is examined in terms of the atomic motions normally required to reverse the polarity of the ferroelectric crystal. The observations can be explained by a model which relates the lack in α-alanine of the prototypic symmetry possessed by glycine I to the inhibition of the ferroelectric switching mechanism. Substituted α-alanine molecules are shown to lead to local irreversible dipoles which can “pole” a TGS crystal in a single sense provided that only one optically active form (L) is used. In this case crystals grown either below or above Tc behave similarly. Thus crystals can be grown in the non-polar phase, which become spontaneously, fully poled when cooled below Tc. Using dl-alanine as the additive for crystals grown below Tc, large permanently poled regions of e...
152 citations
IBM1
TL;DR: In this paper, it was shown that the residual depolarization field in a ferroelectric thin film which arises from the incomplete cancellation of polarization and compensation charge in a semiconducting electrode, introduces modifications in the spontaneous polarization and transition temperature.
125 citations
IBM1
TL;DR: In this paper, high purity single crystals of PbZrO3 suitable for electrical measurements were grown from solutions in the PbO-ZRO2-PbF2-B2O3 system.
Abstract: High-purity single crystals of PbZrO3 suitable for electrical measurements were grown from solutions in the PbO-ZrO2-PbF2-B2O3 system. Dielectric, hysteresis-loop, and optical measurements confirmed the existence of an intermediate ferroelectric (FE) form, previously observed only in ceramics, just below the transition temperature (Tc#232°C). The temperature stability range of the FE phase, which cooling curve measurements show to vary from 12° to 26°C, appears to be related to crystal stoichiometry. The maximum value of spontaneous polarization is P8(max)#24 μC/cm2, assuming that the FE phase possesses rhombohedral symmetry.
104 citations
TL;DR: In this paper, the integrated Raman scattering cross-section in BaTiO3 has been measured near and above the ferroelectric phase transition as a function of temperature and the results indicate that there is disorder which breaks the crystal inversion symmetry in the cubic phase of Ba TiO3.
97 citations
TL;DR: In this paper, it was shown that polyvinylidene fluoride (PVF2) can be made significantly pyroelectric and optically nonlinear by poling in a field ∼ 106 volt/cm.
Abstract: Oriented films of polyvinylidene fluoride [(CH2CF2)n] can be made significantly pyroelectric and optically nonlinear by poling in a field ∼ 106 volt/cm. Pyroelectric coefficients as large as 2.4 nC/cm2 °C (comparable to single-crystal LiNbO3) and nonlinear optical coefficients comparable to d11 of crystal quartz are observed. Simple, inexpensive and fairly rugged pyroelectric detectors for electromagnetic radiation of any wavelength can be made from the poled films. Polyvinylidene fluoride (PVF2) crystallizes in a polar phase and it is found that its polarization can be switched. In the sense that it is a switchable pyroelectric PVF2 can be regarded as a ferroelectric polymer.
95 citations
TL;DR: In this article, a phenomenological theory of the electromechanical properties of various types of oxygen-octahedra ferroelectrics is presented, and the electrostrictive constants reduced to those of perovskite-type oxide are nearly constant with the values Q11p ≥ 0.10m4/C2, Q12p ≥−0.034m4 /C2 and Q44p≈ 0.029m 4 /C 2.
Abstract: A phenomenological theory of the electromechanical properties of various types of oxygen‐octahedra ferroelectrics is presented. The electrostrictive constants reduced to those of the perovskite‐type oxide are nearly constant with the values Q11p≈0.10 m4/C2, Q12p≈−0.034 m4/C2, and Q44p≈0.029 m4/C2. These constants are obtained by assuming that the piezoelectric effect in the ferroelectric phase is due to the electrostrictive effect in the paraelectric phase biased by the spontaneous polarization. The oxygen‐octahedra ferroelectrics can be treated approximately as elastically isotropic and the stiffnesses normalized to those of the perovskite‐type oxide c11p and c44p are shown to be proportional to their melting points TM, i.e., c11p≈1.3×108TM(°K) N/m2 and c44p≈0.47×108TM(°K) N/m2. The potential usefulness for ultrasonic applications of oxygen‐octahedra ferroelectrics is discussed for dielectrically isotropic plates under perpendicular field excitation. The orientation of the plate which has the largest cou...
91 citations
TL;DR: In this article, the elastic, piezoelectric, and dielectric constants of a new ferroelectric crystal 5PbO · 3GeO2 have been measured.
Abstract: The elastic, piezoelectric, and dielectric constants of a new ferroelectric crystal 5PbO · 3GeO2 have been measured. The measurements involve mostly the use of thickness modes in small plates of various crystallographic orientations. The electromechanical coupling factors turn out to be small, which makes this material unattractive for ultrasonic applications. The temperature characteristics of some piezoelectric constants are presented. The piezoelectric constant d31 vanishes above the Curie point (177 °C), while d22 remains constant above and below the Curie point.
79 citations
TL;DR: In this article, the temperature behavior of the TO-phonon frequencies and line shapes in NaN${\mathrm{O}}_{2}$, as observed by Raman spectroscopy, is reported for temperatures from 20 to 250\ifmmode^\circ\else\textdegree\fi{}C.
Abstract: The temperature behavior of the TO-phonon frequencies and line shapes in NaN${\mathrm{O}}_{2}$, as observed by Raman spectroscopy, is reported for temperatures from 20 to 250\ifmmode^\circ\else\textdegree\fi{}C. The Raman spectra of the ferroelectric phase obeyed the selection rules of the ${C}_{2V}^{20}$ space group. In the paraelectric Raman spectra, extra resonances (six instead of the expected three) were found. This anomaly and accompanying line asymmetries are accounted for by recognizing the effect of the nitrite-ion disordering along the $b$ axis upon lattice states. Additionally, in the paraelectric Raman spectra [polarized and ($\mathrm{bc}$)], a redundant appearance of the symmetric internal vibrations was observed, from which we conclude that above the phase-transition temperature there is a large torsional oscillation of the N${\mathrm{O}}_{2}^{\ensuremath{-}}$ ion about the $a$ axis. Significantly, the librational frequency associated with this torsional oscillation softened at key temperatures, the temperatures at which long- and short-range orders are lost. From our data, we conclude that the nitrogen atom jumps between two equivalent lattice sites by the flipping of the nitrite ion about the $a$ axis, and we suggest that temperature-dependent coupling between normal modes precipitates this flipping. A careful search of the Raman spectra 3 ${\mathrm{cm}}^{\ensuremath{-}1}$ from the frequency of the incident laser revealed no "Cochran" soft modes or supernumerary modes, such as a dipole wave, that might explain the ferroelectric phase transition in NaN${\mathrm{O}}_{2}$.
77 citations
TL;DR: In this article, the state of the art for these applications and materials development needed for further progress are reviewed, with emphasis on preparative problems, optimization of film structure and of electrical properties and application in devices.
TL;DR: The Raman and ir spectra of ammonium sulphate and its fully deuterated analogue have been measured at temperatures above and below the ferroelectric transition temperature No marked changes in the spectra occur at T c, although several small peaks appear below T c and increase in intensity as the temperature is reduced as discussed by the authors.
TL;DR: In this article, an analysis is made of the mechanical defects in KH2PO4 compatible with the crystal symmetry, and the most important result is the possible explanation in terms of mechanical phenomena of the long-range interaction between domains, and domain freezing at low temperatures.
Abstract: An analysis is made of the mechanical defects in KH2PO4 compatible with the crystal symmetry. With the theory of crystal dislocations, one can explain several experimental results on domain equilibrium states, domain velocities, and the critical electric field to move the domains in the plane perpendicular to the ferroelectric axis c. The most important result is the possible explanation in terms of mechanical phenomena of the long‐range interaction between domains, and domain freezing at low temperatures.
TL;DR: In this article, the cause of the cracking phenomenon was found from DTA and dielectric property measurements to be a possible phase transformation occurring at 935°C, with an energy of 1 kcal/mole.
Abstract: The compound Bi2WO6 has been prepared as a ceramic and in single crystal form. Growth of Bi2WO6 single crystals from the melt by the Czochralski method produced boules as large as 20 mm in diameter by 60 mm long. On cooling to room temperature these boules invariably cracked, yielding for experimental investigations small prismatic rods bounded by (001) and (111) faces. The cause of the cracking phenomenon was found from DTA and dielectric property measurements to be a possible phase transformation occurring at 935°C, with an energy of 1 kcal/mole. A low-energy relaxation process was also detected in the temperature region 300-450°C. The low-iemperature modification of Bi2 WO6 is ferroelectric and crystallizes with the orthorhombic crystal structure B2cb(C172v), a -5.458 A, b = 5.438 A and c = 15.434 A. The structure of the higher temperature phase was not determined because of the severe recrystallization of the samples.
TL;DR: In this paper, the second-harmonic coefficient d31 was found to be the highest for any room-temperature ferroelectric and phase matched SHG is not possible, but nondegenerate three-frequency mixing should be possible.
Abstract: Optical transmission, refractive‐index, and nonlinear optical properties of single domain PbTiO3 have been measured between room temperature and the Curie temperature Tc. The second‐harmonic coefficient d31 is found to be the highest for any room‐temperature ferroelectric. Since the birefringence is small (approximately 0.008), phase‐matched SHG is not possible, but nondegenerate three‐frequency mixing should be possible. The Miller δ coefficients are analyzed in terms of Jerphagnon's formulation and poor agreement is observed.
TL;DR: In this paper, the pyroelectric properties of hot-pressed lanthanum doped PZT X/65/35 ferroelectric ceramics have been evaluated to evaluate their potential as pyro-electric infrared detector materials.
Abstract: The pyroelectric properties of hot-pressed lanthanum doped PZT X/65/35 ferroelectric ceramics have been studied to evaluate their potential as pyroelectric infrared detector materials. The pyroelectric coefficients ranged from 3.5 × 10-8 to 17.0 × 10-8 (coul/cm2 °C) for lanthanum compositions from X = 0 to 8. The dielectric properties have also been measured over this compositional range. Thermal noise is shown to be dominant in detectors made from these materials for frequencies between 1 Hz and 1000 Hz. A detectivity at 100 Hz of 108 cm(Hz)4/W has been achieved in these materials.
TL;DR: In this paper, a theory was given that accounts qualitatively for the observations of thin and thick domain walls in ferroelectric and ferroelastic crystals, with special reference to the 90° walls in BaTiO 3 and to the 180° wall in GMO.
TL;DR: In this article, the changes induced in some properties of triglycine sulphate (TGS) single crystals by X-irradiation in the presence of an external electric field are found to be beneficial to the pyroclectric applications of this material.
Abstract: The changes induced in some properties of triglycine sulphate (TGS) single crystals by X-irradiation vi the presence of an external electric field are found to be beneficial to the pyroclectric applications of this material The variations of dielectric and pyroelectric properties are investigated as a function of radiation dose Optimum properties are found after irradiation sufficient to cause the development of a self-bias of a few kV/cm on the crystal which keeps it in a single domain state This effect is accompanied by an increase in the pyroelectric coefficient and a decrease in the dielectric constant at room temperature Properties comparable to those recently reported for TGS crystals containing L-alanine are thus obtained The annealing effects of elevated temperatures and electric fields on the irradiation induced self bias are documented The relevance of the present results to applications of TGS and to the recent structural studies of irradiation/field treated TGS crystals are discussed
TL;DR: In this article, dielectric and optical fatigue effects in 8/65/35 lanthana modified lead zirconate-lead titanate (PLZT) ferroelectric ceramics have been observed in respense to 60 Hz sine wave switching.
Abstract: Dielectric and optical fatigue effects in 8/65/35 lanthana modified lead zirconate-lead titanate (PLZT) ferroelectric ceramics have been observed in respense to 60 Hz sine wave switching. Erratic behavior in Ee is attributable to microcracking near the surface electrodes. In addition, after N ∼ 105 cycles, the remanent polarization, PR, decreases as the logarithm of N. The birefringence parameter decreases linearly with PR over the entire range of 102 << N << 108 cycles.
TL;DR: An enantiomorphic transition was observed for the first time by observing Airy's spirals of the oppositely polarized ferroelectric 5PbO 3GeO2 single crystals, which were grown by the Czochralski method as discussed by the authors.
Abstract: An enantiomorphic transition was observed for the first time by observing Airy's spirals of the oppositely polarized ferroelectric 5PbO 3GeO2 single crystals, which were grown by the Czochralski method. Switching time follows an exponential law at moderate field strengths and a power law at higher field strengths.
TL;DR: In this article, the phase transition in ammonium Rochelle salt is interpreted from the group-theoretical point of view following the Landau theory of phase transition and shown to be improper since it is induced by a two-dimensional representation at k =(1/2) b 1 which correctly describes the observed phase change from the space group D 2 3 to C 2 2.
Abstract: The phase transition in ammonium Rochelle salt is interpreted from the group-theoretical point of view following the Landau theory of phase transition and shown to be improper since it is induced by a two-dimensional representation at k =(1/2) b 1 which correctly describes the observed phase change from the space group D 2 3 to C 2 2 . The expression of the free energy is given in terms of the doubly-degenerate transition parameter, besides the macroscopic polarization and deformation.
TL;DR: In this paper, a preliminary study has been made of the structure, optical properties and polarization reversal behavior of epitaxial bismuth titanate films grown by sputtering on MgO substrates.
Abstract: A preliminary study has been made of the structure, optical properties and polarization reversal behavior of epitaxial bismuth titanate films grown by sputtering on MgO substrates. As grown, the films are twinned on a coarse scale, with alternate regions oriented with the monoclinic (100) and (010) plane parallel to the (110) MgO surface. Optical birefringence measurements on these regions yielded Δna and Δnb values as a function of temperature which were in general agreement with those measured for bulk crystals. By annealing film sections detached from the substrate, a single orientation of the type (010) was obtained, and regions of such samples could be poled to a single-domain condition. Hysteresis data, with the field applied along the a and c axes, for single domain regions yielded spontaneous polarization results comparable to those reported previously for bulk crystals, but indicated somewhat higher coercive fields. Similar measurements with the field along the [101] axis showed that it is possib...
TL;DR: In this article, it is shown that crystallographic disorder and non-stoichiometry can lead to anomalous behavior in dielectric properties such as permittivity and loss, and that if care is taken to produce homogeneous and well-crystallized structures, polarization reversal effects similar to those characteristic of the bulk ferroelectric can be obtained.
Abstract: Some of the problems of fabricating thin films of mixed oxide ferroelectrics possessing electrical properties comparable to those of the bulk material are discussed. It is shown that crystallographic disorder and non-stoichiometry can lead to anomalous behavior in dielectric properties such as permittivity and loss. If care is taken to produce homogeneous and well-crystallized structures, polarization reversal effects closely similar to those characteristic of the bulk ferroelectric can be obtained. In particular, the crystalline anisotropy of polarization and optical properties in epitaxial bismuth titanate films follows closely that observed in single crystals. Moreover, bulk-type electro-optic switching behavior is observed in these structures, offering good prospects of using them as display media. The optimization of ferroelectric properties for capacitors, memories and displays is discussed and some of the new device potentialities for ferroelectric films in general are evaluated.
TL;DR: In this article, the temperature dependence of the relaxation time τ0 was analyzed on the basis of a formula deduced from a molecular field approximation, with a Curie constant C = 4.63 × 103 K and the temperature independent electronic dielectric constant e∞, is equal to 6.40 eV at 40°C.
Abstract: Dielectric dispersion in ferroelectric AgNa(N02)2 has been measured along the polar direction of [010] in a temperature region of 20°C ∼ 80°C. The dipolar polarization disperses in a frequency region below 1 MHz, and the dispersion can be fairly well described by Debye monodispersive process except in a narrow temperature region of about 2°C above the Curie point of 37.80°C. The temperature dependence of the relaxation time τ0 is analyzed on the basis of a formula deduced from a molecular field approximation:[image omitted] with a Curie constant C = 4.63 × 103 K and the temperature independent electronic dielectric constant e∞, is equal to 6. The activation energy δU is 0.40 eV at 40°C. Slight temperature dependence of δU is attributed to thermal expansion.
TL;DR: In this article, a single crystal was made of a sodium nitrite (NaNO 2 ) single crystal which had been partially polarized with an external d. c. electric field at room temperature.
Abstract: X-ray topographic study was made of a sodium nitrite (NaNO 2 ) single crystal which had been partially polarized with an external d. c. electric field at room temperature. Images with characteristic diffraction contrast found in topographs of the crystal suggest the following process of polarization reversal. By increasing thickness of pre-existing domain boundary walls the intermediate state regions having the same crystal structure as that of the domain boundary walls, are formed first, and on the next step the intermediate state regions once formed are eroded by the domains having the right direction of polarization. Rotation of NO 2 radicals by 180° around their O-O axes will be the molecular mechanism of the polarization reversal under electric field at room temperature.
TL;DR: In this article, a synthetic compound SrTeO3 was discovered to exhibit ferroelectricity in the temperature range between 312 and 485°C, and small single crystals could be grown by the Kyropoulos method.
Abstract: A synthetic compound SrTeO3 was discovered to exhibit ferroelectricity in the temperature range between 312 and 485°C. Small single crystals could be grown by the Kyropoulos method. The crystal belongs to the monoclinic system and its space group is C2/ c − C2 h6 at room temperature. A pronounced dielectric anomaly was observed along the b axis at 485°C. The value of the spontaneous polarization, obtained by the D‐E hysteresis loops at 50 Hz, is 3.7 μC/cm2 at 312°C.
TL;DR: In this article, the Raman spectra of the soft-phonon behavior in the ferroelectric transition in SbSI was studied by means of a new technique in which the phase transition is induced by hydrostatic pressure.
Abstract: The Raman spectra of the soft-phonon behavior in the ferroelectric transition in SbSI is studied by means of a new technique in which the phase transition is induced by hydrostatic pressure. The crystal temperature is maintained constant and the ferroelectric transition is created by a linear shift of the Curie temperature. Evidence is provided for the existence of two distinct mode couplings involving three phonons.