Showing papers on "Ferroelectricity published in 1975"
TL;DR: In this paper, a general symmetry argument is presented, and experiments on newly synthesized p-decyloxybenzylidene p'-amino 2-methyl butyl cinnamate are described, demonstrating that chiral smectic C and H liquid crystals are ferroelectric.
Abstract: A general symmetry argument is presented, and experiments on newly synthesized p-decyloxybenzylidene p'-amino 2-methyl butyl cinnamate are described, demonstrating that chiral smectic C and H liquid crystals are ferroelectric. Some of the properties of this new class of ferro-electrics are discussed.
1,357 citations
TL;DR: In this article, a ferroelectric field effect transistor (FET) was constructed using a thin film of bismuth titanate (Bi4Ti3O12) deposited on a Si substrate by rf sputtering.
Abstract: A ferroelectric field‐effect transistor has been investigated using a thin film of bismuth titanate (Bi4Ti3O12) deposited on a Si substrate by rf sputtering. Achievement of the ferroelectric polycrystalline Bi4Ti3O12 films without any cracks necessitates postdeposition heat treatment in air at temperatures ?550 °C for 30 min. The film, heat treated at 650 °C, has a remanent polarization of 4.0 μC/cm2 and a coercive field of about 250 kV/cm at 1 kHz. A FET having a gate structure of Bi4Ti3O12‐SiO2‐Si was fabricated, where the SiO2 served to prevent charge injection from Si into the ferroelectric film. (This process would degrade the retention of memorized states.) The FET can be switched by voltages of as low as 15 V applied to the gate. The on and off states are very stable at room temperature.
191 citations
TL;DR: The phase transition temperatures of other solid solutions, partially replacing Sr by Ca, Pb or Ba, are also studied on ceramic samples as mentioned in this paper, where the Curie-Weiss temperature θ 0 and Curie constant C P are: θ0 =161 K(=-112°C) and C P =0.84×10 5 K.
Abstract: Single crystals of Sr 2 Ta 2 O 7 and Sr 2 Nb 2 O 7 are grown by a floating zone technique. Strontium tantalate belongs to D 2 h 14 or D 2 h 17 space group at room temperature. Ferroelectric phase transition temperature is -107°C. The Curie-Weiss temperature θ 0 and the Curie constant C P are: θ 0 =161 K(=-112°C) and C P =0.84×10 5 K. Spontaneous polarization and coercive field are 1.9 µC/cm 2 and 0.4 kV/cm at -190°C, respectively. Strontium niobate belongs to C 2υ 12 space group at room temperature. Its ferroelectric phase transition occurs at T c =1342±2°C, with θ 0 = T c and C P =1.2×10 5 K, and second phase transition occurs at -156°C. Solid solution Sr 2 (Ta 1- x ·Nb x ) 2 O 7 exists in the entire composition range and its ferroelectric phase transition temperature increases markedly from -107°C to 1342°C, according to the increase of x . Phase transition temperatures of other solid solutions, partially replacing Sr by Ca, Pb or Ba, are also studied on ceramic samples.
141 citations
TL;DR: In this article, it has been found that in NH 4 LiSO 4 another transition point 186.5°C exists in addition to the already known one 10°C and this substance is ferroelectric between these two transition points.
Abstract: It has been found that in NH 4 LiSO 4 another transition point 186.5°C exists in addition to the already known one 10°C and this substance is ferroelectric between these two transition points. Anomalies of dielectric constant at the transition points are very small as compared with those of proper ferroelectrics. The Curie-Weiss law holds within a narrow temperature range in the phase above the upper transition, where the Curie constant has a very small value of 5.6 K. Moreover the spontaneous polarization shows a curious increase with lowering temperature. Thus NH 4 LiSO 4 can be said to be one of improper ferroelectrics.
126 citations
TL;DR: In this paper, impact-loading techniques are used to investigate the electromechanical response of poled specimens of a ferroelectric ceramic, PZT 95/5, to long−duration shock pulses.
Abstract: Reproducible and predictable electrical pulses with peak powers of a few hundred kilowatts lasting for a few microseconds can be obtained from shock−wave compressed ferroelectrics. In this work, impact−loading techniques are used to investigate the electromechanical response of poled specimens of a ferroelectric ceramic, PZT 95/5, to long−duration shock pulses. The experiments are conducted in the normal mode in which the shock propagation vector is perpendicular to the remanent polarization. Current histories are obtained as a function of load resistance for a fixed shock amplitude of 1.4 GPa, and few additional experiments investigate the stress dependence of the electrical response. A simple, though specific, model is developed that gives good agreement with observed results. The extension of this model to other materials and shock−loading conditions is discussed.
111 citations
TL;DR: In this article, the ferroelectric phase transition of BiFeO3 solid solution was studied by the method of differential thermal analysis, showing that the endothermal effect observed at about 820°C is related to the phase transition.
108 citations
TL;DR: In this paper, the ferroelectric properties of fine-grained PbTiO3 ceramics modified by small amounts of La and Mn have been investigated using both quasi-static (∼ 0.05 Hz) and more dynamic (0.5-50 Hz) electric driving fields.
Abstract: The ferroelectric properties of fine-grained PbTiO3 ceramics modified by small amounts of La and Mn have been investigated using both quasi-static (∼ 0.05 Hz) and more dynamic (0.5-50 Hz) electric driving fields.Information about the domain reorientation processes were obtained from lateral switching strain and hysteresis loop measurements with low-frequency fields. The lateral remanent switching strain is ∼70.10-5, the remanent polarization ≲ 30 μC/cm2, and the coercive field strength ≳ 40 kV/cm. The number of domains switched by 90° is small (≲10%) but 180° domain alignment is virtually perfect. The spontaneous polarization of PbTiO3 single crystals is estimated to be ∼75 μC/cm2. Polarization reversals under more dynamic conditions (10-50 Hz sine wave excitation) result in the occurrence of fatiguing effects. SEM techniques revealed microcracking as the cause of this degradation behaviour. The cracks run along grain boundaries and they are confined to a surface layer of ≲ 15 grain diameters.
94 citations
TL;DR: In this paper, the phase diagram of (NH 4 ) 2 SO 4 -K 2 SO4 mixed crystal system was obtained from dielectric and pyroelectric study, and it was found that the ferroelectric phase transition temperature T c decreases with the increase of concentration of K + ions.
Abstract: The phase diagram of (NH 4 ) 2 SO 4 -K 2 SO 4 mixed crystal system was obtained from dielectric and pyroelectric study. It was found that the ferroelectric phase transition temperature T c decreases with the increase of concentration of K + ions, and ferroelectric phase disappears if mixed crystals contain more than 70% of K 2 SO 4 . It was also found that the spontaneous polarization of mixed crystals with low concentration of K + ion (up to 30%) increases first to maximum, and then gradually decreases as the temperature is lowered. These experimental observations suggest that in this system single homogeneous polarization may not be an order parameter and the dipole arrangements of this system may be not ferroelectric but ferrielectric as was first pointed out by Unruh.
93 citations
TL;DR: In this paper, the soft-mode Raman spectra of KDP in both the paraelectric (PE) and ferroelectric (FE) phases are reported, and the results demonstrate that the proton motion remains coupled to an optic mode of the lattice for $Tl{T}_{C}
Abstract: Measurements of the pressure and temperature dependences of the soft-mode Raman spectra of potassium dihydrogen phosphate (KDP) in both the paraelectric (PE) and ferroelectric (FE) phases are reported. The soft-mode response is overdamped throughout the PE phase at atmospheric pressure, but can be made underdamped with pressure in this phase. Measurements at high pressure in the PE phase where the response is underdamped therefore allow a more accurate determination of the parameters for the coupled-mode system than one can obtain from measurements at atmospheric pressure. Measurement of the pressure dependence in the FE phase allows one to identify the soft mode of the system in this phase, and the results demonstrate that the proton motion remains coupled to an optic mode of the lattice for $Tl{T}_{C}$. The temperature and pressure dependences of the microscopic parameters are examined within the framework of both the pure tunneling and the coupled proton-optic-mode models for the phase transition. It is found that the pure tunneling model is inadequate for a detailed description of the spectra, whereas the modified tunneling model, or coupled-mode model, gives a more quantitative description of the results. While this model can be used for quantitative comparison between the Raman scattering and dielectric measurements in these materials, there are inadequacies of the model in describing the microscopic interactions. These features are discussed in detail.
90 citations
TL;DR: In this article, the authors show that orthorhombic CsH 2 PO 4 undergoes a ferroelectric transition at T c = −119.5° C, whereas the ferroelectric transition temperature in isomorphous CsD 2 PO4 is Tc = −5.55° C.
79 citations
TL;DR: In this article, rare earth-modified ferroelectric crystals with the formula (Sr1−xBax)1− 3y/2 RyNb22O6, where R = La, Nd, Sm, Gd, and Lu, have been prepared and studied.
Abstract: Rare-earth-modified ferroelectric crystals with the formula (Sr1−xBax)1− 3y/2 RyNb22O6, where R = La, Nd, Sm, Gd, and Lu, have Been prepared and studied. When R = La, Nd, x ≃ .5 and y = 0.02, the modified material, at room temperature, exhibited twice the pyroelectric coefficient and four times the dielectric constant of the unmodified Sr1−xBaxNb2O6 (x ≃ .5). Curie temperatures decreased, dielectric constants increased, while loss factor and detector signal-to-noise ratios remained nearly the same with the addition of rare earth doping. The calculated response based on the measured properties agree with the measured response of actual detectors. These properties suggested that the modified SBN are good materials for small element or array pyroelectric infrared detector applications.
TL;DR: In this article, the authors studied the case where the polarization is created by applying a shear velocity parallel to the smectic planes, and showed that the helicoidal structure is distorted by the shear.
Abstract: The existence of ferroelectricity in the chiral smectic C phase has been established from polarization measurements in the presence of an electric field [I]. In this communication we study the case where the polarization is created by applying a shear velocity parallel to the smectic planes : The helicoidal structure is distorted by the shear : The alignment effect induces the average dipoles in the smectic C planes to align perpendicular to the plane of the shear. The dynamics of the effect gives information on the elasticity and viscosity of the process. A significant increase of the polarization observed near the smectic A transition is discussed. (*) Article paru dans le Journal de Physique 36 (1975) 1005. Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1976325
TL;DR: In this paper, a single lead potassium niobate (PKN) crystal is extracted from a melt and the Curie temperature is 450±10˚°C at room temperature, which is considered to be isomorphous with PbNb2O6.
Abstract: Ferroelectric, optical, and other related properties of single crystals of lead potassium niobate (PKN) have been measured. This crystal is pulled from a melt and the Curie temperature is 450±10 °C. PKN belongs to the orthorhombic system with space group C142v‐Cm2m at room temperature and it is considered to be isomorphous with PbNb2O6 which has the tungsten‐bronze structure with its spontaneous polarization perpendicular to the tetragonal c axis. From the measured temperature dependence of refractive indices and the obtained values of electro‐optic coefficients, it is concluded that the ferroelectric and optical properties of PKN are similar to those of other oxygen‐octahedra ferroelectrics except PbTiO3 and PZT, although PKN contains Pb as a constituent element.
TL;DR: In this article, the dielectric constant of KTaO 3 has been measured as a function of the applied uniaxial stress normal to the (100), (110) and (111) faces.
Abstract: The dielectric constant of KTaO 3 has been measured as a function of the applied uniaxial stress normal to the (100), (110) and (111) faces. Under the stress normal to (100) or (110), the induced ferroelectric phase transition has been observed at liquid-helium temperatures. From the analysis of the stress dependence of the dielectric constant in the paraelectric phase, the electrostrictive constants for this crystal have been determined as Q 11 =9.69±0.7, Q 12 =-2.55±0.2 and Q 44 =3.3±2.6 in 10 -13 cgs at 4.2 K. Their magnitude was found to decrease at the rate of 8×10 -4 in 10 -13 cgs/K with increase of temperature. Characteristics of the dielectric constant in the stress-induced ferroelectric phase are also discussed.
TL;DR: A liquid phase epitaxial dipping process for the growth of thin films of ferroelectric LiNbO 3 on isostructural LiTaO 3 substrates was reported in this paper.
TL;DR: In this paper, the pyroelectric measurements show that fully transparent glass-ceramics can be ferroelectric, even in the transparent state, the crystal size is limited to ∼2000 A. Piezoelectric and hysteresis loop measurements have failed to detect evidence of Ferroelectricity.
Abstract: When the network system is limited, most ferroelectric glass-ceramics will produce a fully crystallized transparent body when cerammed at low temperatures. Higher-temperature heat treatment results in crystal growth and gradual loss of transparency. In the transparent state, the crystal size is limited to ∼2000 A. Piezoelectric and hysteresis loop measurements have failed to detect evidence of ferroelectricity, but the present pyroelectric measurements show that fully transparent glass-ceramics can be ferroelectric.
TL;DR: In this paper, the elastic and piezoelectric constants of ferroelectric lead potassium niobate were measured by the use of the thickness vibrations of plates, and it was shown that the y-cut plate has the largest coupling factor of 0.73 for the shear mode and the z−cut plate had the smallest coupling factor (0.59) for the extensional mode.
Abstract: All the elastic and piezoelectric constants of ferroelectric lead potassium niobate were measured by the use of the thickness vibrations of plates. Calculating the electromechanical coupling factors of rotated cuts, it was shown that the y‐cut plate has the largest coupling factor of 0.73 for the shear mode and the z‐cut plate has the largest coupling factor of 0.59 for the extensional mode. If the piezoelectricity arises from the effect of each oxygen octahedron, the metal ions seem to displace parallel to one of the 4mm axes of the oxygen octahedron within the tetragonal c plane.
TL;DR: In this paper, the effects of electrical field and mechanical stress on domain wall motion have been quantitatively determined for gadolinium molybdate (GMO) and similar compounds.
Abstract: The effects of electrical field and mechanical stress on domain wall motion have been quantitatively determined for gadolinium molybdate (GMO) and similar compounds. The ratio of the stress driven wall mobility μτ to the electrical field driven wall mobility μE is shown to be equal to the ratio of the spontaneous strain γ0 to the spontaneous polarization P0 and to have the numerical value 1.53×104 cm2/C. The dynamics of domain wall motion in GMO are discussed in relation to the crystal structure of this material.
TL;DR: In this paper, X-ray, dielectric and elastic measurements were made and the space groups were determined as I, T4-P213; II, C22-P21; III, C11-P1 and IV, D42-P212121 as the temperature is decreased.
Abstract: Tl2Cd2(SO4)3 undergoes phase transitions at –145°, –153° and –181°C successively. The X-ray, dielectric and elastic measurements were made. The [001] component of spontaneous polarization is almost independent of temperature between –145°C and –181°C, and the additional [110] component appears at –153°C and increases gradually with decreasing temperature. Below –181°C, the polarization vanishes. The dielectric constant and the elastic compliance coefficients show abrupt changes at the transition points. Using the extinction rules as well as the result of spontaneous polarization measurement, the space groups are determined as I, T4-P213; II, C22-P21; III, C11-P1 and IV, D42-P212121 as the temperature is decreased. This assignment agrees with the proposal of B\urezina et al.
TL;DR: In this paper, the first measurements of the nonlinear optical properties of fluorides (BaMgF4 and BaZnF4) were made and they showed these air-stable compounds to be noncritically phase matchable at room temperature for a 1.06μ pump.
Abstract: These first measurements of the nonlinear optical properties of fluorides (BaMgF4 and BaZnF4) show these air‐stable compounds to be noncritically phase matchable at room temperature for a 1.06‐μ pump. The highly ionic compounds are also quite resistant to optical damage (∼109 W/cm2). The materials should find applications as frequency doublers in cases where spatial power distribution makes crystals with walk off less desirable and/or cases where high pump powers require crystals which are resistent to damage.
TL;DR: In this article, the effects of pressure and temperature on the dielectric properties and ferroelectric transition in SbSI were investigated, and it was shown that at sufficiently high pressure ω 0 becomes real and the crystal becomes stable against the FE mode at all temperatures.
Abstract: The effects of pressure and temperature on the dielectric properties and ferroelectric (FE) transition in SbSI were investigated. Among the important features of the results are (i) the observation of the vanishing of the FE state at 0 K and high pressure (> ∼ 9.5 kbar), and (ii) the observation of a new, pressure-induced effect in some samples of this material. The FE transition temperature Tc → 0 K with a finite slope dTc/dP, as we have observed for other displacive soft mode ferroelectrics. In these ferroelectrics the strictly harmonic frequency ω0 of the soft FE mode in the paraelectric phase is imaginary at 1 bar, and all of the stabilization of the mode frequency is provided by high-order anharmonicities. At sufficiently high pressure ω0 becomes real and the crystal becomes stable against the FE mode at all temperatures, i.e. the FE state vanishes. It is postulated that the new effect, which is manifested by a peak in the static susceptibility which grows rapidly with pressure, is associated with cr...
Patent•
21 Apr 1975TL;DR: In this article, a ferroelectric liquid crystal display device employs capacitance spoiling layers to minimize unneeded capacitances created by crossovers of "X" and "Y" address lines.
Abstract: A ferroelectric liquid crystal display device employs capacitance spoiling layers to minimize unneeded capacitances created by crossovers of "X" and "Y" address lines and to accurately define desired capacitances. The spoiler layers comprise low dielectric constant layers which space electrodes from the ferroelectric at crossover points where capacitance is not needed for device operation.
TL;DR: In this paper, the authors used a reciprocity coupler to measure g33 and KT33 accurately as a function of one-dimensional stress to high values of stress, and found that the peaks are due to a phase transition from the ferroelectric tetragonal to the Ferroelectric rhombohedral state.
Abstract: Highly accurate data obtained from measurements on three different formulations of lead zirconate titanate piezoelectric ceramic material show the dependence of g33, d33, and KT33 on one‐dimensional stress (applied parallel to the direction of polarization) to high values of stress (0–400 MPa). The constants for one type of ceramic vary with stress less than those of the other two types for high values of stress. A peak in the curve of tanδ as a function of T3 for two types of materials is a function of the material, and it is believed that the peaks are due to a phase transition from the ferroelectric tetragonal to the ferroelectric rhombohedral state. The experimental feasibility and practicability of using a reciprocity coupler to measure g33 and KT33 accurately as a function of one‐dimensional stress to high values of stress has been established.
Patent•
23 Jun 1975
TL;DR: In this paper, a periodic non-uniform electric field is generated by subjecting portions of the ferroelectric material to an alternating potential to alternately polarize the portions, while allowing other portions to remain polarized in the same direction.
Abstract: Polarizable particulate material, such as organic and inorganic colloidal particles such as small pieces of metal, oxides and the like, zwitterionic molecules, and even living organisms and viruses can be preferentially removed from a liquid by dielectrophoresis, by passing the liquid containing the polarizable particulate material to be removed over a ferroelectric apparatus which generates a periodic non-uniform electric field near the boundary between alternately polarized portions of the ferroelectric material. The periodic non-uniform electric field is generated by subjecting portions of the ferroelectric material to an alternating potential to alternately polarize the portions, while allowing other portions of the ferroelectric material to remain polarized in the same direction.
TL;DR: In this paper, the authors considered a non-zero spontaneous polarization in a liquid ferroelectric phase with rod-like non-centrosymmetric molecules with permanent dipole moment and showed that it can not exist in a homogeneous nematic state.
TL;DR: In this article, pressure dependence of the Raman spectra in the ferroelectric phase of KDP has been used to identify the soft mode of phase transition and demonstrate that it is coupled to an optic mode of the lattice in this phase.