Showing papers on "Ferroelectricity published in 1974"
TL;DR: In this article, the phase transition temperature and Curie point decrease monotonically with increasing SrTiO3 concentration, and an intermediate antiferroelectric phase has been observed in the composition range of 0 ⩽ χ⩽ 0.5 of this system.
Abstract: Phase transitions in the solid solution Sr χ(Na 0.5Bi 0.5)l-χTiO3 have been studied by dielectric, pyroelectric and D-E characteristic measurements. An intermediate antiferroelectric phase has been observed in the composition range of 0 ⩽ χ ⩽ 0.5 of this system. These compositions undergo a ferroelectric-antiferroelectric-paraelectric sequence of transitions at elevated temperatures. The antiferroelectric phase transition temperature and Curie point decrease monotonically with increasing SrTiO3 concentration.
399 citations
TL;DR: In this article, the metal-ferroelectric-semiconductor transistor (MFST) was proposed to control the surface conductivity of a bulk semiconductor substrate and perform a memory function.
Abstract: The ferroelectric field effect has successfully been demonstrated on a bulk semiconductor (silicon) using a thin ferroelectric film of bismuth titanate (Bi 4 Ti 3 O 12 ) deposited onto it by RF sputtering. A new memory device, the metal-ferroelectric-semiconductor transistor (MFST); has been fabricated. This device utilizes the remanent polarization of a ferroeletric thin film to control the surface conductivity of a bulk semiconductor substrate and perform a memory function. The capacitance-voltage characteristics of the metal-ferroelectric-semiconductor structure were employed to study the memory behavior. The details of the study together with a preliminary results on the MFST are presented.
395 citations
TL;DR: In this article, the authors studied the piezoelectric properties of ferroelectric ceramics comprising bismuth compounds with layer structure, such as PbBi2Nb2O9 and Na0.5Bi4.5Ti4O15.
Abstract: Piezoelectric properties have been studied on ferroelectric ceramics comprising bismuth compounds with layer structure, PbBi2Nb2O9, PbBi4Ti4O15, SrBi4Ti4O15 and Na0.5Bi4.5Ti4O15. These ceramics have the high mechanical quality factor Q(2000~7200), low aging rate of frequency constant Nt(30~60 ppm/time decade), low temperature coefficients both of Nt(-50 ppm/°C) and of coupling factor kt(70 ppm/°C), low Poisson's ratio σ(0.23~0.27), and large anisotropy in coupling factor. A small value of kt in these ceramics probably relates to two-dimensional restriction on permissible rotation of the spontaneous polarization. The poling characteristics in the ceramics can be improved by some additives. Grain boundaries in these ceramics are of nearly rectangular shape, and an etch pattern of fine stripes appears always in parallel to the length of the boundary.
162 citations
TL;DR: Ferroelectricity was observed in a lanthanum titanate single crystal (La2Ti2O7), a monoclinic crystal of the space group C22-P21 as mentioned in this paper.
Abstract: Ferroelectricity was observed in a lanthanum titanate single crystal (La2Ti2O7), a monoclinic crystal of the space group C22-P21. The Curie temperature was found to be about 1500°C. It was determined by a D-E hysteresis loop at room temperature that the spontaneous polarization Ps = 5 μC/cm2 and that the coercive field Ec = 45 kV/cm. Ferroelectric domains were observed using a crystal etched by an aqueous solution of nitric acid. The La2Ti2O7crystal showed strong piezoelectric and linear electro-optic effects: electromechanical coupling factor k22 = 0.29; half-wave voltage [E l]δ/2 = 2000 V at a wavelength of 6328 A.
162 citations
TL;DR: In this article, the diffuse, paraelectric/ferroelectric, phase transition of Potassium Strontium Niobate is discussed and several possible causes of the diffuse phase transition (DPT) are discussed.
Abstract: The diffuse, paraelectric/ferroelectric, phase transition of Potassium Strontium Niobate is discussed. It is found that the Curie point is strongly dependent on the K and Sr content. Several possible causes of the diffuse phase transition (DPT) are discussed. An empirical relationship describing the behaviour of the inverse dielectric constant in the transition region, is presented. A statistical analysis of the DPT is described in terms of microscopic composition variations within the crystal arising from non-stoichiometry. Plots of the polar dielectric constant and spontaneous polarization against temperature, derived from this model, compare well with the experimentally measured quantities.
133 citations
TL;DR: In this paper, the bias characteristics of the dielectric constant of ferroelectric ceramics of the Pb(Zr,Ti)O3 type have been investigated.
Abstract: Bias (dc electric field) dependence of the dielectric constant of ferroelectric ceramics of the Pb(Zr,Ti)O3 type has been investigated. Measurements were carried out at various temperatures in the ferroelectric phase and at several frequencies between 1 kHz and 1 MHz. The bias characteristics of the dielectric constant show a temperature‐dependent asymmetry in the electric field direction. A model in which the coercive fields of the 180° and 90° domains are distributed around some average value is considered. The total dielectric constant of the material is calculated by considering the contributions of each type of domain, taking into account the difference between the differential and incremental dielectric constants. This model explains the dependence of dielectric constant on electric field. A comparison of the calculated and experimental results is presented.
99 citations
TL;DR: In this article, the spontaneous polarization is 14 μCoulomb/cm2 in the direction of 20°C and the coercive field is 750 V/cm, respectively, at the same temperature.
98 citations
TL;DR: Electrical control of holographic diffraction efficiency in PLZT ceramics and electrical fixation and erasure of holograms recorded in SBN single crystals are reported.
Abstract: After defining photoferroelectrics as photosensitive and nonlinear electrooptic materials, we report electrical control of holographic diffraction efficiency in PLZT ceramics and electrical fixation and erasure of holograms recorded in SBN single crystals On the basis of experimental data, these effects are explained in terms of the local field amplitude, computed as the sum of the applied field and the photoinduced space charge field and high nonlinear electrooptic effects associated with ferroelectric phase transitions
87 citations
72 citations
TL;DR: In this paper, the authors used differential Raman spectroscopy to detect impurity modes in KTaO3 doped with Na and Li ions, and showed that the Na ions do not occupy center of inversion positions.
72 citations
TL;DR: In this article, the photoconductivity of ferroelectric niobates and 5PbO has been studied and anomalous properties of the Curie temperature region have been discussed.
Abstract: Certain peculiarities of photoconductivity in ferroelectrics are discussed. On the example of the ferroelectric SbSI, the nature of anomalies in electrical conductivity and photoconductivity in the Curie temperature region is discussed. For the first time the photoconductivity in certain ferroelectric niobates and the ferroelectric 5PbO. 3GeO2 was studied
TL;DR: In this paper, Brillouin-scattering measurements have been performed on potassium dihydrogen phosphate (KDP) in the temperature range $113lTl291$ \ifmmode^\circ\else\textdegree\fi{}K with electric fields between 0 and 3937 V/cm.
Abstract: Brillouin-scattering measurements have been performed on potassium dihydrogen phosphate (KDP) in the temperature range $113lTl291$ \ifmmode^\circ\else\textdegree\fi{}K with electric fields between 0 and 3937 V/cm. Values of the adiabatic $x\ensuremath{-}y$ shear elastic constant ${c}_{66}^{E,S}$ deduced from the experiment are presented in tabular form. The data are compared with the predictions of several free-energy expressions. The Slater-SUS (Silsbee, Uehling, and Schmidt) theory is shown to predict values of the elastic constant in reasonable agreement with the experimental values, but the SUS parameters which provide the best fit to the elastic-constant data are somewhat different from those which give a best fit to spontaneous-polarization data. The data are also compared to the predictions of three phenomenological free-energy expressions which are all variants of the Landau-Devonshire power-series expansion. The simple molecular-field expression is shown to give poor agreement with the ${c}_{66}^{E,S}$ data, and to require parameter values for even a poor fit which then predict unreasonably large values for the spontaneous polarization. Two other phenomenological free energies are considered, one having a tenth-power nonlinear polarization term and predicting a second-order transition, and another, proposed by Benepe and Reese, having fourth-and eighth-power nonlinear polarization terms and predicting a slightly first-order transition. These two phenomenological free energies have previously been utilized in the analysis of various thermodynamic properties of KDP, and it is found that both are able to predict values for the elastic constant ${c}_{66}^{E,S}$ in reasonable agreement with experiment while providing adequate predictions for the spontaneous polarization with the same parameters. The behavior of ${c}_{66}^{E,S}$ within 0.1 \ifmmode^\circ\else\textdegree\fi{}K of the transition, however, favors the Benepe-Reese free energy.
TL;DR: The profile refinement of neutron powder patterns permits a rapid and precise determination of structural transitions as mentioned in this paper. But the profile refinement is not suitable for high-energy X-ray measurements, since it requires a large amount of energy.
Abstract: The profile refinement of neutron powder patterns permits a rapid and precise determination of structural transitions. For example, the room temperature structure of the rather complex distorted perovskite NaNbO3has been obtained independently in good agreement with the X-ray measurements of Sakowski-Cowley, Lukaszewicz and Megaw. The speed and ease of neutron powder data collection means that structures can be compared for many different conditions of temperature, pressure and chemical composition.
TL;DR: In this article, the vanishing of ferroelectricity at 0°K and high pressure has been investigated in displacive (K1-χNaχTaO3 and SbSI) and hydrogen-bonded (KDP-type) ferroelectrics.
Abstract: The vanishing of the ferroelectricity at 0°K and high pressure has been investigated in displacive (K1-χNaχTaO3 and SbSI) and hydrogen-bonded (KDP-type) ferroelectrics. The manner in which T c → 0°K is markedly different in the two classes emphasizing the basic differences in the mechanisms for their transitions. Comparisons between the results on deuterated and non-deuterated KDP-type crystals reveal differences pertaining to the importance of tunneling.
TL;DR: In this article, the effect of the grain size on unit-cell dimensions and dielectric properties has been studied in ceramic lanthana-substituted lead titanate of the general composition Pb1-αxLaxTiO3+x (15-α) with α = 120 and x = 007 (PLT7) and X = 018 (PLTs18) The grain size ranges from 06 to 11 µm and the effects are most pronounced on the smaller sizes.
Abstract: The effect of the grain size on unit-cell dimensions and dielectric properties has been studied in ceramic lanthana-substituted lead titanate of the general composition Pb1-αxLaxTiO3+x (15-α) with α = 120 and x = 007 (PLT7) and x = 018 (PLT18) The grain size ranges from 06 to 11 µm and the effects are most pronounced on the smaller sizes The tetragonal distortion, characterized by the ratio c/a of the unit-cell dimensions c and a, decreases by decreasing grain size This effect becomes relatively smaller by decreasing temperature A decrease of the grain size leads to a decrease of the maximum value of the dielectric constant e' at the Curie temperature T'c and to an increase of e' at lower temperatures The Curie temperature shifts to a lower temperature while the phase transition is less sharp with decreasing grain size The results can be discussed in terms of an average value of internal compression stresses in the direction of the c-axis of the crystal
TL;DR: In this paper, a method for determining the Curie constant (Cc) of ferroelectric crystals below Tc from the pyroelectric response is described, where the material parameter is given by p/ϵ =PS/Cc, where Ps is the spontaneous polarization.
Abstract: A method is described for determining the Curie constant (Cc) of ferroelectric crystals below the Curie temperature (Tc) from the pyioelectric response. It is shown from Devonshire's phenomenological theory of ferroelectricity that the material parameter (p/ϵ) of the pyroelectric response is given by p/ϵ =PS/Cc , where Ps is the spontaneous polarization. This relationship is tested in detail for Sr0.5Ba0.5Nb2O6 crystals. The value of Cc obtained from the Curie-Weiss law, ϵ = CC /(T - Tc ), which is valid above Tc , is compared to the value of Cc obtained below Tc for SBN and other ferroelectric crystals and reasonable agreement is observed.
TL;DR: In this paper, an anomalous decrease in the proton spin-lattice relaxation timeT1 on approaching the Curie point in a rather pure KH2PO4 single crystal is explained by magnetic dipolar coupling to the ferroelectric mode.
Abstract: The observed anomalous decrease in the proton spin-lattice relaxation timeT1 on approaching the Curie point in a rather pure KH2PO4 single crystal is explained by magnetic dipolar coupling to the ferroelectric mode. The isolated “non-interacting” O−H...O proton flipping time is estimated from theT1 data as τ=0.66·10−12 sec for the paraelectric phase and τ=2.24·10−12 sec for the ferroelectric phase, in good agreement with the results obtained from other methods.
TL;DR: In this paper, it is shown that at morphotropic phase boundaries of ferroelectric solid solutions, a maximum in the electromechanical activity is found at the phase boundaries, and that fluctuations of the Zr-concentration are jointly responsible for the coexistence region at these phase boundaries.
Abstract: At morphotropic phase boundaries of ferroelectric solid solutions a maximum in the electromechanical activity is found. This is essential for technical application of Pb(ZrxTi1_x)O3. It is demonstrated that at those phase boundaries the mixture of phases can be analysed by dielectric measurements. Thus an exact phase diagram near the morphotropic phase boundary can be obtained. The measurements also indicate that fluctuations of the Zr-concentration are jointly responsible for the coexistence-region at these phase boundaries.
TL;DR: In this paper, a working hypothesis for explanation of peculiar behaviors in Ca 2 Sr(C 2 H 5 CO 2 ) 6 (DSP) observed with respect to its ferroelectric phase transition is proposed.
Abstract: A working hypothesis is proposed for explanation of peculiar behaviors in Ca 2 Sr(C 2 H 5 CO 2 ) 6 (DSP) observed with respect to its ferroelectric phase transition On the basis of consideration of crystal structure it is pointed out that the Mitsui theory for Rochelle salt is applicable to DSP, and strain in the ferroelectric phase is dicussed
Abstract: The lattice parameters have been determined as a function of temperature for single crystals of the ferroelectric PbZr0.9Ti0.1O3. By associating the difference in rhombohedral angle with the square of the order parameter, Ps, the critical index beta has been determined for the ferroelectric to paraelectric phase transition. This transition appears to be of second order with beta approximately=0.33 for (T0-T)/T0
TL;DR: In this paper, a method for observing insulating samples in the scanning electron microscope without excessive specimen charging is presented, in which antiparallel domains can be directly observed without modification of the sample.
Abstract: A method is reviewed for observing insulating samples in the scanning electron microscope without excessive specimen charging. In this way antiparallel domains may be directly observed without modification of the sample. The scanning electron microscope operating in the back-scattered electron mode reveals topography, and operation in the secondary electron mode at low voltage reveals surface potential variation. We have observed antiparallel domains on T.G.S., these domains disappear above the Curie point. The same method applied to BaTiO3 crystals reveals a ferroelectric surface layer, which has a domain structure different from the bulk and persists above the Curie point. KD2P and conducting WO3 crystals have also been studied.
TL;DR: In this article, the ferroelectric and antiphase domain structures of Gd2(MoO4)3 have been studied by means of electron microscopy and the lattice distortions around them were analyzed by the use of the moire technique.
Abstract: The ferroelectric and antiphase domain structures of Gd2(MoO4)3 have been studied by means of electron microscopy. Anomalous right-angled ferroelectric domain walls in (001) films were observed and the lattice distortions around them were analysed by the use of the moire technique. The existence of antiphase boundaries due to the space group of the ferroelectric phase was proved in the dark-field images produced by the superlattice reflections.
TL;DR: In this paper, a method for growing a single crystal of Li 2 Gd 4 (MoO 4 ) was proposed and a few physical properties of the material were reported, such as magnetic susceptibility at room temperature is 59.55 × 10 -6 cm 3 /g and characteristic ferroelectric domains are observed along the c-axis.
Abstract: Methods for growing single crystal of Li 2 Gd 4 (MoO 4 ) 7 and a few of its physical properties have been reported here. This material is a new addition to the group of ferroelectric and paramagnetic materials. The value of its magnetic susceptibility at room temperature is 59.55 ×10 -6 cm 3 /g and the characteristic ferroelectric domains are observed along the c -axis.
TL;DR: In this paper, the authors measured the 90° ferroelectric domain boundaries of pure BaTiO3 and (Ba,Pb)TiOO3 solid solutions using a densitometer-trace-curvefitting technique.
Abstract: 90° ferroelectric domain boundaries were observed by direct transmission electron microscopy in single crystals of pure BaTiO3 and (Ba,Pb)TiO3 solid solutions. Domain‐wall thickness measurements were made from electron image plates by a densitometer‐trace‐curve‐fitting technique. Boundary widths varied from 50 to 150 A. These results are compared with theoretical estimates of 90° domain‐wall thicknesses and correlated with the relative purity levels of the crystals. The temperature variation of the 90° wall thickness is reported for the (Ba,Pb)TiO3 solid solutions.
TL;DR: In this article, the authors considered the problem of condensation of a given set of degenerate soft modes with respect to hard modes of zero-wavenumber and showed that soft modes are not restricted to ferroelectric or ferroelastic ones.
Abstract: The problem “By a condensation of a given set of degenerate soft modes what hard modes are induced to condense and what hard modes are not?” (here either soft or hard modes are not restricted to ferroelectric or ferroelastic ones) is treated theoretically in a general and unified way with an extension of the concept of faintness index for ferroelectricity and ferroelasticity. Also, this general theory is applied to more concrete cases where the prototypic phase belongs to a specified point group and the soft modes are of zero wavenumber and belong to a specified irreducible representation; for all these cases an evaluation is made of the faintness indices of each possible ferroic phase with respect to all hard modes of zero wavenumber.
TL;DR: In this paper, a thermodynamic approach of ferroelectric transition in which the polarization P goes to zero asymptotically when the temperature T increases is presented, where the second derivatives of the free energy: dP dT, the susceptibility, and the specific heat exhibit maxima, but at different temperatures.
TL;DR: In this paper, the doublet splitting in triglycine sulphate has been investigated in the presence of electric dipoles, which interact with the microscopic internal field at the trapping sites.
Abstract: Epr spectra of VO +-doped triglycine sulphate crystals have indicated that the proton configuration in defective hydrogen bonds surrounding the impurity ions yields more than two differently oriented crystalline fields. On annealing the crystals at 80°C or above, these protons are rearranged in a stable configuration, resulting in simpler spectra. The stable VO2+ complexes have C2 symmetry, and the ligand hyperfine splittings due to a proton pair are partially resolved in their spectra. The observed anisotropics are slightly temperature dependent, implying that V02+ions execute a random motion with a small amplitude in the crystalline potential.VO2+ ions possess electric dipoles, which interact with the microscopic internal field at the trapping sites. In the ferroelectric phase, VO2+ spectra from well-annealed crystals exhibit a doublet splitting on each of the sl V hyperfine components. The equilibrium intensity-ratio of the doublet has been found to follow exp (ePs(T)lkT), where Ps(T) is the macroscopi...