Showing papers in "Ferroelectrics in 1986"
TL;DR: In this paper, the authors show that the electrical field at the grain boundaries of undoped SrTiO3 and BaTiO 3 (at T > Tc) shows a pronounced Maxwell-Wagner relaxation at ultra low frequencies.
Abstract: Ceramics of undoped SrTiO3 and BaTiO3 (at T > Tc) show a pronounced Maxwell-Wagner relaxation at ultra low frequencies. This indicates thin nonconducting barrier layers at the grain boundaries and some residual conductivity in the grain. Degradation of the ceramic starts when the electrical field, which develops at the grain boundaries, exceeds breakdown strength.
114 citations
TL;DR: In this article, the porosity of porosity in the order of 0.4 to 0.5 was investigated with a view to their application for ultrasound transducers, and it was found that the dielectric and elastic constants of porous porosity can be satisfactorily described on the basis of Bruggeman's theory.
Abstract: Porous ceramics with type 3–3 connectivity were prepared and investigated with a view to their application for ultrasound transducers. Ceramics with a porosity in the order of 0.4 to 0.5 exhibit sufficiently high permittivity (≈ 500), a thickness coupling factor equalling that of dense material (≈ 0.5), a low transverse coupling factor, a low vibrational Q (≈ 20) and low acoustic impedance (≈ 9·106kg/m2·s), all of which indicates their eminent suitability as a material for the fabrication of transducers as used in medical diagnostics. The experimentally determined influence of the porosity on the dielectric constants of these materials was used for the critical testing of various theories for calculating the constants of multiphase materials. It was found that the dielectric and elastic constants of porous piezoelectric ceramics can be very satisfactorily described on the basis of Bruggeman's theory, which has fallen somewhat into obscurity. Their piezoelectric properties are discussed with refer...
86 citations
TL;DR: In this article, a brief review of the experimental results of the hydrostatic pressure effect on the lock-in transitions in various tetramethylammonium tetrahalogenometallic compounds, {N(CH3)4}2XY4 (X: Mn, Fe, Co, Ni, Cu, Zn; Y: Cl, Br).
Abstract: A brief review is given for the experimental results of hydrostatic pressure effect on the lock-in transitions in various tetramethylammonium tetrahalogenometallic compounds, {N(CH3)4}2XY4 (X: Mn, Fe, Co, Ni, Cu, Zn; Y: Cl, Br). The pressure-temperature phase diagrams of the chloride compounds with X = Mn, Fe, Co, Zn can be arranged in a unified reduced p-T phase diagram. Detailed observations are described as to the stabilization of the ferroelectric phase in the p-T space for the -MnCl4, -FeCl4, and -ZnCl4 compounds. The phase transition in the -ZnBr4. -MnBr4, and -CoBr4 compounds corresponds to the high pressure state in the chloride compounds. The deuteration effect on the phase transitions at high pressure is discussed.
85 citations
TL;DR: In this article, the authors show that the aging of Fe-doped PZT and Cr-Doped BT ceramics can be understood as a reduction of vibrating 90°-domain wall areas.
Abstract: The time dependence of the complex dielectric constant e of ferroelectric ceramics is well known as aging which is ascribed by most authors to a modification of the 90°-domain walls. Measurement of aging of Fe-doped PZT ceramic (rhombohedral) and Cr-doped BT ceramic (tetragonal), show that aging in these ceramics can be understood as a reduction of vibrating 90°-domain wall areas. This reduction of the domain wall contribution to the dielectric constant can be due either by pinning of parts of 90°-domain walls having high activation energies and/or by an increase in domain sue in time which reduces the total domain wall area. The increase of the domain sue during aging is ascribed to a thermally activated relief of internal stresses just by rearrangement of the domain configuration. The stress relaxes in a logarithmic time law which results from uniformly distributed activation energies between an upper and a lower limit. The measurements allow to distinguish clearly the bulk contribution and the...
83 citations
TL;DR: In this article, a new type of piezoelectric PZT-polymer 1-3-0 composite was fabricated with a single large void present in the center of the composite.
Abstract: A new type of piezoelectric PZT-polymer 1-3-0 composite was fabricated with a single large void present in the center of the composite. Experimentally and theoretically the addition of this type of void to a 1–3 composite significantly enhances the hydrostatic piezoelectric [dbar] h and [gbar] h coefficients. A comparison of the experimental results and theoretical predictions was made. The pressure and frequency dependences of the properties of the 1-3 and 1-3-0 composites were measured, along with the effect of hydrostatic pressure cycling. The 1-3-0 composites partially depoled from pressure cycling to 600 psi (4.1 MPa), indicating that the limit of hydrostatic sensitivity, physically possible for the soft PZT used, was exceeded.
83 citations
TL;DR: For top seeded solution grown Barium Titanate single crystals in the tetragonal phase, the complete tensors of the elastic compliances, of the low frequency piezoelectric constants and of the coupling coefficients were determined in this paper.
Abstract: For top seeded solution grown Barium Titanate single crystals in the tetragonal phase, the complete tensors of the elastic compliances, of the low frequency piezoelectric constants and of the coupling coefficients were determined. The method used was that of the piezoelectric resonator.
67 citations
TL;DR: In this paper, measurements of the shear piezoelectric coefficients d15 and d24 for uniaxially oriented polyvinylidene fluoride (PVDF) are presented for non-voided sheet of low and high Young's modulus and for a low modulus voided sheet.
Abstract: Measurements of the shear piezoelectric coefficients d15 and d24 are reported for uniaxially oriented polyvinylidene fluoride (PVDF). Results are presented for non-voided sheet of low and high Young's modulus and for a low modulus voided sheet. In all cases samples of high Form I content were prepared, and subjected to comparable poling voltages. It is of interest to note that the values obtained for the shear coefficients are comparatively high (in the range -13 to -38 pCN-1) and in the case of d24 much greater than the calculated value for the Form I PVDF crystal.
67 citations
TL;DR: In this paper, the piezoelectric d and g coefficients of polymer-ceramic composites in hydrostatic mode were characterized as a function of pressure, temperature, and frequency.
Abstract: Polymer-ceramic composites with different connectivity designs have been developed. The piezoelectric d and g coefficients of these composites in hydrostatic mode were characterized as a function of pressure, temperature, and frequency. All composite samples exhibited piezoelectric properties greatly improved over those of conventional piezoelectric ceramics. However, the introduction of soft polymer matrix caused the composite properties to be highly pressure-dependent. The effect of reinforced polymer matrix on the temperature and pressure dependences of the piezoelectric coefficients was also investigated. Prototype hydrophones containing the composite samples were designed and evaluated for their free-field voltage sensitivity. The potential use of polymer-ceramic composites for underwater acoustic applications is discussed.
63 citations
TL;DR: In this article, a variety of recent experimental and theoretical results on thiourea, a compound known for the richness of its phase diagram, are reviewed, and a continuum approach is particularly well suited to understand the modulated phases and the commensurate lock-ins in this compound.
Abstract: In this paper, we review a variety of recent experimental and theoretical results on thiourea, a compound known for the richness of its phase diagram. We show that a continuum approach “a la Landau” is particularly well suited to understand the modulated phases and the commensurate lock-ins in this compound. The locked phase of commensurability order 8 is qualitatively and semi-quantitatively well accounted for. The birefringence anomalies which detect this phase are shown to be related to the gradient amplitude coupling term in the free energy. Our analysis allows an order of magnitude estimate for the thermal extension of high commensurability order lock-ins. We conclude that wide steps of commensurability order 29, or 43 cannot be of intrinsic origin, and that their observation by X-ray spectroscopy is due to irradiation defects. We describe, discuss and analyse theoretically the memory effect of nodulated phases, which we ascribe to the condensation of a Defect Density Wave, due to the diffus...
61 citations
TL;DR: In this paper, the structural investigation of cesium zinc monophosphate CsZnPO4 has been carried out at three different temperatures: room temperature, this salt is monoclinic, Pn21/a with a = 18.33(8), b = 5.45(4), c = 9.493(5), c= 9.406(5) A = Z = 4 (form I).
Abstract: Structural investigation of cesium zinc monophosphate CsZnPO4 has been carried out at three different temperatures. At room temperature, this salt is monoclinic, P21/a with a = 18.33(8), b = 5.45(4), c = 9.25(6) A, β. = 90.14(8)° and Z = 8 (form III):at 260°C, it becomes orthorhombic, Pn21a with a = 9.246(9), b = 5.468(6), c = 9.359(7) A and Z = 4 (form II),at 310°C, it is orthorhombic Pnma with a = 9.191(5), b = 5.493(5), c = 9.406(5) A = Z = 4 (form I). Crystal structures of these three forms have been solved and refined with final R values: R = .043 (at room temperature) for 2914 independent reflections, R = .041 (at T = 280°C) for 735 independent reflections, R = .042 (at T = 340°C) for 644 independent reflections.
57 citations
TL;DR: In this article, the frequency dependence of the complex dielectric constant (DC) of Pb(TixZr1-x)O3 ceramics (x=0.4; 0.48, 0.6) was measured between 10 Hz and 1010 Hz.
Abstract: The frequency dependence of the complex dielectric constant (DC) of Pb(TixZr1-x)O3 ceramics (x=0.4; 0.48; 0.6) was measured between 10 Hz and 1010 Hz. Only one dispersion region was found with the relaxation frequency being independent of x. The spectral shape function for PZT 0.4, which is independent of the temperature between - 123°C and +239°C, corresponds to the many-body universal response described by Jonscher, Dissado and Hill. Our results scarcely corroborate the common idea of domain-wall and phase boundary contributions to the DC.
TL;DR: In this article, a R-a-R3+b pair doping was adopted to balance out the charge fluctuations caused by doping, and the diffuse phase transition was enhanced and the sintering temperature was lowered.
Abstract: By doping Li2CO3, Na2CO3, B2O3 and Bi2O3 into PLZT 8/65/35, the diffuse phase transition is enhanced and the sintering temperature is lowered. In order to balance out the charge fluctuations caused by doping, a R-a-R3+b pair doping is adopted. Low temperature coefficient of capacitance (TCC) of the doped PLZT 8/65/35 can be obtained by Na+-B3+ or Li+-Bi3+ pair dopings. The sintering temperature is lowered down to 1050°C or below. The enhancement in diffuse phase transition is explained by the possible interstitial site occupancy of Li+ and Bi3+. Annealing in air at 970°C can effectively drive out the doped ions, and cause the recovery of the lattice structure.
TL;DR: In this paper, it was shown that the angular dependence of the static susceptibility for the order parameter fluctuation is very sensitive to the value and the anisotropy of the background dielectric susceptibility.
Abstract: It is shown, that in uniaxial ferroelectrics the angular dependence of the static susceptibility for the order parameter fluctuation is very sensitive to the value and the anisotropy of the background dielectric susceptibility.
TL;DR: In this paper, the poling process in composite systems of ferroelectric PZT ceramics with a vinylidene fluoride/trifluoroethylene copolymer has been investigated by the time-domain measurements of the switching transients.
Abstract: The poling process in composite systems of ferroelectric PZT ceramics with a vinylidene fluoride/trifluoroethylene copolymer has been investigated by the time-domain measurements of the switching transients. The bilayer composite undergoes complete polarization reversal, although the switching time is much larger than in pure PZT. The dispersion of PZT particles in the copolymer matrix shows obscured switching transients, but polarization reversal is confirmed by reversal of piezoelectric activity. Since the dielectric constant of the copolymer is much lower than that of PZT, the applied field is greatly reduced in the PZT phase to disable instantaneous polarization reversal. However, the internal field is gradually increased with time to reach the coercive field by accumulation of real charges at the phase boundary due to the dc conductivity in the polymer phase. The conductivity also limits the switching rate to result in a long switching time. The calculated switching curve shows good agreemen...
TL;DR: In this paper, the amplitude of the vibration as a function of the frequency, applied voltage and temperature is analyzed in planar S*c liquid crystals. And the existence and frequency dependence of the linear electromechanical effect is explained within the framework of a continuum theory.
Abstract: Detailed analysis is given of the electromechanical effect in planar S*c liquid crystals Experimental data are presented for the amplitude of the vibration as a function of the frequency, applied voltage and temperature The existence and the frequency dependence of the linear electromechanical effect is explained within the framework of a continuum theory
TL;DR: Domain textures of typical incommensurate phases are constructed as regular domain structures formed by equivalent domain walls of minimum negative energy as mentioned in this paper, and symmetry properties of perfect domain textures are discussed.
Abstract: Domain textures of typical incommensurate phases are constructed as regular domain structures formed by equivalent domain walls of minimum negative energy. Structures with two or three modulation waves can form several stripe textures and textures periodic in two or three directions. Equivalent textures can coexist as textural blocks. Symmetry properties of perfect domain textures are discussed.
TL;DR: In this paper, it was shown that a surprising variety of microstructural phenomena in ferroelectric materials are accessible by high-resolution electron microscopic techniques, such as domain wall widths and surface roughness in LiTaO3, KNbO3 and barium sodium niobate (BNN).
Abstract: It is shown that a surprising variety of microstructural phenomena in ferroelectric materials are accessible by high-resolution electron microscopic techniques. Recent observations are reviewed concerning (i) domain wall widths and surface roughness in LiTaO3, KNbO3 and barium sodium niobate (BNN); (ii) microdomain textures and fluctuations at the cubic/tetragonal phase transition of BaTiO3; (iii) the commensurate superlattice structure of BNN and (iv) the hierarchy of chaotic states coexisting within the incommensurate superstructure phase of strontium barium niobate (SBN) at room temperature.
TL;DR: In this article, the authors found that dielectric and electromechanical properties depend not only on the PZT volume fraction, but also on the pillar shape w/t (width-to-thickness ratio).
Abstract: PZT/polymer composite sheets (PZT pillars embedded in polymer matrix) for high frequency use are fabricated using a dicing and filling technique. These piezo-composite sheets are intended for use as medical ultrasonic probes. It is found that dielectric and electromechanical properties depend not only on the PZT volume fraction v PZT but also on the PZT pillar shape w/t (width-to-thickness ratio). Thickness dilatational electromechanical coupling factor k t is as high as 0.75 when v PZT = 0.25 and w/t = 0.5 ∼ 0.6. The period of the embedded PZT pillar lattice, d, is also important in determining the electromechanical properties. When d is close to the wavelength of laterally propagating transverse waves, lateral mode resonances are observed.
TL;DR: In this article, it was shown that all anomalies of the properties discussed, can be attributed to a local polarization in the low temperature region of the PLZT with diffuse phase transition.
Abstract: In the thermally depoled state, PLZT with diffuse phase transition has no macroscopic polarization in the low temperature region. It is shown, that all anomalies of the properties discussed, can be ascribed to a local polarization.
TL;DR: Inelastic neutron spectra of B quartz were recorded at various temperatures, using triple axis neutron spectrometry as discussed by the authors, and they confirmed the existence of a very low-lying phonon branch along the 1,0,0⟩ directions, which exhibits a marked temperature dependence, in particular near the Brillouin zone center.
Abstract: Inelastic neutron spectra of B quartz were recorded at various temperatures, using triple axis neutron spectrometry. Our observations confirm the existence of a very low-lying phonon branch along the ⟨1,0,0⟩ directions, which exhibits a marked temperature dependence, in particular near the Brillouin zone center. This branch is very anisotropic in the (0,0,1) plane. Within the B phase a maximum of quasi elastic scattering is observed for q ≃ 0.03a*, premonitory to the appearance of satellite reflexions in the modulated phase. In addition, a transverse acoustic mode exhibits an anisotropic behaviour which is attributed to a coupling with the soft-mode. The results are consistent with a phenomenological model of the incommensurate phase transition and with a lattice dynamical model involving rigid SiO4 tetrahedra motions.
TL;DR: In this article, the spontaneous asymmetry of the occupation of the H-bond double well potential is homogeneous in the ab-plan, whereas it is modulated along the c-direction.
Abstract: The pulse NMR methods, the measurements of the conductivity and dielectric permittivity were used to study the sequence of the phase transitions in NH4HSeO4. In the temperature region between ferroelectric and paraelectric phases (Tcl ÷ Ti) the spontaneous asymmetry of the occupation of the H-bond double well potential is homogeneous in the ab-plan, whereas it is modulated along the c-direction. The deuteration drastically increases the incommensurate region. The long-time processes leading to the decay of the long-range order in the structure above Tcl are discussed both in the terms of the topological phase transition and at the assumption of first-order polymorphic transformation.
TL;DR: In this article, the specific heat of various pure, crystalline ferroelectrics was measured between 0.5 K and 40 K. In contrast to earlier results the calculated Debye temperatures, θ 0D, are in excellent agreement with values deduced from elastic constants.
Abstract: The specific heat of various pure, crystalline ferroelectrics—LiNbO3, LiTaO3, NaNO2, BaTiO3, TGS—has been measured between 0.5 K and 40 K. For all samples we observe a pure Debye's T3-dependence of the heat capacity as expected for the low temperature limit (T < θ0D/50). No excess heat capacity could be detected. In contrast to earlier results the calculated Debye temperatures, θ0D, are in excellent agreement with values deduced from elastic constants. Possible origins of previously reported excess heat capacities in numerous ferroelectrics are discussed; it is strongly suggested that these excess heats result from the presence of statistically distributed dipolar defects.
TL;DR: In this paper, the Pb(Ni1/3,Nb2/3)O3-Pb(Mgl/2Wl/2,)O3PbTiO3 ternary system was studied for use as a multilayer capacitor material.
Abstract: The Pb(Ni1/3,Nb2/3)O3-Pb(Mgl/2Wl/2,)O3-PbTiO3 ternary system was studied for use as a multilayer capacitor material. Compositions with a high dielectric constant (e > 10000) and high specific resistivity can be fired at temperatures below 1050° C in this system. Chip capacitors made of one of these materials, with 85%Ag-15%Pd inner electrodes, are fired at 960°C and show good electrical properties and reliability.
TL;DR: In this article, the self-focusing and self-deflection of argon ion laser light for PLZT 11/65/35 ceramic samples were measured in terms of a nonlinear refractive index and a thermal lens model.
Abstract: We report measurements of the self-focusing and self-deflection of argon ion laser light for PLZT 11/65/35 ceramic samples. The results are interpreted in terms of a nonlinear refractive index and a thermal lens model. The far-field patterns of a thermal lens and self-deflected light beams are presented.
TL;DR: In this paper, the authors investigated the mechanical properties of multilayer ceramic actuators with ceramic internal electrodes and found that the strain induced by an electric field in the multilayers was measured using a differential transformer method.
Abstract: Electrostriction and mechanical properties of multilayer ceramic actuators with ceramic internal electrodes were investigated. Insulative BaTiO3 and La-doped semiconductive BaTiO3 were laminated by means of a conventional green sheet method and co-fired into the multilayer structure. The strain induced by an electric field in the multilayer was measured using a differential transformer method. The 4 × 10−4 magnitude of strain at 15 kV/cm is sufficiently applicable to fine movement control devices. Mechanical strength obtained was 50 MN/m2, about three times larger than that for a conventional multilayer ceramic actuator with Pd internal electrodes.
TL;DR: In this paper, a semimicroscopic model for incommensurate crystal phases is applied to three-dimensional systems occurring in nature and the structure and symmetry of the various phases are discussed and compared with experimental results.
Abstract: A semimicroscopic model for incommensurate crystal phases studied earlier is applied to three-dimensional systems occurring in nature. The structure and symmetry of the various phases are discussed and compared with experimental results. The model gives a unifying picture of a large family of compounds with β-K2-SO4 structure. The superspace group symmetry is shown to give a unification of the symmetry of the various incommensurate and commensurate phases.
TL;DR: In this article, the authors investigated the structural phase transitions of LiKSO4 at low temperature and found that the phase transitions are characterised by prolonged equilibration times (days) which strongly depend on the thermal history of the sample.
Abstract: The kinetics and the symmetry changes associated with the low-temperature structural phase transitions in LiKSO4 have been investigated by single crystal neutron diffraction. The study indicated three clear phase transitions at 205 K (from sp. gr. P63 to sp. gr. P31c), at 189 K (to sp. gr. Cc) and 135 K in the cooling cycle; a phase change is also indicated at 165 K. All these transitions show thermal hysteresis. The full crystal does not undergo transformation at any of the transition temperatures but exhibits mixed phases. The kinetics of the phase transitions are characterised by prolonged equilibration times (days) which strongly depend on the thermal history of the sample. With the results of the structural investigations in the temperature range 300 K to 100 K, an attempt has been made to explain the anomalies and variant results observed in the physical properties of LiKSO4 at low temperatures.
TL;DR: In this paper, the sequence of phases formed during the solid state reaction in oxide mixtures has been studied by X-ray diffraction and differential thermal analysis (DTA) in the binary oxide system PbO-Nb2, O5 and the ternary oxide system pbO -nb2O5-Sc2O3.
Abstract: The sequence of phases formed during the solid state reaction in oxide mixtures has been studied by X-ray diffraction and differential thermal analysis (DTA) in the binary oxide system PbO-Nb2, O5 and the ternary oxide system PbO-Nb2O5-Sc2O3. The following compositions have been investigated: 3PbO : 2Nb2O5, 2PbO : Nb2O5, 5PbO : 2Nb2O5, 3PbO : Nb2O5, 4PbO : Nb2O5, and 3PbO : 2Nb2O5 : X, 2PbO : Nb2O5 : X, 5PbO : 2Nb2O5 : X, 3PbO : Nb2O5 : X, 4PbO: Nb2O5 : X, the molar ratio X of Sc2O3 being taken 0; 0.025; 0.05; 0.1; 0.3; 0.5; 0.8; 1.0; 1.2.It is found that the formation of both the binary and ternary compounds includes complicated multistage processes with several intermediate products during the reaction. In all cases, except 3PbO : 2Nb2O5, one or more additional phases less rich in lead oxide coexist with the stoichiometric phase. Obviously, this is due to evaporation of lead oxide above 800°C. Therefore PbSc1/2Nb1/2O3, produced from the stoichiometric proportion of oxides 4PbO : Nb2O5 : Sc2O3 by a solid...
TL;DR: In this paper, the authors underline two main characteristic properties of the incommensurate phases in biphenyl, namely, the existence of a partial lock-in transition between a phase II with a two-dimensional modulation wave and a phase III with only a one-dimensional one.
Abstract: We underline two main characteristic properties of the incommensurate phases in biphenyl. On the one hand, the sequence of incommensurate phases is unusual, with the existence of a partial lock-in transition between a phase II with a two-dimensional modulation wave and a phase III with only a one-dimensional one. On the other hand, the specific dynamic properties of these incommensurate phases can easily be studied due to the low values of phonon damping at low temperature. The remaining incommensurability at absolute zero for the atmospheric pressure has allowed the observation of propagating phasons in phase III. Moreover, both transition temperatures tend towards the absolute zero for moderate pressure and this effect is profitable to study phasons and amplitudons in phase II under better conditions.
TL;DR: Transition metal oxide fillers such as VO2, V2O3 and TiTiO3 were incorporated in polymeric matrices to give composite materials with low room temperature resistivities and sizable thermistor effects as mentioned in this paper.
Abstract: Transition metal oxide fillers such as VO2, V2O3 and Ti2O3 were incorporated in polymeric matrices to give composite materials with low room temperature resistivities and sizable thermistor effects. Percolation limits were determined by mixing ceramic powders in different proportions with both rigid and flexible epoxy resins. These composites exhibited unusually large PTC effects with resistance increases as high as nine orders of magnitude.