Showing papers on "Ferroelectric ceramics published in 1986"
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: Ferroelectric lead zirconate titanate (PZT) ceramics with the polarization vector defined perpendicular to surface were employed, with and without Pt deposition, as photocatalysts for water decomposition under conditions in which either the positive or negative polar surface was irradiated with Xe light as mentioned in this paper.
Abstract: Ferroelectric lead zirconate titanate (PZT) ceramics with the polarization vector defined perpendicular to surface were employed, with and without Pt deposition, as photocatalysts for water decomposition under conditions in which either the positive or negative polar surface was irradiated with Xe light The activity of H/sub 2/ formation was 10-40 times higher for the positive than for the negative polar surface It was shown that PZT is a useful photocatalyst and the activity differences between the oppositely polarized surfaces are associated with the inherent anomalous photovoltaic effects of the ferroelectrics
76 citations
58 citations
01 Jan 1986
TL;DR: Ferroelectric transducers and capacitors are widely used as capacitors, transducers, and thermistors, accounting for about one-half the sales of electroceramic components as mentioned in this paper.
Abstract: Ferroelectric ceramics are widely used as capacitors, transducers, and thermistors, accounting for about one-half the sales of electroceramic components. The historical roots leading to the discovery of ferroelectricity can be traced back to the last century and the work of the famous crystal physicists Weiss, Pasteur, Pockels, Hooke, Groth, Voigt, and the brothers Curie. Beginning with the pioneering work on Rochelle salt and potassium dihydrogen phosphate, the study of ferroelectrics accelerated rapidly during World War II with the discovery of barium titanate. Then came a period of rapid proliferation with more the 100 new ferroelectrics identified in the next decade, including lead zirconate titanate, the most widely used piezoelectric transducer. In the following decade, the concepts of soft modes and order parameters led to the age of high science in the sixties. Neutron experiments authenticated the soft-mode concept and led to the discovery of a number of peculiar improper ferroelectrics such as gadolinium molybdate. In the seventies came the age of diversification in which the electrooptic properties, defect chemistry, and electronic conduction phenomena in ferroelectric ceramics were explored. In the present decade we are witnessing the beginnings of electroceramic integration: Ferroelectric transducers and capacitors are being integrated into multilayer packages along with ceramic substrates, metallic interconnect circuitry, and ceramic resistors. Further integration and miniaturization will take place in the years ahead as electroceramic technology follows the pathways of the semiconductor industry.
51 citations
TL;DR: In this paper, optically transparent ferroelectric ceramics of lanthanum modified lead zirconate titanate (PLZT) have been locally reduced and metallized by means of ultraviolet Kr+ laser irradiation in a hydrogen atmosphere.
Abstract: Hot pressed, optically transparent ferroelectric ceramics of lanthanum modified lead zirconate titanate (PLZT) have been locally reduced and metallized by means of ultraviolet Kr+ laser irradiation in a hydrogen atmosphere. The technique allows maskless single-step metallic patterning of the material.
20 citations
TL;DR: In this article, the properties of transparent ferroelectric ceramics (TFC) were analyzed from the analysis of known materials and it was shown that practically no space charge accumulates on the grain boundaries.
Abstract: Characteristic features of chemical composition, structure and properties of transparent ferroelectric ceramics (TFC) are revealed from the analysis of the known materials. From considerations of the microstructure of TFC, it is shown that practically no space charge accumulates on the grain boundaries. Essential physical and technological factors responsible for light transmittance are analyzed, and criteria that can be used for the search for new TFC compositions proposed. Some TFC properties are explained in terms of highly doped and compensated ferroelectrics. Specific features of TFC in comparison with electrooptic single crystals and opaque ferroelectric ceramics are discussed.
12 citations
TL;DR: In this article, the results of complex X-ray, dielectric, and optical studies of the irradiated ceramics are interpreted in terms of radiation-induced defect interaction with the real structure defects of the initial material taking into account the chemical and phase constitution, as well as the defectness and ordering of structural elements at different levels of the latter.
Abstract: PLZT and PSN transparent ferroelectric ceramics have been subjected to γ-irradiation (energy ≈ 1;15 MeV; power of the dose 1050 r/s; doses up to 3 × 109 rad), electron irradiation (energy ≈ 4.5 MeV; power of the dose ≈ 1012 electr./cm2 · s: doses up to 1018 electr./cm2) and direct irradiation in a thermal reactor channel (neutron energy ≥ 0.1 MeV; flow density from 1.8 × 1011 to 2.4 × 1012 n/cm2 s: the dose up to 1018 n/cm2).Results of complex X-ray, dielectric, and optical studies of the irradiated ceramics are interpreted in terms of radiation-induced defect interaction with the real structure defects of the initial material taking into account the chemical and phase constitution, as well as the defectness and ordering of structural elements at different levels of the latter.
11 citations
TL;DR: In this article, a simple apparatus for measuring the displacement of piezoelectric ceramics at cryogenic temperatures is described, and it has been used to measure the voltage-to-displacement conversion of commercial ferroelectric ceramic materials as a function of temperature from room temperature to liquid helium.
11 citations
08 Jun 1986
9 citations
TL;DR: Asymmetry of electroconductivity in PLZT X/65/35 ferroelectric ceramics has been observed as discussed by the authors, where the density of steady-state current for one direction of field applied along the remanent polarization was 2-5 times larger than the current density in the opposite field direction.
Abstract: Asymmetry of electroconductivity in PLZT X/65/35 ferroelectric ceramics has been observed. The density of steady-state current for one direction of field applied along the remanent polarization was 2-5 times larger than the current density in the opposite field direction. It is shown that a highly doped and compensated ferroelectric has asymmetry of the electroconductivity along the polar axis. The experimental results and theory are compared.
TL;DR: In this article, the problem of the scattering of electromagnetic (light) waves on nonhomogeneities of the dielectric permittivity tensor has been studied and the scattering may be due to multiphase or polycrystalline structures of media, or arise because of the quadratic electrooptic effect.
Abstract: This work deals with the problem of the scattering of electromagnetic (light) waves on nonhomogeneities of the dielectric permittivity tensor. The scattering may be due to multiphase or polycrystalline structures of media, or arise because of the quadratic electrooptic effect. Various field dependencies of the scattering index are considered.
TL;DR: In this paper, a thermodynamic model of phase transitions in ferroelectric ceramics is suggested and the behavior of the basic physical properties of the system with respect to microstructure (grain size, pore density, etc.) and Ferroelectric characteristics (polarization, dielectric constant, Curie Weiss constant) are discussed in the cases of 1st and 2nd order phase transitions.
Abstract: A thermodynamic model of phase transitions (PT) in ferroelectric ceramics is suggested and the behavior of the basic physical properties of the system with respect to microstructure (grain size, pore density, etc.) and ferroelectric characteristics (polarization, dielectric constant, Curie Weiss constant, etc.) are discussed in the cases of both 1st and 2nd order phase transitions. The model is based on geometric and dimensional effects which occur in ferroic systems and assumes ceramics as a single domain matrices consisting of grains and pores.
TL;DR: In this article, a liquid film in a light emitting gas flow was investigated by means of synchronous photoexcitation and photorecording of fluorescence, which was suppressed by a rapid electrooptic shutter made out of transparent ferroelectric ceramics of lanthanum modified lead zirconate-titanate (PLZT).
Abstract: Visual investigation of a liquid film in a light emitting gas flow was carried out by means of synchronous photoexcitation and photorecording of fluorescence. The undesired exposure of the photorecording medium to the gas radiation was suppressed by a rapid electrooptic (EO) shutter made out of transparent ferroelectric ceramics of lanthanum modified lead zirconate-titanate (PLZT).
TL;DR: In this article, anomalous behaviour of the complex dielectric constant at Tt was revealed in thermally depoled samples of PLZT X/65/35 ferroelectric ceramics with X = 9.25 and 10 by means of infra-low-frequency dielectrics spectroscopy in ultra-weak fields.
Abstract: Anomalous behaviour of the complex dielectric constant e* at Tt was revealed in thermally depoled samples of PLZT X/65/35 ferroelectric ceramics with X = 9.25 and 10 by means of infra-low-frequency dielectric spectroscopy in ultra-weak fields (E∼ = 0.1 V/cm). It was observed that the value of the additional maximum e' in the Tt region increased for diminishing measuring field frequencies and tended to drift towards lower temperatures. The frequency-temperature dependence e* of samples affected by biasing electric fields was investigated. The emergence and evolution of polar regions in the ferroelectric ceramics in a quasipolar phase was investigated by measuring the light depolarisation due to the longitudinal effect of light scattering.
08 Jun 1986
TL;DR: In this article, the piezoelectric properties of grain-oriented bismuth layer-structured ferroelectric (BLSF) ceramics, such as Bi4,xPbxTi3,xNbx0~2 (BPTN), and Pbl,x(NaBi)x/2Bi4Ti40i5 (PNBT), were studied from the viewpoint of grain orientation.
Abstract: Piezoelectric properties of grain-oriented bismuth layer-structured ferroelectric (BLSF) ceramics, such as Bi4,xPbxTi3,xNbx0~2 (BPTN) and Pbl,x(NaBi)x/2Bi4Ti40i5 (PNBT) prepared by the hot-forging (H.F.) method, are studied from the viewpoint of grain orientation. The grain orientation (H.F.) makes the piezoelectric properties of BLSF ceramics much more pronounced than those of non-oriented (O.F.) ceramics. The crystal symmetry of the poled H.F. BLSF piezoceramics appears to be pseudo-orthorhombic, namely, piezoceramics have five independent non-zero piezoelectric constants. The coupling factor, k33, abruptly increases as the grain orientation is increased above 80%. H.F. BLSF piezoceramics are elastically hard along the 1and 3-axes and soft along the Z-axis (forging axis). Coupling factors, k33 and k15, along with the piezoelectric constants, d33, d15, 933 and g15, of the H.F. BLSF ceramics are enhanced, and their anisotropies in k33/k31 and k15/k2~ are emphasized.
TL;DR: By application of the digital integral charge measuring method, longlasting pyroelectric, piezoelectric, and polarization relaxation effects have been discovered in ferroelectric ceramics.
Abstract: By application of the digital integral charge measuring method, long-lasting pyroelectric, piezoelectric, and polarization relaxation effects have been discovered in ferroelectric ceramics. Theoretical models of the relaxation were established. The free relaxation and random relaxation laws corresponding to different conditions agreed well with the experimental results.
TL;DR: In this paper, it has been found that the coefficient of light scattering by domains and grains at a wavelength λ = 5 μm is decreased by a factor of about 102 as compared to its value at λ ≥ 0.5 μm.
Abstract: The change of the scattering coefficient in the mid-infrared (IR), as compared to the visible region, is estimated from the theory of electromagnetic wave scattering in inhomogeneous dielectric media. It has been found that the coefficient of light scattering by domains and grains at a wavelength λ = 5 μm is decreased by a factor of about 102 as compared to its value at λ = 0.5 μm. Experimental studies have been performed on electrooptic (EO) properties of ferroelectric ceramics PLZT 10/65/35, the sample thickness being up to 15 mm. Dispersion of the EO effect in the IR region has been studied in PLZT 8/65/35 and PSN ceramics at temperatures beyond Tt—the temperature of disappearance of the macroscopically polarized state.
TL;DR: In this article, the authors discussed the necessity to add an extra amount of lead oxide into the initial mixture of raw materials and the optimum conditions for its removal from the final product during hot pressing.
Abstract: Major problems in the production of transparent ferroelectric ceramics based on lead-scandium niobate Pb(Sc0.5NB0.5)03 with regard to the improvement of both the reproductibility and quality can be solved by increasing the degree of homogeneity and dispersion of the initial mixture of raw materials.The necessity to introduce an extra amount of lead oxide into the initial mixture of raw materials and the optimum conditions for its removal from the final product during hot pressing are discussed.Physical properties of ferroelectric ceramics (FEC) have been analyzed.
TL;DR: In this article, the authors considered the dynamic electromechanical responses of ferroelectric ceramics compatible with the normal mode experiment and formulated the boundary-initial value problem corresponding to this experiment and presented numerical results which exhibit the nature of its responses.
TL;DR: In this paper, a parametric wave equation for displacement in an electroded ferroelectric plate excited by a variable electric current was obtained and a significant property of this equation was considered, namely the parametric instability of acoustic waves under the harmonic external current.
Abstract: Phenomenological description of the acoustic waves in an electroded ferroelectric plate excited by a variable electric current are reported. The ferroelectric is assumed to be cubic and possess electrostriction of the first and second order. A parametric wave equation for displacement, depending on the external current of any form, has been obtained. A significant property of this equation—the parametric instability of acoustic waves under the harmonic external current—is considered and threshold-type acoustic subharmonic excitation is proposed.
TL;DR: Obligatory and auxiliary conditions for successful searching of new transparent ferroelectric ceramic (TFC) types are formulated in this paper, where typical members of three structural groups as potential TFC are present.
Abstract: Obligatory and auxiliary conditions for successful searching of new transparent ferroelectric ceramic (TFC) types are formulated Typical members of three structural groups as potential TFC are present
08 Jun 1986
TL;DR: In this paper, a method for measuring the spatial distribution of combined polarization and space charge in poled polymer electrets was developed, which was modified in order that it could be used with ferroelectric ceramic samples having thicknesses of the order of 1 mm rather than the tens of micrometers found in conventional polymer films.
Abstract: A new method for measuring the spatial distribution of combined polarization and space charge in poled polymer electrets was recently developed. The technique, called the Laser Intensity Modulation Method (LIMM), was modified in the present study in order that it could be used with ferroelectric ceramic samples having thicknesses of the order of 1 mm rather than the tens of micrometers found in conventional polymer films. PZT ceramics with a high Sn content and with compositions close to the PbZrTiOj phase boundary were studied. The effects of poling conditions on polarization and space charge distributions in the two ferroelectric phases were examined. The distributions were unexpectedly nonuniform, possibly due to large amounts of trapped space charge.