Showing papers in "Ferroelectrics in 1990"
TL;DR: The domain twinning in ferroelectric ceramics is dependent on grain size as mentioned in this paper, and the different domain configurations and internal stresses lead to different dielectric properties and to different hysteresis curves.
Abstract: The domain twinning in ferroelectric ceramics is dependent on grain size. In fine grained ceramic a simple lamellar structure allows two- dimensional stress relief, in coarse grained ceramic a banded lamellar structure takes away homogeneous stress in three dimensions. The different domain configurations and internal stresses lead to different dielectric properties and to different hysteresis curves. Inhomogeneous grains of BaTiO3 with some CdBi2Nb2O9 have a core with a normal domain pattern and a shell without domains at room temperature. Core and shell have different transition temperatures. The macroscopic dielectric constant therefore has very high values in a very broad temperature range. Ceramics which are properly prepared in order to have oriented grains exhibit properties which come near to the properties of single crystals.
275 citations
TL;DR: In this paper, the design, fabrication, and operation of a single PZT element combined with the GaAs JFET planar integrated circuit technology to produce nonvolatile programmable random access memories (NVPRAM) are presented.
Abstract: Properties of integrated sol-gel PZT thin-films of various Zr/Ti ratios, evaluated as a function of processing parameters, are presented and discussed. The substrate materials for the PZT depositions encompassed Pt, Si, and GaAs. The design, fabrication, and operation of a single PZT element combined with the GaAs JFET planar integrated circuit technology to produce non-volatile programmable random access memories (NVPRAM) are presented.
201 citations
TL;DR: In this paper, a rhombohedral (Fα)-tetragonal (Fβ) morphotropic phase boundary (MPB) is shown to exist at x = 0.13 by X-ray diffraction data.
Abstract: Piezoelectric properties of bismuth sodium titanate, (Bi1/2Na1/2)TiO3 (BNT)-based solid solution, (Bi1/2Na1/2)(1−x)(St a Pb b Ca c ) x TiO3(a+b+c=1)(BNTX [100x−100a/100b/100c]), are studied as a new substrate material group of lead- free or low lead content piezoelectric ceramics. A rhombohedral (Fα)-tetragonal (Fβ) morphotropic phase boundary (MPB) is shown to exist at x =0.13 by X-ray diffraction data. BNTX ceramics are superior for piezoceramics in high frequency ultrasonic uses, with a lower free permittivity, ϵ33T/ϵ0 (=240 ∼ 340) and a high electromechanical coupling factor, k t or k 33 (=50%), along with a high mechanical strength. Acoustic wave characteristics of the BNTX[14-50/50/0], BNTX[13-0/75/25], and BNTX[1-0/0/100] demonstrate that the ceramics are a new substrate material group for a surface acoustic wave and/or a bulk acoustic wave. Two interdigital transducers can excite an SH plate mode wave whose travelling direction is perpendicular to the poling axis along to the substrate wi...
195 citations
TL;DR: In this article, the effects of reorientation and frustration in the (BA - DBA)-system and (BA- BP)-systems are touched, and the (p, T)-phase diagram of BCCD and its relation to the ANNNI-model is discussed at some length.
Abstract: Phase transitions in betaine compounds are reviewed. Some topics are selected for detailed presentation: Effects of reorientation and frustration in the (BA - DBA)-system and the (BA - BP)-system are touched. The (p, T)-phase diagram of BCCD and its relation to the ANNNI- model is discussed at some length. Recent ESR- and NMR- experiments in BCCD are also mentioned.
166 citations
IBM1
TL;DR: In this paper, a model of these polarization effects in terms of a local, randomly oriented polarization (Pr) that may occur hundreds of degrees above Tc is presented. But the model is not suitable for the case of crystalline ferroelectrics.
Abstract: In this paper we discuss some of the measurements and properties of materials that are crystalline ferroelectrics with a glassy polarization phase. We review measurements of the temperature dependence of the optical index of refraction, n(T), which were first used to observe these properties. Then we discuss a model of these polarization effects in terms of a local, randomly oriented polarization (Pr) that may occur hundreds of degrees above Tc. This local polarization is allowed by the strong breakdown of the translational symmetry that occurs in these systems. We also show how the temperature dependence of the strain, x(T), complements the n(T) results. Lastly, we discuss some recent x-ray and EXAFS measurements and how they are in agreement with the model, and the connection between these high temperature effects and the low-temperature glass-like excitations that are found in these systems.
146 citations
TL;DR: In this paper, the chemistry and physics pertinent to the various steps of MOD processing are discussed, and areas where more basic research is needed are pointed out, and the preparation and properties of MOD films are discussed.
Abstract: The chemistry and physics pertinent to the various steps of MOD processing are discussed, and areas where more basic research is needed are pointed out. The preparation and properties of MOD films of PbTiO3, BaTiO3, Pb(Zr,Ti)O3, (Pb,Sr)TiO3 and (Pb,La)(Zr,Ti)O3 are discussed.
116 citations
TL;DR: In this paper, the critical physico-chemical issues which affect the reproducible fabrication of PZT thin-films are outlined and the low field behavior and the high field switching and stability characteristics of thin-film elements were studied for radiation hard and nonvolatile memory applications.
Abstract: Polymeric sol-gel processing represents an IC technology compatible route to fabricate defect-free and compositionally adjustable inorganic non-metallic thin-films at relatively low temperatures.The critical physico-chemical issues which affect the reproducible fabrication of PZT thin-films are outlined. The low field behavior and the high field switching and stability characteristics of PZT thin-films were studied for radiation hard and nonvolatile memory applications. Performance data of integrated PZT thin-films on solid Pt and sputtered Pt layer on silicon-nitrided GaAs substrates are presented and discussed. A compositionally adjustable low field permittivity of 1200, a dielectric break-down strength exceeding 100 V/μm, ∼1012 polarization reversal cycles, and tm ∼ 100 ns were observed. Compatibility of non-linear PZT thin-film element processing with GaAs JFET planar VLSI technology is addressed.
100 citations
TL;DR: In this article, a strong pyroelectric response can be induced in ferroelectric materials, both at and above their transition temperatures, by the application of an electric field, which can be understood in terms o...
Abstract: A strong pyroelectric response can be induced in ferroelectric materials, both at and above their transition temperatures, by the application of an electric field. This can be understood in terms o...
93 citations
TL;DR: In this article, the current state of the art with respect to the development of materials for use in pyroelectric infra-red detectors is reviewed and their relevant properties are compared using the appropriate materials figures-of-merit with reference to the physics of their operation.
Abstract: The current state of the art with respect to the development of materials for use in pyroelectric infra-red detectors is reviewed and their relevant properties are compared using the appropriate materials figures-of-merit with reference to the physics of their operation. The specific application of these materials to uncooled thermal imaging arrays is discussed and it is shown that the best materials for use in this application are those with high permittivities and high pyroelectric coefficients. The concept of using ferroelectrics in the region of Tc as dielectric bolometers is introduced and it is shown that lead scandium tantalate (PST) is one of the most promising materials for use in this mode. Finally, the technologies for direct deposition of the materials as thin films are introduced and compared and the results of using sol-gel technology for depositing PST thin films are presented.
89 citations
TL;DR: In this paper, different thin film fabrication techniques of ferro-and piezoelectric materials are described with special emphasis on rf sputtering, the relative advantages and disadvantages of oxide and metallic targets, and the control of stoichiometry by adjusting the target substrate distance and composition of target.
Abstract: Different thin film fabrication techniques of ferro- and piezoelectric materials is described with special emphasis on rf sputtering. The relative advantages and disadvantages of oxide and metallic targets, and the control of stoichiometry by adjusting the target substrate distance and composition of target is described. The possible applications of ferroelectric films in non-volative memories, pyroelectric detectors, electro- and acousto-optic devices is briefly presented. The applications of these films in the fabrication of integrated Surface Acoustic Wave (SAW) devices on Silicon is discussed in some detail. Theoretical calculations of SAW transduction in layered media is used to compare selected ferroelectric (PZT, PbTiO3. LiNbO3 and BaTiO3) and piezoelectric (ZnO, AIN and CdS) films on silicon for their use in SAW devices.
83 citations
TL;DR: In this article, the authors used lead zirconate titanate (PZT) as the basic ferroelectric material and integrated it into a standard 1.5μ CMOS process.
Abstract: Ferroelectric materials show a spontaneous electrical polarization that can be reversed in sense by an applied external electric field. It should, therefore, be feasible to build a ferroelectric memory device that can store information in digital form. Early attempts to build such a memory have failed for various reasons, the major one being a lack of a well defined and stable coercive field, which resulted in the eventual loss of data due to half-select pulses applied to unselected cells in the crosspoint array architecture. Fatigue or wear out was also a problem in that the amount of available signal depended upon the number of polarization reversals. We have been able to overcome these problems by a combination of design innovations and process/materials breakthroughs. We have chosen PZT (lead zirconate titanate) as the basic ferroelectric material and integrated it into a standard 1.5μ CMOS process. PZT has a wide temperature range (+ 350°C Curie Temperature), low coercive voltage, high specific polar...
TL;DR: In this paper, tris (methylammonium) nonaiododibismuthate was grown which turned out to be isomorphous with Cs3Bi2I9 and (CH3NH3)3Sb2I 9.
Abstract: Crystals of tris (methylammonium) nonaiododibismuthate were grown which turned out to be isomorphous with Cs3Bi2I9 and (CH3NH3)3Sb2I9. Two phase transitions, at 223 (second order) and 142 K (first order), were revealed. The low temperature phase transition is characterized by a strong dielectric anomaly. The pyroelectric behaviour could indicate a ferrielectric ordering below 142 K.
TL;DR: A short review of acoustic properties of disordered ferroelectric materials is made in this article, where a rather wide class of compounds (relaxators) can be identified as correlated (cluster) polar glasses.
Abstract: A short review of acoustic properties of a number of disordered ferroelectric materials is made. In the first place such characteristics as velocity of ultrasound elastic waves and their attenuation in a phase transition range are discussed. We show that rather wide class of compounds (relaxators) can be identified as correlated (cluster) polar glasses. Experimental data for such materials are interpreted naturally while suggesting strong critical fluctuations and an extremely wide spectrum of relaxation times.
TL;DR: In this article, an optimized sol-gel PZT process was developed and characterized for use in ferroelectric memories, where the pore size was controlled by hydrolysis and different heat treatments at various stages during drying and annealing cycles.
Abstract: The purpose of this work is to develop and characterize an optimized sol-gel PZT process to be used in ferroelectric memories. A review of the sol-gel process is given, including discussions on hydrolysis under acidic and basic conditions. Application of the sol-gel process to thin films is then discussed. Topics such as removal of solvents, stresses in the thin film and how this relates to cracking are mentioned. A review of different synthesis methods of sol-gel PZT is then conducted in order to help determine a device worthy sol-gel PZT process. Methods of controlling the pore size by hydrolysis and different heat treatments at various stages during the drying and annealing cycles are then used. The quality of thin film PZT on Pt is characterized by using dispersive X-ray and X-ray diffraction analyses. Electrical results yield Pr ranging from 7.9-21.9 μC/cm2Ec ranging from 29.1 -92.3 kV/cm and switching times as fast as 56 ns, using a capacitor area of 1 × 104 μm2. However, these results depend on the...
TL;DR: Zinc doping similarly to magnesium doping (eg [2]) reduces the value of photorefraction in LiNbO3 as mentioned in this paper, thus reducing the photoreformability of the LiO3.
Abstract: Zinc doping [1] similarly to magnesium doping (eg [2]) reduces the value of photorefraction in LiNbO3
TL;DR: In this paper, a sol-gel fabrication approach was developed for the fabrication of composite PbTiO3/PLZT thin films, which involves the deposition of a perovskite interlayer prior to deposition of the PLZT film.
Abstract: A novel sol-gel fabrication approach was developed for the fabrication of composite PbTiO3/PLZT thin films. The approach involves the deposition of a perovskite (PbTiO3) interlayer prior to deposition of the PLZT film. Composite PbTiO3/PLZT sol-gel thin films were prepared on (110) sapphire, platinum-coated sapphire, and platinum-coated silicon substrates. These films were highly crystalline and exhibited preferred crystallographic orientation. This perovskite interlayer approach is applicable to a wide variety ferroelectric thin film and substrate materials.
TL;DR: In this paper, single-crystal neutron-diffraction studies of PbTiO3, in its tetragonal (ferroelectric) phase at room temperature, at Tc - 60 K, Tc + 50 K and Tc+ 100 K, give evidence that the phase transition at T, = 763 K is order-disorder in character.
Abstract: Single-crystal neutron-diffraction studies of PbTiO3, in its tetragonal (ferroelectric) phase at room temperature, at Tc - 60 K and at Tc - 20 K, and in its cubic phase at Tc+ 2 K, Tc + 50 K and Tc + 100 K, give evidence that the phase transition, at T, = 763 K, is order-disorder in character. In particular, the Pb atoms can be described as being disordered over six sites above Tc, each displaced -0.2 1 along the ⟨001⟩ directions, and then ordering onto one of these sites below Tc.
TL;DR: In this article, the anomalous behavior of Q-1 and G at infralow frequencies to a great extent depends on crystal lattice imperfections (dislocations, point defects, domain and interphase boundaries).
Abstract: The features of infrasonic frequency (10-3-10-1 Hz) internal friction, Q-1, and shear modulus, G, in different ferroelectric and ferroelastic crystals have been studied using the inverse torsion pendulum technique over a wide temperature range and different external fields which lead to the change of a real crystal structure. It is shown that the anomalous behavior of Q-1 and G at infralow frequencies to a great extent depends on crystal lattice imperfections (dislocations, point defects, domain and interphase boundaries). Physical mechanisms responsible for this behavior are discussed.
TL;DR: In this article, some of the title compounds have been found to exhibit ferroelectricity at room temperature and their structure types can be classified in three series according to the cations coordination number (CN) and size.
Abstract: Some of the title compounds have been found to exhibit ferroelectricity at room temperature Their structure types can be classified in three series according to the cations coordination number (CN) and size: 1- single cation with CN 4: olivine and glaserite; 2- two cations with CN 4: Beryllonite and stuffed tridymite; 3- all cations with CN 4: α-LiZnPO4 is the unique case known
TL;DR: The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date as discussed by the authors, and the accuracy of any instructions, formulae and drug doses should be independently verified with primary sources.
Abstract: The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.
TL;DR: Manganese introduced in BaTiO3 as a substituant of titanium is able to trap the electrons produced during a sintering under a very low oxygen pressure as mentioned in this paper.
Abstract: Manganese introduced in BaTiO3 as a substituant of titanium is able to trap the electrons produced during a sintering under a very low oxygen pressure. However it strongly modifies the vibrational ...
TL;DR: In this article, the transformation of precursors to sol, sol to gel, and gel to crystalline phase were characterized using spectroscopy and x-ray diffraction.
Abstract: Integration of ferroelectrics in the current generation of electronic/photonic devices not only enhances the functional capabilities of these devices but also has potential for a variety of new applications. The fabrication of ceramic thin films and fibers is enabled by sol-gel process. This fabrication process is well-controlled, low-cost and compatible with existing fabrication technologies. This study focussed on the fabrication of PLZT 7/65/35 ceramic thin films and fibers from lead acetate hydrate, lanthanum acetate hydrate, zirconium n-propoxide and titanium n-propoxide utilizing acid catalysis. The transformations of the precursors to sol, sol to gel and gel to crystalline phase were characterized using spectroscopy and x-ray diffraction. The films were formed by spin-coating the hydrolyzed precursor sol on various substrates: conductors (Au, Al, Pt), semiconductors (Si [100], Si [111]) and insulators (fused SiO2, Al2O3, MgO). The fibers were drawn from the similar sols. These films and fibers were...
TL;DR: In this article, the first-prinicipals selfconsistent orthogonalized linear combination of atomic orbitals method was used to calculate the band structures of SrTiO3 BaTio3 and KNbO3 in the cubic perovsikte structure.
Abstract: The band structures of SrTiO3 BaTio3 and KNbO3 in the cubic perovsikte structure are calculated using the first-prinicipals selfconsistent orthogonalized linear combination of atomic orbitals method. In all three crystals, indirect band gaps of about 3 eV are obtained. The top of the valence band is at R and the minimum in the conduction band is at f. Effective charge calculation and the charg. 1 density maps reveal the highly ionic nature of the crystal bonding in these ferroelectric crystals. The optical conductivities and the frequency dependent dielectric functions up to 20 eV in all three crystals are also evaluated using the energy eigenvalues and wave functions obtained from the band calculation. The calculated spectra are found to be in good agreement with the existing experimental measurements.
TL;DR: In this paper, a phenomenological theory of periodic ferroelectric multilayers, consisting of two alternating ferroelectrics with different transition temperatures, is presented, and the authors consider the case of a first order phase transition of first order.
Abstract: A phenomenological theory of periodic ferroelectric multilayers, consisting of two alternating ferroelectrics with different transition temperatures, is presented. We consider the case of a ferroelectric phase transition of first order. Interface modes are shown to exist, resulting from the special form of the inhomogeneous polarization profile in the superlattice close below its first order phase transition temperature. The lineshape of the dynamical polarization correlation function has a characteristic temperature dependence, if the damping of the soft mode within each layer constituent is differently strong.
TL;DR: In this article, the switching of polarization in uniaxial ferroelectrics is considered as the first-order phase transition and it is assumed that the switching process is determined by the oversaturation degree which correspond in ferro electrics to the magnitude of electric field on the domain boundary.
Abstract: The switching of polarization in ferroelectrics is considered as the first-order phase transition. By the analogy with the theory of crystal growth it is assumed that the switching process is determined by the oversaturation degree which correspond in ferroelectrics to the magnitude of electric field on the domain boundary. It is supposed that the mechanism of domain wall motion in strong field is due to the twodimensional nucleation and in weak field is due to the one-dimensional nucleation. The criterion of strong field IS defined. From this point of view it have been explained the peculiarities of domain structure dynamics in two uniaxial ferroelectrics: lead germanate and gadolinium molybdate.
TL;DR: Ferroelectric polymers are reviewed with special interest in the polarization reversal and phase transition behavior of VDF copolymers in this paper, and the transition into a paraelectric phase occurs as a result of conformational disorder associated with rotational molecular motions.
Abstract: Ferroelectric polymers are reviewed with special interest in the polarization reversal and phase transition behavior of VDF copolymers. The ferroelectric phase consists of all-trans molecules packed in a parallel manner. Its spontaneous polarization is reversed at very high fields by eventual 180° rotations of individual chain molecules. The transition into a paraelectric phase occurs as a result of conformational disorder associated with rotational molecular motions. Changes in various properties near the Curie point are consistent with an order-disorder transition of first-order. The Van der Waals force is a primary source of interactions resulting in the ferroelectricity of polymers.