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Showing papers on "Ceramic published in 1990"


Journal ArticleDOI
TL;DR: In this paper, the authors used impedance spectroscopy for unravelling the complexities of such materials, which functions by utilizing the different frequency dependences of the constituent components for their separation, and showed that electrical inhomogeneities in ceramic electrolytes, electrode/electrolyte interfaces, surface layers on glasses, ferroelectricity, positive temperature coefficient of resistance behavior and even ferrimagnetism can all be probed, successfully.
Abstract: Electroceramics are advanced materials whose properties and applications depend on the close control of structure, composition, ceramic texture, dopants and dopant (or defect) distribution. Impedance spectroscopy is a powerful technique for unravelling the complexities of such materials, which functions by utilizing the different frequency dependences of the constituent components for their separation. Thus, electrical inhomogeneities in ceramic electrolytes, electrode/electrolyte interfaces, surface layers on glasses, ferroelectricity, positive temperature coefficient of resistance behavior and even ferrimagnetism can all be probed, successfully, using this technique.

2,004 citations


Book
01 Feb 1990
TL;DR: In this paper, elementary solid state science fabrication of ceramics ceramic conductors: fabrication and applications dielectrics and insulators, pyroelectric materials, electro-optic ceramic magnetoramics, magnetic ceramicas.
Abstract: Overview elementary solid state science fabrication of ceramics ceramic conductors: fabrication and applications dielectrics and insulators piezoelectric ceramics pyroelectric materials electro-optic ceramics magnetic ceramics.

828 citations


Journal ArticleDOI
01 Oct 1990-Nature
TL;DR: In this paper, a simple, inexpensive way of preparing a ceramic material that contains such weak interfaces is described, where Silicon carbide powder is made into thin sheets which are coated with graphite to give weak interfaces and then pressed together and sintered without pressure.
Abstract: THE major problem with the use of ceramics as structural materials is their brittleness. One way of overcoming this problem is to introduce weak interfaces which deflect a growing crack1. Polymer composites of this sort can be easily prepared by surrounding fibres with liquid plastic. To make similar structures with ceramic matrices and fibres is difficult and expensive, however, because traditional ceramic processing techniques of powder compaction and sintering prevent densification and cause cracking2–4. Here we describe a simple, inexpensive way of preparing a ceramic material that contains such weak interfaces. Silicon carbide powder is made into thin sheets which are coated with graphite to give weak interfaces and then pressed together and sintered without pressure. Relative to the monolithic material, the apparent fracture toughness for cracks propagating normal to the weak interfaces is increased more than fourfold, and the work required to break the samples increases by substantially more than a hundredfold. The technique should be readily applicable to other ceramics.

761 citations


Journal ArticleDOI
TL;DR: In this article, the rate of the resistance degradation of doped SrTiO3 ceramics is investigated as a function of various external and material parameters, including voltage, electric field, and thickness of the dielectric.
Abstract: The rate of the resistance degradation of doped SrTiO3 ceramics is investigated as a function of various external and material parameters. The effects of the mutually interrelated parameters dc voltage, dc electric field, and thickness of the dielectric are described by power laws. Electron microscopic potential contrast studies show a Maxwell-Wagner polarization leading to a concentration of the electric field at the grain boundaries during the degradation. Based on this finding, the voltage step per grain boundary, ΔΘgb, is introduced as a rate-determining parameter which allows an explanation of the influence of the grain size on the degradation rate as well as the difference in the power laws for ceramic and single-crystal samples.

602 citations


Book
01 Jan 1990
TL;DR: In this paper, the band theory of solids semiconductors ionic and defect conductors linear dielectrics nonlinear dielectric magnetic ceramics photonic and optical waveguides optical waveguide glass and crystalline lasers ceramic superconductors.
Abstract: Quantum mechanics and the band theory of solids semiconductors ionic and defect conductors linear dielectrics nonlinear dielectrics magnetic ceramics photonic ceramics optical waveguides electro-optical ceramics glass and crystalline lasers ceramic superconductors.

487 citations


Journal ArticleDOI
TL;DR: In this paper, a three-dimensional part comprising eight intersecting planes spaced 0.375 inches apart was constructed using a continuous-jet ink-jet printing technology, which was applied to the production of metal, ceramic, and metal/ceramic composite parts.

394 citations


Journal ArticleDOI
TL;DR: This study focuses on the formulation of model porous metal-CPC materials for use in one-parametric analyses of material factors for enhancing early bone tissue formation in porous metal coatings.

349 citations


Journal ArticleDOI
TL;DR: In this paper, a descriptive account of the surface forces acting between two solids is given, with particular attention paid to the underlying mechanisms, and how they are affected by the nature of the medium between the surfaces.
Abstract: A descriptive account is given of the surface forces acting between two solids. Different contributions to the force are outlined, with particular attention paid to the underlying mechanisms, and how they are affected by the nature of the medium between the surfaces. This is followed by a discussion of the areas of ceramic science and engineering in which surface forces play a role.

325 citations


Journal ArticleDOI
TL;DR: In this article, the authors considered the capacity of multilayer ceramic capacitors (MLC's) for energy storage applications and showed that the best energy density is obtained in high dielectric constant materials but in those materials which display intermediate and the highest ultimate breakdown voltages.
Abstract: Historically, multilayer ceramic capacitors (MLC's) have not been considered for energy storage applications for two primary reasons. First, physically large ceramic capacitors were very expensive and, second, total energy density obtainable was not nearly so high as in electrolytic capacitor types. More recently, the fabrication technology for MLC's has improved significantly, permitting both significantly higher energy density and significantly lower costs. Simultaneously, in many applications, total energy storage has become smaller, and the secondary requirements of very low effective series resistance and effective series inductance (which, together, determine how efficiently the energy may be stored and recovered) have become more important. It is therefore desirable to reexamine energy storage in ceramics for contemporary commercial and near-commercial dielectrics. Stored energy is proportional to voltage squared only in the case of paraelectric insulators, because only they have capacitance that is independent of bias voltage. High dielectric constant materials, however, are ferroics (that is ferroelectric and/or antiferroelectric) and display significant variation of effective dielectric constant with bias voltage. The common ferroelectric materials, whether based upon barium titanate or lead manganese niobate (PMN), in the high-field limit, exhibit an energy storage which increases linearly with bias voltage. Mixed phase, ferroelectric plus antiferroelectric, dielectrics from the lead lanthanum zirconate titanate (PLZT) system, as predicted theoretically, show the best energy density at low to moderate fields. Surprisingly, maximum energy storage is not obtained in high dielectric constant materials but in those materials which display intermediate dielectric constant and the highest ultimate breakdown voltages.

318 citations


Journal ArticleDOI
TL;DR: A review of new and emerging techniques for the low temperature, wet chemical synthesis of barium titanates is presented in this article, along with a brief discussion of the economic viability of these processes.
Abstract: The BaO-TiO2 system contains several technologically important electronic materials. BaTiO3, a ceramic with high dielectric constant, is useful for the manufacture of multilayer ceramic capacitors, thermistors and electro-optic components. Titania rich compounds in this system (such as BaTi4O9 and Ba2Ti9O20) are suitable for the manufacture of miniaturized microwave resonators. Conventional processing of these ceramics relies on the solid-state reactions between readily available raw materials (typically TiO2 and BaCO3) and tends to produce coarse, impure, inhomogeneous and multiphase powders. Low temperature, wet chemical routes offer an exciting possibility for the synthesis of high purity, homogeneous, ultrafine and multicomponent powders from which electronic components with tailored and predictable properties could be prepared. A review of new and emerging techniques for the low temperature, wet chemical synthesis of barium titanates is presented. Salient features of several of these processes based on the use of alkoxides, acetates, citrates, chlorides, hydroxides and oxalates of barium and titanium, and combinations thereof, are described. The reaction pathways for the formation of barium titanates are discussed. A comparative summary of the powder characteristics and electrical properties of the barium titanates obtained by different techniques is presented along with a brief discussion of the economic viability of these processes.

300 citations


Journal ArticleDOI
TL;DR: In this paper, the fracture toughness of a single-phase commercial lead zirconate titanate (PZT) ceramic was measured using the single edge notched beam method above and below the Curie temperature.
Abstract: Fracture toughness, KIC, of a single-phase commercial lead zirconate titanate (PZT) ceramic (Zr/Ti=0.54/0.46) of tetragonal structure (c/a=1.019) was measured using the single edge notched beam method above and below the Curie temperature. Domain switching (poling) under electrical and mechanical loading was examined using X-ray diffraction. Surface grinding, electrical poling, and mechanical poling caused crystallographic texture. Similar texture, indicative of domain switching, was also observed on fracture surfaces of some saples fractured at room temperature. At room temperature, the highest KIC measured was 1.85 MPa·m1/2, while above the Curie temperature it was about 1.0 MPa·m1/2. Cracks emanating from Vickers indents in poled samples were different in the poling and the transverse directions. The difference in crack sizes is explained on the basis of domain switching during crack growth. These results indicate that ferroelastic domain switching (twinning) is a viable toughening mechanism in the PZT materials tested.

Journal ArticleDOI
G. Arlt1
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.

Journal ArticleDOI
TL;DR: In this paper, the authors used impedance spectroscopy for unravelling the complexities of such materials, which functions by utilizing the different frequency dependences of the constituent components for their separation, and showed that electrical inhomogeneities in ceramic electrolytes, electrode/electrolyte interfaces, surface layers on glasses, ferroelectricity, positive temperature coefficient of resistance behavior and even ferrimagnetism can all be probed, successfully.
Abstract: Electroceramics are advanced materials whose properties and applications depend on the close control of structure, composition, ceramic texture, dopants and dopant (or defect) distribution. Impedance spectroscopy is a powerful technique for unravelling the complexities of such materials, which functions by utilizing the different frequency dependences of the constituent components for their separation. Thus, electrical inhomogeneities in ceramic electrolytes, electrode/electrolyte interfaces, surface layers on glasses, ferroelectricity, positive temperature coefficient of resistance behavior and even ferrimagnetism can all be probed, successfully, using this technique.

Journal ArticleDOI
TL;DR: In this paper, the authors studied the mechanism by which a long rod penetrates a steel-encased ceramic block by performing impact experiments at a range of velocities and examining the fracture and deformation in the recovered targets and impactors.



Journal ArticleDOI
TL;DR: In this article, the subcritical growth of fatigue cracks under tension-tension cyclic loading was demonstrated for ceramic materials, based on experiments using compact C(T) specimens of a MgO-partially-stabilized zirconia (PSZ), heat-treated to vary the fracture toughness Kc from ∼3 to 16 MPa·m1/2 and tested in inert and moist environments.
Abstract: The subcritical growth of fatigue cracks under (tension-tension) cyclic loading is demonstrated for ceramic materials, based on experiments using compact C(T) specimens of a MgO-partially-stabilized zirconia (PSZ), heat-treated to vary the fracture toughness Kc from ∼3 to 16 MPa·m1/2 and tested in inert and moist environments. Analogous to behavior in metals, cyclic fatigue-crack rates (over the range 10−11 to 10−5 m/cycle) are found to be a function of the stress-intensity range, environment, fracture toughness, and load ratio, and to show evidence of fatigue crack closure. Unlike toughness behavior, growth rates are not dependent on through0-thickness constraint. Under variable-amplitude cyclic loading, crack-growth rates show transient accelerations following low-high block overloads and transient retardations following high-low block overloads or single tensile overloads, again analogous to behavior commonly observed in ductile metals. Cyclic crack-growth rates are observed at stress intensities as low as 50% of Kc, and are typically some 7 orders of magnitude faster than corresponding stress-corrosion crack-growth rates under sustained-loading conditions. Possible mechanisms for cyclic crack advance in ceramic materials are examined, and the practical implications of such “ceramic fatigue” are briefly discussed.

Journal ArticleDOI
TL;DR: In this article, volatility diagrams for the Si-O and Si-N systems were extended to Si-C-O systems, in which the important ceramic constituents SiO2, Si3N4, Si2N2O, and SiC appear as stable phases.
Abstract: Volatility diagrams—isothermal plots showing the partial pressures of two gaseous species in equilibrium with the several condensed phases possible in a system—are discussed for the Si-O and Si-N systems, and extended to the Si-N-O and Si-C-O systems, in which the important ceramic constituents SiO2, Si3N4, Si2N2O, and SiC appear as stable phases. Their use in understanding the passiveactive oxidation transitions for Si, Si3N4, and SiC are demonstrated.

Journal ArticleDOI
02 Mar 1990-Science
TL;DR: New methods of creating thin films of complex oxides and electronic ceramics allow the integration of these properties with semiconductor technology and raise the possibility of a new range of electronic devices.
Abstract: Ceramics are a distinct class ofmaterials whose properties range from extreme hardness to unique electrical behavior. New methods of creating thin films of complex oxides and electronic ceramics allow the integration of these properties with semiconductor technology and raise the possibility of a new range of electronic devices.

Journal ArticleDOI
TL;DR: The first principles orthogonalized linear combination of atomic orbitals (OLCAO) method for electronic structure studies has been applied to a variety of complex inorganic crystals as mentioned in this paper.
Abstract: The first-principles orthogonalized linear combination of atomic orbitals (OLCAO) method for electronic structure studies has been applied to a variety of complex inorganic crystals. The theory and the practice of the OLCAO method in the local density approximation are discussed in detail. Recent progress in the study of electronic and optical properties of a large list of ceramic systems are summarized. Eight selected topics on different ceramic crystals focusing on specific points of interest are presented as examples. The materials discussed are AIN, Cu2O, β-Si3N4, Y2O3, LiB3O5, ferroelectric crystals, Fe-B compounds, and the YBa2Cu3O7 superconductor. The results include the band structure, density of states, charge density distribution, spin density distribution, effective charges, total energy and totalenergy-derived results, optical absorption, positron annihilation spectra, and more. Extension of the band theoretical approach to the study of other areas of fundamental ceramic science is also discussed.

Journal ArticleDOI
TL;DR: In this paper, an experimental technique whereby pure mode I, mode II, and combined mode I-mode II fracture toughness values of ceramic materials can be determined using four-point bend specimens containing sharp, through-thickness precracks is discussed.
Abstract: An experimental technique whereby pure mode I, mode II, and combined mode I-mode II fracture toughness values of ceramic materials can be determined using four-point bend specimens containing sharp, through-thickness precracks is discussed. In this method, notched and fatigue-precracked specimens of brittle solids are subjected to combined mode I-mode II and pure mode II fracture under asymmetric four-point bend loading and to pure mode I under symmetric bend loading. A detailed finite element analysis of the test specimen is performed to obtain stress intensity factor calibrations for a wide range of loading states. The effectiveness of this method to provide reproducible combined mode I-mode II fracture toughness values is demonstrated with experimental results obtained for a polycrystalline Al2O3. Multiaxial fracture mechanics of the Al2O3 ceramic in combined modes I, II, and III are also described in conjunction with the recent experimental study of Suresh and Tschegg (1987). While the mode II fracture toughness of the alumina ceramic is comparable to the mode I fracture toughness KIc, the mode III fracture initiation toughness is 2.3 times higher than KIc. The predictions of fracture toughness and crack path based on various mixed-mode fracture theories are critically examined in the context of experimental observations, and possible effects of fracture abrasion on the apparent mixed-mode fracture resistance are highlighted. The significance and implications of the experimental methods used in this study are evaluated in the light of available techniques for multiaxial fracture testing of brittle solids.

Journal ArticleDOI
TL;DR: In this paper, a structural model has been proposed for the amorphous silicon carbide phase that is formed during the pyrolysis process, which is formed by a mixture of β-SiC and α -SiC; however, some difficulties in identifying the crystalline phases have been pointed out.
Abstract: The pyrolysis process of a polycarbosilane into a microcrystalline silicon carbide ceramic has been followed up to 1700 ° C mainly by means of solid state29Si and13C nuclear magnetic resonance, transmission electron microscopy and X-ray diffraction analysis. A structural model has been proposed for the amorphous silicon carbide phase that is formed during the pyrolysis process. The ceramic obtained at high temperature is formed by a mixture of β-SiC and α-SiC; however, some difficulties in the identification of the crystalline phases have been pointed out.

Journal ArticleDOI
TL;DR: In this paper, the grain growth kinetics in nanocrystalline materials are examined. But, the initial particle size in green body compacts is not always indicative of the final grain sizes in fully sintered ceramic bodies.
Abstract: This paper reports on scientific interest in ultra-fine grained powders for processing of ceramic components motivated by the possibilities for the enhancement of sintering rates, reduction in flaw sizes and low-temperature superplastic deformation. Previous works have developed a technique, which combines the methods established of inert gas condensation of small particles and in situ powder compaction, for synthesizing materials with grain sizes {lt}10 nm. It has been shown that this method can be adapted for the production of ceramic nanocrystalline particles. Subsequent work has demonstrated that enhanced sintering and superplastic deformation is possible in nanocrystalline ceramics (TiO{sub 2}), but not without significant grain growth. Control of grain growth, however, is necessary if the capability for synthesizing nanoscale powders is to have benefit for structural applications. It is well known that the initial particle size in green body compacts is not always indicative of the final grain sizes in fully sintered ceramic bodies. This study was initiated to examine grain growth kinetics in nanocrystalline materials. TiO{sub 2} was selected for this initial study since sintering, deformation and diffusion data are available.

Journal ArticleDOI
TL;DR: Ceramics can be either crystalline or non-crystalline as discussed by the authors, and they are made by consolidating powders into compacts using either dry-pressing techniques or liquid susp...
Abstract: Ceramics are older than history. But new types of ceramics with properties unlike any made previously are now being produced by the application of new chemical technology. Traditional ceramics are inorganic, nonmetallic solids that are stable at high temperatures, usually up to 1000 °C. Advanced ceramics are being developed that are stable at temperatures to 1500 °C or higher. At the same time, development of ceramics intended for use at less than 1000 °C is driven by the need for materials with new and useful combinations of properties, such as mechanical and electrical performance. Hightemperature ceramics like mullite and yttria-containing zirconia-alumina composites, ceramic-metal composites like boron carbide-aluminum, polymer-ceramic composites, and biomimetic ceramics are all examples of newly developed advanced ceramic materials. Ceramics can be either crystalline or noncrystalline. Crystalline ones are made by consolidating powders into compacts using either dry-pressing techniques or liquid susp...

Journal ArticleDOI
TL;DR: In this article, four topics in the field of electronic ceramics are reviewed: multilayer ceramic capacitors, piezoelectric ceramic, electrooptic and ferroelectric thin films.
Abstract: Four topics in the field of electronic ceramics are reviewed: multilayer ceramic capacitors, piezoelectric ceramics, electrooptic ceramics, and ferroelectric thin films. They all are related to ferroelectric ceramic materials. The scope of this review is limited to oxide compounds, because oxide ferroelectrics, for the most part, exhibit the most useful properties and have found the most applications. The underlying physical concepts, ceramic and/or thin-film fabrication, structure/property relationships, specific applications, and future prospects in each of the four electronic ceramic application areas are discussed. >

Patent
28 Mar 1990
TL;DR: In this article, a method of laser marking ceramic materials, glazes, glass ceramics and glasses that contain at least one radiation-sensitive additive, utilizing a laser beam as radiation energy source which is either applied to, or focused on, the surface of the material to be marked in accordance with the form of the graphic symbols to be reproduced, such that a change in color is induced at the irradiated areas, wherein the wavelength of said laser beam used as energy source is in the near UV and/or visible range, and the radiation sensitive additive is an inorganic
Abstract: A method of laser marking ceramic materials, glazes, glass ceramics and glasses that contain at least one radiation-sensitive additive, utilizing a laser beam as radiation energy source which is either applied to, or focused on, the surface of the material to be marked in accordance with the form of the graphic symbols to be reproduced, such that a change in color is induced at the irradiated areas, wherein the wavelength of said laser beam used as energy source is in the near UV and/or visible range and/or infra-red range, and the radiation-sensitive additive is an inorganic pigment.

Journal ArticleDOI
TL;DR: In this paper, the authors compared mother-of-pearl, the highly filled ceramic composite of mollusc shell, with other, less highly filled, artificial ceramics.
Abstract: Mother-of-pearl, the highly filled ceramic composite of mollusc shell, is compared with other, less highly filled, artificial ceramics. Stiffness is fairly simply related to volume fraction of ceramic, but no model seems to be adequate to describe this relationship. Strength, stress-intensity factor and the work of fracture are also dependent on the ceramic content but in a much more complex manner. Nacre has the highest value for all these parameters.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the mechanical properties and oxidation resistance of Al2O3/Ni composites and demonstrated that dissolved oxygen in the nickel increases the yield strength of nickel and enhances the toughness of the composite.
Abstract: Brittle solids can be toughened by the introduction of ductile metallic inclusions. In the present study, the mechanical properties and oxidation resistance of Al2O3/Ni composites are investigated. The oxidation resistance of the ceramic/metal composite (8 × 10−11 g2 cm−4 s−1 at 1300° C) is comparable to that of many silicon nitrides. The fracture toughness of the composite containing 13 vol.% nickel is twice that of alumina alone. The square of the toughness enhancement for composites containing various amounts of nickel exhibits a linear relationship with the product of volume fraction and inclusion size, as predicted in theoretical models. For the alumina/nickel composite system, it is demonstrated that dissolved oxygen in the nickel increases the yield strength of nickel and enhances the toughness of the composite.

Journal ArticleDOI
TL;DR: In this paper, the authors describe and explain unusual constitutive behavior observed in the insulative ceramic coating layer, and present details of the ceramic cracking damage accumulation process which is responsible for spallation failure.
Abstract: Failure of a two layer plasma deposited thermal barrier coating is caused by cyclic thermal exposure and occurs by spallation of the outer ceramic layer. Spallation life is quantitatively predictable, based on the severity of cyclic thermal exposure. This paper describes and attempts to explain unusual constitutive behavior observed in the insulative ceramic coating layer, and presents details of the ceramic cracking damage accumulation process which is responsible for spallation failure. Comments also are offered to rationalize the previously documented influence of interfacial oxidation on ceramic damage accumulation and spallation life.

Journal ArticleDOI
TL;DR: A review article on active metal/ceramic joining is subdivided into the description of research activities in the fields of active metal brazing and diffusion bonding published in the last decade as discussed by the authors.
Abstract: This review article on metal/ceramic joining is subdivided into the description of research activities in the fields of active metal brazing and diffusion bonding published in the last decade. Informations are given on active metal brazing of oxide, nitride, and carbide ceramics and on diffusion bonding of alumina, zirconia, magnesia, silicon nitride, aluminum nitride and silicon carbide ceramics to metals. Ultra high vacuum diffusion bonding and experiments using the model combination Nb/alumina are also regarded. Emphasis is laid on a concise reproduction of experimental data concerning the bonding conditions and the determintion of bond strength. The review demonstrates that much effort was devoted to studies on the formatin of interfacial reaction layers and on the efficiency of interlayers additonally introduced between the ceramic and the metal part to reduce internal stresses caused by thermal expansion misfit of the materials to be bonded.