Physical and electrical characterization techniques have been applied to the problem of developing a lower temperature process for spin-on Ba0.7Sr0.3TiO3 thin films and capacitors compatible with on-chip aluminum metallization. The films were prepared by spin-coating from carboxylate precursors and were processed at temperatures between 650 °C and 450 °C. Capacitors annealed at higher temperatures have a dielectric constant (κ) of 382, a C/A of 20 fF/μm2, and a leakage current density of 2 × 10−7 A/cm2 at 3.3 V. Those processed at 450 °C show occasionally promising but inconsistent results, correlated using TEM images with locally variable crystallization into the perovskite phase. The kinetics of the spin-on solution chemical decomposition and crystallization has been investigated through the use of x-ray diffraction (XRD), thermogravimetric analysis (TGA), and Raman spectroscopy.

Layers of different composition and/or grain size of yttria partially stabilized zirconia (YPSZ) have been compressed, with the stress perpendicular to the interface of the layers and temperature of 1400 °C, in order to produce a joint using the microstructural feature of superplasticity found in fine-grained ceramics. The pieces joined have been characterized by scanning electron microscopy (SEM), showing a clean interface with no cavitation. The stiffness of the junction was checked using Vickers indentation at room temperature at the interface and compression tests at the same conditions (T = 1400 °C in air) used for the joining and the stress parallel to the interface. The observation and comparison between the cracks developed around the indents at the interface and in the bulk of the pieces joined as well as the absence of cavities along the interface in the samples compressed parallel to the interface shows that this technique is useful to produce a joint with a clean and strong interface.

A round robin test has been performed on sol-gel processing for the deposition of silica and silica-titania films on silicon substrates by spin-coating. Three solution preparation processes for silica coatings and three for silica-titania coatings were used to prepare samples at each of the participating laboratories. The films have been characterized mainly by thickness (profilometry and ellipsometry measurements), refractive index, porosity, and optical scattering. Different processes gave different thicknesses. Thickness differences were found in films prepared by the same process and by the same deposition parameters, but in different laboratories, when heat-treated at 500 °C. Variations were reduced in samples annealed at 1000 °C. Refractive index and porosity measurements suggest that variations were due to structural differences, particularly porosity. Furthermore, films heat-treated at 500 °C were not completely stabilized, and showed index and porosity variations after six months.

Submicrometer-grained (SMG) structures were produced in Cu and Ni using an intense plastic straining technique, and the grain boundaries and their vicinities were observed by high-resolution electron microscopy. The grain boundaries exhibited zigzag configurations with irregular arrangements of facets and steps, and thus they were found to be in a high-energy nonequilibrium state. A similar conclusion was reached earlier for SMG Al–Mg solid solution alloys which have much lower melting points than Cu and Ni, suggesting that nonequilibrium grain boundaries are a typical feature of metals processed by intense plastic straining.

Preparation of β–SiC nanorods with and without amorphous SiO2 wrapping layers was achieved by carbothermal reduction of sol-gel derived silica xerogels containing carbon nanoparticles. The β–SiC nanorods with amorphous SiO2 wrapping layers were obtained by carboreduction at 1650 °C for 1.5 h, and at the end of 1.5 h the temperature was steeply raised to 1800 °C and held for 30 min; they are typically up to 20 µm in length. The diameters of the center thinner β–SiC nanorods within the amorphous SiO2 wrapping layers are in the range 10–30 nm, while the outer diameters of the corresponding amorphous SiO2 wrapping layers are between 20 and 70 nm. The β–SiC nanorods without amorphous SiO2 wrapping layers were produced by carbothermal reduction only at 1650 °C for 2.5 h, and their diameters are in agreement with those of the center thinner β–SiC nanorods wrapped in amorphous SiO2 layers. Large quantities of SiC rod nuclei and the nanometer-sized nucleus sites on carbon nanoparticles are both favorable to the formation of much thinner β–SiC nanorods. The formation of the outer amorphous SiO2 wrapping layer is from the combination reaction of decomposed SiO vapor and O2.

The rate of movement of liquid drops toward their equilibrium position on smooth, horizontal solid surfaces (spreading kinetics) is considered in this study. A model for nonreactive liquid spreading which was developed for low-temperature liquids is applied to results for a set of high-temperature liquids and room-temperature liquids. These data were generated in a single laboratory following a consistent experimental methodology. The liquid-solid pairs were chosen to result in weak or no interfacial chemical reaction. Furnace atmospheres were chosen to provide data for liquid metals with submonolayer, thin or thick oxide films. Analysis of the high-temperature spreading kinetics for liquids covering a broad range of viscosity, surface tension, and density shows that they can be predicted with a constant shift factor applied to the deGennes expression for nonreactive spreading. The consequences of gravitational and inertial forces, substrate roughness, weak interfacial reactions, and liquid-metal oxide films are discussed.

We investigated the interactions between screen printed and fired layers of Bi2O3 and ceramic substrates of alumina and beryllia. It was found that the reaction products are invariably crystalline in nature. Several transitions of Bi2O3 in its polymorphic phases were found to occur on BeO substrates, while newly formed compounds have been observed to grow on alumina substrates, i.e., Al4Bi2O9 on 99.9% Al2O3 and Bi12SiO20 on 96% Al2O3. Bismuth deeply penetrates in the ceramic interstices in all the cases. Until Bi2O3 is not completely reacted, this penetration is diffusion limited (penetration depth , where td is the reaction time) with values of the activation energy ranging from 3.7 ± 0.6 eV (BeO substrate) to 1.4 ± 0.06 eV (96% Al2O3 substrate). It is shown that these processes are notably different to those occurring in PbO/ceramic systems; moreover, they imply different adhesion phenomena of thick films on different substrates.

KxGaxSn8−xO16 (x ≤ 2) powders with hollandite structure were prepared by the sol-gel method using metal alkoxides. Dried gels, when being annealed at 973 K, changed to well-crystallized hollandite powders with about 22 m2/g in BET value which consisted of needle-like crystallites 25 nm wide and 65 nm long in average. The specific surface area was nearly 100 times larger than that of the hollandite produced at 1648 K by the conventional method, and the preparation temperature was lowered by 500 to 700 K. The powders obtained at 973 K were characterized as an attractive porous material showing a pore size distribution profile sharply monodispersed at 10.7 nm in the mesopore range.

Ferroelectric Ba0.7Sr0.3TiO3 thin films were successfully deposited on sapphire (r-cut) substrates by the sol-gel process, and the deposited films were annealed at various temperatures and for various soaking times. The compositional and structural characteristics of the films were systematically examined with the aid of x-ray diffraction, scanning electron microscopy, and medium energy ion scattering techniques. Their dependence on thermal processes was investigated. A planar capacitor structure based on the BSTO films was fabricated to evaluate the electrical and dielectric performance. These results, together with the microstructure characteristics, were analyzed and an optimal process was finally established.

In situ observations of crack propagation in an applied moment double cantilever beam specimen were used previously to obtain the R-curve behavior of ceramic composites. To predict the R-curve using constitutive models, knowledge of the crack profile is required to derive the bridging stress distribution along the crack length and to analyze the toughening effect. To predict the crack profile in an applied moment double cantilever beam test, both the deformation of the crack surface due to the bending moment and the movement of the crack surface due to the rigid body motion of the loading fixture need to be considered. The analytical solution for the crack profile is derived in the present study. The predicted crack profiles agree well with experimental measurements.

The dielectrophoretic effect is a phenomenon in which dipole-dipole interactions are induced between particles in a suspension by an electric field.1−5 This dipole interaction leads to the formation of chains or fibrils parallel to the applied electric field. Recently, the dielectrophoretic effect has been shown to be a possible composite assembly technique permitting property changes to be induced with the appropriate electric fields.6,7 The results presented in this paper show that the dielectrophoretic assembly process can be used to engineer anisotropy into composite materials. Various filler materials are aligned in a thermoset polyurethane matrix and the dielectric properties are measured. Comparisons are drawn between the dielectrophoretically assembled composites and those processed conventionally in the absence of an electric field. Dielectric properties are modeled with modified mixing laws and discussed in relation to the composite microstructure and the alpha relaxations of the polymer phase.

Amorphous to nanocrystalline ZrO2−3 wt. % Y2O3 powders were formed by chemical precipitation from mixed nitrate salt solutions. The powders were cold pressed and presintered in air for 2 to 6 h within the temperature range of 1100 °C and 1300 °C. Hot isostatic pressing was performed for 2 to 3 h within the temperature range of 1150 °C to 1350 °C in argon pressure of 150 MPa. Fully dense pellets with grain size of 22 nm to 45 nm were formed by application of low presintering temperatures.

Epitaxially grown (Ba, Sr)TiO3 thin films were prepared on (100)MgO and (100)Pt ║ (100)MgO substrates by molecular chemical vapor deposition (MOCVD). The lattice parameter increased with increasing Ba/(Ba + Sr) ratio in the film and was higher than the reported value for bulk (Ba, Sr)TiO3. The dielectric constant at room temperature reached the maximum value at a lower Ba/(Ba + Sr) ratio compared to the reported one for bulk (Ba, Sr)TiO3. The temperature showing the maximum dielectric constant was higher than the reported value for bulk (Ba, Sr)TiO3. These results can be explained by the compressive stress applied to the film under the cooling process after the deposition.

This paper discusses the influence of the synthesis technique on the porous structure, phase transformation, and catalytic properties of barium hexaferrite. Barium hexaferrite was synthesized by two different citrate gel methods. The first one involved metal salts, citric acid, and ammonia, while the second dispersed the same components in a polyacrylamide gel. X-ray diffraction analysis was used to determine the nature of the phase while the Brunauer, Emmett, and Teller (BET) analysis was used to study the porous structure of the material which were heat-treated at 700 °C, 900 °C, and 1200 °C. The catalytic activity of all materials in the combustion of methane was also measured.

The study of submicroscopic particles in already known systems has resulted in a renewed interest due to the large differences found in their properties when the particle size is reduced, and because of possible new technological applications. In this work we report the preparation of LaFeO3 particles by the sol-gel route, starting from a solution of the corresponding metallic nitrates and using urea as gelificant agent. Gels were decomposed at 200 °C and calcined 3 h at several temperatures, T, in the range 250–1000 °C. The samples were structurally characterized by x-ray diffraction (XRD) showing that the orthoferrite crystallizes at T as low as 315 °C. From the x-ray diffraction peak broadening, the particle size was determined. The size increases from 60 to 300 nm as the calcination T increases. Infrared spectroscopy was used to characterize gels and calcined samples. From these studies a mechanism for the gel formation is proposed. Study of the magnetic properties of LaFeO3 particles shows the presence of a ferromagnetic component which diminishes as the calcination temperature increases, vanishing at T = 1000 °C.

X-ray photoelectron spectroscopy has been used to examine the chemical states of fluorine in the glasses of composition xCaF2(50 – x)CaO · 50SiO2 (x = 5, 10, 15, 20, and 25 mol %) and xCaF2(50 – x/2)CaO(50 – x/2)SiO2 (x = 5, 10, 15, and 20 mol %). The analysis of the F1s spectra indicated that Ca2+ and F- ions introduced as CaF2 are favorably located among the Si–O skeleton forming Ca–F clusters. The fraction of the bridging and nonbridging oxygen atoms was derived from the O1s spectra, and the network of the fluorine-containing glasses was concluded to depend only on the ratio CaO/SiO2.

The present paper reports data concerning magnesia samples obtained by calcination of different precursor salts at different increasing temperatures (873–1253 K). The oxides are characterized by x- ray diffraction, scanning electron microscopy, and N2 adsorption at subcritical temperatures. The samples appear to be composed, at any temperature, of pure periclase with a degree of crystallinity which increases with the temperature of calcination. Morphologically, the products have the shape either of lamellas or of cubes of variable dimensions, depending on the nature and route of preparation of the precursor salts. The variation of the specific surface area and the degree of porosity with the nature of the precursors and the temperature is discussed.

The crystallography, microstructures, and phase transformation mechanisms in dysprosia (Dy2O3) have been studied. The lattice parameters of B and C phases were refined by x-ray diffraction (XRD). The modulated structures and decomposed structures in the CaO-doped samples were characterized by transmission electron spectroscopy (TEM). A new twin was observed in the modulated B phase. Contrary to the previous studies, the B to C transformation was induced by grinding. The A to B transformation was considered to be ferroelastic and the spontaneous strain was calculated. The major driving force for the B (monoclinic) to C (cubic) transformation is suggested to be the release of lattice strains and cation charge repulsions in the B structure, which is analogous to the β (monoclinic) to γ (orthorhombic) transformation in Ca2SiO4. This transformation can be displacive, if some conditions are provided to overcome the bonding energy of the interlayer oxygens in the B structure.

A kaolinite-organic intercalation compound containing methanol was proved to be a versatile host for further displacement reaction with alkylamines. Kaolinite-organic intercalation compounds with polar molecules, such as N-methylformamide (NMF) and formamide, were used as the starting materials. After stirring the kaolinite-NMF intercalation compound with methanol, the basal spacing increased to 1.11 nm. The 13C MAS NMR result of the product indicated that methanol was intercalated into kaolinite by partial displacement with NMF. By use of the methanol-treated kaolinite intercalation compound as the intermediate, alkylamines were intercalated into the interlayer space of kaolinite by displacing with methanol.

By systematically varying the carbon content, chamber pressure, arc current, and blowing gas velocity in a tungsten-arc encapsulation setup, the effects of each of these variables on the encapsulation of nickel in graphite layers were observed. The data from these optimally designed experiments revealed that the properties of the arc translate into changes in the encapsulated product. Specifically, a larger, hotter arc results in more encapsulation in the final sample. These findings, along with evidence of graphite layers which have formed on precrystallized particles, indicate that the graphite layers may form by two sequential formation steps. The first step is the simple phase segregation of carbon from a cooling liquid particle, resulting in surface graphite. The second step is the growth of carbon on a crystallized nickel particle, regardless of the temperature at which this occurs. The proposed formation mechanism has significant implications for both a scientific understanding of the encapsulation phenomena, and possible commercial applications.