We have studied the crystal structure and the dielectric properties of a scries of Bi-based ceramic compositions as a function of compositional variation and sintering temperature. These dielectrics have dielectric constants hetween 70 and 165 and their temperature coefficients are within ±500 × 10−6/°C. The precise temperature coefficient can be controlled via compositional changes such that dielectrics with temperature coefficients within ±50 × 10−6/°C are easily obtainable. The room temperature dissipation factor is smaller than 0.001 or equivalently, the Q value is greater than 1000. The electrical resistivity is greater than 1014 ohm-cm. Furthermore, these dielectrics are sinterable below 960 °C, rendering it possible to use silver or high silver metallization as the internal electrode in making the multilayer ceramic capacitors.

A new butt joining method for ceramics by microwave heating was developed. Ceramics were heated in a rectangular cavity, and a klystron of maximum 3 kW at 6 GHz was used as the power amplifier. The heating system can control an iris, a plunger, and the microwave power to maintain the power efficiency up to 90% and the accuracy within ±10°C at 1800 °C. This system was applied to alumina-alumina direct joining. The average strength of alumina rods (92% purity) joined for 3 min was 420 MPa, which was equal to the original strength. The joined boundary line at the interface was not observed, and there was little difference in microstructure between before and after joining. This suggests that sintering aids in the grain boundary phase were preferentially heated and melted, resulting in the sound joining of ceramics. Next, silicon nitride ceramics containing yttrium were indirectly joined with an intermediate, which was a sintered ceramic sheet having lower purity and larger dielectric loss factor than the base material. The microwave energy was concentrated on the ceramic sheet, so that only the joining area was locally heated. The strength of the joined rods was in excess of 70% of the base material, but a deficient layer of yttrium occurred in the area of the joined boundary.

Nanoindenter techniques have been used to determine the hardness. Young's modulus, and strain rate sensitivity of nanophase TiO2, which is currently available only in very small quantities and which cannot be tested by most conventional techniques. Hardness and Young's modulus both increase linearly with sintering temperature over the range 25–900°C but come to within only 50–70% of the single crystal values. Strain rate sensitivity, on the other hand, is measurably greater for this material than for single crystal rutile, and the value of strain rate sensitivity increases as the grain size and the sintering temperature are decreased. In its as-compacted form, the strain rate sensitivity of nanophase TiO2 is approximately a quarter that of lead at room temperature, indicating a potential for significant ductility in these ceramic materials. Finally, a significant scatter in hardness values has been detected within individual nanophase samples. This is interpreted as arising from microstructural inhomogeneity in these materials.

Dense polycrystalline thin films of ZrO2 (3 and 8 mol % Y2O3) were produced by the pyrolysis of zirconium acetate precursor films, which were deposited on single crystal Al2O3 substrates by spin-coating aqueous solutions of zirconium acetate and yttrium nitrate. Dense films were heat treated to encourage grain growth. With grain growth, these films broke into islands of ZrO2 grains. Identical areas were examined after each heat treatment to determine the mechanism that causes the polycrystalline film to uncover the substrate. Two mechanisms were detailed: (a) for a composition which inhibited grain growth and produced a polycrystalline film with very small grains, the smallest grains would disappear to uncover the substrate, and (b) for a composition which did not inhibit grain boundary motion, larger grains grew by enveloping a smaller grain and then developed more spherical surface morphologies, uncovering the substrate at three grain junctions. In both cases, the breakup phenomenon occurred when the average grain size was larger than the film thickness. Thermodynamic calculations show that this breakup lowers the free energy of the system when the grain-size-to-film-thickness ratio exceeds a critical value. These calculations also predict the conditions needed for polycrystalline thin film stability.

Transmission electron microscopy observations were conducted on some zwitterionic polymers. Our observations were concentrated on the morphology of the solid state of poly (4-vinyl pyridine-sulfopropyl bctaines), with different degrees of quaternization. Among the morphological features, a microstructure arising from aggregated regions in the range of 50 to 200 Å is observed. Quite striking is the fact that this structure is absent in the micrographs for the base polymer, indicating that the aggregates are due to the interactions of the ion pairs of the polyzwitterions, as in the ionomer case. It is also found that the density of the aggregates increases when we increase the zwitterionic content of the copolymers.

The estimated bulk moduli and Poisson's ratio of binary, ternary, and quaternary rare earth tellurite glasses have been calculated using the bond compression model according to the cation-anion bond of each oxide present in the glass. Information about the structure of the glass can be deduced after calculating the number of network bonds per unit volume, the value of the average stretching force constant, the average ring size, the structure sensitivity factor, and the mean crosslink density. Comparisons between the calculated and the experimental elastic moduli and Poisson's ratio have been carried out. Also, the longitudinal and shear elastic stiffnesses of binary rare earth tellurie glasses are compared and analyzed with those of other binary rare earth glasses.

Transmission electron microscopy (TEM) was used to investigate the nanostructure of sputter-deposited MoS2 films; these films represent the early stages of growth under deposition conditions that produce a zone 2 columnar morphology. Analysis reveals that the early-growth film morphology consists of anisotropic (plate-like) islands in which the (001) basal planes are generally perpendicular to the substrate (forming “edge islands”) or parallel to the substrate (forming “basal islands”). Within the context of an active-sites nucleation model, localized regions of the substrate surface can lack the active sites needed to induce edge orientation. The edge islands evolve into the zone 2 morphology, shadowing and inhibiting the continued growth of the basal islands. Basal plane (002) lattice image curvature and kinking were observed in the edge islands. Dark-field analysis showed intensity variations within the edge islands. The edge island plates appear to be imperfect crystals of aligned basal planes. These crystals can bend, kink, or twist, apparently because of variations in local growth conditions. The ability of crystal growth to deviate has implications for the morphological evolution of thicker films. The ability of the MoS2 crystal lattice to bend supports the idea that localized deviation can occur during sliding wear.

Solutions of zirconyl salts can be treated in a variety of ways to precipitate hydrous amorphous ZrO2. The phases formed upon heating these precipitates are described and rationalized based upon a theory of hydrolytic polymerization which had been proposed at an earlier stage.

Oxidation kinetics of microwave plasma assisted CVD diamond and diamond-like carbon (DLC) films in flowing oxygen were evaluated in the temperature range of 500 to 750 °C and were compared with those of graphite and natural diamond. The diamond and DLC films were prepared using CH4/H2 ratios of 0.1, 0.25, 0.5, 1.0, and 2.0%. The films deposited at 0.1% ratio had a faceted crystalline structure with high sp3 content and as the ratio increased toward 2%, the films contained more and more fine crystalline sp2 bonded carbon. The oxidation rates were determined by thermal gravimetric analysis (TGA), which shows that the films deposited at ratios of 2, 1, and 0.5% oxidized at high rates and lie between the rates of natural diamond and graphite. The oxidation rate decreased with lower CH4/H2 ratio and the films deposited at 0.25 and 0.1% exhibited the lowest oxidation rates associated with the highest activation energies in the range of 293–285 kJ/mol · K. The oxidation behavior of microwave plasma assisted diamond films was similar to that of DC plasma assisted CVD diamond films. The results suggest that the same mechanism of oxidation is operational in both DC and microwave plasma assisted diamond films and is probably related to the microstructure and preferred orientation of the crystallites.

The relation between the oxygen adsorption and the voltage dependence of the resistor (VDR effect) in (Sr, Ca)TiO3−x based ceramics has been investigated. The nonlinearity of the voltage-current characteristics increased with increasing the barrier height, which is thought to be generated by the oxygen chemisorption. Acceptor type trap levels were detected by means of a zero biased DLTS technique at high temperatures. These interfacial energy levels changed with reoxidizing temperatures, and the change can be explained by the degradation of the chernisorbed oxygen. The high temperature type of the chemisorbed oxygen as O2− and O is relatively stable due to the strong pinning effect of trapped electrons, with reoxidizing anneals of grain surfaces above the oxidation temperature, and it contributes greatly to the VDR effect. It is concluded that energy barriers are caused by the interface states generated by the chemisorbed oxygen on grain surfaces and that they determine the VDR effect.

The oxygen-related defect in an aluminum nitride (AIN) single crystal and in polycrystalline ceramics is investigated utilizing photoluminescence spectroscopy, thermal conductivity measurements, x-ray diffraction lattice parameter measurements, and transmission electron microscopy. The results of these measurements indicate that at oxygen concentrations near 0.75 at.%, a transition in the oxygen accommodating defect occurs. On both sides of this transition, simple structural models for the oxygen defect are proposed and shown to be in good agreement with the thermal conductivity and lattice parameter measurements, and to be consistent with the formation of various extended defects (e.g., inversion domain boundaries) at higher oxygen concentrations.

The joining of aluminum nitride by active metal brazing with a Ag–Cu–Ti foil has been investigated in cross section by transmission electron microscopy. The reaction of AIN with the braze alloy results in the formation of continuous TiN and (Ti, Cu, Al)6N (η-phase) layers at the interface. AIN grains at the interface often display arrays of dislocations, presumably arising from thermal expansion mismatch between the AIN and the TiN (the coefficients of thermal expansion are 43 ⊠ 10−7/°C and 80 ⊠ 10−7/°C, respectively). The adjoining TiN contains small Cu precipitates and may also contain numerous defects. Titanium preferentially penetrates the AIN grain boundaries, resulting in finger-like TiN intrusions into the substrate, which sometimes cover entire AIN grains in a TiN shell. On the other side of the TiN, a continuous layer of equiaxed, defect-free η–nitride grains is found. Beyond this η–nitride layer is the remaining mixture of metallic Ag and Cu. High-resolution electron microscopy demonstrates that the AIN–TiN and TiN–η boundaries are abrupt and contain no additional crystalline or amorphous intervening phases. Particular orientation relationships are occasionally observed at the AIN–TiN interface; these are not always the ones that produce the minimum lattice mismatch. The implications of the observed morphology with respect to the reaction sequence, transitional phases, and structural integrity of the joint are discussed.

Spherical and rod-like SnO2 particles of narrow size distribution have been obtained by aging at 100°C acidified tin(IV) chloride solutions in the presence of urea or formamide. It was shown that spherical particles, the x-ray diffraction of which was characteristic of cassiterite, consisted of a large number of much smaller subunits. The rod-like particles had the same structure, but of higher degree of crystallinity. Infrared spectra of these powders were evaluated in terms of the theory of the average dielectric constant (TADC), in order to gain additional information on the particle morphology and the state of aggregation.

From a number of studies on ferroelectric and related materials based on complex lead perovskites [Pb(Bx′B1−x″)O3], it is apparent that the B-site cation order influences the crystallography, phase transitions, and other physical properties. A classification of complex lead perovskites is presented based on the relative scale of long-range cation order. In particular, we discuss the implications of cation order in relation to relaxor and normal ferroelectric behavior.

The pyrolysis process of polytitanocarbosilane, precursor for SiC/TiC ceramics, has been followed step by step using x-ray photoclectron spectroscopy. This study shows that Ti–O bonds, present in the precursor, are stable up to 700 °C. Above this temperature, Ti–C bonds, precursor for TiC network, start to form. From a detailed analysis of Ti(2p) and Si(2p) peaks, the formation of intermediate species such as SiCxOy and TiCxOy has been detected.

Aerosol droplets of a dilute aqueous solution of Ni(II) and Fe(III) nitrates were used to synthesize fine nickel ferrite powders by pyrolysis at temperatures ranging from 450 °C to 810 °C. The aerosol product was characterized by thermal analysis, x-ray diffraction, scanning electron microscopy, and BET surface area determination. At low temperature (480 °C), very active fine, hollow, noncrystalline spheres were formed. As the pyrolysis temperature increased, sintering occurred, larger particles with broader size distribution were obtained, and a higher degree of crystallinity of nickel ferrite was produced. The products at pyrolysis temperatures of 660 °C and above exhibited magnetic properties. The powders prepared from the aerosolization process at low temperatures had high reactivity and crystallized rapidly. The effect of the initial solution concentration was also studied, and dilute solutions produced spheres with fine size and narrow size distribution.

The fracture toughness of a macro-defect-free (MDF) cement was calculated from two measurement techniques: (1) indentation-strength method and (2) fracture surface analysis (FSA). It was found that the indentation-strength method, which showed good agreement with FSA, was applicable for estimating the fracture toughness of MDF cement. The ultimate toughness was found to be 1.25 MPa m1/2 for this MDF cement, which contained 3 wt. % polymer. An R-curve (crack-growth-resistance) bchavior was also observed. Scanning electron micrographs showed extensive microcracking on the fracture surface. Microstructural effects are discussed.

A new miniature Surface Forces Apparatus (SFA Mark III) is described for measuring the forces between surfaces in vapors and liquids. The apparatus employs similar techniques to those used in current SFAs, but it is easier to operate and is generally more user-friendly. Four stages of increasingly sensitive distance controls replace the three control stages of previous apparatuses. The first three stages allow for rapid manual control of surface separation to within 10 Å, while the fourth piezo-control stage has a sensitivity of better than 1 Å. All four distance controls have been specially designed to produce perfectly linear displacements of the surfaces. In addition, the SFA Mk III is more robust, less susceptible to thermal drifts, easier to clean, and requires smaller quantities of liquid than conventional SFAs. The high performance of this new instrument is illustrated in the succeeding paper (Part II), which describes the subtle effects of surface lattice mismatch on the oscillatory forces in water in the distance regime from 0 to 10 Å.

Hard amorphous hydrocarbon films have been deposited by RF glow discharges in methane/hydrogen mixtures with different hydrogen isotopes. For CH4 + D2 and CD4 + H2 gas mixtures, the film growth rate, the density, the refractive index, and the isotopic hydrogen content are obtained as functions of the process gas composition. Further, the hydrogen loss induced by 15 keV helium ions is studied. The results are qualitatively interpreted in terms of different effects of ion bombardment during film deposition which influence the properties of the resulting films.