We have prepared a series of SnxSiO2)100−x granular metal films by RF magnetron sputtering with nominal Sn compositions from x = 30 to x = 90 at. %. X-ray diffraction and transmission electron microscopy measurements confirm that these films consist of small Sn particles, ranging from about 10 nm to 200 nm in mean diameter, embedded in an amorphous SiO2 matrix. These measurements also indicate that the mean Sn particle size decreases and the particle size distribution becomes more narrow as the Sn concentration is reduced. A differential scanning calorimeter has been used to study the size dependence of the melting temperature of the Sn particles. The melting temperature has been found to be increasingly depressed from the bulk value as the Sn particle size decreases. No evidence of an enhancement in the melting temperature at any particle size has been found. The evolution of the melting behavior of each sample with repeated melting and solidification cycles has also been studied.

Homogeneous and stoichiometric PbTiO3 and PbZr0.52Ti0.48O3 gel fibers were drawn from viscous solutions prepared by sol-gel processing of alkoxide precursors. The fibrous gels on heating at 450 and 600 °C, respectively, formed the well-crystallized phases of PbTiO3 and PbZr0.52Ti0.48O3. Fibers heat treated at 700 °C are a few centimeters long and 50 to 150 μm in diameter. PbZr0.52Ti0.48O3 fibers subjected to heat treatment at 700 °C for 1 h consisted of fully dense submicron grains (0.15 to 0.2 μm). However, PbTiO3 fibers under analogous conditions showed a few micropores with grains of ∼0.1 μm. Dielectric constants of these PbTiO3 and PbZr0.52Ti0.48O3 fibers were approximately 300 and 800, respectively.

Both natural and synthetic crystals of pyrite, FeS2−x, have been analyzed chemically and examined structurally by transmission electron microscopy and x-ray powder diffraction. Chemical analysis and density measurements have shown the synthetic crystals, grown at 850 K, are frequently deficient in sulfur, with a composition of FeS2−x with x ⋚ 0.15. From a refinement of the pyrite structure using the integral intensities of the x-ray powder pattern, a variation in the sulfur population parameter was obtained ranging from 0.87(2) to 1.03(3). A correlation according to Vegard's rule between the population factor and the lattice parameter a0 has been proven. Transmission electron microscope examination revealed that the crystals did not contain a significant population of disorder defects which may account for this apparent sulfur deficit. Therefore the nonstoichiometry in pyrite has to be interpreted in terms of S vacancies which can be understood as the tendency of the material to reduce the high anion content in the unit cell. The structural nature of nonstoichiometric pyrite is discussed in relationship to other related disulfides.

Layered perovskites (Ruddlesden–Popper phases), (CaxSr1−x)n+1 TinO3n+1 with n = 3, ∞ and x ranging from 0 to 1, have been investigated by XPS and XAES. The structural transitions, identified in other studies, have been correlated with changes in the chemical environments of the constituent species. In particular, the tetragonal to orthorhombic transition at x = 0.65 ± 0.1 appears to generate nonequivalent cation environments for the alkaline earth species in (Ca, Sr)O12 coordination. Other binding and kinetic energy shifts can be correlated with changes in and distortions of unit cell volumes.

With the aim of identifying effective dispersants that would yield stable, high solids loading (≥60 vol.%) suspensions of oxides, carbides, or nitrides in nonaqueous carriers such as paraffinic oils, a number of dispersants were evaluated, using in most cases A16SG grade alumina from Alcoa as the filler. Among those evaluated were some common dispersants, such as menhaden fish oil and oleic acid, and commercial dispersants not commonly used in ceramic processing, such as polymeric fatty esters and petroleum sulfonates. More importantly, a few dispersants were synthesized and evaluated. The latter dispersants contained straight or cyclic (benzenic) side chains located far from the head group on 18 carbon main-chain fatty acid molecules. Among these, the dispersants with a 5–10 carbon side chain or with a benzenic side chain yielded very fluid suspensions (≥60 vol.%) compared to those with long polymeric or oligomeric side chains, or with no side chains, or the commercial dispersants; in some cases, for the same solid loading, the suspension viscosities were an order of magnitude lower with the synthesized side chain dispersants. These results indicate that molecules with an optimum side chain length located sufficiently far from the head group and an optimum backbone (main chain) constitute the most effective dispersants for concentrated suspensions. By combining the advantages provided by wider particle size distributions and by these effective dispersants, suspensions highly concentrated (up to 74 vol.%), and yet processable and “flowing” paste-like have been prepared.

The effect of starting materials purity, crucible material, and melting conditions on the optical scattering of AlF3-based glasses has been investigated. Platinum and vitreous carbon crucibles have been used to melt the glasses under nitrogen and reactive atmosphere (RAP) conditions. The optical quality of the bulk glass was evaluated by molecular light scattering in the Mie and Rayleigh regimes as a function of scattering angle and polarization at 0.647 μm. From an analysis of the angular scattering of both vertically and horizontally polarized beams, the sizes of the scattering sites have been estimated to be in the range of 0.02 to 2.0 μm. Glasses made with EM (BDH Limited) materials and melted in platinum crucibles without any reactive atmosphere exhibit lower values of scattering losses than those melted in the vitreous carbon crucibles under RAP.

Lead zirconate titanate (PZT) thin films were prepared by excimer laser ablation on platinum coated silicon substrates. The composition of the films showed dependence on the fluence at low energy densities (<2 J/cm2), and less dependence on the ablation fluence was observed beyond a fluence of 2 J/cm2. A correlation among the fluence, ablation pressure, and substrate temperature has been established. Crystalline perovskite PZT films showed a dielectric constant of 800–1000, a remnant polarization of 32 μC/cm2, and a coercive field of 130 kV/cm. Films showed fatigue behavior that may be used in a device, and a close comparison of fatigue behavior between the films deposited at different energy densities indicated a better fatigue behavior for a fluence of 4 J/cm2.

Since its first application to thin films in the 1950's the bulge test has become a standard technique for measuring thin film mechanical properties. While the apparatus required for the test is simple, interpretation of the data is not. Failure to recognize this fact has led to inconsistencies in the reported values of properties obtained using the bulge test. For this reason we have used the finite element method to model the deformation behavior of a thin film in a bulge test for a variety of initial conditions and material properties. In this paper we will review several of the existing models for describing the deformation behavior of a circular thin film in a bulge test, and then analyze these models in light of the finite element results. The product of this work is a set of equations and procedures for analyzing bulge test data that will improve the accuracy and reliability of this technique.

In as-sintered silicon nitride with yttria as a sintering aid, the intergranular glassy phase contains Y, Si, O, and N. Results of crystallization of partly crystalline, as-quenched melt samples containing 28–40 mol% Y2O3 in the Y2O3–SiO2 system are presented. Three different compositions were melted in tungsten crucibles at 2100 °C in 1 and 50 atm nitrogen and heat treated in air in the temperature range of 1200 to 1600 °C. Phase identification by x-ray diffraction (XRD) and transmission electron microscopy (TEM) showed crystallization to β, γ, and δ polymorphs of Y2Si2O7.

The direct energy gaps, Eg, and the indirect gaps at the X point, E(X), of GaAs and AlxGa1−xAs alloys are essentially linear functions of hydrostatic pressure, P. Recent photoluminescence measurements of Tozer et al. for InP under high pressures, however, found that Eg(P) is not quite linear, but bends down slightly at high pressures. Using the first-principles pseudofunction method, we have calculated Eg and E(X) as functions of pressure, as well as the zero-temperature equation of state P(V). Our calculated gap curve for InP, Eg(P), bends down slightly, as found in photoluminescence studies. The slope dEg/dP is 8.8 meV/kbar for small pressures P, and is in good agreement with the experimental value, 8.32 meV/kbar. The observed nonlinearity in the dependence of Eg on pressure for InP is attributed to a large derivative of the bulk modulus with respect to pressure. The calculated bond length, bulk modulus, and critical pressure for a phase transition from the zinc blende to a rocksalt structure, and the unit cell volume change at this phase transition are all in good agreement with the data.

Ceramic (Sr1−xCax)2CuO3 samples have been prepared with x = 0.00, 0.25, 0.50, 0.55, 0.75, and 1.00 in order to study the change in lattice constants with the ratio of Sr/Ca. This phase is frequently an impurity phase in the fabrication of Bi–Sr–Ca–Cu–O superconductors, and it is important to be able to connect the lattice constants with stoichiometry. The behavior of the lattice constants closely follows Vegard's law.

The effect of the interfacial thermal resistance and the laser energy density on film morphology and the extent of evaporation was studied in the excimer laser processing of copper-sapphire couples. Copper films of 80 nm thickness were sputter-deposited on sapphire substrates and laser-irradiated with energy densities in the range of 0.2 to 3.5 J/cm2. The changes in film morphology and thickness as a function of laser energy density were analyzed by energy dispersive x-ray spectroscopy. Four regimes can be established as a function of the laser energy density. First, for low energy densities up to a critical value, the film is partially removed by thermal stresses. Second, as the energy density is increased above that critical value, larger portions of the film remain attached to the substrate. In this regime adhesion enhancement takes place. Third, a further increase in the energy density results in film evaporation. Finally, the decrease in the specific mass removal rate of copper is related to the formation of a laser generated plasma that shields the sample from the incoming radiation. In this last regime, an intermediate compound may form at the substrate surface. The data were correlated with results from a computer model of the heat flow during laser processing of metal-ceramic couples.

We have calculated the mobility of electrons in n-type Mercury Cadmium Telluride (MCT) and compared it to a calculation of the mobility of electrons in n-type Mercury Zinc Telluride (MZT) with nearly the same energy gap and with the same number of donors and acceptors. We also compared the results of the MZT calculation with experiment. We found for equivalent energy gaps that the mobilities in the two compounds (MCT, MZT) were nearly the same. The calculations for both MCT and MZT were based on the best set of material parameters that we could compile from the literature. Using these parameters, the comparison with experiment for MZT yielded good results. Since MZT is harder and structurally more stable with respect to Hg retention than MCT, the possibility of equivalent mobility for MCT and MZT is significant. This calculation is one of the first extensive calculations of the mobility of MZT, and we compared it with another which appeared to be less extensive. Our calculation involves scattering of the electrons by longitudinal optic phonons, acoustic phonons, ionized impurities, holes, and compositional disorder. Since not all of these interactions can be approximated by elastic scattering, the corresponding Boltzmann equation was solved by a variational principle. We also discuss directions for future work.

To obtain quantitative details about the structure of binary tellurite glasses, the thermal properties have been measured. The thermal properties (linear thermal expansion coefficient α and transformation temperature Tg) of a set of tellurite glasses containing rare earth oxides in the form (TeO2)0.9 (AnOm)0.1 have been measured. The vitreous systems containing the rare earth cations are La, Ce, and Sm. The coefficient of thermal expansion in the range of 300–500 K and the transformation temperatures were determined to detect local structural changes that might be induced by the modifiers. The thermal properties α and Tg are discussed in terms of (i) structure, by calculating the volume of structure unit, the average crosslink density, and the average stretching force constant of each glass system; (ii) vibrations, by correlating the mean long wavelength acoustic mode Griineisen parameter γel and the expansion coefficient α.

Crack morphology in brittle materials exposed to thermal shock is studied by means of Monte Carlo simulations based on simple three-dimensional lattice systems. Thermal shock-induced crack growth is modeled as a series of processes of storage, release, and transfer of strain energies in the system of grains. Special attention is devoted to the crack pattern on the surface exposed to thermal shock and the crack penetration in the direction perpendicular to the surface. The dependences of the crack pattern and the crack penetration on the grain boundary strength and the temperature difference of thermal shock are explored through the simulations. The results of the simulations are qualitatively consistent with crack features in available experimental reports.

A structural study using x-ray diffraction and simulation calculations was performed on a–NiPS3, the highly disordered phase of the nickel thiophosphate, synthesized through a soft chemistry process. The structure of the wet gel is shown to be entirely amorphous; its x-ray pattern exhibits diffusion peaks according to the disordered anionic network. For the powdered samples, measurements of the width of the diffraction lines show that there are small crystallized c–NiPS3-type crystallites with a volume V equal to (25 × 25 × 40) Å3 (i.e., 4a × 3b × 6c in terms of volume cell). The simulation calculations of the x-ray diagrams have indicated that the stacking of these crystallites is quite imperfect: the suggested crystallite structures must contain rotated or shifted layers.

The indentation load-displacement behavior of six materials tested with a Berkovich indenter has been carefully documented to establish an improved method for determining hardness and elastic modulus from indentation load-displacement data. The materials included fused silica, soda–lime glass, and single crystals of aluminum, tungsten, quartz, and sapphire. It is shown that the load–displacement curves during unloading in these materials are not linear, even in the initial stages, thereby suggesting that the flat punch approximation used so often in the analysis of unloading data is not entirely adequate. An analysis technique is presented that accounts for the curvature in the unloading data and provides a physically justifiable procedure for determining the depth which should be used in conjunction with the indenter shape function to establish the contact area at peak load. The hardnesses and elastic moduli of the six materials are computed using the analysis procedure and compared with values determined by independent means to assess the accuracy of the method. The results show that with good technique, moduli can be measured to within 5%.

The sequence of structural evolution in the gelation of vanadic acid to form vanadium pentoxide gels was studied using cryogenic transmission electron microscopy (cryo-TEM) and scanning tunneling microscopy (STM). Small whiskers form from initially homogeneous solutions, and then grow into crystalline ribbon-like colloidal particles. It is proposed that the whiskers form from polymerization of dioxovanadium cations. The ribbons then grow by continued addition of dioxovanadium cations which are supplied by the decomposition of decavanadate ions. In solution, the ribbon-like particles have dimensions of approximately 25 nm × 3 nm × over 1 μm. These ribbons are flexible perpendicular to the plane of the ribbon. Upon drying, a flat rigid mass of ribbon-like particles is formed. The ribbons examined by STM showed striations 3 nm wide, a value that corresponds with the width of the unit cell proposed by J. Legendre and J. Livage [J. Colloid. and Interf. Sci. 94, 75 (1983)].

Porous hydroxyapatite ceramics with porosity up to 73% have been fabricated by microwave processing at 1150 to 1200 °C for 1 to 5 min. Various porosities in these ceramics have been obtained by using starting materials with different morphology, adjusting green density, changing sintering time and temperature, as well as optionally mixing ammonium carbonate in the hydroxyapatite powder during the consolidation process. Porosity, microstructure, and diametral tensile strength of the porous hydroxyapatite ceramics have been studied.