This study investigates the use of the environmentally benign precursor tri(dimethylamino)silane (TDMAS) with NH3 to synthesize silicon nitride films by low pressure chemical vapor deposition. The growth kinetics are investigated as a function of deposition temperature, total pressure, and NH3/TDMAS flow ratios. The deposits are found to be essentially stoichiometric and to contain ∼5 at. % carbon when appropriate NH3 concentrations are present. The films are found in all cases to be amorphous and highly tensile. For optimized processing conditions, values of the refractive index are close to those reported for Si3N4. The film density is observed to increase with higher deposition temperatures up to 800 °C and then decrease due to the onset of gas phase nucleation effects. This behavior is readily reflected in the etch rate of those films. FTIR spectra reveal the presence of hydrogen even at high deposition temperatures (900 °C). Hardness and Young's modulus of the films are seen to increase with higher deposition temperatures, reaching saturation values near 20 and 185 GPa, respectively, above 800 °C.

As-deposited Al contacts were ohmic with a room-temperature contact resistivity of 8.6 × 10−5 Ω · cm2 on Ge-doped, highly n-type GaN (n = 5 × 1019 cm−3). They remained thermally stable to at least 500 °C, under flowing N2 at atmospheric pressure. The specific contact resistivities (ρc) calculated from TLM measurements on as-deposited Al layers were found to range from 8.6 × 10−5 Ω · cm2 at room temperature and 6.2 × 10−5 Ω · cm2 at 500 °C. Annealing treatments at 550 °C and 650 °C for 60 s each under flowing N2 resulted in an overall increase of contact resistivity. Cross-sectional, high-resolution electron microscopy (HREM) revealed that interfacial secondary phase formation occurred during high-temperature treatments, and coincided with the degradation of contact performance. Electron diffraction patterns from the particles revealed a cubic structure with lattice constant a = 0.784 nm, and faceting occurring on the {100} faces. Spectroscopic analysis via electron energy loss spectroscopy (EELS) revealed the presence of nitrogen and small amounts of oxygen in the Al layer, but no appreciable amounts of Ga. The results of microstructural and crystallographic characterization indicate that the new interfacial phase is a type of spinel Al nitride or Al oxynitride.

Positive temperature coefficient of resistivity barium titanate ceramic is a semiconductor at room temperature, so it is self-heated under certain applied voltage, and then changes into an insulator. The electrical breakdown has been investigated with the resistance-temperature characteristics of the three samples which have different compositions. The grain size effect on the breakdown voltage also is discussed. As the applied voltage increased, the electrical breakdown was initiated when the specimen interior was heated above the temperature corresponding to the maximum resistance on the resistance-temperature curves by joule heat.

The PbO/MoO3 system with 47%: 53%, 53%: 47%, and 50%: 50% molar ratios at various processing temperatures has been studied with x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and differential thermal analysis (DTA) methods. It is found that in addition to the crystallization of primary PbMoO4 phase, subphases such as Pb2MoO5 and PbMo2O7 are also formed. The remaining PbO and MoO3 are detected at certain stages of the thermal process due to localized powder inhomogeneity. Physical processes, such as sublimation, eutectic melting, solid to liquid, and liquid to vapor transformations are also investigated. In particular, evaporations of excessive PbO or MoO3 in the nonstoichiometric PbO/MoO3 can be correlated to thermal processing parameters. The current study has led to the following three processing guidelines to obtain stoichiometric PbMoO4: (i) for high temperature application, such as the Czochralski melt growth, it is suggested an excessive MoO3 (a few mol %) must be included and a slow heating rate should be employed; (ii) for low temperature synthesis, the stoichiometric PbO–MoO3 can be used, but with a fast heating rate; and (iii) PbO-rich PbO/MoO3 system is not recommended in PbMoO4 synthesis.

Residual stress was measured in sintered and heat-treated Fe2TiO5 samples with various grain sizes. The influence of texturing was assessed by comparing the residual stress states of samples having randomly oriented grains and highly oriented grains produced through magnetically assisted processing. The residual stress was measured with x-ray diffraction using Cr Kα radiation. Due to the significant texture and the consequential oscillations in the dφψ vs sin2ψ data, the residual stress was calculated using the Marion–Cohen method. Textured samples showed significantly lower residual stresses except when spontaneous microcracking accompanied grain growth in the randomly oriented systems. Elastic modulus measurements showed a direct correlation between the decrease in residual stress and the microcrack density.

A recently developed diol sol-gel route has been modified in order to produce multilayer PbZr0.53Ti0.47O3 films on platinized sapphire substrates. Up to 20 depositions of a 1.1 M sol were carried out leading to a final film thickness of 10 μm. A similar thickness could be achieved from 12 coatings of a more concentrated 1.6 M sol. Decomposition and crystallization of the multilayer coatings were performed using a two-stage prefiring sequence, at 350 °C and 600 °C, followed by a final firing step at 700 °C. Ferroelectric remanant polarization increased with increasing film thickness to a value of 40 μC cm−2 for a 10 μm film, with a corresponding coercive field of 30 kV cm−1; the relative permittivity of this film was ∼1000 and the dissipation factor 0.04. The thickness dependence of relative permittivity could be modeled on a simple series capacitor circuit representing the ferroelectric Pb(Zr, Ti)O3 (PZT) film and low-permittivity interface layers; but other possible contributory factors are also discussed.

Colloidal spherical particles of SiO2, Al(OH)3, and BaTiO3 of narrow size distributions were produced in a continuous static mixer tubular reactor system. Several experimental parameters, including the flow rate, reaction temperature and time, reactant concentrations, and the dimensions of the reactor, were varied in order to establish the optimum conditions required for each material. The results were compared with those obtained in batch systems. Monodispersed colloids can be generated at a rate as high as 50 pounds per day using the described laboratory scale continuous reactor.

Density, grain size, lattice parameter, and dielectric properties were measured on BaTi0.8Zr0.2O3 sintered at 1100–1600 °C. The hydrothermally prepared BaTi0.8Zr0.2O3 particles of 128 nm diameter were consolidated by filtration of 2-methoxyethanol suspensions and subsequently compressed by isostatic pressing under a pressure of 294 MPa to form a uniform microstructure of high density (52% of the theoretical density). These green compacts were sintered to a relative density of above 99% in the temperature range from 1350 to 1600 °C where rapid grain growth to above 30 μm occurred. Increase of sintering temperature was accompanied by the increase of lattice parameter and dielectric constant of BaTi0.8Zr0.2O3 at room temperature. The sintered BaTi0.8Zr0.2O3 showed a diffuse phase transition from paraelectric (higher temperature) to ferroelectric state (lower temperature) at 32 °C.

Si–N–B films have been deposited by LPCVD from SiH4/B2H6/NH3 gas mixtures. The influence of the temperature and the composition of the gas mixture on the deposition process and film properties has been investigated. At 1000 °C, for the highest ammonia flow rate (SiH4 :B2H6 : NH3, 10 : 25 : 500), a mixture of turbostratic boron nitride and silicon nitride was deposited. For decreasing ammonia flow rates the Si–N–B ternary system was formed (1260 cm−1 band in the infrared spectra), which co-exists with the unstable turbostratic boron nitride structure. Finally, for a low NH3 flow rate of 100 sccm, stable amorphous films are obtained. On the other hand, at 800 °C, stable films with a high content in the ternary Si–N–B compound were obtained for a wide range of ammonia concentrations (100–500 sccm). At this temperature (800 °C), the composition of the films, as measured by Auger and photoelectron spectroscopies, strongly depends on the [SiH4]/[B2H6] ratio in the gas mixture. The improvement in the mechanical and chemical properties of the samples has been associated with the increase in the content of Si–N bonds in the Si–N–B films.

A family of sealant materials has been developed for use in the solid oxide fuel cell (SOFC) and in other applications in the temperature range of 800–1000 °C. These materials are based on glasses and glass-ceramics in the SrO–La2O3–Al2O3–B2O3–SiO2 system. The coefficients of thermal expansion (CTE) for these materials are in the range of 8–13 × 10−6/°C, a good match with those of the SOFC components. These sealant materials bond well with the ceramics of the SOFC and, more importantly, form bonds that can be thermally cycled without failure. At the fuel cell operating temperature, the sealants have viscosities in the range of 104–106 Pa-s, which allow them to tolerate a CTE mismatch of about 20% among the bonded substrates. The gas tightness of a sample seal was demonstrated in a simple zirconia-based oxygen concentration cell.

BaTi4O9 and PbxBa1−x Ti4O9, where x is 0.1, 0.2, 0.3, 0.4, or 0.5, have been prepared by a combustion synthesis process. The process starts with spray drying aqueous solutions of Pb(NO3)2, Ba(NO3)2, TiO(NO3)2, and β-alanine with appropriate ratios. Combustion reactions occur when heating the spray-dried products to 300 °C, which convert them to BaTi4O9 and PbxBa1−xTi4O9 directly. PbxBa1−xTi4O9 (x ≧ 0.1) are low temperature, metastable phases and have not been reported before. Pb0.5Ba0.5Ti4O9 is unstable above 800 °C and cannot be sintered. All PbxBa1−xTi4O9 compositions will decompose by 1300 °C, the temperature for solid state synthesis of BaTi4O9. Single-phase PbxBa1−xTi4O9 (x = 0.1, 0.2, 0.3, 0.4), however, have been sintered at relatively lower temperatures.

The isopropyl alcohol gas sensitivity of LaCrO3 at 250 °C is found to depend on the amount of TiO2 content and cation stoichiometric ratio of the sample. The gas sensitivity enhancement is related to the defect structure and electrical conduction behavior of p-type, donor-doped semiconductive oxides. The high resistivity coupled with the increasing point defects by the donor dopants are responsible for the high gas sensitivity of TiO2 doped LaCrO3. It is believed that the positively charged ionic-type defects created by dopants act as trapping sites to adsorb oxygen.

Powder x-ray diffraction (XRD) and Raman evidence are presented for the formation of crystalline diamond in the “hydrothermal” pressure-temperature regime 1–5 kbars, <1000 °C. Two different methods appear to enable diamond to nucleate and grow. One—a Low Pressure Solid-State Source (LPSSS) route—utilizes special solid precursors, especially low temperature glassy carbon (GC-500), with very fine diamond seeds in sealed gold capsules with H2O at, say, 800 °C and 1 kbar. The other includes pyrolysis of highly selected organic solid/liquid precursors (halogenated aliphatics such as iodoform) onto similar diamond seeds. In all the cases, powder x-ray diffraction evidence shows a marked increase of the diamond XRD peaks, likewise the Raman spectrum shows a strong increase of the 1331 cm−1 line. However, the crystals apparently are too small to be seen in the SEM. TEM diffraction data, on the other hand, seem to lend support to the possibility of all the grown diamonds being very small.

Particle packing techniques employing a liquid phase were used for preparation of dense disks of SiC and diamond particulates. Forty-one SiC and fifteen diamond compositions in the ternary-component particle systems were used to determine the optimum percentages of coarse, medium, and fine particles for achieving high packing densities: over 80% for SiC and over 62% for diamond. High packing densities were achieved without vibration by simply mixing the three size fractions in ethanol followed by stirring during the initial evaporation stage. The packing density results for SiC were successfully correlated with the percentages of the coarse and fine particles using multiple regression analysis; however, the data for diamond could not be similarly correlated with particle composition because the experimental work was done in a narrow range of compositions and the range of packing densities was small.

The coprecipitation technique has been used to prepare ZrO2 (Y2O3 3 mol %) nanopowder. The influence of residual NH4Cl and pH value on the crystallization of ZrO2 (Y2O3 3 mol %) nanopowder have been investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), x-ray diffraction (XRD), infrared spectrometry (IR), and transmission electron microscopy (TEM) techniques. The IR spectra proved that the presence of residual NH4Cl increased the amount of the hydroxo group. This led to serious gel agglomerate and free enthalpy decrease. Therefore, the crystallization of ZrO2 (Y2O3 3 mol%) nanopowder is greatly influenced by the residual NH4Cl. While there is no residual NH4Cl, the crystallization takes place at 445 °C and is an exothermic process. On the contrary, with NH4Cl the crystallization takes place at 376 °C and is an endothermic process. However, the pH value does not influence the crystallization of ZrO2 (Y2O3 3 mol%) nanopowder.

Microstructure, microchemistry and mechanical properties of hardened macro-defect-free (MDF) composites processed at various rotor rates in a Banbury mixer were investigated. A quiescently formed calcium aluminate-polyvinyl alcohol composite served as a substitute for an unmixed system. Results from the Banbury studies in conjunction with microchemical analysis of the unmixed composite showed evidence that the polymer-particle interaction is a mechanically induced crosslinking reaction. The rate of the mechano-chemistry increases with mixing speeds. Scanning electron micrographs (SEM) and transmission electron micrographs (TEM) of hardened composites mixed for 15 min at 30, 50, 100, and 200 rpm indicate that much of the mechanical strength of MDF is due to the crosslinked interphase zones that blanket the cement grains. Stresses in the paste due to mixing can destroy the interphase layer, leading to a weaker hardened composite. Microchemical analysis revealed that the mechano-chemistry of the system did not vary with changes in the mixing conditions studied.

Conductive SrRuO3 thin films were epitaxially grown on (100) LaAlO3 substrates by pulsed laser deposition over a temperature range from 650 °C to 825 °C. Well-textured films exhibiting a strong orientation relationship to the underlying substrate could be obtained at a deposition temperature as low as 450 °C. The degree of crystallinity of the films improved with increasing deposition temperature as confirmed by x-ray diffraction, transmission electron microscopy, and scanning tunneling microscopy. Scanning electron microscopy revealed no particulates on the film surface. The resistivity of the SrRuO3 thin films was found to be a strong function of the crystallinity of the film and hence the substrate temperature during film deposition. A residual resistivity ratio (RRR = ρ300 K/ρ4.2 K) of more than 8 was obtained for the SrRuO3 thin films deposited under optimized processing conditions.

Phase transformations, including chemical vapor deposition (CVD) of diamond, taking place by nucleation and growth are commonly described by Avrami or Johnson-Mehl type models. In order to avoid the restrictions of such models with respect to assumptions concerning nucleation rates and growth velocities, the variation with time of nucleation and growth of diamond particles during the deposition of microwave plasma-assisted CVD was studied. The size distributions obtained from image analysis enabled us to trace back details of the nucleation and growth history. Three sources of particle formation were operating during deposition. A general growth law suitable for all particles did not exist. These observations limited the applicability of Avrami-type models to describe space filling. Computer simulation of surface coverage and particle growth was successful because one particular mode of particle formation and growth dominated surface coverage. Based on image analysis and the determination of the film growth rate, the evolution of the diamond volume fraction with time, starting from three-dimensional particle growth followed by a continuous transition to one-dimensional film growth, was described.

A parametric study of titanium silicide formation by rapid thermal processing was conducted to determine the effects of annealing temperature (650 °C, 750 °C), annealing time (30 s, 60 s), wet etching (no HF dip, with HF dip), sputter etching (no sputter etch, with sputter etch), and annealing ambient (Ar, N2) on the completeness of conversion of 60 nm Ti on (111)-Si to C54–TiSi2 based on sheet resistance and the uniformity of the sheet resistance measurements across the entire wafer. Statistical analysis of the results showed that temperature, annealing ambient, and sputter etching had the greatest influence. Increasing the temperature and using argon gas instead of nitrogen promoted conversion of the film to C54–TiSi2. On the other hand, sputter etching retarded it. The results also indicated significant interactions among these factors. The best uniformity in sheet resistance was obtained by annealing at 750 °C without sputter etching. The different sheet resistance profiles showed gradients that were consistent with expected profile behaviors, arising from temperature variations across the wafer due to the effect of a flowing cold gas and the effects of the wafer edge and flats.

Inversion domain boundaries (IDB's) in ZnO ceramics, associated with Sb2O3 doping, have been characterized using a range of electron microscopy techniques. The IDB's lie primarily on basal planes, but frequently are stepped along prismatic planes. The basal IDB can be characterized as (i) an inversion that causes an antisite exchange of cations and anions across the boundary, (ii) an effective displacement of the sixfold screw axis in the wurtzite structure vectors by a translation of 1/3 and (iii) a displacement normal to the boundary. Significant Sb segregation is detected in the basal IDB segments in agreement with previous work, and in ceramics doped with Sb2O3 and Bi2O3. These IDB's contained both Sb and Bi, suggesting that while Bi does not participate in IDB nucleation, it resides in the boundary. Comparison of experimental and calculated HREM images suggests that the IDB is composed of a monolayer of Type I (111) zinc antimonate spinel, consisting of a single layer of octahedrally coordinated zinc and antimony cations.