Diamond film was synthesized on thin Ti wafers (as thin as 40 μm) via hot filament chemical vapor deposition (HFCVD). The hydrogen embrittlement of the titanium substrate and the formation of a thick TiC interlayer were suppressed. A very low pressure (133 Pa) was employed to achieve high-density rapid nucleation and thus to suppress the formation of TiC. Oxygen was added to source gases to lower the growth temperature and therefore to slow down the hydrogenation of the thin Ti substrate. The role of the very low pressure during nucleation is discussed, providing insight into the nucleation mechanism of diamond on a titanium substrate. The as-grown diamond films were characterized by scanning electron microscopy (SEM), Raman spectroscopy, and x-ray analysis.

Ultrafine BaFe12O19 with uniform particle size was synthesized from an alcohol-in-oil (nonaqueous) microemulsion system where the metal ions were supplied by the surfactant (metal di-2-ethylhexylsulfosuccinate) molecules themselves. A monodisperse, fine-grained precipitate (Ba-Fe oxalate) was ensured by the steric barrier provided by the surfactant monolayer, while the nonaqueous environment promoted stoichiometric coprecipitation. Pure BaFe12O19 was obtained by calcining the oxalate precursor at or above 950 °C. Structural and magnetic properties of the resulting ultrafine magnetic material are reported.

Polysulfones, such as poly(oxy-1,4-phenylenesulfonyl-1,4-phenyleneoxy-1,4-phenyleneisopropylid-ene-1,4-phenylene), poly(phenylene ether sulfone), poly(phenylene sulfone), and aliphatic polysulfone, poly(bicycloheptene sulfone), were employed as a host resin. N-ethyl-N-hydroxyethyl-4-(4'-nitrophenylazo)phenylamine (Disperse Red 1) acted as a guest molecule and was dispersed in those hosts with a concentration of 5 wt. % to 10 wt.%. Their second harmonic generation properties were characterized and compared. Xijk values obtained varied from 11 pm/V to 21 pm/V. The merits of polysulfones as a host material are good optical clarity, easy film forming, and fairly high glass transition Tg temperature (140 °C to 190 °C). Chemically, compared to polyimides they have good resistance to moisture, i.e., less vulnerable to hydrolysis. It is a good candidate for electro-optical materials.

Ni2+ ions in aqueous solutions were electrochemically deposited within pores of alumina compacts attached to carbon or Pt electrode at room temperature. The deposition behavior of Ni metal in the pores of alumina compacts was expressed by an empirical power law equation of W = ktn, where W is the weight of Ni deposited, k the deposition rate constant, t the deposition time, and n the experimental constant (0.52-0.56). The shape of Ni deposited was dependent on the geometry of positive electrode.

MgO films and YBa2Cu3O7−δ/MgO multilayer films were developed with the pulsed organometallic beam epitaxy (POMBE) growth technique, and grain boundary junctions were fabricated from the films to demonstrate the utility of the multilayers. High-quality MgO films were grown on LaAlO3 substrates by POMBE using a Mg(dpm)2 precursor. MgO crystallinity, as assessed by x-ray diffraction rocking curves, improved with the use of CuOx or YBa2Cu3O7−δ buffer layers. YBa2Cu3O7−δ films grown on the MgO layer by POMBE exhibited a Tc0 of 83 K and a Jc (12 K) exceeding 106 A/cm2 for applied magnetic fields up to 3 × 104 G. Grain boundary junctions were formed by growing YBa2Cu3O7−δ on MgO films that had been pretreated with a simple sputtering technique. This sputtering induces a controlled, 45°grain boundary in subsequently deposited YBa2Cu3O7−δ films. The resulting boundary showed weak-link current-voltage behavior and an IcRn product of 52 μV at 10 K, demonstrating that sputter-induced grain boundary junctions are compatible with multilayer technology.

A bidirectional gradient furnace with sample displacement was used for the growth of large meet-powder-meet-growth (MPMG) YBCO samples. The optimization of the macrogranular structure with consequent extension of the central part of the sample, characterized by large aligned domains, was studied. Considering the large cross section of our samples, we studied the combined effects of different ratios between the longitudinal and transversal temperature gradients, different pulling rates (R = 0, 0.5, 1, and 2 mm/h), and one or more stages at the beginning of the sample growth on grain nucleation, dimension, and orientation. Different mechanical pretreatments of sample surfaces were also tested in order to control domain nucleation. We obtained 20 × 25 × 45 mm3 samples with low misoriented extended domains. Moreover, we were able to vary their c-axis directions from perpendicular to parallel with respect to the sample length.

We present a theoretical study of the effective Poisson's ratio of elastic solids weakened by porosity and microcracks. Explicit expressions of the effective Poisson's ratio are obtained using the Mori-Tanaka mean-field approach as applied to macroscopically isotropic solids containing randomly distributed and randomly oriented spheroidal pores. We focus on the influence of pore shape and concentration and devote special attention to the limiting cases of spherical, penny-shape, and needle-shape pores. A key result of this study is that the effective Poisson's ratio depends only on pore concentration, pore shape, and Poisson's ratio of the bulk solid. In other words, it is independent of any other elastic constants of the bulk solid. Also, the ratio of the shear and bulk moduli behaves similarly. Unlike other elastic constants which monotonically decrease with pore concentration, Poisson's ratio may increase, decrease, or remain unchanged as a function of pore concentration, depending on the pore shape and Poisson's ratio of the bulk solid. We discuss ramifications of these findings with regard to the elastic constants of oxide superconductors, especially the bismuth cuprates, which show unusually low Poisson's ratios. We also discuss these low Poisson's ratios, including the possibility of negative Poisson's ratios.

0.25 μm thick, single crystal, n-type, silicon carbide (β-SiC) films thermally grown on p-type Si(100) were doped with boron by using KrF excimer laser radiation and a spin-on dopant with a boron concentration of 1020/cm3. The threshold fluence for the doping to occur was approximately 0.08 J/cm2. Similarly, p-SiC/n-SiC diodes were fabricated by laser-induced doping of single-crystal β-SiC (n-type, 6 μm thick) films on n-type Si(100). The diodes obtained at 0.25 J/cm2 showed good rectifying characteristics. The threshold fluence for surface modification and/or ablation was approximately 0.3 J/cm2, indicating that doping and diode formation have to be accomplished within the fluence window of 0.08 J/cm2-0.3 J/cm2 for these films.

Changes in particle size, surface properties, and composition brought about by planetary grinding of silicon in air and various permittivity liquids were investigated. Using a variety of spectroscopic techniques (ESR, IRS, and XPS), a mechanically induced surface oxidation was proved. While at grinding in air and organic liquids a part of the centers originating from dangling orbitals on SiIII are preserved, the properties of water-ground silicon are fully governed by the oxide surface shell. The most effective particle size reduction and surface protection can be reached by grinding in nonpolar liquids.

The relation between stresses of sputtered a-Si: H films and the film deposition conditions are investigated. The film stresses change from a large compressive stress of 1000 MPa to an almost stress-free one. They arise from distortions of the Si network via the following two mechanisms. The first results from the inclusion of the Ar-sputtering gas into the films, which provides volume expansion of the film network. The other is due to structural disorders, such as a deviation of the Si bond angle which is generated during the deposition processes. Moreover, it is found that Si–H terminations in the films contribute to reducing the film stresses because the Si–H termination breaks and relaxes the Si network. These effects can be realized as long as the Si–H terminations are homogeneously distributed in the films.

Extended dislocations including partial dislocations and a stacking fault in Al70Pd20Mn10 icosahedral quasicrystal have been observed and identified for the first time. The diffraction contrast and defocus convergent-beam electron diffraction experiments show that the dissociation of the extended dislocations is of the form 1/2<1 −2 0 0 −2 1> → 1/4<1 −3 1 −1 −1 1>+ 1/4<1 −1 −1 1 −xs3 1> with a stacking fault between these two partial dislocations. For the partial dislocations, the Burgers vector components in physical space b¶part are along different fivefold axes with a magnitude of 0.17 nm, which is about one seventh of that in complementary space. For the perfect dislocation, the Burgers vector component in physical subspace b¶perf is along a twofold axis with a magnitude of 0.183 nm, which is about an eleventh of that in complementary space.

BaZrO3 films were grown on zirconium metal substrates by immersing thin Zr foils in an alkaline solution under hydrothermal conditions. The films were produced at temperatures ranging from 200 °C to 270 °C in a 0.25 M barium hydroxide solution for 3 to 8 h. The resulting films did not have visible pores or defects, and displayed a grain structure which depended on the treatment conditions, especially temperature. X-ray photoelectron and Auger spectroscopies revealed that (a) after removing the surface layer, films were clean, not displaying OH groups nor carbon contamination; (b) the Ba concentration steadily decreased as the depth increased, and did not behave as in BaTiO3 or SrTiO3 films prepared under similar conditions; and (c) the BaZrO3/Zr interface was very broad. Grazing angle x-ray diffraction analysis showed BaZrO3 (cubic), ZrO2 (hexagonal), and Zr (hexagonal), suggesting a layered structure: BaZrO3/ZrO2/Zr. The relative dielectric constant was ≍70 and was independent of the frequency between 100 Hz and 1 MHz. The dielectric loss factor (tan δ) was between 0.01 and 0.02. Dielectric breakdown occurred between 25 and 40 MVm−1.

The formation mechanism and ferroelectric properties of Pb(Li1/4Fe1/4W1/2)O3 prepared by solid-state reaction have been investigated in this study. The formation processes of Pb(Li1/4Fe1/4W1/2)O3 are characterized to be an initial reaction of lead tungstates PbWO4 and Pb2WO5 at a low temperature range, followed by a subsequent reaction to produce Pb(Li1/4Fe1/4W1/2)O3 from above 650 °C. Through a two-stage calcination (700 °C/quenching-regrinding-710 °C/8 h), a nearly single phase of Pb(Li1/4Fe1/4W1/2)O3 is obtained. This compound exhibits a cubic perovskite structure (α = 8.0113 Å) with a partial ordering arrangement of B-site cations. Above 720 °C, becomes Pb(Li1/4Fe1/4W1/2)O3 thermodynamically unstable and gradually decomposes in forming elongated Pb2WO5 grains, thereby resulting in a nonhomogeneous microstructure. As the ac frequency increases, the maximum dielectric permittivity of Pb(Li1/4Fe1/4W1/2)O3 significantly decreases; in addition, the corresponding temperature increases. The strong frequency dependence of dielectric properties, as well as the critical exponent and diffuseness evaluated through a modified permittivity-temperature equation proposed in this study, verify the relaxor characteristics of Pb(Li1/4Fe1/4W1/2)O3

Niobium-doped lead zirconate stannate titanate thin films have been prepared by a modified sol-gel spin on technique, utilizing the hydrolysis-resistant precursor lead acetylacetonate. Films of compositions in the antiferroelectric tetragonal and antiferroelectric orthorhombic phases were prepared and phase-switched with the application of appropriate electric fields. A distinctly “square” hysteresis response was observed in a low titanium, low tin, orthorhombic composition, with a maximum polarization, Pmax, of 40 μC/cm2 and switching field values of Ef = 175 kV/cm and Ea = 75 kV/cm, while varying degrees of squareness, along with lower polarizations and switching fields, were observed in the higher tin, tetragonal compositions. Electric field-induced strains of up to 0.33% have been measured in the orthorhombic composition, with tunable electromechanical coefficients. Film properties showed only slight variation with electrode size over a range of diameters from 0.8 mm to 6.35 mm; large area electrodes are vital for practical actuator and sensor devices. With a capacitance density of 30–35 μF/cm2, films of the orthorhombic composition are promising as power plane decoupling capacitors in multichip modules.

The dielectric temperature characteristics and microstructures of BaTiO3-based ceramics sintered with additives such as Sm2O3, CeO2, and Bi2O3:Nb2O5 were investigated using TEM, XRD, and EDS. For a Sm2O3-modified BaTiO3 ceramic whose additives were uniformly distributed in grains, the ferroelectric transition temperature (Tc) was shifted to a lower temperature, while the transition temperatures (T1 and T2) were shifted to a higher temperature. The additions of CeO2 and Bi2O3: PbO to BaTiO3 formed the chemical inhomogeneity which was composed of grain core, grain shell, and concentration gradient region. The dielectric curve versus temperature of CeO2-modified BaTiO3 has the shape of one strong peak, whereas BaTiO3 ceramics sintered with Bi2O3:Nb2O5 exhibit the broad dielectric constant at the low temperature region and 130 °C ferroelectric transition peak. The dielectric temperature characteristics of additives modified BaTiO3 were determined in terms of the chemical inhomogeneity and stress induced by the difference of the unit cell volume between grain core and grain shell.

Thin films of Lead Lanthanum Titanate (PLT) corresponding to 28 at. % of La were prepared by the metal-organic decomposition (MOD) process. The films were fabricated from two solutions of different composition. The composition of the first solution was determined, assuming that the incorporation of La3+ in the PbTiO3 structure gives rise to A-site or Pb vacancies, whereas for the composition of the other solution the creation of B-site or Ti vacancies was assumed. The effect of excess lead on the microstructure and the optical and electrical properties was studied for 0% to 20% excess PbO. The x-ray diffraction patterns of all films at room temperature indicated a cubic structure with a lattice constant of 3.92 Å. Optical and electrical measurements showed the films made assuming B-site vacancies had better properties. In general, excess PbO was found to improve the optical transmittance as well as the electrical properties of films. However, in films assuming the formation of B-site vacancies, PLT showed improved electrical properties only up to 5–10% excess PbO, while higher PbO additions had a deleterious effect. The films had a high resistivity, good relative permittivity, low loss, very low leakage current density, and high charge storage density. A type-B film with 10% excess Pb had a relative permittivity of 1340 at 100 kHz and a charge storage density of around 16.1 μC/cm2 at a field of 200 kV/cm at room temperature.

We prepared sol-gel titania by using different hydrolysis catalysts, and characterized it by x-ray powder diffraction. The structure of the crystalline phases—brookite, anatase, and rutile—in the samples annealed between 70 and 900 °C was refined by using the Rietveld technique. From the refinement we obtained the structure parameters, the concentration of each phase, and their average crystallite size. These quantities and their evolution with temperature depended on the hydrolysis catalyst. Anatase and rutile were deficient in Ti, suggesting that their crystalline structure contained hydrogen atoms, forming OH− ions inside. In anatase this deficiency depended on its crystallite size, but it was constant in rutile. When anatase was annealed, it dehydroxylized, producing either crystallitc growing up or its conversion into rutile. From the analysis we also found the conditions for obtaining single-phase samples that could be used as precursors for making up titania single-phase thin films.

Polycrystalline LiTaO3 (LT) thin films have been prepared on (001)Si substrates by the sol-gel method. A Li-Ta double alkoxide prepared from lithium methoxide and tantalum ethoxide precursors was spin coated on Si and heated up to 950 °C. The dependence of the film quality upon the process variables, alkoxide concentration before hydrolysis, the water to double alkoxide ratio, and the final double alkoxide concentration, has been established. Preferential alignment of the (104) LT planes was observed parallel to the (100)Si surface. Most films present resistivities of the order of 30 kΩ · cm and breakdown field in excess of 200 kV/cm.

TiN films were ehemical-vapor-deposited on the inner wall of a tubular reactor. Films deposited in the upstream region of the reactor consisted of small and sharp crystals with (111)-preferred orientation or random orientation. On the other hand, films deposited in the downstream region or at lower partial pressure of TiCl4 consisted of columnar crystals with (110)-preferred orientation, having polyhedral shapes on the surface. For the films deposited under different conditions at different axial positions, relationships were investigated among the temperature, the calculated concentrations on the substrate, and the degree of preferred orientation of the films. As a result, it was shown that formation of films with (110)-preferred orientation is related to the conditions of high temperature and low partial pressure of TiCl4. Films deposited at the higher gas flow rate had lower degrees of (110)-preferred orientation. Decrease in partial pressure of TiCl4 along the axial direction in the reactor was calculated to be smaller at higher gas flow rate, and provided suitable conditions for deposition of films having small and sharp crystals.

The rheological properties of boehmite-coated silicon nitride aqueous suspensions and gels are reported. In unidirectional rheological tests, it was found that the boehmite coating reduces the viscosity of the suspensions over a wide range of shear rates and volume fractions of particles. The suspension shear stress as a function of shear rate can be described by the Bingham model, and the Bingham yield stresses of boehmite-coated silicon nitride suspensions are lower than those of the uncoated suspensions. The reduction in the viscosity and the Bingham yield stress is attributed to a shallower secondary minimum in the Derjaguin-Landau-Verwey-Overbeek (DLVO) potential between coated particles than that for uncoated silicon nitride particles. Moreover, at low values of pH, the coated silicon nitride suspensions gelled over time, and the viscoelastic behavior of the gels was studied by dynamic oscillatory tests. It was found that the shear modulus (G′) and loss modulus (G″) remain constant up to a certain strain amplitude, γ°, beyond which G′ and G″ begin to vary. The value of G′ in the linear region increases exponentially, whereas γ° decreases exponentially with the volume fraction of coated silicon nitride particles. The exponential behavior of the shear modulus G′ of the gels is similar to the exponential pressure-density relationship found in the previous pressure filtration study, indicating that particulate rearrangement occurs as volume fraction of particles is increased.