We investigated effects of postdeposition heat treatment (HT) on the properties of plasma polymer films deposited by plasma-enhanced chemical vapor deposition using a mixture of decahydronaphthalene and tetraethyl orthosilicate as the precursors, which were referred to as plasma-polymerized decahydronaphthalene:tetraethyl orthosilicate (PPDHN:TEOS) films. HTs at 350, 450, and 500 °C decreased the relative dielectric constant k of the PPDHN:TEOS films from 3.16, the k value of the as-deposited film, to 2.82, 2.72, and 3.02, respectively. The change of k value as a function of HT temperature was correlated with the change of Fourier transform infrared absorption peaks of O–H, C = O, and Si-related groups. As the HT temperature increased, the thermal stability of the PPDHN:TEOS film increased. PPDHN:TEOS films, as-deposited or heat treated, showed leakage current density in the order of 10−7 A/cm2 at 1 MV/cm.

The dynamic piezoelectric response of SrBi4Ti4O15 ceramics with Aurivillius structure was investigated at high alternating stress, low frequencies (0.01 to 100 Hz), and temperatures from 20 to 200 °C. The piezoelectric nonlinearity, observed only at high pressures (>10 MPa) and elevated temperatures (>150 °C), is interpreted in terms of contributions from non-180° domain walls. At weak fields, the frequency dependence of the longitudinal piezoelectric coefficient was explained in terms of Maxwell–Wagner piezoelectric relaxation. The Maxwell–Wagner units are identified as colonies that consist of highly anisotropic grains which sinter together, and whose distribution in the ceramic is strongly dependent on sintering conditions.

The stability of Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass (BMG) upon isothermal annealing near the glass transition temperature has been investigated by using x-ray diffraction, differential scanning calorimetry, and the pulse echo overlap method. The density, elastic constants, and thermodynamic parameters as well as their annealing time dependence have been determined. The microstructural and properties changes of the annealed BMG were checked by acoustic measurement. Obvious structural and property changes were observed with prolonged annealing of the BMG near the glass transition temperature.

Multilayers of TiC/Ti and TiC/B4C have been deposited by pulsed laser deposition. Ti, B4C, and TiC targets were used to deposit multilayer films onto 440C steel and silicon substrates at 40 °C. The structural, compositional, and mechanical properties of the multilayers were examined by x-ray diffraction, x-ray photoelectron spectroscopy, transmission electron microscopy, and nanoindentation techniques. Tribological properties were also evaluated using a pin-on-disc friction and wear test. The TiC/Ti films were found to have a crystalline structure, and both (200)TiC/(100)Ti and (111)TiC/(101)Ti orientation relationships were found in these films. In the TiC/B4C films, only the sample with the largest bilayer thickness (25 nm) had significant crystallinity and only the TiC layer was crystalline. X-ray photoelectron spectroscopy depth profiles confirmed the presence of composition modulations in these films. Nanoindentation tests of the TiC/Ti multilayers showed hardness levels exceeding that predicted by the rule-of-mixtures. The TiC/B4C multilayers showed increasing hardness with decreasing bilayer thickness but reached only 22 GPa. The pin-on-disc tests gave friction values ranging from 0.3 to 0.9 for both sets of films. These results were correlated with the degree of crystallinity and grain structure of the films.

Neodymium(III) oxide nanocrystals prepared by an inverse microemulsion technique have been dispersed in sol-gel titania/(γ-glycidoxypropyl)trimethoxysilane composite thin films at low temperature. Transmission electron microscopy and x-ray diffraction were used to characterize the phosphor nanoparticles and show that the neodymium(III) oxide nanoparticles have a nanocrystal structure and the size of the nanoparticles is in the range from 5 to 60 nm. An intense up-conversion emission in violet (399 nm) color from neodymium(III) oxide nanocrystals upon excitation with a yellow light (577 nm) has been observed. Two ultraviolet emissions at 347 and 372 nm and a blue emission at 466 nm have also been observed, and those are assigned to electronic transitions appropriately. A relatively strong room-temperature photoluminescence emission at 1064 nm corresponding to the 4F3/2 → 4I11/12 transition of neodymium ion has been measured as a function of the heat treatment temperature. In addition to this emission, two other emissions at 890 and 1336 nm have also been observed. Especially, a clear shoulder peak at 1145 nm, which could probably be resulting from the host matrix, was observed in all measured samples, and this shoulder peak reached a maximum intensity after a heat treatment at 300 °C.

The crystal structure of Bi2Zn2/3Nb4/3O7 was determined using a combination of electron, x-ray, and neutron powder diffraction. The compound crystallizes with a monoclinic zirconolite-like structure [C2/c (No.15) space group, a = 13.1037(9) Å, b = 7.6735(3) Å, c = 12.1584(6) Å, β = 101.318(5)°]. According to structural refinement using neutron diffraction data, Nb preferentially occupies six-fold coordinated sites in octahedral sheets parallel to the (001) planes, while Zn is statistically distributed between two half-occupied (5 + 1)-fold coordinated sites near the centers of six-membered rings of [Nb(Zn)O6] octahedra. The Nb/Zn cation layers alternate along the c-axis with Bi-layers, in which Bi cations occupy both eight- and seven-fold coordinated sites. The eight-fold coordinated Bi atoms exhibited strongly anisotropic thermal displacements with an abnormally large component directed approximately along the c-axis (normal to the octahedral layers).

Nanocomposite Ni/Al2O3 films were electrodeposited from a suspension of Al2O3 nanoparticles in aqueous nickel sulfamate solution. The volume fraction of particles incorporated increased with electrode rotation rate and decreased with deposition current density. The composition, microstructure, hardness, and magnetic properties of these nanocomposite films were characterized. The mechanical strengthening due to particle dispersion in the films was interpreted by considering an Orowan dislocation bowing mechanism. The coercivity of the films increased with increasing particle concentration in the film. The saturation magnetization showed a weak dependence on particle concentration.

The effect of Ni substitution on the structure and photocatalytic H2 and O2 evolutions of InTaO4 under visible light irradiation (λ > 420 nm) from aqueous CH3OH/H2O and AgNO3/H2O solutions were investigated. The photocatalysts were prepared by the solid-state reaction method and characterized by powder x-ray diffraction and Rietveld structure refinement. These photocatalysts crystallize in the same wolframite structure, but lattice parameters decrease with increase of x in In1−xNixTaO4 (0 ≤x ≤ 0.2). The photocatalytic activity changed with the variation of x in In1−xNixTaO4and the photocatalyst at x = 0.1 showed the highest activity, which increased 8 times compared with nonsubstituted photocatalyst.

Crystalline, pure or Mn-doped ZnGa2O4 powders have been prepared in situ in urea (with or without enzyme urease)-containing Zn and Ga nitrate (and Mn nitrate) solutions by simply holding those for 24–48 h, at 90 °C, in screw-capped glass bottles in a constant-temperature laboratory oven. Single-phase pure or Mn-doped zinc gallate powders synthesized with the spinel crystal structure had an average particle size around 15 to 18 nm. Powders were characterized by x-ray diffraction, scanning electron microscopy, energy-dispersive x-ray spectroscopy, inductively-coupled plasma atomic emission spectroscopy, simultaneous thermogravimetry and differential thermal analysis, Fourier-transformed infrared spectroscopy, and carbon and nitrogen analyses. Calcination behavior of the as-filtered powders was later studied in an air atmosphere over the temperature range of 90 to 1200 °C.

The flow of gas-phase products in three-dimensional porous bodies was modeled for the case when a source term is present. Analytical solutions to the governing partial differential equations were obtained for bodies of parallelepiped and cylindrical geometry. An important feature of the model is that it treats the case where the permeability in the body may be anisotropic. The evolution of pressure within the body depends on a number of parameters, including the rate of production of gas-phase species, and on the dimensions of the body. The model is thus able to describe the pressure within a porous ceramic body arising from flow during a number of elevated-temperature processing operations such as drying, binder burnout, and sintering.

We have examined the mechanical behavior of Zr57Ti5Cu20Ni8Al10 bulk metallic glass under uniaxial compression at strain rates from 10−4to 3 × 103 s−1. The failure stress decreases with increasing strain rate, and shear-band formation remains the dominant deformation mechanism. A consideration of basic properties of adiabatic shear bands makes it appear unlikely that shear bands formed under quasi-static loading are adiabatic; in the dynamic case, the time scales of deformation and thermal conduction are similar, indicating that a more sophisticated calculation is required. In the dynamic tests, however, high-speed cinematography reveals evidence that the mechanism of failure involves an adiabatic component.

Substitution effects of Ta5+ by Nb5+ in BiTa1−xNbxO4(0 ≦ x ≧ 1.0) on photocatalytic, photophysical, and structural properties were investigated. The powder x-ray diffraction and Rietveld structural refinement showed that the structure of BiTa1−xNbxO4 at R = Nb/Bi = 0.0 and 0.5 is a triclinic system with space group P1. However, the structure at R = 0.2, 0.8, and 1.0 is an orthorhombic system with space group Pnna. Ultraviolet-visible diffuse reflectance spectroscopy measurement revealed that the band gap of orthorhombic samples is narrower than that of triclinic compounds. The H2 evolution was obtained from an aqueous CH3OH/H2O solution and pure H2O with BiTa1−xNbxO4 under ultraviolet irradiation. The orthorhombic samples exhibit much higher activity than that of triclinic compounds. The orthorhombic compound at R = 0.2 showed the highest activity, which is higher than that of the well-known TiO2 photocatalyst.

SrBi2Ta2O9 (SBT) thin films were prepared by the radio-frequency (rf ) magnetron sputtering method on Pt/Ti/SiO2/Si substrates. The composition and orientation of SBT thin films were changed by the control of sputtering parameters such as pressure and rf power. As the sputtering pressure increased from 2.5 to 300 mtorr, the film was changed from Sr- and Bi-deficient SBT film to stoichiometric film. The SBT thin films with stoichiometric composition showed good electrical properties. As the rf power increased from 25 to 40 W, the Sr content decreased. However, the Bi content was maximized in the power of 30 W, where the (200)-predominant SBT thin films were fabricated. In lower power of 25 W, typical polycrystalline SBT films were obtained. The Sr and Bi contents in both films were not deficient. However, at the higher power of 35 and 40 W, the secondary phase appeared due to the Sr deficiency. The Bi content of (200)-predominant SBT film was higher than that of polycrystalline films. The degree of the (200) orientation depended on the magnitude of excess Bi content. It is also suggested that the (200)-predominant SBT films were formed by the decomposition of SBT phase to the Bi and Sr atoms caused by rf power control and the lower atomic migration energy along the a axis.

The crystallization kinetics of Sr0.7Bi2.3Ta2O9 (SBT) and 0.7SrBi2Ta2O9–0.3Bi3TiTaO9 (SBT-BTT) thin films formed by the sol-gel and spin coating techniques were studied. Phase formation and crystal growth are greatly affected by the film composition and crystallization temperature. Isothermal kinetic analysis was performed on the x-ray diffraction results of the thin films heated in the range of 730 to 760 °C at 10 °C intervals. Activation energy and Avrami exponent values were determined for the fluorite-to-Aurivillus phase transformation. A reduction of approximately 51 kJ/mol in activation energy was observed for the SBT-BTT thin films, and an Avrami exponent value of approximately 1.0 was obtained for both the SBT and SBT-BTT. A comparison is made, and the possible crystallization mechanism is discussed.

Textured as well as epitaxial thin AlN films are of great interest for a wide range of electro-acoustic and optoelectronic applications. Reduction of the deposition temperature is of vital importance in a number of applications due to thermal budget limitations. In this work we systematically studied the influence of the process parameters on the film properties and identified the factors leading to improved film quality as well as reduced deposition temperature with pulsed direct current sputtering in an Ar/N2 atmosphere. We demonstrated that fully textured (0002) films can be grown under a wide range of conditions. At the same time the full width at half-maximum (FWHM) of the rocking curve of the (0002) XRD peak was found to vary systematically with process conditions—depostion rate, process pressure, gas composition, and substrate temperature. The best films showed a FWHM of 1.2°. We found that by far the most important factor is the arrival energy of the sputtered Al atoms, which is primarily controlled by the process pressure. We report for the first time that fully textured AlN films with a FWHM of under 2° can be grown at room temperature. Other important factors are the ion and electron bombardment of the films and substrate temperature as well as gas composition, although their influence is not as dramatic. Generally, the film quality increases with temperature. Bias and electron bombardment within a certain range also lead to better films.

The dissolution behavior and kinetics of spinel lithium manganate LiMn2O4 with different particle sizes have been investigated in this study. The dissolution of manganese cations from LiMn2O4 is confirmed to occur when LiMn2O4 particles are immersed in the electrolytes. The amount of dissolved manganese ions markedly increases with a rise in temperature and a decrease in particle size, which implies that the capacity fading of LiMn2O4 at elevated temperatures is associated with manganese dissolution. On the basis of the isothermal analysis of reaction kinetics, the rate of manganese dissolution from LiMn2O4 is dominated by the rate of dissolution reaction. Smaller particles exhibit a larger reaction rate constant and higher activation energy of the dissolution process than the larger ones. Therefore, an increase in temperature has a more pronounced effect on the dissolution reaction of small particles than on that of large particles.

Highly porous microcrystalline hydroxyapatite (HAP) coatings have been prepared from calcium nitrate and phosphoric acid based sols by the aerosol-gel process. The coatings were studied after sintering at different temperatures with the use of Fourier transform infrared spectroscopy, x-ray diffraction, energy disperse x-ray microanalysis, scanning electron microscopy, and transmission electron microscopy. The composition, structure, and morphology of the coatings sintered at 650 °C fit fairly well highly porous HAP. These coatings were reproduced onto TiO2/Si substrates and studied by Rutherford backscattering. It is shown that even after chemical etching, an adherent calcium phosphate phase remains attached to the TiO2/Si substrate.

Spectrophotometry in the ultraviolet-visible-infrared range was used to investigate the optical properties of polymer bilayers obtained by spin coating polycarbonate films about 1 μm thick on top of pyrromethene-doped polyvinylcarbazole (PVK) layers deposited on glass. Due to the light confinement in the PVK plane, the laser-dye photoluminescence collected along the polymer plane was linearly polarized and shifted from green to yellow according to the active film thickness. To laterally contain light, microstructures were imprinted on laser-dye-doped PVK films by soft lithography. The photoluminescence coming out of a microstructured film and the film topography were analyzed by scanning near-field optical microscopy.

In his classic paper on thermal grain boundary grooving Mullins [W.W. Mullins, J. Appl. Physics 28, 333 (1957)] assumes that the dihedral angle at the groove root remains constant and predicts that the groove width and depth grow αt0.25. Here, we derive models describing groove growth while the dihedral angle changes. In our grooving experiments with tungsten at 1350 °C in which the dihedral angle decreased, the growth exponent for the groove depth reached values as high as 0.44 while the growth exponent for the width decreased slightly from Mullins' value of 0.25. Hence groove width data alone are not sufficient for verifying Mullins' growth law unless the dihedral angle is constant. The observed changes in the dihedral angle are used as an input for numerical simulations. With the simulations we are able to extract the surface diffusion constants. Atomic force microscope observations of groove widths and depths in tungsten are in excellent agreement with the simulations.

The permittivity of two primary phases within the Bi2O3–ZnO–Ta2O5 system was measured from 100 Hz to approximately 8.7 GHz. A cubic pyrochlore (Bi3/2Zn1/2)(Zn1/2Ta3/2)O7 phase (a phase) exhibited a dielectric constant of 71 at low frequency which decreased to 64 at approximately 10 GHz. A lower symmetry zirconolite Bi2(Zn1/3Ta2/3)2O7 phase (β phase) was also measured and had a frequency independent dielectric constant of 60. The temperature dependence of the capacitance (τC), measured from −55 to 120 °C, was 78 ppm/°C for the β phase and nonlinear for the α phase having no unique slope. The primary difference in dielectric properties between these two phases was a low-temperature relaxation of the α phase, which is modeled as a basic Debye-type relaxation.