The phase relations and microwave dielectric properties of (1−x)ZnNb2O6–xTiO2 were investigated using x-ray powder diffraction and a network analyzer. Four phase regions were studied with increasing TiO2 mol% (x): columbite solid solution, ixiolite (ZnTiNb2O8) solid solution, mixture of ixiolite and rutile solid solutions, and rutile solid solution. It was suggested that the microwave properties depend on crystal structure rather than chemical composition. In the columbite solid solution region, an order–disorder transition was found with an increasing amount of TiO2, and the quality factor decreased sharply. ZnTiNb2O8 (x = 0.5), has a fully disordered structure and possesses a quality factor of 42,500, relative dielectric constant (εr) of 34.3, and temperature coefficient of resonant frequency (τf) of −52 ppm/°C. In the mixture region of ixiolite and rutile structure, τf was modified to around 0 ppm/°C.

Computer simulations have been designed to elucidate the evolution of microcracking in a nanocomposite using appropriate material values for alumina and silicon carbide. These are compared to a single-phase material using elastic and thermal expansion coefficients for alumina. It is found that the region and the fracture mode where microcracking ensues are determined by the intensity and the length scale of the residual stress fields, which interact. Of specific interest are the region, fracture mode, and length of ensuing microcracks for materials with different inclusion locations (at the grain boundary or within the grain) and with different grain size to inclusion size ratios.

Mullite powder with a nearly stoichiometric composition was doped with 1.5–5 wt% SiO2 or 0.5–1.0 wt% Y2O3 and hot pressed at 1525–1550 °C to produce almost fully dense materials. The effect of the additives on the grain growth of the dense systems was investigated during subsequent annealing at temperatures above that of the eutectic (∼1590 °C) for the SiO2–Al2O3 system. The average length and width of the grains were measured by image analysis of polished and etched sections. At 1750 °C, anisotropic grain growth was relatively rapid, leading to the formation of rodlike grains. Compared to the undoped mullite, the addition of SiO2 and Y2O3 produced a small reduction in the grain growth kinetics. Transmission electron microscopy revealed that the glassy second phase was concentrated at the three-grain junctions or distributed inhomogeneously at the grain boundaries. For the materials annealed at 1750 °C, the indentation fracture toughness at room temperature increased from 2.0 to 2.5 MPa m1/2 for the undoped mullite to values as high as 4.0–4.5 MPa m1/2 for the doped mullite. The implications of the data for enhancing the fracture toughness of mullite by the in situ development of a microstructure of elongated grains are considered.

The sintering and properties of cordierite–borosilicate glass composites were investigated. For the composites with ≥35% low-viscosity glass, the sintered densities decreased with the increasing sintering temperature above 850 °C. No crystallization of the glass was found. For the composites with 50–90 wt% high-viscosity glass, the sintered densities remained nearly constant (>95%) in a wide sintering temperature range. However, cristobalite crystallized from the glass phase, resulting in an undesirably high coefficient of thermal expansion. Presintering processing and a lower heating rate improved the densification of the composites with low-viscosity glass while limiting that of the composites with high-viscosity glass. This result is explained by the difference in crystallizability between these two glasses. As low- and high-viscosity glass powders were simultaneously added, the density reduction was reduced and the coefficient of thermal expansion was closer to that of Si because of the absence of cristobalite phase. The dielectric constant of all the composites was in the typical range of 4.9–5.7 at 1 MHz.

Electrical conductivity and thermopower of Bi2Sr3Co2Ox sintered bodies were first investigated in the temperature range 440–1060 K in air for high-temperature thermoelectric application. The samples fabricated by the sinter-forging method increased their bulk densities and electrical conductivity. The value of thermopower and the temperature dependence of electrical conductivity of the sinter-forged samples were close to that of the single crystal. Evaluating the thermal conductivity of the polycrystalline sample, we calculated a thermoelectric figure of merit Z to be 0.107 × 10−3 K−1 at 1060 K.

Stoichiometric yttrium aluminate garnet (Y3Al5O12) precursors with a wide range of chemical compositions were precipitated by dripping a mixed solution of ammonium aluminum sulfate and yttrium nitrate into ammonium bicarbonate solutions. The resultant precursors were characterized by chemical analysis, infrared spectroscopy, differential thermal analysis/thermogravimetry, x-ray diffractometry, and scanning electron microscopy. The effects of reaction temperature, precipitant concentration, dripping speed of the salt solution, and the molar ratio of precipitant/total-cations on the composition, thermal behavior, and particle morphology of the resultant precursors were investigated. The precipitation conditions that yield carbonate precursors composed of ammonium dawsonite [NH4Al(OH)2CO3] and yttrium normal carbonate [Y2(CO3)3 · 3H2O] were determined.

The oxygen chemisorption on nanocrystalline SnO2 at temperature range between 100 and 450 °C was studied with differential thermal analysis (DTA) and electrical conductivity measurement. The O2−, O−, and O2m ionosorptions were observed and could be distinguished from each other only on nanocrystalline SnO2 with grain size less than 5 nm. Assuming steady-state adsorption, the heats of adsorption for O2− and O− (or O2−) on nanocrystalline SnO2 are 1.09 and 1.50 eV respectively from the results of DTA.

Temperature dependence of in situ fiber strength, effective interface shear stress, Young's modulus of matrix, and matrix fracture energy in a polymer-infiltrationpyrolysis (PIP)-processed two-dimensional plain-woven fabric carbon-coated Nicalon™ SiC fiber-reinforced SiC matrix composite was studied through a tensile test in air at 298 (room temperature), 800, and 1200 K. In situ fiber strength and effective interface shear stress were determined by fracture mirror size and fiber pullout length measurements, respectively. The fiber strength was insensitive to test temperature up to 800 K but dropped significantly at 1200 K. Conversely, the interface shear stress showed a strong temperature dependence, decreasing at 800 K and drastically increasing at 1200 K. The temperature dependence of both values was reasonably explained. Temperature dependence of Young's modulus of matrix was derived from Young's modulus of the composite and fiber and ranged from ≈40 to ≈38 GPa. Matrix fracture energy was also determined from the transverse matrix cracking stress and ranged from ≈16 to ≈5.5 J/m2. Both Young's modulus of matrix and the matrix fracture energy showed only slight temperature dependence up to 800 K; however, both values decreased significantly at 1200 K.

Thin films of highly (100) textured fine-grain (lateral grain size ≅0.1 to 0.15 μm) PbZrxTi1−xO3 (PZT) (x = 0 to 0.7) were grown on conductive perovskite LaNiO3-buffered platinized Si substrates by metalorganic chemical vapor deposition. Domain configuration and crystalline orientation were studied using x-ray diffraction and transmission electron microscopy. The predominant domain boundaries of Ti-rich tetragonal-phase PZT and Zr-rich rhombohedral-phase PZT were found to be on the (110) planes and (100) planes, respectively. The equilibrium domain widths were observed and estimated numerically on the basis of transformation strain, grain size, and domain boundary energy. The peak value of the dielectric constant was 790 near the morphotropic boundary. Hysteresis behavior of these PZT thin films was demonstrated. A decrease in coercive field with the increment of Zr content was found; this variation was attributed to domain density and the multiplicity of polarization axes. Furthermore, the low leakage current (J ≤ 5 × 10−7 A/cm2 at V = 4 V) was observed for all samples, and the involvement of several possible conduction mechanisms was suggested.

Crystals of merwinite were prepared at 1550 °C from chemical reagents, and their intracrystalline microstructures were examined by the combined use of x-ray diffraction and optical microscopy. The crystals were composed of pseudomerohedral twins. The adjacent twin domains were related by the pseudosymmetry two-fold axis parallel to ⟨011⟩with the composition surface {811} The overall twin structure was constructed by introducing the pseudo-symmetry three-fold axis normal to (100), which must originally be a symmetry element of the former high-symmetry phase. The transition from the primitive trigonal (point group 3m) to the primitive monoclinic (space group P21/a) was accompanied by the combination of reducing the order of the point group and the change in the size of the unit cell. The order of the point group was reduced from 12 to 4, resulting in three twin domains with six different interfaces. This accounted for the experimentally observed microstructure consisting of repeated lamella twins in several orientations. Because the unit lattice translation would be lost during the transition, the formation of antiphase domains was expected. The lost translation vectors were 1/2[011], 1/2[100], and 1/2[111] resulting in four antiphase domains. As a result, the total number of domains possible in the transition was 3 × 4 = 12.

The average thermal residual stress in a continuous boundary phase in polycrystalline ceramic composites was calculated with a simple thin boundary layer model, and a criterion for the self-cracking of the boundary phase was derived under a certain assumption. From the proposed model, the toughness of the materials can be increased by both tensile and compressive stress at boundaries when the crack propagates transgranularly. The toughness will be increased when the stress at boundary is compressive for intergranular fracture mode. The maximum increase is predicted to be achieved at boundary phase contents below 33%. The experimental results for yttria-stabilized tetragonal zirconia polycrystalline ceramics doped with different kinds of grain-boundary phase is in a qualitative agreement with the prediction by the model, but the toughness increase is largely dependent on the distribution feature of glass phases.

Amorphous iron oxide (Fe2O3) was prepared by the pyrolysis of iron pentacarbonyl [Fe(CO)5] in a modified domestic microwave oven in refluxing chlorobenzene as a solvent under air. The reaction time was 20 min. Partially separated particles of iron oxide, 2–3 nm in diameter, were obtained. The other part showed aggregated spheres with a diameter of 25–40 nm. Differential scanning calorimetry measurements showed an amorphous/crystalline phase transition at about 250 °C.

Aligned slicon dioxide nanotubes with diameters of 30–40 nm synthesized by the sol-gel template method are presented. This process involves the growth of nanotubes from ordered nanochannel-array pores in anodic alumina. For a silica sol aged at room temperature and dipped for 1 min, nanowires were formed in a shorter period of aging time (2 days); nanotubes connecting with solid nanofibers were obtained in a longer aging time (30 days). The formation of nanotubes depends strongly on the temperature of the sol. For a short dipping time (<1 min), bamboolike nanofibers were prepared when the sol was at high temperature (50 °C); however, perfect nanotubes with the sharp wall were synthetized for the lower sol temperature (5 °C). The lower sol temperature is, the smoother the inside wall of nanotubes is. It is proved that viscosity plays an important role on the morphology of nanotubes.

Depth-sensing indentation tests were used to determine the hardness of amorphous W–C–Co coatings deposited on different steel and copper substrates. The hardness of the film, Hf, was chosen to be always greater than the hardness of the substrate Hs and within the range Hf/Hs = 2 to 18.5. The influence of the ratio Hf/Hs on the ratio (t/hD)C between the film thickness t and the critical value of the indentation depth (hD)C, for which the substrate starts to deform plastically, was studied. Two independent methods were used to determine (hD)C values. One utilized the differential analysis of the loading part of the indentation curve, and the other was based on the plot of (Hc – Hs)/(Hf − Hs) versus t/(hD), Hc being the measured hardness of the film/substrate composite at a given indentation depth (hD). A good correlation between both methods was found.

Lead zirconate titanate [Pb(ZrxTi1−x)O3 (PZT)] powders and ferroelectric thin films with a composition near the morphotropic phase boundary [Pb(Zr0.52Ti0.48)O3] were prepared by a modified sol-gel process using zirconium oxynitrate-2-hydrate as the zirconium source and ethylene glycol as solvent. The precursor solution was prepared from lead acetate-3-hydrate, tetrabutyl titanate, and zirconium oxynitrate-2-hydrate. Perovskite PZT powders were obtained after sintering at 450 °C for 2 h. Films rapid-thermally annealed at 650 °C for 1 min formed well-crystallized perovskite.Microstructures of these films indicated the presence of nano-sized grains (∼50 nm). The remnant polarization was 28.5 μC/cm2, and the coercive field was 39.8 kV/cm. Ferroelectric polarization fatigue test of In/PZT/Pt/Ti/SiO2/Si showed a high fatigue resistance up to 3 × 1010 cycles before Pr decreased by 50%.

BaxSr1−xTiO3 (x 4 0.6) (BST) thin films were successfully prepared on a Pt(111)/TiO2/SiO2/Si(100) substrate by spin coating, using the polymeric precursor method. BST films with a perovskite single phase were obtained after heat treatment at 700 °C. The multilayer BST thin films had a granular structure with a grain size of approximately 60 nm. A 480-nm-thick film was obtained by carrying out five cycles of the spin-coating/heating process. Scanning electron microscopy and atomic force microscopy analyses showed that the thin films had a smooth, dense, crack-free surface with low surface roughness (3.6 nm). At room temperature and at a frequency of 100 kHz, the dielectric constant and the dissipation factor were, respectively, 748 and 0.042. The high dielectric constant value was due to the high microstructural quality and chemical homogeneity of the thin films obtained by the polymeric precursor method.

Stability of submicron contacts under high current density has been an outstanding reliability issue in advanced Si devices. Polarity effect of failure was observed in Ni and Ni2Si contacts on n+-Si and p+-Si. In this report, we studied the failure due to high current density in contacts to n+- and p+-silicon-on-insulator (SOI). We found similar polarity effects below certain current: the p+-SOI failed preferentially at the cathode, while the n+-SOI failed preferentially at the anode. At higher current, damage occurred at both contacts. The effect of current crowding was evident in both cases.

The small-angle x-ray scattering (SAXS) technique was used to investigate inhomogeneities on the scale of 10 to 600 Å in acid-catalyzed titania–silica and zirconia–silica xerogels. SAXS of (TiO2)x(SiO2)1−x and (ZrO2)x(SiO2)1−x xerogels with x < 0.1, in which there was no phase separation, showed the presence of two types of inhomogeneity. For Q < 0.05 Å−1 there was a clear departure from Porod scattering which showed that xerogel powder particle surfaces were rough. For 0.1 < Q < 0.4 Å−1 there was a plateau feature corresponding to micropores within the silica-based network, and this feature changes with heat treatment. SAXS of xerogels with x > 0.3 showed the presence of phase-separated regions of metal oxide, which were initially amorphous and crystallized at higher temperatures. A (TiO2)0.18(SiO2)0.82 xerogel that was not initially phase separated became phase separated after heat treatment at 750 °C due to reduced solubility of Ti in the silica network.

High-epsilon (HE) and ferroelectric (FE) perovskites such as (Ba, Sr)TiO3 and SrBi2Ta2O9 are attracting substantial interest for use in dynamic random-access memory and nonvolatile memory. In this paper, we describe how an easily decomposable PdO bottom electrode layer may be used as a marker for possible HE/FE damage induced by exposure to reducing environments. Oxygen loss from PdO films with and without a HE/FE overlayer was monitored by in situ x-ray diffraction during heating in an inert ambient. Additional measurements were performed on PdO films in contact with Pt underlayers. A Pt underlayer was found to reduce the temperature of oxygen release from PdO, suggesting that it may be possible to custom-design PdO-based oxygen sources with specific oxygen release characteristics to resupply the HE/FE with oxygen lost during processing.

We investigated the photoluminescence as well as the crystal structure and optical energy gaps of the Zn1-xCdxAl2Se4-4xS4x solid solution system based on the Al-related compounds of ZnAl2Se4, ZnAl2S4, CdAl2Se4, and CdAl2S4. The single crystals of the system with 0.0 ≤ x ≤ 1.0 were grown by the chemical transport reaction technique. The Zn1-xCdxAl2Se4-4xS4x crystallizes in a defect chalcopyrite structure for a whole composition and has an optical energy gap ranging from 3.525 to 3.577 eV at 13 K. The photoluminescence spectra at 13 K showed a strong emission band in the blue spectral region and a weak broad emission band in the visible region due to donor–acceptor pair recombination. The composition and temperature dependence of these bands were examined in the investigated regions. The simple energy band scheme for the radiative mechanisms of the Zn1-xCdxAl2Se4-4xS4x is proposed on the basis of our experimental results along with photo-induced current transient spectroscopy measurements.