Spherical particles of α–Fe2O3 80 to 100 nm in size were prepared with the polyol method. Scanning electron microscopy, x-ray powder diffraction, and measurements of the diffuse reflection were used to characterize the powder material. The characteristic red color of hematite was adjusted after brief heating (250 °C, 15 min) which did not lead to further particle growth. The polyol method turned out to be suited for the preparation of quite concentrated (up to 20 wt%) and very stable suspensions of submicron Fe2O3 particles. Based on such suspensions, the red emitting phosphor Y2O2S:Eu was coated as a model substrate. As a result, very homogeneous coatings of α-Fe2O3 on the phosphor material were realized. Individual iron oxide particles on the phosphor surface confirm the presence of nonagglomerated Fe2O3 particles in the polyol medium.

The crystallization and nanoindentation behavior of a Zr–10Al–5Ti–17.9Cu–14.6Ni (at.%) bulk amorphous alloy (BAA) were studied. Resulting from the kinetic nature of phase transformation in multicomponent alloys, the crystallization path is complex. Despite the complexity of different crystallization paths, the main final crystallized product in the Zr-based BAA is Zr2Cu. Young's modulus and hardness of the BAA were found to increase with an increase in annealing temperature. The observed mechanical properties were correlated with the microstructure of the material. Also, in the present paper, both the observed crystallization and nanoindentation behavior are compared with existing data. Zr-based BAAs exhibit a ratio of hardness to Young's modulus (H/E ratio) of about 1/10, suggesting the interatomic bonding in the alloys is close to being covalent.

BxC1−x (x = 0.1 and 0.25) oriented platelets were intercalated with alkali metal vapor (M = K, Rb, Cs), giving first-stage M(B0.1C0.9)8 and M(B0.25C0.75)10. The presence of M(BxC1−x)5 dense domains interstratified in the first-stage structure were brought out from the 00.ℓ simulations. The presence of these domains is attributed to the acceptor electron effect of boron, which slightly enhances the intercalation rate as compared to pure carbon. Intercalation of Cs in liquid ammonia is improved using 1600 °C heat-treated B0.25C0.75 as a host material, and the composition Cs(B0.25C0.75)12 is reached after intercalation. In intercalation compounds of Cs in liquid ammonia obtained from heat-treated B0.25C0.75, as the heat-treatment temperature (HTT) was increased from 1600 to 2000 °C, the segregation of first stage was observed in two structures Cs(BxC1−x)8 and Cs(BxC1−x)10 with the respective 2 × 2 0° and 2.23 × 2.23 two-dimensional lattices of the cesium atoms. The presence of these two structures is assigned to the heterogeneity of the host material induced by the formation of B4C boron carbide domains and the consecutive boron elimination of the BxC1−x lamellar phase with increasing HTT.

Carbon microcoils obtained by the catalytic pyrolysis of acetylene at 770 °C were heat treated at 3000 °C for 6 h in a CO + CO2 atmosphere. The effect of the heat treatment on the morphology, microstructure, and properties was examined. The coiling morphology of the carbon coils was almost preserved even after the heat treatment, though it became brittle. The ruptured cross section of the two fibers, which form the coils, generally has either a trigonal pyramidlike form or negative pyramidal hollow. These characteristic ruptured patterns demonstrate the growth mechanism of the carbon coils. Distinct graphite layers (d = 0.339 nm) were developed by the heat treatment with an inclination of 10–40° versus the fiber axis to form a “herringbone” structure. The bulk electrical resistivity, density, and specific surface area were 10–0.1 Ωcm, 2.2077–2.087 g/cm3, and 6–8 m2/g, respectively.

Lanthanum phosphate glasses were synthesized by melt quenching and characterized by x-ray diffraction, electron microprobe analysis, and solid-state nuclear magnetic resonance spectroscopy. A range of compositions near the metaphosphate composition (75 mol% P2O5) was examined. Comparison of 31P chemical shifts and shielding anisotropies of glasses with those of the crystalline phases of La(PO3)3 (metaphosphate) and LaP5O14 (pentaphosphate) were consistent with the presence of primarily chainlike Q2 phosphate groups.

The fabrication process of an Al thin-film optical polarizer on LiNbO3 waveguides after CF4 plasma dry etching of a previously deposited SiO2 buffer layer was investigated. The problem in this process is a precipitation of compounds containing C, O, F, and Li on the etched LiNbO3 surface and a chemical deterioration of the Al caused by a reaction with these precipitates. Most notably, the growth of amorphous phase in addition to the crystalline Al metal grains and a partial oxidization of Al were found at the interface using transmission electron microscopy and x-ray photoelectron spectroscopy.

Thin-film composites of BaTiO3 particles in a polymeric matrix were processed by reacting films of a titanium alkoxide, mixed with a polybutadiene-polystyrene triblock copolymer, in aqueous solutions of 1.0 M Ba(OH)2 at temperatures ranging from 60 to 90 °. After reaction, the composite films displayed distinct surface and subsurface morphologies. The film surface consisted of a continuous layer of BaTiO3 grains, the film grain size decreasing from 180 to 60 nm as the reaction temperature increased from 60 to 90 °. The subsurface growth of BaTiO3 depended on the presence of a percolating network of hydrolyzed titanium alkoxide, which enabled the reaction solution to permeate throughout the thin film. The resulting subsurface film morphology was composed of segregated regions of BaTiO3 particles dispersed throughout the polymeric matrix. The growth of subsurface BaTiO3 particles appeared to be constrained by the polymer matrix, resulting in a subsurface particle size of approximately 5 to 10 nm that was independent of the hydrothermal processing temperature. The reacted films displayed a dielectric constant ranging from 10 to 15 at room temperature and a frequency of 10 kHz.

The ferrite with composition Cu0.5Fe2.5O4 was heat treated in air and in reducing atmospheres to different temperatures within the solid solution region confirmed by dynamic high-temperautre x-ray characterization. The samples were quenched in oil and air, and lattice parameter, Curie temperature, and saturation magnetization measurements were completed. The magnetization measurements for these samples showed a maximum 4πMs of 0.7729 and 0.5426 T at 10 and 300 K, respectively. The cationic distribution based on the low-temperature 4πMs measurements is (Cu+0.24Fe3+0.76)A[Cu+0.26Fe3+1.74]BO4 → 4.9 µ B. X-ray-pure Cu0.5Fe2.5O4 samples were also synthesized by slow cooling from the formation temperature to 900 °C in a reducing atmosphere. A temperature–PO2 diagram for the stability of Cu0.5Fe2.5O4 under the conditions of the experiment was determined. Low-temperature 4πMs measurements did not indicate an increase in the Cu+ A site occupancy for the samples cooled to 900 °C in a reducing environment above those samples that were quenched from high temperature. Curie temperatures for all Cu0.5Fe2.5O4 samples ranged from 348 to 369 °C. Lithium additions (0.1 mol/unit formula) to copper ferrite Li0.1Cu0.4Fe2.5O4 decreased the room-temperature 4πMs values to 0.5234 T with a corresponding decrease in the 10 K measurements to 0.7047 T. From the low-temperature magnetization measurements, the distribution was (Cu+0.15Fe3+0.85)A[Cu+0.25Li+0.1Fe3+1.65]BO4 → 4.48 µ B.

We have found that by varying only the substrate temperature and oxygen pressure five different crystallographic orientations of V2O5 thin films can be grown, ranging from amorphous to highly textured crystalline. Dense, phase-pure V2O5 thin films were grown on SnO2/glass substrates and amorphous quartz substrates by pulsed laser deposition over a wide range of temperatures and oxygen pressures. The films' microstructure, crystallinity, and texturing were characterized by electron microscopy, x-ray diffraction, and Raman spectroscopy. Temperature and oxygen pressure appeared to play more significant roles in the resulting crystallographic texture than did the choice of substrate. A growth map summarizes the results and delineates the temperature and O2 pressure window for growing dense, uniform, phase-pure V2O5 films.

The metastable immiscibility region in the Al2O3–SiO2 system was calculated by conventional thermodynamic equations using thermodynamic parameters obtained from molecular dynamics simulation. The calculated miscibility gap has a consolute temperature of around 1500 °C at the critical composition of about 20 mol% Al2O3 and spreads more widely towards the Al2O3-rich composition side than the SiO2-rich side. The calculated miscibility gap in this study showed a fair agreement with that reported by Ban et al. [T. Ban, S. Hayashi, A. Yasumori, and K. Okada, J. Mater. Res. 11, 1421 (1996)] calculated by a regular solution model, but the present calculated region is somewhat narrower in the Al2O3-rich composition side than that reported by Ban et al.

The residual stresses present in a thin film and the curvature formed at its substrate during deposition have been a great concern to electrochemists and process engineers. Here a new hybrid analytical method is presented to reanalyze the flexural problem subjected to a strain differential in the general case. It was shown that the present solutions for ultrathin films agree with Stoney's equation. Moreover, single or dual neutral axes resulted, depending on materials and thickness ratios between the film and the substrate. Quantitative differences with others in the solutions of deformed curvature and residual stress are discussed in a representative case of GaAs top coat/Si substrate wafers.

A simple model was presented for intrinsic stress generation in thin films resulting from surface stress effects. This mechanism can explain the origin of compressive stresses often observed during island growth prior to coalescence, as well as intrinsic compressive stresses reported for certain continuous, fully grown films. In some cases, surface stress effects may contribute to a sudden change in the intrinsic stress during island coalescence.

Commercially available poly(propylene)imine (DAB-Am-32 and DAB-Am-64) dendrimers were used as single-molecule templates to tailor the porosity of silicas via a nonacidic sol-gel method. X-ray diffraction on both the as-prepared (oven-dried at 373 K) and the calcined (833 K) materials revealed that modest contraction took place on template removal and that the cavities created did not achieve three-dimensional ordering under the current synthesis conditions. Transmission electron microscopy of “Pt-stained” samples supported this picture. A modified Horvath–Kawazoe analysis of the argon adsorption isotherms indicated that DAB-Am-64 is a much more effective template than DAB-Am-32. Pyrolysis and oxidation protocols for template removal are also presented.

The compounds GexNbTe2 (0.39 ≤ x ≤ 0.53) have been studied for their thermoelectric properties. By changing x, the carrier concentration can be adjusted so that the material changes from a p-type metal to a p-type semiconductor. The maximum germanium concentration at about Ge0.5NbTe2 is also the most semiconducting composition. High- and low-temperature electrical resistivity, Hall effect, Seebeck coefficient, and thermal conductivity were measured. Evidence of electronic ordering was found in some samples. The thermal conductivity is reasonably low and glasslike with room temperature values around 20–25 mW/cm K. However, the power factor is too low to compete with state-of-the-art materials. The maximum thermoelectric figure of merit, ZT found in these compounds is about 0.12. The low ZT can be traced to the low carrier mobility of about 10 cm2 /Vs. The related compounds Si0.5NbTe2 and Ge0.5TaTe2 were also studied.

Microstructural changes in sol-gel-derived SrxBa1−xNb2O6 (SBN) thin films were monitored as a function of Ba-to-Sr ratio (from x = 0 to x = 1), choice of substrate (Si or MgO), and processing variations. Sols were created using Ba, Sr, and Nb alkoxides dissolved in acetic acid. The relatively high decomposition temperature for the organics led to a tendency to form defects, but careful control of thermal process parameters could be used to produce a uniform film microstructure. An unexpected phase, interpreted as a hexagonal (pseudo-orthorhombic) variant of hexagonal BaNb2O6, was encountered in Ba-rich sol-gel-derived SBN powders and thin films annealed at 750 °C. Increased (001) orientation was observed for SBN thin films deposited on (100) MgO when fast thermal processing was used.

Microporous silicotitanates can potentially be used as ion exchangers for removal of Cs+ from radioactive waste solutions. The enthalpies of formation from constituent oxides for two series of silicotitanates at 298 K have been determined by drop-solution calorimetry into molten 2PbO · B2O3 at 974 K: the (Na1−xCsx)3Ti4Si3O15(OH) · nH2O (n = 4 to 5) phases with a cubic structure (P43m), and the (Na1−xCsx)3Ti4Si2O13(OH) · nH2O (n = 4 to 5) phases with a tetragonal structure (P42/mcm). The enthalpies of formation from the oxides for the cubic series become more exothermic as Cs/(Na + Cs) increases, whereas those for the tetragonal series become less exothermic. This result indicates that the incorporation of Cs in the cubic phase is somewhat thermodynamically favorable, whereas that in the tetragonal phase is thermodynamically unfavorable and kinetically driven. In addition, the cubic phases are more stable than the corresponding tetragonal phases with the same Cs/Na ratios. These disparities in the energetic behavior between the two series are attributed to their differences in both local bonding configuration and degree of hydration.

Micro-Raman spectroscopy was used to study the formation of BaFe12O19 (BaM) powders derived from water-in-oil microemulsion at different calcination temperatures. With increase in the calcination temperature, the Raman spectra of the BaM powders become narrower and stronger without apparent frequency shifts of the Raman bands. The calcination temperature dependence of the Raman spectra and the magnetic properties of the BaM powders result from the crystallization rather than size effect. Our results show that there is a strong correlation between the crystallinity and the magnetic properties, which could be explained in terms of the crystallization effect on the superexchange interaction between ferric ions. The γ–Fe2O3 phase occurred in the BaM precursor and the powder calcined at 500 °C. The α–Fe2O3 phase was developed in the powders calcined at 500, 600, and 700 °C, which was not detected by x-ray diffraction. With increasing calcination temperature, the γ–Fe2O3 phase can either react with oxide containing barium to form the BaM phase or transform to the α–Fe2O3 phase. The amount of α–Fe2O3 decreases due to reaction with BaCO3 to form BaM phase at higher calcination temperature.

We have demonstrated that the optimum Ta–Si–N compositions for use as oxygen diffusion barriers in stacked-capacitor dynamic random-access memory structures with perovskite dielectrics are in the range Ta(20–25 at.%)–Si(20–45 at.%)–N(35–60 at.%). Twenty-two different Ta–Si–N compositions were evaluated, starting from six sputter-deposited Ta–Si alloys of which four were reactively deposited in 2–8% nitrogen in an argon plasma. The barriers were evaluated after an aggressive 650 °C/30 min oxygen anneal to determine if they remained electrically conductive, prevented oxygen diffusion and formation of low dielectric constant oxides, and had minimal interaction with the Pt electrode and underlying Si plug. Rutherford backscattering spectroscopy, four-point probe sheet resistance, through-film-resistance, and x-ray diffraction analysis techniques were used in the evaluation.

A new type of aluminum ionized center associated with the copper ion [AlO4−/Cu++]+ has been observed in a copper(I)-containing silica glass upon γ-irradiation at room temperature. The center, unlike many other previously reported monovalent cation-compensated aluminum ionized hole centers [AlO4/M+]+, where M+ = H+, Li+, Na+, Ag+, etc., behaves more like a simple ionized center rather than an ionized hole center. We argue that complete compensation of the hole on the aluminum ion of the center becomes possible because of the compensating copper ion. This is accomplished by the donation of an electron by the cuprous ion to the neighboring irradiationgenerated [AlO4]0 hole via that oxygen atom of the (AlO4), which is nearest to the cation.

Pb(Zr0.52Ti0.48)O3 thin films were grown on p-InP (100) substrates by using radio-frequency magnetron-sputtering at a relatively low temperature (∼450 °C). X-ray diffraction measurements showed that the Pb(Zr0.52Ti0.48)O3 film layers grown on the InP substrates were polycrystalline, and Auger electron spectroscopy measurements indicated that the compositions of the as-grown films consisted of lead, zirconium, titanium, and oxygen. Transmission electron microscopy measurements showed that the grown Pb(Zr0.52Ti0.48)O3 was a polycrystalline layer with small domains and that the Pb(Zr0.52Ti0.48)O3/InP (100) heterointerface had no significant interdiffusion problem. Room-temperature current–voltage and capacitance–voltage (C–V) measurements clearly revealed a metal–insulator–semiconductor behavior for the Pb(Zr0.52Ti0.48)O3 insulator gates, and the interface state densities at the Pb(Zr0.52Ti0.48)O3/p-InP interfaces, as determined from the C–V measurements, were approximately low 1011 eV−1 cm−2 at an energy of about 0.6 eV below the conduction-band edge. The dielectric constant of the Pb(Zr0.52Ti0.48)O3 thin film, as determined from the C–V measurements, was as large as 907.2. These results indicate that the Pb(Zr0.52Ti0.48)O3 layers grown on p-InP (100) substrates at low temperatures hold promise for potential high-density nonvolatile memories and high-speed infrared sensors based on InP substrates.