We report a method for preparing Pr-doped ceria by pyrolysis at 600 °C of aerosols consisting of aqueous solutions of Ce(III) nitrate and Pr(III) chloride. This procedure involves an important decrease of the temperature of solid solution formation (several hundred degrees) when compared with the ceramic and other previously reported methods, and does not require the addition of fluxes. The prepared samples and their products after thermal treatment were characterized in terms of particle shape and size distribution, composition, and crystalline structure. The color properties of these solid solutions were also evaluated as a function of the heating temperature and composition; the optimum red pigment was obtained for samples with a Pr/Ce mole ratio = 0.063 heated for 3 h at 600 °C. The oxidation state of the Pr cations and their distribution in the CeO2 matrix were investigated by x-ray absorption near-edge spectroscopy and x-ray photoelectron spectroscopy. A mixture of trivalent and tetravalent Pr was detected in all studies samples. The Pr(IV)/Pr(III) ratio increased as the Pr content or the heating temperature increased. These Pr(III) cations were found to be mainly located in the particles' outer layers, in which an enrichment of Pr was detected for all samples heated at 600 °C. The further calcination of the pigments at 1200 °C gave rise to a certain diffusion of the Pr cations toward the particle core, which was more significant for the sample with the highest Pr content (Pr/Ce mole ratio 4 0.091).

The effects of an interposed Cu layer and a surface Cu layer on the C49–C54 TiSi2 transformation temperature were studied. For the Ti/Cu/(100)Si samples the interposed Cu layer significantly enhanced the thermal stability of C49 TiSi2. The temperature for complete C49–C54 TiSi2 transformation was raised from 710 to 735 to 750 °C with the thickness of the interposed Cu layer increasing from 0 to 1.5 to 3.5 nm, correspondingly. Cu was insoluble in C54 TiSi2. For the Cu/Ti/(100)Si samples, the surface Cu layer did not at all enhance the thermal stability of the C49 phase. In the present study, the enhanced thermal stability of C49 TiCuxSi2–x can be attributed to its reduced electron/atom ratio and larger grain size relative to those of C49 TiSi2.

In this work, Fe2Mo intermetallic powder, produced by H2 gas reduction of Fe2MoO4 was characterized by techniques like x-ray diffraction (XRD) and transmission electron microscopy (TEM). The TEM studies confirmed the presence of nano- and microcrystalline grains of Fe2Mo. The above powders when compressed uniaxially showed a logarithmic relation with “relative density”, δr, of the compacts. The multiple compaction mechanisms were analyzed by Kawakita's and Balshin's models. Vickers hardness number, VHN, was found to increase linearly with δr of the compacts. The hardness of Fe2Mo intermetallic when δr = 1 was estimated as 343 VHN. Using Tabor's analysis, the yield strength of Fe2Mo was found to be about 1100 MPa. This value was further confirmed from the details of relative broadening (112) Bragg peak of Fe2Mo obtained from XRD analyses of Fe2Mo at different compaction pressures.

The microstructures and mechanical behavior of bulk nanocrystalline γ–Ni–xFe (n-Ni–Fe) with x = ∼19–21 wt%, synthesized by a mechanochemical method plus hot-isostatic pressing, were investigated using microstructural analysis [x-ray diffraction, energy-dispersive spectroscopy, light emission spectrum, atomic force microscopy (AFM), and optical microscopy (OM)], and mechanical (indentation and compression) tests, respectively. The results indicated that the yield strength (σ0.2) of n-Ni–Fe (d ∼ 33 nm) is about 13 times greater than that of conventional counterpart. The change of yield strength with grain size was basically in agreement with Hall–Petch relation in the size range (33–100 nm) investigated. OM observations demonstrated the existence of two sets of macroscopic bandlike deformation traces mostly orienting at 45–55° to the compression axis, while AFM observations revealed that these bandlike traces consist of ultrafine lines. The cause for high strength and the possible deformation mechanisms were discussed based on the characteristics of microstructures and deformation morphology of n-Ni–Fe.

Results of a chemical vapor deposition crystal growth method intended to produce large amounts of InN needed for thermodynamic experiments are reported. Polycrystalline films of InN were grown by reaction of InCl3 and NH3 in a hot-wall silica reactor under nearly atmospheric pressure. Samples were analyzed using x-ray diffraction and chemical analysis. The decomposition of InN was studied in both thin film and powder form. InN films were investigated by isothermal heating under nitrogen and subsequent microscopic inspection. The removal of the nucleation barrier of forming the first liquid phase was emphasized. InN powder decomposition experiments involved two different customized thermogravimetric methods: (i) dynamic oscillation thermogravimetric analysis (TGA), and (ii) isothermal stepping TGA for a higher resolution of the decomposition start. The decomposition start was found consistently at (773 ±5) K under 1 bar of nitrogen. Nevertheless, it is suggested that InN may be metastable even below room temperature based on Computer Coupling of Phase Diagrams and Thermo chemistry-type thermodynamic analysis of all available phase equilibrium and thermodynamic data. This included the determination of the absolute entropy of InN, 31.6 ±3 J/mol-formula K, based on a Debye and Einstein analysis of the experimental data on the heat capacity. All calculations of pressure are corrected for the fugacity of nitrogen, which becomes crucial above 1000 bar. The contradictory literature data in the In–N system are discussed based on three different internally consistent thermodynamic analyses of the system that highlight the consequences of different choices made on the decomposition temperature of InN. Widely reproduced data in the literature are shown to produce thermodynamically impossible negative absolute entropy of InN. Complete P-T-x phase diagrams are given, which strongly suggest that solid InN is metastable under ambient conditions. To find out that InN crystals could be reproducibly superheated more than 500 K before they actually decompose comes as a surprise compared to other III-V systems, especially Ga–N.

A planetary ball-mill device that enables one to perform solid-gas reactions at constant pressure was developed. Titanium powders were ball milled under nitrogen at a spinning rate of 960 rpm. The influence of the nitrogen pressure on the mechanochemical reactivity of titanium was analyzed at 1.5 and 11 bars. A spontaneous combustion took place during the grinding process, leading to a high yield of TiN for short milling times. The conversion of titanium into titanium nitride was facilitated by increasing the nitrogen pressure. At 11 bars, full conversion was reached for grinding times shorter than 5 h. Titanium nitride obtained in this way exhibited a high sintering activity.

The texture development during cold rolling and recrystallization of L12-type Co3Ti alloys was investigated as functions of alloy composition and rolling reduction. Two kinds of fully annealed Co3Ti alloys with different alloy compositions (Co77Ti23 and Co78Ti22), whose initial textures and grain sizes were almost identical, were used. After 70% reduction, the cold-rolling textures of both alloys were composed of strong α-fiber and weak β-fiber textures, in which the intensity of {011}〈211〉 orientation was higher than those of {112}〈111〉 and {123}〈634〉 orientations, indicating that texture transition from copper type to brass type occurred in cold-rolled Co3Ti alloys. This texture transition was more prominently recognized in the Co78Ti22 alloy, whose chemical composition was more off-stoichiometric. On the other hand, the recrystallization textures of both alloys were considerably weak, and their orientation spreads were more significant with increasing rolling reduction. Also, the recrystallization textures were basically independent of alloy composition in contrast to the rolling textures.

Transmission losses were monitored in the ultraviolet-visible spectra of irradiated hydroxyethyl methacrylate (HEMA) copolymer at elevated temperatures. The transmission in irradiated HEMA in the ultraviolet and visible wave length range was almost the same for doses 400 kGy ≤ Φ ≤ 1000 kGy, but was smaller than that of the nonirradiated HEMA copolymer. The reduction in transmission in the irradiated specimens was attributed to the presence of color centers. The concentration of color centers was enhanced by thermal annealing. The transmission data (or absorption data) at 467 nm was found in good agreement with the theoretical model in which the color center production followed a first-order kinetic process. The rate constant satisfies the Arrhenius equation, and the corresponding activation energy is 17.37 kJ/mol and is independent of the dosage. The results were compared with those reported in the literature.

Multilayer oxides of SrNb0.1Ti0.9O3/La0.8Sr0.2MnO3/SrTiO3 have been grown by computer-controlled laser molecular beam epitaxy and characterized by transmission electron microscopy. Electron microdiffractions and high-resolution imaging reveal that the as-prepared thin film of La0.8Sr0.2MnO3 with thickness of 200 nm is epitaxially grown on the SrTiO3(001) substrate and the SrNb0.1Ti0.9O3 with thickness of 250 nm epitaxially on the as-received La0.8Sr0.2MnO3 film. The microstructures in the La0.8Sr0.2MnO3 film are clarified in terms of the oriented microdomains. In contrast, microstructures in SNTO are featured by the formation of superstructures due to charge ordering. Crystallographic relationships of these domains are discussed on the basis of an orthorhombic cell and rationalized by theoretical calculations based on a geometrical model.

A fine NiO powder and a Sm-doped ceria powder with a composition of Ce0.8Sm0.2O1.9 were synthesized by heating the oxalate precursors at 300–1200 °C in air to produce a cermet (anode material) for solid oxide fuel cell. A 0.2 M Ni(NO3)2 solution and a 0.2 M Ce(NO3)3–Sm(NO3)3 solution were mixed with 0.4 M oxalate solution, respectively, to produce the oxalate precursors. Only the cubic phase of Ce0.8Sm0.2O1.9 was formed in the calcined powders from the Sm-doped cerium oxalate. However, the mixed phases of NiO and Ni were produced in the NiO precursor after the calcination at 300–600 °C. At higher temperatures, only NiO was detected. The primary particle sizes, which were determined from the Brunauer-Emmett-Teller analysis surface areas, were 60 nm for NiO and 10 nm for Ru/Sm-doped ceria (SDC) after the heat treatment at 400 °C. The oxalate precursors of SDC and NiO provided 433 and 259 kJ/mol of the activation energy, respectively, for sintering/grain growth in the temperature range from 600 to 1200 °C. As-produced SDC precursor formed platelike secondary particles of 0.5–2-μm length by the heating at 800 °C. Heating of Ni oxalate at 800 °C produced isotropic fine NiO secondary particles of 0.5–2-μm sizes.

A microstructural model of steady-state creep that couples grain-boundary transport, micromechanics, and grain sliding is employed to investigate the grain-boundary diffusional creep response of an idealized microstructure with variable boundary diffusivities. Both numerical and analytical methods were used to determine the stress state and, in some cases, the strain rate associated with an applied uniaxial, tensile stress. Various types of boundaries are considered, and the implications of our results for more general microstructures are discussed.

Prediction of density–time curves, i.e., using the sintering curves for one green density to predict those of another during isothermal sintering, was demonstrated for 3 mol% yttria-stabilized zirconia and titania, as well as for data from the literature on various ceramic powder compacts. The predictions utilized only a median green pore size term as the scaling parameter for densification rates between samples of different green densities. Despite the simplicity of the approach, the resulting predictions of density–time curves were in relatively good agreement with the measured data.

Some tungsten-bronze compounds in the BaO–Nd2O3–TiO2–Nb2O5 system were prepared and characterized. Ba4Nd2Ti4Nb6O30 and Ba5NdTi3Nb7O30 had the filled tetragonal tungsten-bronze structure, and Ba3Nd3Ti5Nb5O30 consisted of the tetragonal tungsten-bronze major phase and a minor amount of secondary phase BaNd2Ti3O10. These compounds had significant relaxor behaviors, and the Curie temperatures (at 1 MHz) were 0 and 55 °C for Ba3Nd3Ti5Nb5O30 and Ba5NdTi3Nb7O30 ceramics, respectively. A high dielectric constant (213) combined with low dielectric loss (0.004 at 1 MHz) was obtained in Ba3Nd3Ti5Nb5O30 ceramics. In addition, the solid-solution range of BapNd6−pTi8−pNb2+pO30 was 3 < p ≤ 6.

The absence of a low dielectric constant layer at the barium strontium titanate (BST)/Pt interface and a decreased roughness are critical issues in the production of (Ba0.5Sr0.5)TiO3 thin films with high tunabilities and low losses. An improvement in dielectric properties was achieved by the insertion of seed layers at the BST/Pt interface by pulsed laser deposition. The higher tunability can be attributed to (100) texturing of the BST films, which is independent of grain size and grain morphologies, thus leading to a variation in seed layer thicknesses. The tunability and dielectric constant of 1600-Å-thick BST films showed a maximum of 53% and 720, respectively, at a seed layer thickness of 100 Å. Dielectric loss is dependent on the roughness of BST films and reached a minimum of 0.8% at a root mean square roughness of 28 Å. The maximum figures of merit, defined as the ratio of tunability to dielectric loss, of approximately 58 at 100 kHz and 198 kV/cm were obtained at a seed layer thickness of 70 Å. The optimized seed layer thickness for BST deposition onto Pt/Ti/SiO2/Si substrates plays an important role in maintaining the high tunabilities and low loss, which are suitable for microwave device applications.

Nanocomposite materials consisting of ZrO2 and Pd phases were prepared by heating the amorphous Zr65Pd35 alloy for 24 h at 553 K in air. The maximum hydrogen absorption amount is about 2.4 mass% (H2/Pd) at 323 K and 2.2 mass% (H2/Pd) at 423 K at hydrogen pressure of 1 MPa. The absorption amount of Pd nanoparticles in the nanocomposite is a few times larger than those for the bulk and powder Pd metals. The remarkable increase in the hydrogen absorption/desorption amounts seems to result from the isolated dispersion state of Pd nanoparticles in the ZrO2 phase containing a tremendously large interface area in the nanocomposite.

β-Spodumene (Li2O · Al2O · 4SiO2, LAS4) precursor powders were obtained through a sol-gel process using Si(OC2H5)4, Al(OC4H9)3, and LiNO3 as starting materials and LiF as a sintering aid. X-ray diffraction, scanning electron microscopy, scanning transmission electron microscopy with a wavelength dispersive spectrometer, and electron diffraction analysis were utilized to study the phase transition of the β-spodumene glass–ceramics prepared from the gel-derived precursor powders with LiF additive. For the LAS4 precursor powders containing no LiF, the only crystalline phase obtained was β-spodumene. For the pellets containing less than 4.0 wt% LiF and sintered at 1050 °C for 5 h, the crystalline phases were β-spodumene solid solution and β-eucryptite (Li2O · Al2O3 · 2SiO2, LAS2) solid solution. When the LiF content was 5.0 wt% and the sintering process was carried out at 1050 °C for 5 h, the crystalline phases were β-spodumene solid solution, β-eucryptite solid solution (triclinic), and eucryptite [rhombohedral (hex.)]. When the LiF addition attains 3.0 wt%, the fully densified grains are formed, accompanied with an increase in grain size for LiF addition. At the triple junction of grain boundaries a second phase segregates which is identified to be β-spodumene solid solution. In the sintering period of LAS4 precursor powders with LiF additive, the grains converted to β-eucryptite solid solution and β-spodumene solid solution remains at the grain boundaries.

Single-phase polycrystalline ceramics in the MO–La2O3–TiO2 (M = Ca, Sr, Ba) system, such as cation-deficient hexagonal perovskites CaLa4Ti4O15, SrLa4Ti4O15, BaLa4Ti4O15, and Ca2La4Ti5O18 and the orthorhombic phases CaLa4Ti5O17 and CaLa8Ti9O31, were prepared through the solid-state ceramic route. The phases and structure of the ceramics were analyzed through x-ray diffraction and scanning electron microscopy. The microwave dielectric properties of the ceramics were studied using a network analyzer. The investigated ceramics show high εr in the range 42 to 54, high quality factors with Q ×f in the range 16,222 to 50,215 GHz, and low Tf in the range –25 to +6 ppm / °C. These high dielectric constant materials with high Q × f up to 50,215 GHz are suitable for applications where narrow bandwidth and extremely low insertion loss is necessary, especially at frequencies around 1.9 GHz.

The dissolution in de-ionized water (DIW) at 90 and 150 °C of Cs and Ba from mechanically polished Cs-doped Ba hollandite samples is essentially congruent. The normalized Ba and Cs release rates were <0.001 g/m2/day after 56 days in DIW at 90 °C, and the Ba normalized release rate of a Cs-free sample was 0.01 g/m2/day after 56 days in DIW at 150 °C. Varying the pH between approximately 2.5 and 12.9 affected only the Ba dissolution rates of hollandite by half an order of magnitude. The dissolution rates of all species decrease with increasing leaching time due to the formation of partly impervious surface coatings of Al- and Ti-rich species. These surface coatings were investigated by scanning electron microscopy, and in some cases by cross-sectional transmission electron microscopy and x-ray photoelectron spectroscopy.

Titanium diboride has been claimed as a very promising candidate material for protective applications in the magnetic recording. Its oxidation resistance at room temperature is a critical criterion in assessing this application potential. In this paper, the oxidation characteristics of ultrathin TiB2 thin films, such as overcoat erosion and oxide thickness, are investigated via a combination of x-ray reflectivity, x-ray photoelectron spectroscopy (XPS), and atomic force microscopy. It was found that a <2-h exposure to air at room temperature led to the formation of approximately 15-Å-thick, well-defined oxides at the expense of an approximately 9-Å erosion of the TiB2 overcoats, coupled with the existence of a sharp oxide/TiB2 interface. XPS studies confirmed the existence of the oxides. Considering the decreasing allowable thickness for such protective overcoats, oxidation and the resultant thickness gain negate such a potential of ultrathin TiB2 films. The results in our current report provide a new perspective on its potential as protective overcoats in magnetic recording.

Sequential pulsed-laser irradiation of silicon in SF6 atmospheres induced the formation of an ensemble of microholes and microcones. Profilometry measurements and direct imaging with an intensifying charge-coupled device camera were used to study the evolution of this microstructure and the laser-generated plume. Both the partial pressure of SF6 and the total pressure of an SF6-inert gas mixture strongly influenced the maximum height that the microcones attained over the initial surface. The cones first grew continuously with the number of pulses, reached a maximum, and then began to recede as the number of laser pulses increased further. The growth of the cones was closely connected with the evolution of the laser-generated plume.