Ten years after the discovery of high-Tc superconductivity in the system Bi–Sr–Ca–Cu–O, the superconducting compounds have been identified, and their structures, crystal chemistry, phase equilibria, and properties have been extensively investigated. In this review, the results of studies of crystal chemistry and phase equilibria are presented to give materials scientists a comprehensive insight into the phase equilibria and crystal chemistry of these challenging materials.

Tetragonal ferroelectric materials are polarized to induce the anisotropy necessary for the piezoelectric effect. This poling of the material is inherently an orientation process. Pole figure texture measurements of poling and cross-poling in a lead zirconate titanate Navy VI material show domain motion. The resulting axisymmetric and three-dimensional textures demonstrate the contribution of 90° domain motion to piezoelectricity. Cross-poling results in strong orientations with lower applied fields than in the initial poling steps.

A new approach was used for combining GaN and porous Si with the goal of producing high-quality GaN epitaxial layers for optoelectronic integrated circuit devices based on Si substrates. Reflection high-energy electron diffraction (RHEED), x-ray diffraction (XRD), photoluminescence (PL), and Van der Pauw–Hall effect measurements were performed to investigate the structural, optical, and electrical properties of the GaN epitaxial films grown on porous Si(100) by plasma-assisted molecular-beam epitaxy with a two-step method. The RHEED patterns were streaky with clear Kikuchi lines, which was direct evidence for layer-by-layer two-dimensional growth of GaN epitaxial layers on porous Si layers. The XRD curves showed that the grown layers were GaN(0001) epitaxial films. The results of the XRD and the PL measurements showed that the crystallinities of the GaN epilayers grown on porous Si by using a two-step growth were remarkably improved because the porous Si layer reduced the strains in the GaN epilayers by sharing them with the Si substrates. Hall-effect measurements showed that the mobility of the GaN active layer was higher than that of the GaN initial layer. These results indicate that high-quality GaN epitaxial films grown on porous Si(100) by using two-step growth hold promise for potential applications in new kinds of optoelectronic monolithic and ultralarge integrated circuits.

The influence of electropulsing on the damage of 1045 steel was studied. The results show that electropulsing can substantially increase the strength and ductility of the damaged material, with a little decrease of the Martensite hardness. After the treatment of electropulsing, the microstructure around the crack is modified, and the new structure can prevent the crack from growing. The healing effect of electropulsing on crack is discussed. It is thought that the temperature and thermal compressive stress caused by electropulsing are the main factors causing the healing effect.

The effect of strain rate on tensile ductility of moisture-induced embrittlement of Co3Ti alloys was investigated at ambient temperatures (298–353 K) by tensile test and scanning electron microscope fractography. The anomalous increase of tensile elongation and ultimate tensile stress was observed in a very low strain rate region and also at high temperatures, accompanied by an increase of area fraction in ductile transgranular fracture pattern. The anomalous strain rate dependence of tensile ductility was shown to become more evident with decreasing grain size and also with deviation from alloy stoichiometry. Oxidation on the alloy surface was suggested as a process counteractive to the hydrogen decomposition process from moisture in air.

An in situ temperature measurement was performed during spraying of A2-tool steel, and the results were used to verify an axisymmetric two-dimensional computer simulation program, which was developed for the prediction of shape and temperature variation in a spray-forming process. A thin thermocouple was placed inside of the chamber in advance and brought to the surface of the deposit during spraying. The temperature was then recorded. The surface temperature of the deposit was also measured by an infrared video camera. The emissivity of the surface of A2-tool steel during spraying was determined to be 0.23 through comparison of the temperatures measured by the thermocouple with the ones measured by the infrared video camera. The heat transfer coefficient at the top surface was estimated by comparing the calculated results with the experimental data. The cooling curve predicted on the basis of the numerical simulation showed good agreement with the experimental data.

BN films consisting of c-BN and h-BN phases were synthesized using an ion-beam-assisted deposition process. In contrast to conventional observations, the c-BN and h-BN phases did not form separate layers, but were distributed in the form of nano-sized grains throughout the film thickness. No distinctly aligned h-BN layer was observed before the c-BN phase. Such a mixed character of the film was attributed to a localized ion bombardment effect instead of the macro-stress. Possibly because of the presence of scattered h-BN phases, the thin film described here possessed a low hardness of about 20 GPa and a low stress of about 5 GPa, compared with other reported c-BN-containing films.

Bi-2212 cylindrical rods were obtained using a laser-induced directional solidification system. Although as-grown Bi-2212 samples are well textured, they do not exhibit superconducting behavior and, as a result, need further heat treatments. The modifications taking place during annealing were analyzed in the present work, in particular with respect to the evolution of the microstructure with the annealing time and the phase content. Diffusion processes in which the Bi-2212 phase grows along the thickness of the platelets take place during annealing. The presented results show that the physical properties of these samples improve during the initial approximately 60 h of annealing and that they remain constant thereafter.

A detailed compositional analysis of high-critical-current-density (Jc) (55 and 65 kA/cm2 at 77 K) (Bi,Pb)2Sr2Ca2Cu3Oy (Bi-2223) tapes was undertaken by energy dispersive spectroscopy in the transmission electron microscope. Structural features were coupled with characteristic compositions of the Bi-2223 phase. The average of all compositional measurements of the Bi-2223 phase was determined to be Bi1.88Pb0.23Sr1.96Ca1.95Cu2.98Oy. However, spatial variations in the Bi-2223 composition and differing phase equilibria were found throughout the filament structure. In particular, a considerable range of Bi-2223 compositions can be found within a single tape, and the lead content of the Bi-2223 phase is significantly depressed in the vicinity of lead-rich phases. The depletion of lead in the Bi-2223 phase around the 3221 phases may be a current-limiting microstructure in these tapes.

In the process of developing electro-optic devices from ferroelectric z-cut LiNbO3 wafers, a repolarization throughout the wafer thickness occurs due to a localization of electric charges on the wafer. The repolarization not only generates microdomains causing light to scatter but also large defects in the crystal that become the origin of wafer fracture. The size of such defects is comparable to the wafer thickness (0.5 mm), and an anomaly in the chemical and crystalline structures can be found in them. X-ray diffractometry and x-ray photoelectron spectroscopy confirm that a chemical reduction in the defective region occurs.

The effects of doping on the morphological and microstructural properties of TiO2 nanopowders produced by laser pyrolysis were investigated mainly by x-ray diffraction (XRD) and electron microscopy. Samples of TiO2 powders were prepared by doping with different trivalent cations (Al and Ga). The powders were calcined at different temperatures in the range 400–1000 °C for 18 h, as well as at constant T = 700 °C up to 160 h. After each thermal treatment, XRD patterns were collected. The analysis of XRD patterns allowed us to estimate the microstrains and average crystallite size and to observe the evolution of the microstructural parameters with temperature. Both Al and Ga inhibited the crystallite growth of TiO2 anatase and the rutile phases, this effect being larger in the Al-doped powders.

The mechanism of bubble formation when He is implanted into silicon is described. Many experiments are reviewed and several techniques are considered. During implantation and subsequent annealing, complex Hen–Vm clusters are formed, trapping vacancies, while Si self-interstitials recombine directly at the surface. By increasing temperature He atoms out-diffuse, and the entire process produces a supersaturation of vacancies (void formation). Their evolution is studied during isothermal and isochronal annealing, describing the mechanisms involved; that is, direct coalescence or Ostwald ripening. The internal surface is an efficient trap for self-interstitials and for metals. The gettering mechanism is governed by a surface adsorption at low impurity concentration while at high value a silicide phase is observed. The high getter capability is ensured by the large number of traps introduced (1017–1019 cm−3). Finally, voids introduce mid gap energy levels that act as minority carrier recombination centers, providing a powerful method to control lifetime locally in silicon devices. The reviewed results demonstrate that the trap levels are due to the dangling bonds present on the void surface. This property can be used in many applications.

Co3O4 was prepared in aqueous solutions through a staged oxidation process. When the mole ratio of starting chemicals Co2+:OH− is ≤1:2 (Co2+ as a limiting reagent), the formation reaction follows the brucitelike phase to cobalt oxide-hydroxide, and then to cubic spinel. However, when the ratio of Co2+:OH− is > 1:2 (OH− as a limiting reagent), the reaction path changes to the brucite-like to hydrotalcite-like phase, and then to the spinel. Using the present method, Co3O4 can be formed at a temperature as low as 40 °C, and single-phase spinel Co3O4 can be prepared at 50 °C within hours under normal atmospheric pressure.

Chemical vapor deposition of carbon nanotubes by catalytic decomposition of acetylene on V2O5 microtube crystals is presented. The catalyst was prepared by laser irradiation of vanadium sheets and treated with cobalt acetate solution. The carbon deposits generated on this novel type of catalyst were characterized by transmission electron microscopy measurements. Both carbon nanofibers and carbon nanotubes were found to be formed. This catalyst system, generated by the combined laser irradiation and chemical impregnation methods, is a new and promising way to study the differences in the mechanism of the generation of nanostructures.

The optical transparencies and electrical conductivities of thin films of In2O3 mixed with ZrO2 have been investigated. These films were deposited on glass substrates at room temperature using pulsed-laser deposition. Indium–zirconium oxide films with a ZrO2 content up to a 15 wt% were conducting and more than 80% transparent from 450 to 700 nm. As the ZrO2 content increased from 0 to 15 wt%, the electrical resistivities increased from 1.28 × 10−3 to 6.48 × 10−2 Ω cm, the carrier densities were decreased from 2.14 × 1020 to 1.0 × 1018/cm3, and the Hall mobilities decreased from 21 to 5 cm2 V−1 s−1, all monotonically.

The subsolidus equilibria and the primary phase field (crystallization field) of the 110 K high-Tc (Bi,Pb)-2223 ([Bi,Pb]:Sr:Ca:Cu) phase have been determined in the presence of Ag under a 92.5% Ar/7.5% O2 atmosphere (volume fraction). A total of 29 six-phase volumes that include both the (Bi,Pb)-2223 and Ag phases was observed. These subsolidus volumes are similar to those observed without the presence of Ag. The compositional range of initial melts of these volumes (mole fraction basis) covers BiO1.5 from 5.6% to 25.3%, PbO from 0.4% to 13.8%, SrO from 8.4% to 31.9%, CaO from 12.2% to 33.3%, CuO from 21.7% to 40.9%, and AgO0.5 from 1.2% to 6.3%. Based on these data, the primary crystallization field for the (Bi,Pb)-2223 phase in the presence of Ag was constructed using the convex hull technique. A section through this “volume” was portrayed by holding the AgO0.5, SrO, and CaO components at the median value of the 29 compositions while allowing projection on the other three axes (BiO1.5, PbO, and CuO). The net effect of Ag on the melt composition is a reduction in the PbO concentration and an increase in the SrO content. Applications of the liquidus data are also discussed.

This research involves using molten magnesium (Mg) to remove neodymium (Nd) from NdFeB magnet scrap by diffusion. Mg was melted over pieces of NdFeB scrap and held at temperatures in the range 675–705 °C for 2–8 h. The Mg was allowed to solidify, and the castings were then sectioned and characterized using scanning electron microscopy, x-ray diffraction, and chemical analysis. Nd was found to have diffused out of the solid scrap into the molten Mg. The thickness of the diffusion layer was measured, the diffusion of Nd through the NdFeB scrap into liquid Mg was described, and the diffusion coefficient of Nd in liquid Mg was estimated.

The evolution in both stress and microstructure was investigated on sputtered Cu0.57Ni0.42Mn0.01 thin films of 400 nm thickness during the first temperature cycle up to 550 °C. Samples from stress–temperature measurements up to various maximum temperatures were analyzed by x-ray diffraction, scanning and transmission electron microscopy, and Auger electron spectroscopy. The columnar grains with lateral diameters of about 20 nm in the as-deposited state coarsen to about 400 nm above 300 °C. Probably due to the impurity (Mn) drag effect, the coarsening occurs by abnormal grain growth rather than by normal grain growth, starting near the film–substrate interface. The stress development results from a combination of densification due to grain growth and plastic stress relaxation.

The yield strength of Cu–Nb filamentary microcomposites was predicted as a function of Nb content by modifying the barrier strengthening model. To predict the variation of the yield strength with Nb content, the interfilamentary spacing was calculated as a function of Nb content on the basis of the assumption that Nb filaments are distributed regularly along the sides of triangular unit cells. The yield stress can be described as the sum of the substructural strengthening component and the filament boundary strengthening term. The good agreement between the prediction and the experimental data suggests that the strength increase in Cu–Nb filamentary microcomposites with increasing Nb content results mostly from increasing the volume fraction of Nb filaments, which act as barriers to plastic flow.

Chemical solution epitaxy was used to deposit an epitaxial film of Gd2O3 on roll-textured nickel. A 2-methoxyethanol solution of gadolinium methoxyethoxide was used for spin-coating and dip-coating. Films were crystallized using a heat treatment at 1160 °C for 1 h in 4% H2/96% Ar. Single-layer films were approximately 600 Å in thickness, and thicker films could be produced using multiple coatings. θ/2θ x-ray diffractograms revealed only (0041) reflections, indicating a high degree of out-of-plane texture. A pole-figure about the Gd2O3 (222) reflection indicated a single in-plane epitaxy. Scanning electron microscopy showed that the films were smooth, continuous, and free of pin holes. Atomic force microscopy revealed an average surface roughness of 53 Å. Electron diffraction indicated that the misalignment of the majority of the grains in the plane was less than 10°. High-current (0.4 MA/cm2) Yba2Cu3O7–δ films were grown on roll-textured nickel substrates using Gd2O3 as the base layer in a three-layer buffer structure.