By adsorption of monosilicic acid on aluminum hydroxide, an amorphous aluminosilicate (AAS) of Si/Al ratio of 1/3 was formed. When the AAS was heated to 1000 °C, mullite (3Al2O3 · 2SiO2) crystallized directly without the formation of a spinel phase. It was clearly evidenced that correct adjustment of three factors, the Si/Al ratio, the proportion of 4- and 6-coordinated aluminums, and the single environment of a unit (no Si–O–Si bond), is important for the direct mullitization from AAS.

The limitation of the long-range order parameter and the necessity of the short-range order parameter for the thermodynamic description of Pb()O3-type perovskites are discussed. Based on the discussion, a statistical thermodynamic model that takes into account the configuration of the neighboring B-site ions (B′ and B″ cations) was developed. A pair-correlation approximation was used in the calculation of the configurational entropy and the long-range coulombic interaction energy between the nearest B-site ions. The theoretical calculations using Pb(Sc1/2Ta1/2)O3 (PST) and Pb(Sc1/2Nb1/2)O3 (PSN) systems indicate that the short-range order parameter persists over a wide range of temperatures examined (0–1800 K) and that there possibly occur consecutive long-range order-disorder transitions in the configuration of B-site cations. The possibility of the existence of short-range ordering above the long-range order-disorder transition temperature was also examined using the annealed PSN specimen as a typical example of Pb()O3-type perovskites.

A classification scheme of Pb()O3-type perovskites with respect to the B-site order parameters was proposed based on the theoretical calculation of the short-range order parameter (σ) using the pair-correlation model. The calculated order parameters predict that a Pb()O3-type perovskite without any charge difference between B′ and B″ cations [e.g., Pb(Zr1/2Ti1/2)O3 (PZT)] is represented by a completely disordered state with the absence of a finite coherence length. On the other hand, a Pb()O3-type perovskite system having different ionic charges is characterized either by the short-range ordering with a nanoscale coherence length or by the macroscopic long-range ordering, depending on the magnitude of ionic charge difference between B′ and B″ ions. The normal ferroelectricity in Pb()O3-type complex perovskites was then correlated either with a completely disordered state (σ = 0) or with a perfectly ordered state (σ = 0), whereas the relaxor behavior was attributed to the nanoscale short-range ordering (0 < σ < 1) in the configuration of the B-site cations.

The slip system of TiN at room temperature has been determined to be {110} 〈110〉 by Burgers vector analysis using transmission electron microscopy and slip trace analysis of indents made on a TiN(001) film deposited on a MgO(001) substrate. Both small indents (0.4 mN maximum load) and large indents (40 mN maximum load) were used to study the dislocation structure in TiN. The nucleation of dislocations was investigated using small indents. Further development of the plastic zone was studied using large indents and microhardness indents (1.6 N). The critical resolved shear stress evaluated at the load when pop-in occurs was estimated to be 3.7 GPa, assuming a Hertzian elastic contact. Indents made with a 0.4 mN maximum load show a complex dislocation pattern with loops and straight segments that belong to the same slip system. Dislocations of mixed screw and edge type are dominant. The cascade of dislocations generated during pop-in is likely to nucleate from loops. For larger indents, the plastic zone extends more than three times the diameter of the imprint. The straight dislocations outside the large imprint are arranged in arrays along the 〈100〉 and 〈110〉 directions. A scanning force microscopy study of the surface outside a microhardness indent revealed a raised surface along 〈110〉 and formation of troughs along 〈100〉.

Superlattices of Fe3O4–NiO layers have been studied by high-resolution transmission electron microscopy (HRTEM). These superlattices are grown by oxygen-plasma-assisted molecular-beam epitaxy (MBE) on (001) oriented MgO substrates, and exhibit a high degree of ordering at the interfaces between the interlayers. The lack of misfit dislocations at the Fe3O4–NiO interfaces suggeststhat lattice strain is largely accommodated by changes in the lattice spacing. By quantitative HRTEM analysis of Fe3O4–NiO interfaces, possible atomic models are discussed, having implications in magnetic ordering and spin exchange mechanisms for such interlayer systems.

Changes in structure and phase transition behavior of (Na1/2Bi1/2)1−xSrxTiO3 were investigated using x-ray diffraction (XRD) analysis and dielectric measurements. A decrease in the degree of lattice distortion was observed when the structure was rhombohedral (x < 0.26). Further substitution of Sr2+ (x ≥ 0.26) caused (Na1/2Bi1/2)1−xSrxTiO3 to show no macroscopic lattice distortion. However, all investigated samples (0.1 ≤ x ≤ 0.5) were ferroelectric at room temperature regardless of the lack of lattice distortion found in XRD patterns. Further XRD investigations revealed that nonuniform strains caused by nonuniform polarized islands were responsible for this behavior. A-site cation substitution of Sr2+ also resulted in the decrease of Tmax (the temperature where dielectric constant is maximum). Typical relaxor ferroelectric phase transition behavior, associated with the shift of Tmax, with respect to the measuring frequencies, was found above x = 0.18. This could be also ascribed to the decrease of Tmax—this reveals the increase in the shift of Tmax with frequency, with associated decrease in ionic displacement and space charge contributions and associated increase in the relative contribution to the polarization by microdomains and domain walls at temperatures near Tmax.

Highly (100)-oriented thin films of PbTiO3 were prepared on (100)-textured LNO/Pt/Ti/SiO2/Si substrates by rf magnetron sputtering at temperatures ≥480 °C, while randomly oriented PbTiO3 films were obtained on Pt/Ti/SiO2/Si substrates. The textured LNO layer can help to control the orientation of PbTiO3 thin films, and reduce their surface roughness quite significantly. The dielectric constant (εT) of PbTiO3 films deposited on LNO was lower than that of films on Pt and the dielectric loss (tan δ) increased when a higher deposition temperature or longer time was used. The highly (100)-textured PbTiO3 films also showed different ferroelectric hysteresis characteristics, i.e., a higher coercive field and a lower remanent polarization, from that of randomly oriented films deposited on Pt.

In this research, two tasks were pursued: (1) determination of the onset temperature of ferroelectric hysteresis properties of SrBi2Ta2O9 thin films by structure development study, and (2) low temperature processing for thin film fabrication. For task (1), a nondestructive optical method using spectroscopic ellipsometry was utilized for characterizing the structure development of SrBi2Ta2O9 thin films. The optical constants and film thickness were measured as a function of annealing temperature by spectroscopic ellipsometry. By observing the changes in refractive indices and film thickness, the temperatures of phase transformation and grain growth were determined. Consistent results were obtained from x-ray diffraction measurements. By comparing the results of the structure development study and ferroelectric hysteresis properties investigation, the onset temperature of the hysteresis curve of SrBi2Ta2O9 with 50% excess Bi was determined to be about 700 °C. The critical factor for the compound to exhibit a well-defined hysteresis curve was found to be the grain size. For task (2), the effects of excess Bi content and Nb/Ta ratio of SrBi2(Ta1−xNbx)2O9 on the ferroelectric hysteresisproperties were studied. It was found that the onset temperature for obtaining well-defined hysteresis properties can be reduced by adding excess Bi or increasing Nb/Ta ratio. By choosing SrBi2Nb2O9 with 50% excess Bi, the onset temperature of the hysteresis curve was reduced to about 650 °C.

Nanocrystalline maghemite, γ–Fe2O3, can be synthesized in a microwave plasma using FeCl3 or Fe3(CO)12 as the precursor. Electron microscopy revealed particle sizes in the range of 5 to 10 nm. In general, this material is superparamagnetic. The magnetic properties are strongly dependent on the precursor. In both cases the production process leads to a highly disordered material with the consequence of a low magnetization. The assumption of a disordered structure is also supported by electron energy loss (EEL) and Mössbauer spectroscopy. The structure of this material shows a nearly identical number of cations on tetrahedral and octahedral lattice sites.

We report the electronic structures and associated optical properties of three inorganic oxides, namely lanthanum oxide, aluminum phosphate, and lanthanum phosphate, calculated by the first principles augmented spherical wave (ASW) and full potential linear muffin tin orbital (FP-LMTO) band structure methods, and the self-consistent field Xα scattered wave (Xα SW) molecular orbital cluster approach. Our calculations indicate negligible effect of the choice of exchange correlation potentials on the position, shape, and relative ordering of the energy bands. The ASW energy gaps in lanthanum phosphate and aluminum phosphate agree satisfactorily with the measured values. A comparison of the electronic density of states for an isolated phosphate group from molecular orbital calculation and that of the valance band from the band structure methods indicates that the nature of bonding within the phosphate groups does not change in aluminum and lanthanum phosphates. The states near the top of the valence band and bottom of the conduction band are mostly due to the phosphate bonding and antibonding orbitals, indicating that optical absorption near the band edge involves excitation of electrons from the bonding levels to antibonding levels associated with phosphate groups. This explains why the optical gaps in many rare earth phosphates are nearly equal.

The influence of organic binders on fiber/matrix bonding during the powder metallurgy fabrication of sapphire fiber-reinforced NiAl matrix composites (sapphire/NiAl) was investigated. One composite panel was fabricated using a poly(methyl methacrylate) (PMMA) fiber binder and a teflon matrix powder binder; another panel was fabricated by binderless powder metallurgy consolidation. The effect of the binders on fiber/matrix bonding was evaluated by fiber push-out testing from room temperature to 900 °C. Examination of mating fiber and matrix-trough fracture surfaces by scanning electron microscopy (SEM) and Auger electron spectroscopy (AES) revealed differences in interfacial morphology and chemistry, depending on the use of binders in fabrication. The primary difference between the two composites was the much higher concentration of carbon at the fiber/matrix interface in sapphire/NiAl fabricated with binders. This carbon residue from binder burnout prevented clean contact between the sapphire fiber and NiAl matrix surfaces, resulting in a weak, thermomechanically clamped fiber/matrix interface, in contrast to the stronger, less temperature dependent, interfacial bonding observed without binders.

High refractive index composites of iron sulfides and poly(ethylene oxide) (PEO) have been prepared by co-precipitation from aqueous solution. Several reaction parameters were varied: inorganic reactants, reactant ratios, reaction temperatures, and reaction times. Selected samples were characterized with organic microelemental analysis, x-ray fluorescence spectroscopy, x-ray diffraction, DSC, and TEM. The nanocomposites with the highest refractive indices have been prepared using PEO, Mohr's salt, and H2S or NaHS. The analyses indicate that the iron sulfides in these materials consist of finely dispersed mackinawite and greigite (“amorphous” FeS) and, partially, also pyrite. The refractive indexes of the resulting composites are clearly above 2 at 632.8 and 1295 nm and can assume values between 2.5 and 2.8.

Transmission of acoustic waves in two-dimensional composite media composed of arrays of Duralumin cylindrical inclusions embedded in a poly vinyl chloride (PVC) matrix is studied. Experimental and theoretical results for the transmission spectrum of a periodic array of cylinders organized on a square lattice are reported. Local gaps in the first two-dimensional Brillouin zone are predicted and observed. The experimental measurements of power spectra for a random array of inclusions show a weak correlation between disorder and acoustic absorptions up to a high degree of disorder. Only in the case of highly random arrangements does the transmission spectrum diverge from the one obtained with a periodic array of inclusions.