A model based on the state-of-the-art, first-principles layer Korringa-Kohn-Rostoker (LKKR) method has proven to be very effective in describing the electronic and magnetic structure of metal/ceramic interfaces. We have performed self-consistent field computations incorporating spin polarization both for Fe/MgO superlattice (bulk technique) and for MgO/Fe/MgO sandwich (layer technique) systems. Muffin-tin potentials were employed for both materials in our computations. Iron layer was embedded in MgO, the host material, to have a [110](100)Fe / [100](100)MgO contact configuration. A large enhancement of magnetic moments has been found at the interface.

The ability to tailor thin film interface structure is illustrated by the growth of thin ferric oxide films using different deposition parameters. Low-pressure chemical vapor deposition (CVD) has been used to grow α-Fe2O3 on sapphire while pulsed-laser ablation (PLA) followed by low temperature oxidation has been used to grow γ-Fe2O3 on MgO. The structure of the films and of the film-substrate interfaces has been characterized using transmission electron microscopy (TEM) and selected-area diffraction (SAD) in plan view. The different deposition techniques lead not only to the growth of two different polymorphs of ferric oxide but also to different growth mechanisms and film-substrate interface structures. In addition, changes in the thermodynamic conditions during deposition can give rise to different interface structures between the individual structural domains of the film.

Interphase interfaces in the directionally solidified eutectics.(DSEs) of NiO-ZrO2(CaO), NiO-Y2O3 and MnO-ZrO2 have been investigated using a variety of TEM techniques. The unique lamellar morphology of the DSEs allows characterization of interfaces and identification of relaxations along multiple directions, aiding visualization of interface structure in three dimensions. Possible low energy interface orientations were identified through examination of facets. The low energy interface planes almost invariably correspond to polar surfaces of adjacent crystals. An attempt has been made to experimentally identify the variety of interfacial relaxation mechanisms using a variety of analytical TEM techniques and only HRTEM results are summarized in this paper. It was found that most of the DSE systems exhibit very little relaxation and possess tight interface cores.

Potassium was deposited onto stoichiometric TiO2 (110) surfaces and the chemical bonding and structure were studied with UPS, XPS, LEED, and RHEED. Potassium interacts strongly with the oxygen anions of the TiO2 and reduces the valency of Ti cations at the interface. At submonolayer potassium coverages, a large charge transfer to the substrate causes a sharp drop in work function, a population of electronic states within the bulk TiO2 band gap, and surface band bending. After large potassium doses at 300 K, multilayers of K2O are formed by diffusion of oxygen anions from the substrate, creating a substoichiometric TiO2−x interface composition. No metallic potassium is present even after large doses. The K2O layers remain stable after annealing as high as 900 K, and LEED indicates that they are disordered. RHEED characterization is limited by the roughness of the stoichiometric TiO2 (110) surface.

Domain boundary structures of flux-grown poly-domain lead titanate single crystals have been studied using transmission electron microscopy. 90° and 180° domain boundaries were seen in the crystals and were systematically analyzed under various diffraction conditions. Although 90° domain boundaries are supposely δ-type boundaries in BaTiO3, our results show that displacement plays an important role at boundaries and the extreme fringe contrast (EFC) behavior of 90° boundaries is of the mixed type. In the present work, an analysis based upon the two beam dynamical theory was conducted and a rule similar to stacking-fault contrast analysis was established to predict the geometric configuration of a 180° domain boundary using EFC behavior. Examples are given and verified by tilting experiments and electron diffraction. The results are consistent and offer a convenient way to distinguish between 90° and 180° boundaries.

High resolution transmission electron microscopy (HRTEM) is used to investigate the transformation mechanism responsible for the occurrence of the many stable layered phases in the pseudo-binary Y2Ba4Cu6+xO14+x system. In particular, HRTEM results are compared with microstructural configurations generated by an earlier theoretical study which modeled this transformation by means of an intercalation mechanism. HRTEM images of partially transformed Y-Ba-Cu-O reveal that the predominant structural change is limited to the CuO planes. The location of the transformation front, revealed in the micrographs by the presence of these partial dislocations, suggests that the transformation is nucleated at grain boundaries and internal surfaces within the material. The observation of local CuO layer ordering along the [001] direction is taken as evidence for the presence of longer range interactions. A two-dimensional approximation to the bulk Monte Carlo simulation incorporating long range screened Coulomb [001] interactions is used to investigate the possibility and nature of local, transient stage orderings.

A new type of twin structure is found to exist quite commonly in the Bi2Sr2CaCu2O8+δ superconductor obtained by annealing melt quenched amorphous precursors. From transmission electron microscopy and electron diffraction, the twinning plane is determined to be the (015) plane (disregarding the period of incommensurate modulation in the b-direction). Further, the twin boundary is found to be coherent with a specific coincidence condition. The analysis of the morphologies indicates that the twins nucleate at the early stages of the grain growth in these materials.

The results of systematic computer simulations of the deposition and growth of Y-Ba-Cu-0 thin films is reported. The deposition process is modeled by means of a three-step Monte Carlo simulation incorporating one sorption deposition mode and two modes of film annealing addressing surface and bulk diffusion. The simulation is used to investigate the evolution of surface morphology and film microstructure, growth rate anisotropy, and the dependence of film texture on deposition parameters. Characteristic defects and surface morphologies observed by simulation are found to be in good agreement with those observed experimentally. It is observed that surface kinetics can dominate the evolution of film microstructure.

Electron diffraction and high resolution electron microscope observation for CaMnO3−x (x=0. 02 and 0. 05) showed unique features of the ordered structure. A coherent intergrowth of several phases with a long period in CaMnO3−x composed of extended perovekite units was observed. The relation in crystallography in the family of ordered perovskite related oxides in CaMnO3−x, which could help towards an understanding of magnetic properties and catalytic action of CaMnO3−x, is discussed.

The microstructures of post-sintered reaction-bonded Si3N4 materials (SRBSN) were investigated. The materials consist of large elongated β-Si3N4 grains embedded in a finegrained matrix. Amorphous secondary phases exist at triple grain junctions owing to the liquid phase sintering involved during densificacition. Those amorphous phases can be crystallized (nearly completely) by post-sintering heat treatment. Apart from these crystalline grain pockets the grains of all materials are covered with thin (<l-2 nm) amorphous intergranular films on both Si3N4/Si3N4 grain boundaries as well as on secondary-phase/Si3N4 phase boundaries. A control of the intergranular films is most desirable since they limit the high-temperature mechanical properties of Si3N4-based ceramics. Therefore, the required characterization was performed by analytical and high-resolution transmission electron microscopy (AEM/HREM). Si3N4 materials with different rare-earth and transition-element oxide additions were studied. AEM and HREM investigations revealed marked differences in thicknesses and chemical compositions of the different intergranular films depending on the system analyzed indicating a strong dependence of film thickness on chemical composition. However, a given composition of each investigated material showed a characteristic intergranular film thickness, independent of grain misorientation, with the only exception of low-energy grain boundaries. The thickness of the intergranular films was constant within 0.2 nm. In addition, the film thickness of phase boundaries was always greater (by 1–2 nm) compared to grain-boundary films.

The whisker/matrix interfaces in a β-Si3N4w/60 61Al composite were structurally characterized by high resolution transmission electron microscopy (HRTEM). It was shown that there was a nearly amorphous layer (2–3 nm thickness) at a whisker/matrix interface. The magnesium segregation at the whisker/Al interface was revealed by electron dispersive analysis of x-ray (EDAX). MgO and MgAl2O4 nanocrystal particles were formed at the whisker/matrix interface due to the Mg segregation there during the manufacturing of the composite. The Mg2Si particles preferred to precipitate at the whisker/Al interface when the composite was processed with T6 heating treatment. There were specific orientation relationship of the MgAl2O4 or Mg2Si particles with the β-Si3N4 whiskers.

The metal-ceramic interface in an XDTM Al/TiCp metal matrix composite has been characterized in as-extruded, recrystallized, and high temperature heat-treated conditions. In both the as-extruded and recrystallized composite, the interface is atomically abrupt. Localized orientation relationships exist between Al and Tic that lead to some degree of coherency at the interface. Recrystallization produces semicoherent interfaces by formation of subgrains in the Al adjacent to the Tie particles. Few interfaces show cracking, even after extensive deformation. Lack of cracking together with the direct contact down to atomic level, observed between the two phases are evidence for excellent bonding between the carbide particles and the aluminum matrix. Heat treating samples at 913 k for 24 hours produces reaction products like Al3Ti and Al4C3. These reactions are explained on the basis of thermodynamic data.

Interfacial microstructure can have a significant influence on the microfracture processes of discontinuous reinforced metal matrix composites (DMMCs). The fracture properties, however, are largely influenced by the microfracture and deformation mechanisms associated with the matrix microstructure and with the interface microstructure. Also, it is known that the paniculate morphology and distribution can modify the deformation process by influencing the stress state that develops in the matrix materials near the reinforcement. Along with the matrix microstructure, characterizing the role of the interfacial and the near-interfacial microstructure is essential for a broader understanding of fracture behavior in DMMCs. To characterize the microstructure of cast DMMCs, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and electron microprobe (EMP) examinations were conducted at the interface and in regions near the particulate/matrix interface. Materials studied consisted of cast Al-4.5Cu and Al-7Si matrix alloy systems with B4C and SiC reinforcement. In general, the interfacial and matrix microstructure of Al-4.5Cu/SiC and Al-4.5 CuB4C composites exhibited little variance, i.e. the reinforcement type had no apparent effect on the resultant microstructures. For the Al-7Si system, however, significant microstructural variance was observed both in the matrix and interfacial regions. In the Al-7Si/B4C composite, an extensive reaction zone was found at the B4C interface. Interfacial compounds observed in Al-7SiC/B4C were Ti(O,B), Si, and MgB6 precipitates. In the near-interface region compounds such as Alx(B, C, 0)y, AlxMg(1−x)B2, and Al4C3 were found. In sharp contrast to Al-7SiC/B4C, an extensive interfacial reaction zone was not revealed for Al-7Si/SiC MMC. Only isolated, extremely fine second phase precipitates were observed on SiC paniculate interfaces. Fracture surface evidence suggested that both the matrix and the interface microstructure influenced deformation and microfracture mechanisms in DMMCs.