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Termination structures of surfaces of zeolite L crystals are studied by high-resolution electron microscopy (HREM). By comparing observed HREM images with simulated ones based on some ideal models ...

First, constitution of a simulation program for high-resolution electron microscopy is outlined. In order to record high-resolution images accurately, (S/N) and DQE (detective quantum efficiency) characteristics for new recording materials like the imaging plate are presented. It is shown that digital data of high-resolution microscope images appropriately recorded on the imaging plate can quantitatively be analyzed through image simulation with a residual index. Finally, quantitative high-resolution microscopy with a residual index is briefly discussed by comparing with the X-ray and neutron diffraction analysis with the so-called R-factor.

A new method for analysing antiphase domains using high-resolution electron micrographs is described. A high-resolution electron microscope image taken at a zone axis is treated as the sum of many sets of interference fringes. The analysis extracts the information concerning the variations in the image periodicities as a function of position. In particular, the amplitude and phase variations of these fringes are analysed separately. The amplitude images reveal the antiphase boundaries in a similar way to a conventional dark-field experiment whilst the phase produces images of the translation domains and defines the associated translation vectors. The phase variations can also be related to the strain field associated with the corresponding lattice planes. Experimental images of antiphase boundaries in Cu3Au taken at [001] are used to demonstrate the technique. Antiphase boundaries perpendicular and parallel to the electron beam are characterized. The phase images are used to characterize disorder...

We present the results of a parallel study of the atomic structure of the ∑ = 5, (210), θ = 53·13° and (310), θ = 36·87°, [001] tilt axis grain boundaries in bcc Mo, by computer simulation and high-resolution electron microscopy (HREM). Excess energy values of different boundary configurations are obtained via a quasidynamical minimization scheme while cohesion is described by a new n-body central-force, phenomenological potential which satisfactorily reproduces static and dynamical properties of the bulk material. HREM observations and numerical modelling both show the symmetric configuration of the ∑ = 5, (210), θ = 53·13° boundary to be of the lowest energy. The calculations also show that the stable ∑ = 5, (310), θ = 36·87° configuration is nearly mirror symmetric, although the experimental verification in this case is still incomplete. After a few oscillations, the interplanar spacing near the boundaries converges rapidly to its bulk value while producing an overall expansion of the bicrysta...

In the alloy Ti3 Al-Nb, several phases appear after cooling at various rates from a high temperature. These are B2, D0 (alpha-phase), L1 (eta-phase) and an 19 2 0 omicro-type phase. A high-resolution electron microscopy observation is presented - 1 of an alloy continuously cooled at 10 K s from 1200oC, which shows very small regions of the eta-phase at the boundaries between the alpha-phase and B2 phase. An opportunity is thus provided to observe the early stages of the formation of the eta-phase. Orientation relationships for the phases are given.

An investigation on the real structure of Gd6Cl5C3 has been carried out by means of high-resolution electron microscopy. The occurence of lamellar defects is interpreted as chemical intergrowth of the two closely related phases Gd6Cl5C3 and Gd2Cl2C. Loading of the samples, which are very sensitive to air and moisture, and the insertion of the sample holder into the microscope has been realised using a specially designed transfer system. Chemische Verwachsung in Gadoliniumcarbidchlorid – eine HRTEM-Untersuchung Die Realstruktur von Gd6Cl5C3 wurde mittels hochauflosender Elektronenmikroskopie untersucht. Das Auftreten lamellarer Defekte wird als chemische Verwachsung der zwei eng verwandten Strukturen von Gd6Cl5C3 und Gd2Cl2C interpretiert. Die sehr luft- und feuchtigkeitsempfindlichen Proben wurden mit einem eigens entwickelten Transfersystem in das Mikroskop eingeschleust.

A method is described to prepare a high-resolution electron micrograph for quantitative comparison with a simulated high-resolution image. The experimental data are converted from the darkening of film used to acquire the image to units of electrons per incident electron, the same units used in the simulation. Also, distortions in the image arising from distortions in the image-forming lenses of the electron microscope are removed to improve the quality of the data. Finally, an alignment procedure is described which gives precise, pixel-by-pixel alignment of the experimental image with the simulated image. Examples of the procedure are shown to illustrate how actual data are prepared for quantitative analysis.

In order to determine the mechanisms of twin growth, a high-resolution electron microscopy study of the tip morphology in (1012) twin in zinc has been carried out. In a new model presented here, the twin tip is described as a series of (1012)//(1012) step faces, containing one or more interfacial dislocations. They are separated by incoherent (0001)//(1010) interfaces resulting from a pile-up of twinning dislocations. The stress around the twin tip is accommodated through the emission of (c + a)⅓ 〈1123〉 lattice dislocations and formation of residual dislocations b D ≈ 0·47[1011] which are of the opposite sign to the twinning dislocation. This relaxation process can be associated with a blunting mechanism which finally stops the twin growth along the [1011] direction.

Twin boundaries in the massively transformed γ-TiAl phase, which is formed in a Ti-48 at.% Al alloy quenched from the high-temperature α-Ti phase field, have been investigated by high-resolution electron microscopy. At the twin boundaries and ledges, a characteristic periodic contrast with a spacing of about 0·7 nm is frequently observed, which corresponds to the three-times periodicity of d{111}γ. This contrast is quite similar to those reported previously for12Aug1996 severely deformed γ + α2 two-phase Ti-Al alloys, which was attributed to the formation of the 9R structure with ABC/BCA/CAB stacking sequence. From close examination of this contrast with the aid of image simulation, it is concluded that the contrast is caused by overlapping twin-related crystals along the incident beam direction and not by formation of the 9R structure. The configuration of overlapping twins is explained by complex ledge structures, which result from the formation of twin-related crystals in the α → γ massive tra...

The damage induced by heavy ion irradiation in a wide palette of materials, extending from metals to insulators, is presented. The damage creation and the track morphology have been investigated by electron microscopy and especially HRTEM when available. It is shown that heavy ion irradiation in the electronic stopping power regime is a very efficient tool to amorphize the solids. But the sensitivity to irradiation of each material is strongly variable since the electronic stopping power threshold for damage creation can vary between 1 and 40 keV/nm. The wide difference in sensitivity to heavy ion irradiation between the insensitive materials such as some semiconductors and insulators and the very sensitive ones like the quartz and some magnetic ferrites is a real challenge for any general model of damage creation in solids.

Bi V O and Bi V O have been prepared by solid state reaction and their 4 2 11 6 3 16 structural chemistry has been investigated using X-ray powder diffraction, highresolution electron microscopy, solid-state nuclear magnetic resonance and electron-energy-loss spectroscopy. Their structures are closely related to each other and are both derived from-Bi V O with Bi O layers partially 4 2 11 2 2 depressed in an ordered manner, forming various superstructures and implying a location of oxygen vacancies in the Bi O layers, rather than the V-O layers as 2 2 previously believed. These results necessitate a reconsideration of the mechanism of ionic conductivity in these materials.

Basic theory of high-resolution electron microscopy is described in view point of lattice images and structure images of crystalline samples. Image formation process, factors determining the resolution, contrast transfer functions, dynamical diffraction effect and relativistic effect are explained in detail.

The structures of martensites in a Cu–11.2 wt% Al–3 wt% Ni specimen, which was quenched from 1173 K, have been studied by high resolution electron microscopy (HREM) and diffraction techniques. Two kinds of martensites, i.e. β′1 and γ′1, coexisting adjacent to each other in the specimen were observed. The γ′1 matensite consists of microtwins with monoclinic structure. Three variants of the twin structure, i.e. {1 2 1}, {2 1 0} and {1 0 1} twins, are arranged within a single plate. The β′1 martensite possesses basically ordered N9R structure, but mixed with thin 2H domains. Some diffraction spots of this martensite shift along the [0 0 1] direction. In addition, extra weak reflections appear in the diffraction pattern due to heterogeneous atomic displacements. The microstructural features of the martensites are examined and discussed.

Atomic arrangements of austenite fcc and martensite bcc near the interface in an Fe Ni Mn alloy have been observed by high-resolution electron microscopy. It is found that atom rows along the close-packed directions of two phases are completely coherent at the interface, but there exist deformed lattices which are neither fcc nor bcc. These lattices are regarded as transient lattices changing continuously from fcc to bcc lattice. By observation of these transient lattices we can deduce the lattice deformation in the fcc to bcc martensitic transformation. It is concluded that the lattice deformation proposed by Kurdjumow and Sachs is perfectly consistent with the observed atomic arrangements near the interface. The Bogers and Burgers mechanism is inadequate to explain the present observations. It is emphasized that the austenite martensite interface in the present alloy is not a monoatomic layer but has a width of about 0 7 nm in which the transient lattices are contained.

The internal structure of monodisperse CdS particles was investigated by high-resolution electron microscopy of thin sections prepared with an ultramicrotome. High-resolution images of the thin sections clearly revealed the arrangements and the crystallographic orientations of subcrystals as components of the particles. It was found that the central part of a particle was composed of randomly oriented small subcrystals about 10 nm in diameter, while near the surface of the particle, relatively large subcrystals about 50 nm in maximum width were observed. Furthermore, stacking faults and twins on the {1 1 1} planes were observed in the sections.

The structure of the Al-Rh-Cu decagonal quasicrystal with periodicity of about 0.4 nm has been investigated by high-resolution electron microscopy. A high-resolution structure image taken with the incident electron beam parallel to the tenfold axis can be interpreted as an aperiodic tiling composed of three kinds of subunit. The atomic arrangements in these subunits have been proposed according to the structure of the Al-Co-Cu decagonal quasicrystal determined by single-crystal X-ray analysis. A calculated image using the present model reproduces well the contrast features of the high-resolution structure image.

High-resolution electron microscopy was used to examine the structural features of grain boundaries in Al–1.5% Mg and Al–3% Mg solid solution alloys produced with submicrometer grain sizes using an intense plastic straining technique. The grain boundaries were mostly curved or wavy along their length, and some portions were corrugated with regular or irregular arrangements of facets and steps. During exposure to high-energy electrons, grain boundary migration occurred to reduce the number of facets and thus to reduce the total boundary energy. The observed features demonstrate conclusively that the grain boundaries in these submicrometer-grained materials are in a high-energy nonequilibrium configuration.

For two γ-TiAl grains exhibiting a 180° twin relationship, the junction between a {111}γ1 // {111}γ2 twin plane and a perpendicular {121}γ1 // {121}γ2 interface has been investigated by high-resolution electron microscopy. The {111}-(121} junction exhibits a region of complex contrast due to dislocations at the end of both the {111} and the {121} facets. The {121}γ1 // {121}γ2, twin interface can be produced either by γ → γ shear or as the result of two α → γ transitions and subsequently undergoes a rigid-body shift at the interface in order to relax its structure. Both the structure and the mobility of {121}LI0 interfaces are discussed.

This article reviews the application of high resolution electron microscopy techniques to zeolite structural characterization. Examples given in this article include identification of structural intergrowth, stacking faults and framework projection net from high resolution images. Slow-scan CCD (charge-coupled device) cameras, representing the latest advance in electron microscopy instrumentation, are briefly introduced. Low-dose, high resolution electron microscopy using commercial CCD cameras is discussed. With slow-scan CCD cameras, it is shown that it is possible to directly read off the underlying zeolite structures from experimental high resolution images when suitable image processing techniques are employed. This latest advance greatly enhances the power of high resolution electron microscopy techniques in solving unknown zeolite structures.

The formation process of the decagonal quasicrystalline phase (D-phase) with 1.2 nm periodicity from a crystalline approximant in the Al70Pd13Mn17 alloy has been identified by high-resolution electron microscopy. At the early formation stage, decagonal atom clusters, which are the most important structural units of the D-phase, were observed to segregate from the crystalline matrix with an atomic correlation determined by the structural characteristics of the crystal. A non-equilibrium structural state (a mixture of the segregated atom clusters and the crystalline matrix phase) was also observed, and its structural characteristics clearly revealed. The equilibrium D-phase, whose structure is characterized by an aperiodic arrangement of decagonal atom clusters with definite linkages and a long-range quasiperiodic correlation, was formed by fully annealing at 800degreeC for a long time. The linear phason strain in the equilibrium D-phase formed from the crystalline approximant may be related to the structur...

By high-resolution electron microscopy, chemical intergrowth was studied of dimeric Mo10O16 and trimeric Mo14O22 clusters in reduced tin oxomolybdates within the SnxMo10O16SnyMo14O22 system. The variety of observed intergrowth patterns includes polysynthetically twinned structures as well as a number of different superstructures. For an orthorhombic superstructure formed by alternating layers of dimeric and trimeric clusters, the lattice parameters and the Sn content were determined. The chemical reason for the amazing abundance of structures in the considered system is discussed. Chemische Verwachsung dimerer und trimerer Cluster in reduzierten Zinnoxomolybdaten: eine Untersuchung mittels Hochauflosungs-Elektronenmikroskopie Mittels Hochauflosungs-Elektronenmikroskopie wurde die chemische Verwachsung dimerer Mo10O16-und trimerer Mo14O22-Cluster in reduzierten Zinnoxomolybdaten des Systems SnxMo10O16SnyMo14O22 untersucht. Die Vielfalt der beobachteten Verwachsungsmuster schliest polysynthetisch verzwillingte Strukturen und eine Anzahl verschiedener Uberstrukturen ein. Fur eine orthorhombische Uberstruktur, die aus alternierenden Schichten dimerer und trimerer Cluster besteht, wurden die Gitterparameter und der Zinngehalt bestimmt. Die chemischen Ursachen fur die im untersuchten System beobachtete, erstaunliche Fulle von Strukturen wird diskutiert.

Lattice image simulations appropriate to high resolution electron microscopy (HREM) imaging conditions have been produced for partial dislocations in Si under the condition that the electron beam is parallel to the normal to the stacking fault plane. It is shown that the positions of partial dislocations can be determined by the difference in the lattice image between the faulted and unfaulted regions; hence the existence of kinks can be resolved under appropriate conditions. Image simulations have also been made for reconstructed 90°- and 30°-partial dislocations. The results show that the reconstruction may be detected by HREM for the 30° partial but not for the 90° partial. HREM experiments on dislocations in Si introduced by plastic deformation reveal that: (i) the positions of partial dislocations can be determined for thin samples, (ii) 30° and 90° partials are easily distinguishable, (iii) high density kinks are observed, but it is concluded that these are produced, during observation, by ...

A method based on a simulated annealing algorithm is applied for the reconstruction of the projected crystal potential belonging to a periodic high-resolution electron microscopy exit plane wave function. Using simulated exit plane wave functions of GaAs at different specimen thicknesses, the convergence behaviour and the accuracy of the algorithm are investigated. It is demonstrated that the reconstruction is possible even under strongly non-linear scattering conditions at small specimen thicknesses. Further, the convergence of the algorithm to an ambiguous solution beyond a certain specimen thickness is discussed.

A new type of ordered structure in a Ti-48at%Al alloy quenched from the disordered α-Ti phase field has been determined by high-resolution electron microscopy and image simulation. The structure is based on an h.c.p. structure having an orthorhombic unit cell with the lattice parameters a = 0.45 nm, b = 0.28 nm and c = 0.49 nm, and belongs to a B19 type. The B19 TiAl can be described as the AB… stacking of close-packed /(111/) planes in γ-TiAl with an L1 0 structure, and the ordered arrangement of Ti and Al for the B19 structure is interpreted as a local arrangement in the sample.

Pressure-induced irreversible amorphization and crystallization were definitively observed at the atomic scale, using high-resolution electron microscopy, in the uniaxially compressed icosahedral phase of Al68Pd23Mn9, at pressures from 10 to 20 GPa at ambient temperature. The pressure-amorphized state was found to comprise a random packing of atomic clusters. The pressure-induced crystalline phase was identified to have a fcc structure with a lattice parameter a = 0·38 nm which is not an approximant of the icosahedral phase of Al[sbnd]Pd[sbnd]Mn.

A cubic member of the M41S family with a three-dimensional pore system, denoted as MCM-48, was synthesised. By combining X-ray powder diffraction (XRD) with high-resolution electron microscopy (HREM), a cubic symmetry with an Ia 3 d space group was determined for the as-synthesised and the calcined MCM-48 material. Upon calcination the unit cell decreased from around 10.09 nm to about 8.1 nm. The overall pore structure was found to be quite unaffected by local variations in the structure and the decrease in the unit cell size upon calcination.

A new method of high-resolution electron microscopy image analysis is presented which improves considerably the visibility of nanocrystals in amorphous materials. The technique is based on individual Bragg filtering of the lattice fringes in the image. The significant feature is that the amplitude and phase of the fringes as functions of position are calculated separately. This is similar to a holographic reconstruction with the Bragg interference representing the carrier wave. The phase information is shown to be particularly robust with respect to noise due to amorphous material. The images so produced are in a form suitable for statistical analysis, and criteria for judging quantitatively the extent of the crystal are proposed. The application of the technique to a wide range of similar problems concerning partially ordered materials is discussed.

Using high-resolution electron microscopy (HREM) the core structure of a 1/2(112) superdislocation in TiAl is examined and observed to have dissociated into an extrinsic stacking fault and an intrinsic stacking fault, bounded by three 1/6(112) partial dislocations. The core structure is non-coplanar, with the extrinsic stacking fault lying on two adjacent [111] planes bounded by a dissociated b = 1/6(112) partial dislocation whose deiocalization can pin the dislocation core and may lead to the formation of ±1/6(112)dipoles.

High-resolution electron microscopy observations have been performed on nickel silicide (Nisi2) precipitates in the ∑ = 25 grain boundary area of silicon bicrystal. The two orientation relationships type A and type B, usually encountered in monocrystalline silicon, have been recognized with respect to one of the grains. Details of the silicide/silicon interface structures are reported. In addition to most of the interfaces previously observed in the case of epitaxial growth, we have found evidence of two new ∑ = 1 Si(111)/(111)NiSi2 atomic structures. The interfacial Ni atoms, belonging to both new structures, have been determined to be sevenfold and eightfold coordinated. The growth of precipitates has been found to occur along the (111) planes, but ending by steps. For type A precipitates, 1/2[100] complete steps with the vector 1/2[101] have been identified while type B precipitates have 1/3[111] steps associated with a vector of 1/2[110].

C 60 crystals grown by vapour transport may exhibit rough surfaces depending on the cooling conditions at the end of growth. The rough surfaces are due to hillocks of about 0.1–0.3 μm on “002” and “111” faces. Hillocks on “002” faces are square pyramids bounded by “111” surfaces or surfaces deviating from “111”. Hillocks on “111” faces are triangular pyramids bounded by stepped “111” surfaces. The density of crystal defects in as-grown and cleaved crystals is much lower than in crushed crystals. The high density of defects in crushed crystals is induced by specimen preparation. HREM imaging and simulation has confirmed that the cleaved surfaces are clean and free of lattice relaxation.

High-resolution imaging of ordered polymers is described both theoretically and experimentally. The relationship between the actual three-dimensional specimen structure and the resultant two-dimensional image intensity distribution is developed using the multislice formalism. The influence of the electron optical conditions on the image is demonstrated with experimental data, as well as with image simulations. Practical details of specimen preparation, as well as the effects of specimen structural defects on the image, are presented. A significant challenge for polymer microscopists is to minimize the deleterious effects of electron beam damage and to identify image artifacts resulting from damage. Future applications of ultrahigh-resolution capabilities are illustrated with respect to direct imaging of the anisotropic potentials present in covalently bonded materials.

A structure model of octagonal quasicrystals has been obtained using electron microscopy and crystallographic image processing. Octagonal quasicrystals in a rapidly solidified Mn-Si-Al alloy were studied by high-resolution electron microscopy (HREM). HREM images taken along the main symmetry directions, that is the eightfold and the two twofold axes were combined into a density map. The symmetry of the model is 84/mmc. Within each unit-cell repeat of 0.63 nm along the eightfold direction there are four layers. Alternating layers have eightfold and fourfold symmetry. Projections of the model match the HREM images. The shortest interatomic distances, 0.24 nm, and the density of 6.9 g cm−3 for the model are in good agreement with expected values.

On utilise la microscopie electronique en haute resolution pour mettre en evidence des boucles de dislocations partielles provenant de l'amincissement par bombardement ionique d'un echantillon de ZnO. Les defauts d'empilement crees par insertion d'une double couche de Zn-O dans le plan basal sont du type 1Δ

Interface structures in nanocrystalline metals, ceramics, carbon-60 and their composites were compared, using high-resolution electron microscopy, to understand the origin of unusual properties reported systematically by Gleiter and the co-workers. The observations showed that voids are not to be an inherent structure of nanocrystalline materials. Atoms in the grain boundaries are found influenced by the two neighboring crystals just as in usual polycrystalline aggregates. No concrete evidence of nanocrystalline anomaly was found in the density of atoms in the grain boundaries.

Core structures of edge and screw dislocations in CoTi were studied by high-resolution electron microscopy (HREM). An HREM image of an edge dislocation showed that the spreading of the dislocation core was limited within a distance of about 1.2 nm. From an HREM image of screw dislocations in CoTi, it was shown that the core was spreading on the (010) plane and the spreading of the core was limited within a distance of about 1.8 nm. It was suggested that the core spreading on the {010} plane, which was different from the slip plane of {110}, affected the abnormal temperature dependence of yield stress of CoTi.

SSZ-25 has been known to have high catalytic activity, but no structure has been reported. A combination of electron microscopy techniques was employed to characterize this new zeolite. This allowed us to determine the unit cell and its relationship to the crystal morphology. The unit cell was hexagonal with a = 1.41 nm and c = 2.52 nm. The individual crystals tend to be thin flakes, and high-resolution electron microscopy (HREM) revealed that this zeolite has a multi-dimensional channel system. The results of this work showed that there are large-pore zeolite channels arranged parallel to the c direction. The HREM results, when taken with other physical characterization methods, confirmed why this zeolite has high catalytic utility.

The structure of a new crystalline phase (O-phase) in an Al72Pd18Cr10 alloy, which is closely related to an Al3Mn crystalline phase and the Al-Pd-Mn decagonal quasicrystal, was investigated by electron diffraction and high-resolution electron microscopy. The O-phase has an orthorhombic structure with the lattice parameters a=1.25 nm, b=3.28 nm and c=2.38 nm, and the space group is Pmmn (no. 59). This structure is characterized as a periodic tiling constructed with two types of tiles, a squashed hexagon and a star-shaped pentagon, formed with pentagonal atom columns which are structural units in the Al3Mn crystalline phase and in Al-Pd-Mn decagonal quasicrystal. Structural relationships among the O-phase, the decagonal quasicrystal and some crystalline phases are discussed.

The decomposition process of the model precipitation-hardening Al + 4 wt. % Cu supersaturated solid solution induced by Ar+ ions irradiation. Using X-ray diffraction, high- resolution electron microscopy methods and microhardness measurements, it was established, that, already at low temperatures (T < 60 °C), ion irradiation causes accelerated decomposition of solid solution, with precipitation of 9' and 9-phase particles at a depth greatly exceeding the Ar+ ions projected range. This work was performed in the framework of the State Task, no. 0389-2414-0002, supported in part by RFBR (project No. 15-08-06744-A). We thank E. Wieser for the idea and participation in discussing the results.

Microstructures of the NiFe/AlOx/NiFe magnetic tunnel junctions and the barrier shape profile have been studied with atomic resolution using high-resolution electron microscopy and electron holography. A clear relationship between the growth morphologies of the electrodes and the quality of the barrier has been obtained. Although the bottom interface between electrode and barrier is very sensitive to the oxidation condition, a sharp interface can be achieved in optimumally oxidized junctions. The top interface, on the other hand, is always slightly oxidized due to the three-dimensional growth of top electrode above the barrier, independent of the oxidation condition of the barrier. Furthermore, charge accumulation seems to exist at the sharp interfaces. It is also interesting, yet surprising, that both interfaces are actually sharp in underoxidized junctions. Furthermore, charge accumulation seems to exist at the sharp interfaces.

Electron microscopy with atomic sensitivity enables us to obtain a direct image of the intra-molecular structure of metallofullerenes encapsulated inside single-walled carbon nanotubes. By a comparison of high-resolution images with a simulation to extract the relative atom positions for encaged metal atoms in each molecule, the distribution of the molecular orientations and interactions between adjacent molecules in metallofullerene peapods have been statistically analyzed. The results are suggestive of strong interactions between fullerene–fullerene and fullerene–tube in peapods at room temperature.

Studies of high-pressure synthesized Hg-Ba-Ca-Cu-O superconductor by electron diffraction and high-resolution electron microscopy are reported. The results of electron diffraction indicate that two superconducting phases 1212 and 1223 exist in the sample and their cell parameters are a=b=3.8 Angstrom, c=12.7 Angstrom and a=b=3.8 Angstrom, c=15.8 Angstrom, respectively. High-resolution electron micrographs were taken from the two phases Hg-1212 and Hg-1223 and from the region of the intergrowth of the two phases. The relation between the structure and superconducting transitional temperature T-c is discussed.

Translation twins (T twins) of γ-TiAl (L1O-type structure) in an as-cast two-phase TiAl-Ti3Al intermetallic alloy with Cr addition are characterized by high-resolution electron microscopy and supported by image simulation. The T twin and the matrix are connected through a glide reflection plane at the {111} twin interface, and the glide vector is ½ [101] parallel to the interface. The formation mechanism of the T twins and their possible influence on the deformation mechanism of the material are discussed.

The direct confirmation of the existence of Cd-stabilized β″″-ferrite prepared as a stable phase in a K2O-Fe2O3-CdO system was done by high-resolution electron microscopy. It was confirmed that the Cd-stabilized β″″-ferrite had a rhombohedral symmetry with lattice constants a = 0.600 and c = 5.026 nm. The structure is composed of an alternate stacking of ion-conductive layers and spinel-like blocks which have six cubic close-packed oxygen layers expressed as · · · A1(BCABCA)B1(CABCAB)C1(ABCABC)A1 · · ·. In addition, twins which had reversed stacking sequences were observed in the spinel-like blocks.

A more complete form of contrast transfer theory is derived using a partial coherency approach for both electron holography and conventional high resolution electron microscopy.

High-resolution electron microscopy indicates that the edge-type dislocations observed in small-angle boundaries on Al 62 Cu 20 Co 15 Si 3 decagonal quasicrystals dissociate into two partial dislocations. The projected Burgers vectors of these partial dislocations on the plane normal to the twofold A2D axis are b 1 =[a 1 /2, a 2 , 0, 0, 0, 0] and b 2 =[a 1 /2, -a 2 , 0, 0, 0, 0] respectively. The modulus of the total Burgers vector b=[a 1 ,0,0,0,0,0] is about 0.4 nm corresponding to the periodicity along the tenfold axis of the decagonal quasicrystal

High-resolution electron microscope (HREM) images of ω-phase crystals in Ti-11.1at%Mo alloy single crystals formed by aging are discussed by comparing with the calculated images. The calculation was carried out using the multi-slice method at different defocus values for ω-phase crystals at three different positions in the matrix. It is found that bright spots of HREM images of ω-phase crystals appear at the positions of atoms, which are displaced in the opposite direction and make atom pairs in the model, as was proposed by de Fontaine et al. This fact was previously predicted in 1987. It is also found that bright spots of HREM images appear at the position of atoms, which are not displaced in the model. These results suggest that the proposed model is satisfactory.

The alloying behaviour of copper atoms into gold clusters has been studied by high-resolution electron microscopy. Preparation of nanometre-sized gold clusters and subsequent copper deposition onto the gold clusters has been carried out with the use of a miniature double-source evaporator that has been directly set at the tip of a specimen holder. Upon the deposition of copper, nanometre-sized gold clusters quickly changed into Au-Cu solid solution clusters even at ambient temperature. It has been confirmed that such spontaneous alloying takes place not via a quasi-melting process but via a purely solid-state process.

Local atomic arrangements and wide tilings for two types of decagonal quasicrystals, which are formed in alloys with compositions near Al 70 Ni 15 Co 15 , were studied by high-resolution electron microscopy. The decagonal quasicrystals can be interpreted as structures formed with different tilings, so-called rhombic and pentagonal ones, which are constructed with definite linkages of similar atom clusters