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X-ray diffraction is one of the most popular experimental methods employed for determination of dislocation densities, as it can recognize both the strain fields and the local lattice rotations produced by dislocations. The main challenge of the quantitative analysis of the dislocation density is the formulation of a suitable microstructure model, which describes the dislocation arrangement and the effect of the interactions between the strain fields from neighboring dislocations reliably in order to be able to determine the dislocation densities precisely. The aim of this study is to prove the capability of X-ray diffraction and two computational methods, which are frequently used for quantification of the threading dislocation densities from X-ray diffraction measurements, in the special case of partially bunched threading dislocations. The first method is based on the analysis of the dislocation-controlled crystal mosaicity, and the other one on the analysis of diffuse X-ray scattering from threading dislocations. The complementarity of both methods is discussed. Furthermore, it is shown how the complementarity of these methods can be used to improve the results of the quantitative analysis of bunched and thus inhomogeneously distributed threading dislocations and to get a better insight into the dislocation arrangement. [ABSTRACT FROM AUTHOR]

Various nominally undoped, hydrothermally or melt grown (MG) ZnO single crystals have been investigated by standard positron lifetime measurements. Furthermore, optical transmission measurements and structural characterizations have been performed; the content of hydrogen in the bound state was determined by nuclear reaction analysis. A positron lifetime of 165-167 ps, measured for a brownish MG ZnO sample containing (0.30 ± 0.03) at.-% of bound hydrogen, matches perfectly the value found for colorless MG ZnO crystals. The edge shift, observed in the 'blue light domain' of the optical absorption for the former sample with respect to the latter samples, is estimated to be 0.70 eV, and found equal to a value reported previously. The possible role of zinc interstitials is considered and discussed. Microstructure analysis by X-ray diffraction and transmission electron microscopy revealed the presence of stacking faults in MG crystals in a high concentration, which suggests these defects to be responsible for the observed positron lifetime. [ABSTRACT FROM AUTHOR]

Epitaxial BiFeO3 films pulsed laser deposited on SrTiO3, Nb:doped SrTiO3, and DyScO3 were studied using variable angle spectroscopic ellipsometry, vacuum ultraviolet ellipsometry, micro-Raman spectroscopy, and x-ray diffraction. The energy band gap of the film deposited on DyScO3 is 2.75 eV, while the one for the film deposited on Nb:doped SrTiO3 is larger by 50 meV. The blueshift in the dielectric function of the BiFeO3 films deposited on Nb:doped SrTiO3 compared to the films deposited on DyScO3, indicates a larger compressive strain in the films deposited on Nb:doped SrTiO3. This is confirmed by Raman spectroscopy and by high resolution x-ray diffraction investigations. [ABSTRACT FROM AUTHOR]

A new approach is described that is applicable for structural characterization of any heteroepitaxially grown (strained or relaxed) III-nitride superlattices (SLs). The proposed method utilizes X-ray reciprocal space mapping measured in the vicinity of an asymmetrical reflection to determine the SL period, thickness, and strain state of a quantum well/barrier. On the example of a GaN/AlN SL, it is demonstrated that the structure parameters obtained from the proposed method agree very well with the parameters revealed by the currently preferred approach that is based on the measurements of ̉/2ϑ X-ray diffraction profiles. Furthermore, it is shown that the shape of the reciprocal lattice points measured in the asymmetrical diffraction geometry contains additional information about the density of threading dislocations (TDs) in the GaN substrate and in the GaN/AlN SL. The comparison of the density of TDs in the substrate and in the SL allows analysis of the relaxation mechanism and development of new techniques for the improvement of the structural quality of the SL. [ABSTRACT FROM AUTHOR]

In order to explore the possible surfactant effect of Ag on the formation of electrodeposited multilayers, Co/Cu(Ag) multilayers were prepared by this technique and their structure and giant magnetoresistance (GMR) were investigated. The multilayers were deposited from a perchlorate bath with various amounts of Ag+ ions in the solution for incorporating Ag atoms into the multilayer stack. Without Ag addition, secondary neutral mass spectroscopy (SNMS) indicated a well-defined composition modulation of the undermost Co/Cu bilayers. However, already at an Ag content as low as 1.8 at.% incorporated, SNMS showed a deterioration of the periodic multilayer structure. In agreement with the SNMS results, superlattice satellites were visible in the X-ray diffraction (XRD) patterns of the multilayers with up to 0.3 at.% Ag. The satellites were, however, very faint even for multilayers without Ag addition, indicating that the multilayers have high interface roughness and/or poor periodicity. In the absence of Ag and at the smallest Ag content investigated by XRD. a strong central multilayer peak and the weak superlattice satellites were complemented by weak diffraction maxima from non-periodic Co and Cu domains. In the Co/Cu(Ag) multilayer containing about 25 at.% Ag, i.e., nearly as much as Cu, XRD found a separate Ag(Cu) phase. In spite of the imperfect layered structure, a multilayer-type GMR behavior was observed in all samples up to about 10 at.% Ag incorporated in the multilayer stack. The GMR magnitude increased for Ag contents up to about 1 at.%, which implies that a small amount of Ag may have a beneficial effect through a slight modification of the layer growth and/or interface formation. However, for higher Ag contents beyond this level, the GMR was reduced in line with the structural degradation revealed by XRD and SNMS. For the highest Ag contents (above about 10 at.%), the GMR exhibited a behavior characteristic of a granular magnetic alloy, in agreement with the results of the structural study. [ABSTRACT FROM AUTHOR]

A method is presented which determines the stacking fault energy in facecentred cubic materials from the critical stress that is induced via sample bending in the early stages of plastic deformation. The critical stress is gauged by in situ X-ray diffraction. This method utilizes the results of Byun's consideration of the stress dependence of the partial dislocation separation [Byun (2003). Acta Mater. 51, 3063-3071]. Byun showed that the separation distance of the partial dislocations increases rapidly when the critical stress is reached and that the critical stress needed for the rapid separation of the partial dislocations is directly proportional to the stacking fault energy. In the approach presented here, the partial dislocation separation and the corresponding triggering stress are monitored by using in situ X-ray diffraction during sample bending. Furthermore, the in situ X-ray diffraction measurement checks the possible interactions between stacking faults present on equivalent lattice planes and the interactions of the stacking faults with other microstructure defects. The capability of the proposed method was tested on highly alloyed austenitic steels containing chromium (~16 wt%), manganese (~7 wt%) and nickel as the main alloying elements. For the steels containing 5.9 and 3.7 wt% Ni, stacking fault energies of 17.5 ± 1.4 and 8.1 ± 0.9 mJ m-2 were obtained, respectively. [ABSTRACT FROM AUTHOR]

Abstract: The effect of point defects, dislocations and grain boundaries on the electron scattering in molybdenum thin films having a constant thickness of 500nm was described quantitatively in form of a dependence of the electrical resistivity on the concentration of impurity atoms, stress-free lattice parameter, microstrain and grain size. The concentration of impurity atoms and the dislocation density were modified by depositing the Mo thin films using different techniques (DC magnetron sputtering, pulsed DC magnetron sputtering and RF magnetron sputtering) and by varying the substrate temperature (25°C, 150°C, 250°C and 350°C). As expected, the electrical resistivity of the Mo films decreased with decreasing density of microstructure defects. For all deposition methods, the dislocation density decreased with increasing substrate temperature, which led to an overall decrease of the measured resistivity with increasing substrate temperature. Due to the deposition equipment constraints during the RF sputtering, up to 3at.% of Fe, Cr and Ni were incorporated at the regular lattice positions in the crystal structure of molybdenum, which increased the resistivity of the Mo films nearly two times as compared to the DC and pulsed DC sputtered films. [Copyright &y& Elsevier]

Tungsten carbide (WC) powder having a crystallite size around 55 nm and the Brunauer-Emmett-Teller specific surface area 2.75 m2/g was sintered using the field assisted sintering/spark plasma sintering technique. Sintered samples were investigated using different analytical methods providing detailed information on the microstructure and mechanical properties of materials. Density and porosity of specimens were determined using the Archimedes principle and optical and scanning electron micrographs. The X-ray diffraction investigations provided the information on the crystal real structure and crystallite sizes. The electron backscatter diffraction measurements yielded the details about the grain size, frequency, and distributions of grain boundaries. Finally, the essential mechanical properties of sintered samples were obtained from the hardness and fracture toughness measurements. The influences of individual sintering conditions: sintering temperature and sintering time especially, on the microstructure and mechanical properties of sintered specimens were derived. Fully compact samples having the Vickers hardness HV10 around 29 GPa and fracture toughness KIc approximately 7.2 MPa m1/2 were sintered from temperatures of 1800 ° C and holding times 1 min. Specimens sintered at lower temperatures showed lower density which resulted in a significant drop in the sample hardness. [ABSTRACT FROM AUTHOR]

The influence of the local crystallographic orientation of the polycrystalline bottom platinum electrode on the crystallization of niobium pentoxide thin films during their rapid thermal annealing was investigated by X-ray diffraction, X-ray reflectivity and transmission electron microscopy. The NbO thin films under study were reactively sputtered in a mixed O/Ar atmosphere and subsequently subjected to the annealing in argon atmosphere at temperatures ranging from 500 C to 700 C. The X-ray diffraction confirmed a transition from the amorphous niobium oxide to the crystalline orthorhombic NbO for temperatures between 500 C and 600 C. The X-ray reflectivity measurements showed that the crystallization process was accompanied by a continuous increase of the electron density in NbO and by a rapid increase of the surface roughness at 700 C. It was further observed by transmission electron microscopy that NbO crystallizes selectively and that the crystalline domains of NbO possess a strong orientation relationship to the platinum from the bottom electrode. The orientation relationship $(\bar{1} 1 1)_{\mathrm{Pt}}\,{\parallel}\, (\bar{1} \bar{6}0)_{\mathrm{Nb}_{2}\mathrm{O}_{5}}$ was identified as the most beneficial one for crystallization of NbO. [ABSTRACT FROM AUTHOR]

Abstract: The influence of the microstructure of the as-deposited cathodic arc evaporated Ti1-xAlxN coatings and, in particular, the influence of the intrinsic lattice strains on their thermal stability were investigated by in-situ synchrotron high temperature glancing angle X-ray diffraction (HT-GAXRD) experiments up to 850°C. The microstructure of the as-deposited coatings was adjusted by the bias voltage (UB =−40V, UB =−80V and UB =−120V) and by the [Al]/([Ti]+[Al]) ratio (0.4, 0.5 and 0.6) of the used Ti–Al targets. The microstructure evolution during annealing was described in terms of the phase composition of the coatings, the aluminium content, aluminium distribution and residual lattice strains in fcc-(Ti,Al)N. Independent of the deposition parameters ([Al]/([Ti]+[Al]) ratio and bias voltage), all coatings contained a mixture of fcc-(Ti,Al)N, fcc-AlN and w-AlN after annealing at 850°C. The [Al]/([Ti]+[Al]) ratio was found to control the amount of fcc-(Ti,Al)N, whereas the bias voltage was mainly responsible for the relative amount of fcc-AlN and w-AlN. Finally, the interplay between lattice strains and the kinetics of the spinodal decomposition of fcc-(Ti,Al)N was illustrated. [Copyright &y& Elsevier]

Dense TRIP-matrix composites containing 5 vol.% Mg-PSZ as reinforcing phase were produced by employing the spark plasma sintering technique. A continuous and seamless interface between the ceramic particles and the steel matrix was achieved. Compression tests revealed better mechanical properties of the 5 vol.% Mg-PSZ-TRIP steel composites in comparison with both, pure and Al2O3 reinforced TRIP steel. The underlying deformation mechanism within the austenitic matrix entailed a pronounced martensite formation. An additional phase transformation was observed within the ZrO2 particles. The enhanced mechanical properties of the 5 vol.% Mg-PSZ composite are dedicated to the transformation strengthening of the ceramic particles. Finally a model of the reinforcing mechanism is proposed. [ABSTRACT FROM AUTHOR]

Distinct orientation relationships between face-centred cubic austenite (γ-Fe) and cubic c-ZrO2 were found and assigned using high-resolution transmission electron microscopy (HRTEM) that was complemented by the Fast Fourier Transform (FFT) of the HRTEM micrographs. These orientation relationships were described as [110] γ-Fe || [111] c-ZrO2 and ( $1{\bar {1}}1$) γ-Fe || ( $02\overline {2} $) c-ZrO2. They imply the heteroepitaxial growth of the counterparts that improved substantially the adhesion between γ-Fe and c-ZrO2. The analysed specimens were prepared by magnetron sputtering from an unstabilized ZrO2 ceramic target in argon atmosphere on TRIP steel substrate. The microstructure of the thin zirconia films was analysed using glancing-angle x-ray diffraction (GAXRD), scanning electron microscope (SEM) and TEM. [ABSTRACT FROM AUTHOR]

Abstract: The effect of aluminium contents and bias voltage on the microstructure of cathodic arc evaporated Ti1−xAlxN coatings was investigated with the aid of X-ray diffraction experiments and transmission electron microscopy. The coatings were deposited from mixed Ti–Al targets with different Ti:Al ratios (60:40, 50:50, 40:60 and 33:67) at bias voltages ranging between −20V and −120V. The microstructure of the coatings was described in terms of the phase composition, crystallite size and residual stress and related to the indentation hardness. The microstructure features were found to be related to the uniformity of the local distribution of Ti and Al in (Ti,Al)N, which was controlled, for a certain overall chemical composition of the coatings, by the bias voltage. The consequences of large local fluctuations of the Ti and Al concentrations in Ti1−xAlxN that occurred at higher bias voltages were the phase segregation, which was indicated through the formation of the fcc-(Ti,Al)N/fcc-AlN nanocomposites and the increase of the compressive residual stress in the face-centred cubic (Ti,Al)N. Concurrently, the increasing bias voltage contributed significantly to the reduction of the crystallite size. Higher residual stress and smaller crystallite size increased the hardness of the coatings. The overall chemical composition of the coatings influenced mainly their phase composition. The high concentration of Al in (Ti,Al)N led to the formation of wurtzitic AlN in the coatings. [ABSTRACT FROM AUTHOR]

Abstract: Formation of structure defects and other microstructure phenomena in hard Cr–Al–(Si–)N, Ti–Al–(Si–)N and Zr–Al–N nanocomposite coatings with different aluminium and silicon contents deposited by using cathodic arc evaporation was investigated using a combination of X-ray diffraction and transmission electron microscopy. The subject of the microstructure studies was the analysis of the phase composition and, for the cubic phase, the determination of the stress-free lattice parameters, the crystallite size and the local disorientation of crystallites. It was found that the formation of structure defects starts with a fragmentation of the deposited clusters having the size of several tens of nanometers into nanocrystallites having the size below 12 nm. This fragmentation was driven by formation of dislocation networks. The formation of structure defects continued with the segregation of the excessive aluminium and silicon from the host structure of the transition metal nitrides that was followed by the growth of the wurtzitic AlN and an amorphous silicon nitride at higher aluminium and silicon concentrations. The microstructure of the coatings was correlated with their hardness. In all systems under study, an increase of the hardness with increasing density of the microstructure defects was observed. The maximum of the hardness was observed in the coatings containing both the cubic transition metal nitride (accommodating also aluminium and silicon) and the wurtzitic AlN. [Copyright &y& Elsevier]

Abstract: The relationship between the microstructure and the hardness of Ti1−x−y Al x Si y N nanocomposite thin films was investigated using X-ray diffraction and high-resolution electron microscopy. It was found that a high hardness is accompanied by a partial crystallographic coherence of the nanocrystalline domains. The degree of crystallographic coherence depends strongly on the chemical composition and microstructure of the nanocomposites. The silicon present in the thin films creates an amorphous phase, which in excess obstructs the crystallographic coherence and the creation of coherent lattice strains. Consequently, an excess of silicon decreases the hardness of the Ti–Al–Si–N nanocomposites. [Copyright &y& Elsevier]

Abstract: Formation of partially coherent nanocrystalline domains, development of intrinsic residual stresses and the relationship between the partial coherence of crystallites and the hardness of vacuum-arc-deposited Ti–Al–N and Ti–Al–Si–N nanocomposites were investigated for different chemical compositions of the nanocomposites using a combination of the electron probe microanalysis, X-ray diffraction, transmission electron microscopy with high resolution and hardness measurement. Partial coherence of nanocrystalline domains was found to be a very important microstructural feature, which is strongly related to the correlated orientation of neighbouring crystallites and to the atomic ordering at the crystallite boundaries. Appropriate mutual orientation of neighbouring crystallites and suitable atomic ordering at the crystallite boundaries facilitate the development of intrinsic residual stresses, which influence directly the hardness of the nanocomposites. [Copyright &y& Elsevier]

Uranium nitride thin films were prepared by reactive sputter deposition at temperatures between -200 and +400 °C. These conditions provided a large variety of microstructure. At low temperatures, nanocrystalline layers (mean crystallite size 17 nm) grew with a strong preferred orientation {1 1 1} perpendicular to the substrate, with a large compressive residual stress and with a high density of structure defects (i.e. with large microstrain). At elevated temperatures, the crystallites had only a moderate preferred orientation; the residual stress was partly relaxed and the density of structure defects lower. For the first time, for an actinide material, we have investigated how the microstructure influences the formation of magnetic moments and magnetic ordering. Bulk UN is an itinerant antiferromagnet. The increasing disorder suppresses the long-range antiferromagnetism and induces a ferromagnetic component in exchange interactions, leading to a cluster glass type of ordering at low temperatures. In highly disturbed thin films (low temperature deposition), UN exhibits a weak Pauli paramagnetism. [Copyright &y& Elsevier]

Microstructure of titanium aluminium nitride thin films deposited using arc evaporation was investigated for different aluminium contents. From Ti0.96Al0.04N to Ti0.38Al0.62N, the dominant phase in the coatings was the fcc Ti1-xAlxN. In this concentration range, the compressive residual stress as well as the hardness of the coatings increased with increasing aluminium contents. Crystallites of Ti1-xAlxN were strongly textured; the preferred orientation was found to be related to the deposition geometry, not to the composition of the coatings. Concurrently, preferred orientation of crystallites was found to be a very important parameter influencing the crystal anisotropy of lattice deformation and the coherence of neighbouring crystallites. At higher aluminium contents (x>0.8), the dominant phase was the hexagonal AlN; the hardness of the films decreased. [Copyright &y& Elsevier]

High degree of ordering was observed in the SrTiO3, Ba0.1Sr0.9TiO3 and BaTiO3 thin films grown by injection metal-organic chemical vapour deposition on sapphire substrates. Orientation of the Al2O3 substrates was (0 0 1) perpendicular to the surface; orientation of the films was (1 1 1). Atomic ordering at the interface between the substrates and the films approached locally heteroepitaxial growth. Two distinct in-plane orientations of the films were observed. The projection of the [1 0 0] direction in the cubic or cubic-like films was rotated either +30 or −30° with respect to the [1 0 0] crystallographic direction of the substrate. Still, a slight disorientation of the films from the dominant directions was observed. The in-plane disorientation of the films increased with increasing barium contents. In SrTiO3, the in-plane disorientation of crystallites was 1.5°, in BaTiO3 3.2°. The residual stress analysis has shown that the films grew without residual stress at the deposition temperature (800 °C). Consequently, the interface layer between films and substrates was very strained but able to pass the in-plane orientation of the substrate to the film. [Copyright &y& Elsevier]

• Potential and limits of the lattice strain control via composition profile are shown. • Lattice strains produced by lattice misfit are reduced by dislocations and V-pits. • V-pits reduce the lattice strain much more effectively than edge dislocations. • Residual stresses and dislocation densities were determined using X-ray diffraction. • A model for simulation of lattice strains and strain reduction is presented. One of the requirements for the functionality of the AlGaN/GaN high-electron mobility transistors is the presence of a specific residual lattice strain in their active region. This lattice strain can be adjusted by depositing a multilayer stack that consists of individual Al x Ga 1 − x N layers with harmonized [Al]/[Ga] ratio, which produces a controlled depth gradient of the lattice misfit and consequently a controlled gradient of the residual lattice strain. However, the lattice misfit at the interfaces between adjacent layers is partially compensated by misfit dislocations and other microstructure features, e.g., V-shaped interfacial pyramids. In this contribution, a non-destructive method for simultaneous quantitative analysis of remaining lattice strains and density of microstructure defects compensating the lattice misfit is presented and illustrated on the example of AlGaN stacks with different composition profiles, which were deposited using metalorganic chemical vapor phase epitaxy on (111)-oriented Si wafers. This technique is based on the mapping of selected reciprocal lattice points using X-ray diffraction. The lattice strains obtained from the reciprocal space mapping were verified by confocal micro-Raman spectroscopy. The presence of the microstructure defects and the depth gradient of their density were confirmed by transmission electron microscopy. The interplay of the composition profile and the thickness of individual layers on the lattice strain is described by a micromechanical model. From the comparison of the experimental results with the lattice strains, which were predicted for a defect-free multilayer stack, the main strain relaxation mechanisms are concluded, and their impact on the strain relaxation is quantified. [ABSTRACT FROM AUTHOR]

Results of powder X-ray diffraction measurements done on the orthorhombic CePtSn in the temperature range 4–300 K are reported. Rietveld refinement of diffraction data collected at each temperature revealed anomalies in the temperature dependence of lattice parameters that can be associated with magnetic phase transitions in this intermetallic compound at 5 (TM) and 7.5 K (TN). The dominant change of the lattice parameters was observed at the magnetic transition, at TN, from the paramagnetic to the antiferromagnetic phase. A shallow minimum of the lattice parameters a and b above TN is tentatively attributed to antiferromagnetic correlations in the paramagnetic range. [Copyright &y& Elsevier]

Among the microstructure defects in hexagonal graphitic boron nitride, the basal plane corrugations are of high relevance for the sp2 to sp3 phase transition under high pressures (HP) and high temperatures (HT). A microstructure model is described, which is capable of quantifying the amplitude of the basal plane corrugations on the basis of the anisotropic X-ray diffraction line broadening. It is illustrated that this model correctly reproduces the specific shape of the diffraction lines from corrugated basal planes, i.e., the characteristic splitting of the 00l peaks. The results from XRD are verified by direct observation in the transmission electron microscope with high resolution. Subsequent HP/HT experiments were performed in order to highlight the difference in the phase transition kinetics between hexagonal boron nitride samples with different amount of basal plane corrugations. The effect of these microstructure defects on the conversion rate and on the obtained synthesis product is discussed. [ABSTRACT FROM AUTHOR]

Ultrahard boron nitride compacts containing nanosized domains of the cubic (c-BN), wurtzitic (w-BN), and hexagonal (h-BN) phase were synthesized at high-pressure/high-temperature (HP/HT) conditions. Hot-pressed and pyrolytic BN, both containing h-BN as a main component, were used as starting materials. The HP/HT products were investigated by x-ray diffraction via Rietveld and line-profile analysis, as well as high-resolution transmission electron microscopy. c-BN was the dominant phase in all products, complemented by up to 25 wt% w-BN and some remaining "compressed h-BN." In particular samples, partial crystallographic coherence of adjacent crystallites to x-rays was observed, which has been previously found in superhard transition metal nitride-based nanocomposite coatings. In the BN nanocomposites, the partial coherence of nanocrystallites to x-rays was improved by their strong local preferred orientation, which is made possible by the well-known orientation relationships among h-BN, w-BN, and c-BN phases. The correlation between the weight fraction and the average size of the c-BN crystallites helped to describe the formation of c-BN/(w-BN) nanocomposites from submicron-sized h-BN domains in the starting materials. The Knoop and Vickers hardness of specimens with crystallite sizes ranging from 6 to ~50 nm was found to be significantly higher than that of c-BN single crystals, despite the presence of residual h-BN. [ABSTRACT FROM AUTHOR]

Abstract: A routine for simultaneous quantification of turbostratic disorder, amount of puckering and the dislocation and stacking fault density in hexagonal materials was proposed and tested on boron nitride powder samples that were synthesised using different methods. The routine allows the individual microstructure defects to be recognised according to their effect on the anisotropy of the X-ray diffraction line broadening. For quantification of the microstructure defects, the total line broadening is regarded as a linear combination of the contributions from the particular defects. The total line broadening is obtained from the line profile fitting. As testing material, graphitic boron nitride (h-BN) was employed in the form of hot-isostatically pressed h-BN, pyrolytic h-BN or a h-BN, which was chemically vapour deposited at a low temperature. The kind of the dominant microstructure defects determined from the broadening of the X-ray diffraction lines was verified by high resolution transmission electron microscopy. Their amount was attempted to be verified by alternative methods. [Copyright &y& Elsevier]

Abstract: US layers (thickness 0.1–0.3μm) were prepared by sputter deposition from US target in Ar atmosphere at temperatures 298–573K. For US thin films, magnetism tends to be suppressed comparing to the bulk US, which is a band ferromagnet with T C =177K. T C decreases down to 85–105K for the layers deposited at room temperature (depending on the deposition parameters) and increases with the increase of the temperature of substrate. Spontaneous magnetization in the ordered state is suppressed considerably for the deposited layers: down to 0.1μB/f.u. or less for all samples studied (compare with 1.55μB/f.u. for bulk US). The changes in the magnetic properties are correlated with the microstructure of the films. Microstructure studies indicated that the US thin films contain a mixture of “nanocrystalline” and “amorphous” parts. The crystallite size in the nanocrystalline parts is approximately 100Å. In all samples, a compressive residual stress was observed, which caused a strongly anisotropic lattice deformation with the easy deformation direction {111}. The compressive residual stress was below −3GPa in most samples. Results are compared with UN layers synthesized by reactive sputtering. [Copyright &y& Elsevier]

Temperature changes of lattice parameters in TbPdIn, DyNiAl and GdNiAl were investigated using the low-temperature X-ray powder diffraction, and related to the magnetic ordering in these compounds. All three compounds exhibit a strong magneto-crystalline anisotropy. Additional powder diffraction measurements were performed in external magnetic fields to assess the orientation of magnetic moments with respect to the crystal axes. No significant preferential orientation of crystallites due to the macroscopic ordering in magnetic field was observed below Tc in TbPdIn. On the contrary, the other compounds became macroscopically well ordered below the magnetic-phase transition temperature. DyNiAl had the preferred orientation 00l parallel to the direction of the magnetic field; the preferred orientation of crystallites in GdNiAl exposed to external magnetic field was hk0. [Copyright &y& Elsevier]

The effect of a locally fluctuating [Ti]/[Al] ratio in the Ti 1−x Al x N coatings on the formation of the lattice strains at the (Ti,Al)N/(Al,Ti)N interfaces and the influence of these interfaces on the stabilization of metastable (Al,Ti)N with face centered cubic structure were investigated using glancing angle X-ray diffraction, transmission electron microscopy and X-ray spectroscopy. A series of Ti 1−x Al x N coatings with different [Ti]/[Al] ratios was deposited using cathodic arc evaporation from a titanium and an aluminum cathode. The overall chemical composition was controlled by the position of the respective sample in the deposition chamber and ranged from x  = [Al]/([Ti] + [Al]) = 0.06 to 0.64. The local fluctuations of the [Ti]/[Al] ratio were produced by interrupting the deposition from the titanium cathode. It was shown that such local fluctuations of the [Ti]/[Al] ratio generate large contrary residual stresses at the respective side of the (Ti,Al)N/(Al,Ti)N interface. These stresses were almost completely relieved after annealing at 750 °C. The stress relaxation after annealing was accompanied by an equalization of the [Ti]/[Al] ratio and by a decay of the composition fluctuations in the Ti 1−x Al x N coatings. The stress relaxation and the reduction of the local composition gradients were concluded from measured residual stresses, stress-free lattice parameters and local concentration profiles. [ABSTRACT FROM AUTHOR]

The evolution of microstructure defects under compression, their mutual interactions at high defect densities and the effect of these phenomena on the hardening were studied in metastable austenitic steel containing 16 wt% Cr, 6 wt% Mn and 9 wt% Ni. At this chemical composition, the estimated martensite start temperature and the stacking fault energy of austenite are about -240 °C and 26 mJ/m², respectively. Consequently, the metastable austenite should be thermodynamically stable far below the room temperature and the formation of stacking faults should be retarded. The microstructure analysis, which was performed by means of XRD, ECCI, EBSD and TEM, revealed that the dislocation slip is the dominant deformation mechanism in the initial stages of the deformation process (εr0.05). After a critical stress level was reached, stacking faults started to form and widen. In regions with high local stacking fault densities, twinning and the formation of ε-martensite were detected simultaneously. The local deformation mechanism and the related microstructure changes were found to depend on the orientation of the respective grain. In favorably oriented grains, deformation bands consisting of ε-martensite and twins were predominantly formed in the primary slip system. In other grains, the dislocation slip remained the dominant deformation mechanism. The coexistence of faulting, twinning and dislocation slip and the interaction between the dislocations and stacking faults are discussed as the main reasons for the high observed density of microstructure defects and high hardening. [ABSTRACT FROM AUTHOR]

Graphitic boron nitride is extremely relevant material for technical and technological applications. It is mainly used as high-temperature isolator and chemically inert material. However, its properties are strongly affected by the presence and stability of microstructure defects. In this study, the amount of microstructure defects in the graphitic boron nitride was manipulated by annealing turbostratic and pyrolytic BN up to 2573 K. For annealing, the field-assisted sintering technique was employed. The X-ray diffraction analysis confirmed that the turbostratic disorder and basal plane corrugations are the dominant microstructure defects, which are complemented by the stacking faults and dislocations. In the as-received samples, the kind of the dominant microstructure defects was found to depend on the concentration of chemical impurities like oxygen and hydrogen. After the thermal treatment, the basal plane corrugations remained stable to much higher temperatures than the turbostratic disorder. Large basal plane corrugations impeded the thermal-activated grain growth. [ABSTRACT FROM AUTHOR]

The high pressure spinel-type γ-Si 3 N 4 was prepared by using shock wave synthesis from amorphous precursors at the peak shock pressures around 34 GPa. Due to the high liability of the precursor to oxidation, it is nearly impossible to obtain oxygen-free high-pressure material. The overall oxygen content varies between 7 and 12 wt%. However, the X-ray and neutron diffraction experiments confirmed that the spinel-like phase dominates the samples. The neutron diffraction revealed that up to 5 wt% of oxygen can be accommodated in the crystal structure of γ-Si 3 N 4 , where it replaces nitrogen. Additional oxygen seemed to increase the amount of an amorphous phase in the samples. The local chemical analysis in a transmission electron microscope proved that the amorphous phase contains more oxygen than the crystalline phase, thus the excess of oxygen was verified to be contained in the amorphous phase. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we describe the preparation and characterization of cadmium sulfide (CdS) particles grown on the Mg and Na-vermiculite (MgV, NaV) fractions of less than 40μm. The Na-vermiculite was prepared in a monoionic full-saturated 12Ǻ form from MgV. The cadmium vermiculites were prepared by the ion-exchange method. The processes of the interlayer cations exchange with Cd2+ as well as the own formation of CdS particles after the reaction of cadmium vermiculite with hydrogen sulfide (H2S) were studied by using X-ray powder diffraction method, scanning electron microscopy with energy dispersive analysis, infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy, atomic force microscopy and UV–VIS diffuse reflectance spectroscopy. The possible ordering of the CdS in the vermiculite interlayer was proposed using the molecular modeling. [Copyright &y& Elsevier]

Abstract: The influence of the electrochemical potential and the deposition mode on the preferred orientation and morphology of crystallites and on the microstrain in electrochemically deposited copper thin films was investigated using a combination of cyclic voltammetry, chronoamperometry, X-ray diffraction, SEM and the diffraction of backscattered electrons. With increasing negative electrochemical potential, the deposition mode changed from the charge transfer controlled one to the diffusion controlled one. At the highest electrochemical potentials, copper deposition was accompanied by hydrogen reduction. In potentiostatically deposited thin films, the preferred orientation of crystallites changed from {111} in the charge transfer controlled deposition mode to {110} in the diffusion controlled one. The increase of the electrochemical potential in the charge transport controlled deposition mode caused an increase of the dislocation density. The increasing electrochemical potential in the diffusion controlled mode led to a decrease of the dislocation density. The copper deposition, which was accompanied by the hydrogen reduction, produced needle-like crystallites with the {100} texture and with the lowest dislocation density. [Copyright &y& Elsevier]