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Other contributors: Markus Hoelzel, Carsten Baehtz, Isabel Sobrados, Jesús Sanz. Sodium hexatitanate Na2Ti6O13 with a tunnel structure has been proposed to be an attractive anode material for lithium ion batteries because of its low insertion voltage, structural stability and good reversibility. In order to obtain a full understanding of the properties of this titanate, a combination of in situ synchrotron X-ray diffraction, neutron diffraction and 7Li MAS solid-state NMR spectroscopy is used in the present work. During the first insertion stage (centered at 1.3 V) lithium is allocated in square planar LiO4 2c (Li1) sites, minimizing electrostatic repulsion with Na ions. During the second lithium uptake (centered at 1.1 V), Li ions pass from 2c to empty 4i (Li2) sites of y/b = 0.5 planes, near Ti3+ cations. Distribution of Li+ and Na+ ions with respect to Ti3+ cations was deduced from Fourier map differences (Rietveld technique) and NMR quantitative analyses in LiNa2Ti6O13 and Li2Na2Ti6O13 samples. 7Li MAS-NMR analysis showed that Li ions occupy three fourfold coordinated sites with reasonable Li+-O-Ti3+ bond distances, while Na cations remain at eightfold coordinated positions near Ti4+ cations as deduced from 23Na MAS-NMR spectroscopy. 7Li MAS-NMR recorded at increasing temperatures suggests that Li ions move along sinusoidal paths to reduce Li-Na electrostatic interactions. Li mobility along the b-axis is favored by partial occupation of interstitial 4i sites (Li3) located at both sides of Na cations in y/b = 0 planes. In lithium inserted samples the most probable - Li1(2c) → Li3(4i) → Li1(2c) - conduction paths were deduced. However, formation of Li pairs at y/b=0 planes (Li2 sites), where Li ions are located near Ti3+ cations, reduce the amount of mobile Li ions that participate in conduction processes. Proximity of lithium to Li and Na ions limits insertion to ca. 2 Li ions per structural formula. [preprint]

Successive crystallization of amorphous Cr-Zr-O thin films, formation of the (Cr,Zr)2O3/(Zr,Cr)O2 nanocomposites and the thermally induced changes in the hexagonal crystal structure of metastable (Cr,Zr)2O3 were investigated by means of in situ high-temperature synchrotron diffraction experiments up to 1100 °C. The thin films were deposited at room temperature by using reactive ion beam sputtering, and contained 3–15 at.% Zr. At low Zr concentrations, chromium-rich (Cr,Zr)2O3 crystallized first, while the crystallization of zirconium-rich (Zr,Cr)O2 was retarded. Increasing amount of zirconium shifted the onset of crystallization in both phases to higher temperatures. For 3 at.% of zirconium in amorphous Cr-Zr-O, (Cr,Zr)2O3 crystallized at 600 °C. At 8 at.% Zr in the films, the crystallization of (Cr,Zr)2O3 started at 700 °C. At 15 at.% Zr, the Cr-Zr-O films remained amorphous up to the annealing temperature of 1000 °C. Metastable hexagonal (Cr,Zr)2O3 accommodated up to ~ 3 at.% Zr. Excess of zirconium formed tetragonal zirconia, which was stabilized by chromium.

In this study we investigated the correlation between microstructure and residual strain relaxation in nanocrystalline Pt films with a thickness of about 20 nm produced by different deposition techniques: magnetron sputtering and ion beam sputtering. X-ray diffractometry was carried out using synchrotron radiation. The out-of-plane interplanar distance was measured during isothermal in situ annealing at temperatures between 130 °C und 210 °C. The thermoelastic expansion coefficient is equal for both types of nanocrystalline Pt films and slightly lower than for coarse grained Pt. The relaxation of residual out-of-plain strain depends on temperature and is significantly stronger in the case of the magnetron sputtered films than for the ion beam sputtered films. Different relaxation of compressive stress is ascribed to the different microstructures which evolve during deposition via the corresponding deposition technique. Thickness fringes around the (1 1 1) Bragg peak deposited via magnetron sputtering reveal that these films are essentially composed of columnar (1 1 1) oriented grains which cover the whole film thickness. In contrast, no thickness fringes are observed around the (1 1 1) Bragg peak of films prepared by ion beam sputtering indicating a significantly different microstructure. This is confirmed by Electron Backscatter Diffraction which reveals a (1 1 1) texture for both types of films. The (1 1 1) texture, however, is significantly stronger in the case of the magnetron sputtered films. Grain growth at low homologous temperatures is considered to be an important contribution to relaxation of residual stress.

X-ray diffraction using synchrotron radiation was used for real-time investigation of the phase evolution of Ni/Ti multilayer thin films during annealing. These multilayers were deposited onto Ti–6Al–4V substrates by dc magnetron sputtering from pure Ni and Ti targets. The deposition parameters were adjusted in order to obtain a near equiatomic chemical composition and modulation periods (Λ) below 25 nm. Along the entire thickness of the films, well-defined structures with alternate Ni- and Ti-rich layers are observed, even for Λ = 4 nm. In this case, a halo characteristic of an amorphous structure is obtained, while for Λ of 12 and 25 nm the as-deposited thin films are nanocrystalline being possible to identify the (111) Ni and (002) Ti diffraction peaks. The nanolayered structure vanishes during annealing due to interdiffusion followed by reaction. The reaction between Ni and Ti to produce NiTi in the cubic B2 structure occurs in a short delay of time and within a narrow temperature range. For Λ of 25, 12 and 4 nm, the reaction temperature is close to 320, 350 and 385 °C, respectively. For higher temperatures, in addition to the austenitic phase, the NiTi 2 phase is identified. The diffusion of Ti from the substrate and Ni towards the substrate could favour the precipitation of NiTi 2 .

The isostructural decomposition of the titanium aluminium nitride supersaturated solid solution crystallising in the face centred cubic (fcc) crystal structure into the titanium-rich fcc-(Ti,Al)N and almost titanium-free fcc-(Al,Ti)N and the transformation of metastable fcc-(Ti,Al)N into the wurtzitic aluminium nitride are discussed from the crystallographic point of view by taking the observed orientation relationships between the adjacent phases into account. It is shown that the isostructural decomposition of fcc-(Ti,Al)N into Ti-rich fcc-(Ti,Al)N and fcc-(Al,Ti)N and the transformation of the metastable fcc-(Ti,Al)N into the thermodynamically stable wurtzitic phase are concurrent processes, which are controlled not only by the thermodynamic stability of the respective compound and by the diffusivity of Al and Ti, but also by the local lattice strains. A part of the local lattice strains is regarded to result from the lattice misfit at the interfaces between the titanium aluminium nitrides having different [Al]/[Ti] concentration ratios and, in the case of the fcc/wurtzite-type interface, also having different crystal structures. The phase transition of the fcc-(Ti,Al)N to the wurtzitic one was predicted to be facilitated by stacking faults. The results of crystallographic considerations were verified experimentally by using in situ high-temperature synchrotron diffraction experiments that were performed on cathodic arc evaporated (Ti,Al)N thin films containing titanium and aluminium in different amounts.

Nickel–Titanium (Ni–Ti) thin film shape memory alloys (SMAs) have been widely projected as novel materials which can be utilized in microdevices. Characterization of their physical properties and its correlation with phase transformations has been a challenging issue. In the present study, X-ray beam diffraction has been utilized to obtain the structural information at different temperatures while cooling. Simultaneously, electrical resistivity (ER) was measured in the phase transformation temperature range. The variation of ER and integral area of the individual diffraction peaks of the different phases as a function of temperature have been compared. A mismatch between the conventional interpretation of ER variation and the results of the XRD data has been clearly identified.

International audience; In order to optimize materials for phase change random access memories (PCRAM), the effect of Ge doping on Ga-Sb alloy crystallization was studied using combined in situ synchrotron x-ray techniques, electrical measurements, and static laser testing. The present data emphasize that the crystallization temperature can be increased up to 390 degrees C with subsequent higher thermal stability of the amorphous phase; phase segregation is evidenced with GaSb, Sb, and Ge phases that crystallize in a two-step crystallization process. The Ge-doped GaSb films exhibit a larger electrical contrast as compared to undoped GaSb alloy (up to x 100). The optical contrast measured by laser testing is shown to follow the mass density change variations upon crystallization, with a negative contrast (higher value in amorphous state) whatever Ge-doping levels. In situ x-ray reflectivity measurements show that zero mass density change can be achieved by low Ge-doping. Ge-doped GaSb alloys look promising since a phase change material with zero mass density change and higher crystallization temperature satisfactorily fulfills the specifications for reliable PCRAM cells in terms of endurance and data retention. (C) 2016 AIP Publishing LLC.

In this work we investigated the structural re-organization of thin nanocrystalline Pt films in the temperature range between 250 °C and 400 °C by in-situ XRD, GIXRD and XRR synchrotron experiments. A re-orientation of (111) atomic planes and a relaxation of residual stress occurs. After heating up, Bragg peak fringes can be observed in the diffractograms. They are a direct proof that the Pt films are built of (111) columnar grains which essentially reach the whole film thickness of about 40 nm. During isothermal annealing a relaxation of the dispersion parameter of the atomic planes takes place which is associated with an activation energy of (0.4 ± 0.1) eV.

Three magnesium-based alloys, Mg 90 Ni 10 , Mg 80 Ni 10 Y 10 and Mg 85 Cu 5 Ni 5 Y 5 , were prepared by melt-spinning and compared regarding their hydrogen desorption properties. Their hydrogen desorption kinetics after activation and hydrogenation was investigated by thermogravimetry at different temperatures in the range from 150 °C to 250 °C. It was found that Mg 80 Ni 10 Y 10 exhibits a much faster desorption kinetics in comparison to Mg 90 Ni 10 and Mg 85 Cu 5 Ni 5 Y 5 of up to 1.3 wt.%-H 2 /min. The corresponding crystal phase transformations were investigated in detail by in situ synchrotron X-ray diffraction. It was found that the kinetics of hydrogenation is controlled by different reaction pathways for Mg 90 Ni 10 , Mg 80 Ni 10 Y 10 and Mg 85 Cu 5 Ni 5 Y 5 .

The thermodynamics of structural phase transformations in thin films depends on the mechanical stress that can be released by plastic deformation. For thin films below a critical film thickness, plastic deformation is energetically unfavourable: thus, the system stays coherent and stress remains. For PdHc films less than 22 nm thick, a new situation emerges: while the interfaces between matrix and hydride precipitates remain coherent throughout the complete phase transition, misfit dislocations form between the hydride phase and the substrate.

A 3 V cathode material for lithium ion batteries, Li 0.33 MnO 2 , was synthesized by solid-state reaction. Two Mn crystallographic positions, Mn (1) and Mn (2) , were determined by X-ray diffraction analysis. The [Mn (2) O 6 ] octahedron had a lower symmetrical degree than that of [Mn (1) O 6 ], which was attributed to the geometrical effects of the non-symmetrical environment around Mn (2) . Li 0.33 MnO 2 delivered a reversible discharge capacity ∼140 mA h g −1 . In situ synchrotron diffraction clearly showed a reversible phase transition of Li 0.33 MnO 2 during electrochemical process. The analysis of X-ray absorption near edge spectroscopy observed the conversion of Mn 4+ to Mn 3+ with Li + intercalation into Li 0.33 MnO 2 , accompanied by the formation of more severely distorted [MnO 6 ] octahedron.

Single phase spinel solid solutions of LixMn3-x-yFeyO4 series with range of 0.5≤x≤1.0 and 0.2≤y≤1.0, have been synthesized by a solid state reaction. By refining the high-resolution X-ray diffraction patterns with Rietveld profile analysis, the lattice parame- ters, interatomic distances and cation distribution were determined. The Fe-for-Mn substitu- tion increases the spinel unit cell constant from a = 8.27A to a = 8.38A, for the Fe/(Fe+Mn) mole ratio of 0.1 and 0.472, respectively. Evidence is given that the lithium ions occupy the tetrahedral sites exclusively, for the molar ratio 0� Fe/(Mn+Fe) � 0.3.

X-ray powder diffraction was employed to reveal the structural changes occurring upon annealing of quenched, hexagonal Ni1.50Sn below its equilibrium ordering temperature, leading finally to long-range ordered, orthorhombic Ni1.50Sn. The changes in the diffraction patterns indicate that the features of the low-temperature phase develop gradually in two main stages. Ex situ and in situ time-resolved X-ray powder diffraction analysis of the first stage was employed to monitor at various temperatures the time dependence of the lattice axial ratio c/a associated with the formation of long-range order in small domains. Data evaluation using an ‘equivalence-time’ method gave a value of 165–170 kJ/mol for the activation energy of the ordering, indicative of lattice-site changes of Ni atoms.

Neutron powder diffraction studies of Na{sub 1/2}La{sub 1/2}TiO{sub 3} and Na{sub 1/2}Tb{sub 1/2}TiO{sub 3}, and a synchrotron X-ray powder diffraction study of Na{sub 1/2}Eu{sub 1/2}TiO{sub 3} have been carried out. Rietveld refinement of the structures confirmed that Na{sub 1/2}Eu{sub 1/2}TiO{sub 3} and Na{sub 1/2}Tb{sub 1/2}TiO{sub 3} crystallizes in GdFeO{sub 3} type of structure (space group Pbnm). The ambiguity in the literature regarding the crystal structure of Na{sub 1/2}La{sub 1/2}TiO{sub 3} has been resolved and the correct space group is found to be R3-bar c. A detailed list of refined structural parameters of these compounds is presented for the first time.

The morphology of micrometer-sized beta-hematin crystals (synthetic malaria pigment) was determined by TEM images and diffraction, and by grazing incidence synchrotron X-ray diffraction at the air-water interface. The needle-like crystals are bounded by sharp {100} and {010} side faces, and capped by {011} and, to a lesser extent, by {001} end faces, in agreement with hemozoin (malaria pigment) crystals. The beta-hematin crystals grown in the presence of 10% chloroquine or quinine took appreciably longer to precipitate and tended to be symmetrically tapered toward both ends of the needle, due to stereoselective additive binding to {001} or {011} ledges. Evidence, but marginal, is presented that additives reduce crystal mosaic domain size along the needle axis, based on X-ray powder diffraction data. Coherent grazing exit X-ray diffraction suggests that the mosaic domains are smaller and less structurally stable than in pure crystals. IR-ATR and Raman spectra indicate molecular based differences due to a modification of surface and bulk propionic acid groups, following additive binding and a molecular rearrangement in the environment of the bulk sites poisoned by occluded quinoline. These results provided incentive to examine computationally whether hemozoin may be a target of antimalarial drugs diethylamino-alkoxyxanthones and artemisinin. A variation in activity of the former as a function of the alkoxy chain length is correlated with computed binding energy to {001} and {011} faces of beta-hematin. A model is proposed for artemisinin activity involving hemozoin nucleation inhibition via artemisinin-beta-hematin adducts bound to the principal crystal faces. Regarding nucleation of hemozoin inside the digestive vacuole of the malaria parasite, nucleation via the vacuole's membranous surface is proposed, based on a reported hemozoin alignment. As a test, a dibehenoyl-phosphatidylcholine monolayer transferred onto OTS-Si wafer nucleated far more beta-hematin crystals, albeit randomly oriented, than a reference OTS-Si.

The influence of rapid quenching on the phase formation of Cu–Si alloys was investigated for silicon contents between 10 and 30 at.%. Rapid quenching leads to formation of different meta-stable states depending on the chemical composition. High temperature phases η, δ and κ can be preserved at room temperature. The formation of the room temperature phase ɛ can be suppressed by rapid quenching from the melt. The crystal structure of the high temperature phases was analysed by X-ray powder diffraction. Annealing of the rapidly quenched alloys at T = 500 °C leads to the transformations of the meta-stable phases. The equilibrium states exhibit phase compositions, which are in agreement with the generally accepted phase diagram.

HT-LiMnO2 was prepared by a solid-state reaction at 900 °C. Electrochemical charge–discharge cycling of HT-LiMnO2 showed an initial charge capacity 113 mA h g− 1, followed by a small first discharge of 25 mA h g− 1. The discharge capacity subsequently increased and reached up to ∼ 120 mA h g− 1 after 30 cycles. In situ synchrotron diffraction showed that HT-LiMnO2 transformed to a new phase (Phase II) during the first charge process, which was metastable and could easily convert to spinel LiMn2O4 in the following cycles. The progressive formation of this spinel phase was responsible for the capacity increase of the battery in the first cycles. The different cycling performance of HT-LiMnO2 and LT-LiMnO2 was attributed to the large stacking faults in LT-LiMnO2, which may facilitate the material to completely convert to spinel LiMn2O4 in the first charge without the medium transition to Phase II.

As-prepared and annealed (up to 3 days at 633 K and 673 K) e-Fe3N1.0 powders were studied by powder diffraction using synchrotron radiation and transmission electron microscopy. The data reveal the formation of γ'-Fe4N in few powder particles and enrichment of the remaining e-phase with N indicating inter-particle N transfer. Structural diffractionline broadening due to local composition fluctuations was identified in the X-ray line profiles by fitting applying a convolution procedure.

Investigations of the structure transformations of lithium deficient Li 0.95 Mn 2.05 O 4 , in the temperature range of 10–1173 K, have been undertaken with X-ray powder diffraction, using synchrotron radiation, at the HASYLAB high-resolution diffractometer (beamline B2). Single phase spinel-like oxide was obtained by a solid state reaction between α-Mn 2 O 3 and Li 2 CO 3 at 1073 K, followed by rapid quenching of the sample in the solid CO 2 . At the room temperature, the lithium deficient sample (with x = 0.95 in Li x Mn 3− x O 4 ) shows a tetragonally distorted spinel lattice, with c / a = 0.98. No phase transition has been observed when temperature decreased and the sample remained tetragonal in the range 300–10 K. A reversible phase transition appears, however, during very mild heating of Li 0.95 Mn 2.05 O 4 above the room temperature. The tetragonal spinel structure ( F 4 1 / ddm ) undergoes a transition into cubic form ( Fd 3 m ) at 393 K. A thermal treatment above 573 K causes a partial decomposition of the sample, resulting in a formation of a nearly stoichiometric LiMn 2 O 4 , with the admixture of manganese oxides.

The influence of the annealing temperature on the degree of cation-disordering in the layered structures was examined for three different compositions of LiNiyCo1-yO2 (y = 0.2, 0.66 and 0.75, respectively). A minimum in cation-disorder is found for annealing temperatures between 700 and 800 °C for y = 0.75, between 750 and 810 °C for y = 0.66 and a less pronounced minimum between 795 and 870 °C for y = 0.2. One optimum annealed sample with y = 0.75 was used for an in situ characterisation using synchrotron radiation. The obtained structural data correlate well with the electrochemical data. The known phase transition occurring during the first cycle was closely observed by ADXRD (angular dispersive X-ray diffraction). The two states of the material during the first cycle could be distinguished and the obtained data were processed by Rietveld refinement.

From pure powders of forms I and II of phenobarbital, X-ray diffraction patterns were recorded at room temperature. The starting crystal structural models were found by a Monte-Carlo simulated annealing method. The structures of the two forms were obtained through Rietveld refinements. Soft restraints were applied on bond lengths and bond angles, all H-atom positions were calculated. The cell of form I is monoclinic with the space group P21/n, Z = 12, Z′ = 3. Form II has a triclinic cell, with the space group P\bar 1, Z = 6, Z′ = 3. For both forms, the crystal cohesion is achieved by networks of N—H...O hydrogen bonds along [101]. The broadening of the Bragg peak profiles is interpreted in terms of isotropic strain effects and anisotropic size effects.

Three different samples of orthorhombic HZSM-5 were analyzed by high-temperature X-ray diffraction and differential scanning calorimetry in order to elucidate the differences in thermal expansion behavior between its hydrated and dehydrated form. The first sample was the as-received orthorhombic HZSM-5, containing three different water species (H 2 O, H 3 O + and OH). The second sample was previously heat treated in a tubular furnace at 550 °C, and, contained only H 2 O, reabsorbed on cooling. The third one was prepared to be completely dehydrated. The dehydrated orthorhombic HZSM-5 sample showed positive thermal expansion from room temperature to 300 °C and negative thermal expansion from 300 °C to 800 °C. On the other hand, the hydrated orthorhombic HZSM-5 exhibited, for the temperature range where water species are present, negative thermal expansion from room temperature to 300 °C (for lattice parameters a and c and volume) and positive thermal expansion from 300 °C to 500 °C. The mechanisms that could explain the thermal expansion behavior of HZSM-5 were discussed.

The isothermal compressibility and bulk thermal expansion of molybdenum diphosphide, MoP2, were measured by in-situ X-ray powder diffraction from ambient conditions to 6.8 GPa and 839 K, respectively. A small anisotropy of the compressibilities in MoP2 appears to be governed by non-bonding interactions in this layer-like material. The thermal expansion data are compared to molybdenum phosphide, MoP, which was measured to 1262 K.

The phase stability of amorphous and nanostructured TiO2 powders was investigated. The surface free energy and the surface stress dominate the thermodynamic phase stability for ultrafine-grained materials. Both parameters may be tuned with sufficient accuracy by modifying the surface chemistry of the nanoparticles and by applied pressure, respectively. Pure and Ag-doped nanostructured titanium dioxide samples were produced using the sol–gel method. Their high-pressure and high-temperature stability domains were determined by in situ X-ray diffraction experiments using synchrotron radiation.

Magnesiumchromite, MgCr2O4, undergoes a structural transition from a cubic spinel structure [space group Fd3m, a=8.32768(4) Å at 16 K] into a tetragonal distorted structure [space group I41/amd, a=5.89199(5) Å, c=8.31677(8) Å at 10 K], isotypic with Hausmannite, Mn3O4. This phase transition is translationengleich and takes place very close or at the antiferromagnetic ordering temperature.

Naphthalene, anthracene and 2,3-benzanthracene were incorporated into the pores of the crystal structure of the zeolite Y. The localisation of the guest molecules was performed by powder diffraction, Fourier analysis and Rietveld refinement. All guests were situated in similar positions in the supercage in front of the sodium cation at position II. However systematic differences in the precise adsorption position of these different guests were observed and can be correlated with the size of the guest molecules.

Besides crystallization time and temperature, the mass density change upon crystallization is a key parameter governing the reliability of phase change random access memory. Indeed, few percentages density change induces considerable mechanical stress in memory cells, leading to film delamination with subsequent electrical failures. This letter presents an extensive study of density change upon crystallization in a series of Ga-Sb thin films with various antimony contents. The mass density of the films is precisely determined by x-ray reflectivity in both their amorphous and crystalline states. The variations of the density in crystalline and amorphous films according to the Sb content found to cross with a zero-density change for 70 at. % Sb. The peculiar behavior of Ga-Sb thin films upon crystallization may be linked to their stress state and mechanical properties.

In this work we compared the relaxation of strain and lattice disorder in thin nano-crystalline Pt films for samples covered with a Si3N4 layer and samples without a cover layer, respectively. We measured thickness and interplanar distance of the Pt film by X-ray reflectometry and X-ray diffractometry during in-situ annealing using synchrotron radiation. The results show that strain and lattice disorder relaxation are impeded if the Pt film is sealed with a cover layer to suppress the creation of vacancies at the Pt surface. This emphasizes the postulated important role of the generation of vacancies at the free surface of thin metal films for strain relaxation during isothermal annealing.

The synthesis of fiber-textured Ti2AlN(0001) films on SiO2 was characterized by in-situ and ex-situ X-ray scattering and Rutherford backscattering spectrometry. Ti2AlN was formed by solid-state reaction between sequentially deposited Ti and AlN layers. A deposition at 275 °C yields a Ti(0001) outof-plane orientation which is maintained for the following AlN(0001)/Ti(0001) layers. Annealing to 600 °C yields AlN decomposition and diffusion of Al and N into Ti, with consecutive transformation into Ti3AlN(111) and Ti2AlN(0001) plus AlN residuals. Despite preferred Ti2AlN(0001) out-ofplane orientation, the in-plane distribution is random, as expected from the self-organized pseudo-epitaxial growth.

Tetrathiafulvalene (TTF) and 7,7,8,8-tetracyano-p-quinodimethane (TCNQ) are included in the pores of the zeolite Y framework structure (NaY), each species individually and both together as charge-transfer complexes by absorption from the liquid phase. The positions of these guest molecules are determined by powder diffraction, difference Fourier methods and subsequent structure refinement. The TCNQ is located in the centre of the 12-ring windows of NaY, while TTF is adsorbed in front of the 6-ring windows in the supercage. Identical positions are found for the guest molecules when both molecules are adsorbed. The effect of coordination on the guest within the zeolite was studied by UV–VIS and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopies. DRIFT measurements show a shift of the CN-valence vibration absorption band of TCNQ in NaY to higher wavenumbers due to a change in the triple bond character. UV–VIS spectra display a bathochromic shift (to lower wavelength) of the absorption bands of TTF after incorporation. On the other hand the shift of the charge transfer band is hypsochromic.

The crystallization of stoichiometric GaSb thin films was studied by combined in situ synchrotron techniques and static laser testing. It is demonstrated that upon crystallization, GaSb thin films exhibit an unusual behaviour with increasing thickness and concomitant decreasing mass density while its electrical resistance drops as commonly observed in phase change materials. Furthermore, beyond GaSb amorphous-to-crystalline phase transition, an elemental segregation and a separate crystallization of a pure Sb phase is evidenced.

Periodic precipitation patterns in C:Ni nanocomposites grown by energetic ion codeposition are investigated. Films were grown at room temperature by ionized physical vapor deposition using a pulsed filtered cathodic vacuum arc. We reveal the role of the film composition, ion energy and incidence angle on the film morphology using transmission electron microscopy and grazing incidence small angle x-ray scattering. Under these growth conditions, phase separation occurs in a thin surface layer which has a high atomic mobility due to energetic ion impacts. This layer is an advancing reaction front, which switches to an oscillatory mode, producing periodic precipitation patterns. Our results show that the ion induced atomic mobility is not random, as it would be in the case of thermal diffusion but conserves to a large extent the initial direction of the incoming ions. This results in a tilted pattern under oblique ion incidence. A dependence of the nanopattern periodicity and tilt on the growth parameters is established and pattern morphology control via ion velocity is demonstrated. Original Publication:Gintautas Abrasonis, Thomas Oates, Gyoergy J Kovacs, Joerg Grenzer, Per Persson, Karl-Heinz H Heinig, Andrius Martinavicius, Nicole Jeutter, Carsten Baehtz, Mark Tucker, Marcela M M Bilek and Wolfhard Moeller, Nanoscale precipitation patterns in carbon-nickel nanocomposite thin films: Period and tilt control via ion energy and deposition angle, 2010, JOURNAL OF APPLIED PHYSICS, (108), 4, 043503.http://dx.doi.org/10.1063/1.3467521Copyright: American Institute of Physicshttp://www.aip.org/

Applied physics letters 95, 232506 (2009). doi:10.1063/1.3271828, The formation of secondary phases in Fe implanted GaN upon annealing in low pressure N$_2$-atmosphere was detected by means of in situ x-ray diffraction and confirmed by magnetization measurements. A repeatable phase change from Fe$_3$N at room temperature and Fe$_3$−$_x$N at 1023 K was observed in situ. The phase transformation is explained by the change of lattice site and concentration of nitrogen within nitrides. The diffusion of Fe toward sample surface and oxidation with increasing annealing cycles limits the availability of secondary phase and hence the repeatability. At high temperature GaN dissolves and Ga as well as Fe oxidize due to presence of residual oxygen in the process gas. The ferromagnetism in the samples is related to nanometer sized interacting Fe$_3$−$_x$Ncrystallites.GaN is a wide band gap semiconductor that has been studied intensively in the last years because of its potential field of applications like in optoelectronics, plasmonics, as well as for high power electronics. By doping with transitional metals like Fe it might also be a diluted magnetic semiconductor (DMS) with a Curie temperature above room temperature (RT) and could then be used for spintronics.1 There are many experimental studies reporting ferromagnetism at RT in Fe doped GaN. In a real DMS, with magnetic atoms randomly substituting cation sites, ferromagnetic coupling is supposed to be due to the indirect exchange coupling between magnetic impurities mediated by holes.1–4 Experimental observation of strong-coupling effects in a DMS Ga$_1$−$_x$Fe$_x$Nwas reported by Pacuski et al.5 Robust ferromagnetism in the region of insulator-to-metal transition was predicted for high hole densities. However, there are also other possible sources of ferromagnetism like spinodal decomposition of Fe or ferromagnetic secondary phases. The detection of those is rather difficult. Bonanni et al.6 prepared GaN:Fe layers by metalorganic chemical vapor deposition (MOCVD) and observed ferromagnetism that was partially accounted to the spinodal decomposition and non-uniform distribution of Fe-rich magnetic nanocrystals. Kuwabara et al.7 reported the formation of nanoclusters and superparamagnetic behavior in GaN:Fe epilayers prepared by rf-plasma-assisted molecular beam epitaxy. In case of ion implantation the reports from different groups are quite controversial. Theodoropoulou et al.8 and Shon et al.9,10 did not relate ferromagnetic response to secondary phases after transition ion implantation into semiconductors. In our experiments, however, the formation of α-Fe nanoclusters, that were responsible for ferromagnetic response, was observed.11 Though the appearance of such precipitates is not desired in a DMS they might be useful for certain applications.12 Li et al.13 detected co-occurrence of α-Fe and ε-Fe$_3$Nin MOCVD prepared GaN:Fe films and pointed out the role of nitrogen pressure and structural disorder in the formation of Fe-rich phases. Bonanni et al.14 have shown that the controlled aggregation of magnetic ions in a semiconductor can be affected by the growth rate and doping with shallow impurities.Recently we reported predominant formation of epitaxially oriented α-Fenanoclusters if Fe-doped samples were annealed in a N$_2$ flow at 1.1 bar pressure.11 In this paper we report the formation of ε-Fe$_3$−$_x$N with x, Published by American Institute of Physics, Melville, NY

The correlation between defect structure, metal segregation, and electrical resistivity of indium-tin-oxide nanopowder upon treatment in reducing atmosphere was investigated. Morphology and defect structure have been investigated by in situ synchrotron x-ray diffraction and transmission electron microscopy, while traces of metallic indium have been detected by susceptibility measurements utilizing the superconducting properties of indium. With increasing treatment temperature under reforming gas the film resistivity decreases down to ρ=1.6×10−2 Ω cm at 330 °C annealing temperature. For even higher treatment temperatures, the resistivity increases further. This is accompanied by extractions of metallic indium. Under forming gas, grain growth could be observed at 350 °C, while in air grain growth starts at 650 °C. Furthermore forming gas causes a lattice expansion of ITO which persists in oxygen, at least for several hours. The results are discussed with respect to results published in the literature.

Neutron powder diffraction studies of Na{sub 1/2}La{sub 1/2}TiO{sub 3} and Na{sub 1/2}Tb{sub 1/2}TiO{sub 3}, and a synchrotron X-ray powder diffraction study of Na{sub 1/2}Eu{sub 1/2}TiO{sub 3} have been carried out. Rietveld refinement of the structures confirmed that Na{sub 1/2}Eu{sub 1/2}TiO{sub 3} and Na{sub 1/2}Tb{sub 1/2}TiO{sub 3} crystallizes in GdFeO{sub 3} type of structure (space group Pbnm). The ambiguity in the literature regarding the crystal structure of Na{sub 1/2}La{sub 1/2}TiO{sub 3} has been resolved and the correct space group is found to be R3-bar c. A detailed list of refined structural parameters of these compounds is presented for the first time.

The literature states different compositions (M/B 1:2 vs. 2:5) and structures for diborides of molybdenum and tungsten.Using X-ray and neutron powder diffraction as well as energy andwavelength dispersive electron microprobe analysis, the Mo/B andW/B systems were now reinvestigated. Molybdenum diboride cry-stallizes as a stoichiometric compound Mo 2 B 4 (formerly describedas Mo 2 B 5 ) in space group R 3¯ m (No. 166, a , b 3.01375(2) A˚ , c 20.9541(3) A˚ ), and as a non-stoichiometric compound MoB 2 x (formerly described as MoB 2 )in P 6 /mmm (No. 191, a , b Introduction For the Mo/B and W/B system, compounds like MB, MB 2 ,M 2 B 5 ,M 0.8 B 3 , and MB 4 are reported in the literature. Suchcompounds have interesting electrical and mechanicalproperties, which indicate possible applications as high-tem-perature ceramic materials [1 7]. Recently, Telle et al.showed that W 2 B 5 -based materials display unique fracturebehaviours and delamination phenomena [6, 8 10].The first one to structurally characterize the dimetalpentaborides Mo

Morphotropic PZT ceramics are the state of the art materials for ferroelectric actuators. Essential performance parameters for these materials are strain and hysteresis. On a microscopic scale the strain provided by an electric field is due to two different mechanisms. The piezoelectric effect causes an elongation of the unit cells, whereas domain switching changes their crystallographic orientation by aligning the polarization axis towards the field direction. A method is outlined to estimate the contribution of the two mechanisms to total strain by combining macroscopic strain measurements and X-ray diffraction (XRD) data. Results from macroscopic measurements of remanent and unipolar strain with the corresponding data on texture, derived from in situ synchrotron radiation XRD patterns, are analyzed and evaluated by a semi-empirical approach. The method was applied to six morphotropic, LaSr doped PZT materials of different Zr/Ti ratios. Results are discussed with respect to the differences between the materials.

Combined in situ X-ray scattering techniques using synchrotron radiation were applied to investigate the crystallization behavior of Sb-rich Ga-Sb alloys. Measurements of the sheet resistance during heating indicated a reduced crystallization temperature with increased Sb content, which was confirmed by in situ X-ray diffraction. The electrical contrast increased with increasing Sb content and the resistivities in both the amorphous and crystalline phases decreased. It was found that by tuning the composition between Ga:Sb = 9:91 (in at.%) and Ga:Sb = 45:55, the change in mass density upon crystallization changes from an increase in mass density which is typical for most phase change materials to a decrease in mass density. At the composition of Ga:Sb = 30:70, no mass density change is observed which should be very beneficial for phase change random access memory (PCRAM) applications where a change in mass density during cycling is assumed to cause void formation and PCRAM device failure.

Focused ion beam techniques are one way to modify locally the properties of magnetic thin films. We report on structural investigations of 50 nm thick non-ordered nano-crystalline Permalloy (Ni81Fe19) films modified by 30 keV Ga+ focused ion beam (FIB) irradiation. From the X-ray diffraction (XRD) measurements a considerable crystallite growth and a material texturing towards (111)-direction with a linearly increasing lattice constant was observed. In addition cross-sectional transmission electron microscope (XTEM) images show that crystallites are growing through the entire film at high irradiation fluences. Extended X-ray absorption fine structure (EXAFS) analysis shows a perfect near-order coordination corresponding to a face-centered (fcc) unit cell for both FeNi and Ga atom surrounding. The structural changes are accompanied by a decrease of saturation polarization with increasing ion fluence. Such behavior is attributed to a simple incorporation of non-magnetic Ga atoms in the Permalloy film.

The formation of secondary phases inside yttria stabilized zirconia (YSZ) crystals implanted with Fe ions was investigated by means of synchrotron radiation x-ray diffraction, conversion electron Mossbauer spectroscopy, and x-ray diffraction reciprocal space mapping. Fe ions have been implanted into single crystals of YSZ(001) at elevated temperatures. As the implanted ion fluence is increased an increase in α-Fe cluster formation was observed, along with the appearance of γ-Fe and secondary phases of Fe oxide(s). The clusters are proposed to consist of a metallic core and an oxide shell. Ferromagnetic hyperfine splitting was detected by Mossbauer spectroscopy and was mainly attributed to the presence of Fe3+ and α-Fe.

Iron nanoparticles embedded in MgO crystals were synthesized by Fe+ ion implantation at an energy of 100 keV and varying fluences from 3×10e16 to 3×10e17 cm-2. Investigations of structural and magnetic properties of Fe nanoparticles have been performed using magnetometry, x-ray diffraction, transmission electron microscopy and Mössbauer spectroscopy, as well as by theoretical Preisach modeling of bistable magnetic systems. It has been found that alpha- and gamma-Fe nanoparticles are formed for all fluences. The content of the alpha- Fe phase increases at higher fluences and after annealing. The influence of post implantation annealing at 800 ºC in vacuum and under enhanced up to 10 kbar hydrostatic pressure in argon atmosphere on the formation of nanoparticles has been analyzed.

The development and commercialisation of the LiFePO4cathode for lithium ion batteries provoked the strong interest to the other members of the olivine-like metallophosphates family LiMPO4 (M = Mn, Fe, Co, Ni). It is well known that lithium extraction from LiFePO4 (triphylite) leads to the formation of the newphase FePO4 (heterosite), which is isostructural to the pristine compound [1]. By the in-situ synchrotron diffraction we studied the structural changes occurring at the delithiation of LiMn0.6Fe0.4PO4 and LiCoPO4. The extraction of lithium fromLiMn0.6Fe0.4PO4 proceeds as a two-step process [2]. The first step (ca. 3.6 V vs. Li/Li) corresponds to the oxidation of iron (Fe/Fe), the second one (ca. 4.1 V vs. Li/Li) to the oxidation ofmanganese (Mn/Mn). In contrast to the mechanism earlier reported for this compound [3], both reactions were revealed to proceed in two-phase manner. A solid solution domain seems to exist in the intermediate state, where Fe/Fe electrochemical reaction ends and Mn/Mn begins. All phases appearing during charging the cell have the same olivine-like structure with different cell parameters. The two step character of lithium extraction for LiCoPO4 was observed also and confirmed by XAS measurements [4, 5]. In in-situ diffraction experiments on LiCoPO4 reveal the formation of lithium-poor olivine-like phase at the earlier stage of charge.