Synchrotron Radiation X-ray Diffraction Techniques Research Articles

High-Pressure Induced Continuous Structural Evolution of Kagome Antiferromagnet MgMn3(OH)6Cl2: A Structural Analogue to Quantum Spin Liquid Herbertsmithite.

MgMn3(OH)6Cl2 serves readily as the classical Heisenberg kagome antiferromagnet lattice spin frustration material, due to its similarity to herbertsmithite in composition and crystal structure. In this work, nanosheets of MgMn3(OH)6Cl2 are synthesized through a solid-phase reaction. Low-temperature magnetic measurements revealed two antiferromagnetic transitions, occurring at ∼8 and 55 K, respectively. Utilizing high-pressure synchrotron radiation X-ray diffraction techniques, the topological structural evolution of MgMn3(OH)6Cl2 under pressures up to 24.8 GPa was investigated. The sample undergoes a second-order structural phase transition from the rhombohedral phase to the monoclinic phase at pressures exceeding 7.8 GPa. Accompanying the disappearance of the Fano-like line shape in the high-pressure Raman spectra were the emergence of new Raman active modes and discontinuities in the variations of Raman shifts in the high-frequency region. The phase transition to a structure with lower symmetry was attributed to the pressure-induced enhancement of cooperative Jahn-Teller distortion, which is caused by the mutual substitution of Mn2+ ions from the kagome layer and Mg2+ ions from the triangular interlayer. High-pressure ultraviolet-visible absorption measurements support the structural evolution. This research provides a robust experimental approach and physical insights for further exploration of classical geometrical frustration materials with kagome lattice.

'Molecular Beam Epitaxy' on Organic Semiconductor Single Crystals: Characterization of Well-Defined Molecular Interfaces by Synchrotron Radiation X-ray Diffraction Techniques.

Epitaxial growth, often termed “epitaxy”, is one of the most essential techniques underpinning semiconductor electronics, because crystallinities of the materials seriously dominate operation efficiencies of the electronic devices such as power gain/consumption, response speed, heat loss, and so on. In contrast to already well-established epitaxial growth methodologies for inorganic (covalent or ionic) semiconductors, studies on inter-molecular (van der Waals) epitaxy for organic semiconductors is still in the initial stage. In the present review paper, we briefly summarize recent works on the epitaxial inter-molecular junctions built on organic semiconductor single-crystal surfaces, particularly on single crystals of pentacene and rubrene. Experimental methodologies applicable for the determination of crystal structures of such organic single-crystal-based molecular junctions are also illustrated.

Effect of defects on the phase transition of Al0.1CoCrFeNi high-entropy alloy under high pressure

Knowledge pressure-driven phase transition in condensed physics requires an understanding of how phase-transition-pressure in a substance is affected by defect concentration and type. The effect of defects on phase transition was investigated in this paper by comparing structure evolutions in Al0.1CoCrFeNi high-entropy alloy (HEA) prepared by mechanical alloying with as-cast one using in situ synchrotron radiation X-ray diffraction technique and high-resolution transmission electron microscope (HRTEM), as well as the calculated dislocation density. Pressure-induced partial irreversible phase transitions from face-centered cubic (fcc) to hexagonal close-packed (hcp) phase has been observed in both ball-milled and as-cast Al0.1CoCrFeNi HEAs. In comparison to the as-cast Al0.1CoCrFeNi HEA, the ball-milled HEA has a large number of defects, especially higher density dislocations, and a low nucleation energy barrier, resulting in a lower phase-transition-pressure of 7.0 GPa and a higher fraction of hcp phase of 32.12% at pressure ∼30 GPa. The HRTEM result confirms that hcp and fcc phases coexist after pressure releasing. The investigation of the link between defects and phase transition process might lead to a potential approach for customizing the percentage of fcc and hcp phases in HEAs, allowing them to improve their structure and characteristics as a novel engineering material.

Pressure–Temperature Phase Diagram of Ta-H System up to 9 GPa and 600 °C

High-pressure hydrogenation behaviors of pure metals have not been investigated extensively, although intense research of hydrogenation reactions under high pressure has been conducted to find novel functional hydrides. The former provides us with valuable information for the high-pressure synthesis of novel functional hydrides. A pressure–temperature phase diagram of the Ta–H system has been determined using the in situ synchrotron radiation X-ray diffraction technique below 9 GPa and 600 °C in this study. At room temperature, the phase boundary obtained between distorted bcc TaH~1 and hcp TaH~2 was consistent with the previously reported transition pressure. The experimentally obtained Clapeyron slope can be explained via the entropy change caused by hydrogen evolution from TaH~2.

Synchrotron Radiation X-ray Diffraction Techniques Applied to Insect Flight Muscle.

X-ray fiber diffraction is a powerful tool used for investigating the molecular structure of muscle and its dynamics during contraction. This technique has been successfully applied not only to skeletal and cardiac muscles of vertebrates but also to insect flight muscle. Generally, insect flight muscle has a highly ordered structure and is often capable of high-frequency oscillations. The X-ray diffraction studies on muscle have been accelerated by the advent of 3rd-generation synchrotron radiation facilities, which can generate brilliant and highly oriented X-ray beams. This review focuses on some of the novel experiments done on insect flight muscle by using synchrotron radiation X-rays. These include diffraction recordings from single myofibrils within a flight muscle fiber by using X-ray microbeams and high-speed diffraction recordings from the flight muscle during the wing-beat of live insects. These experiments have provided information about the molecular structure and dynamic function of flight muscle in unprecedented detail. Future directions of X-ray diffraction studies on muscle are also discussed.

Observation of the negative pressure derivative of the bulk modulus in monoclinic ZrO2

Using synchrotron radiation x-ray diffraction techniques, the equation of state of monoclinic ZrO2 has been investigated under a hydrostatic pressure condition at 298 K. Monoclinic ZrO2 transformed to the orthorhombic I phase at between 5.7 and 7.0 GPa. Lattice constants of monoclinic ZrO2 refined from the Reitveld analysis showed extreme anisotropic pressure dependence. From the pressure–volume data, using least-squares fit of the Birch–Murnaghan formula, the bulk modulus, K0 and its pressure derivative: K0′, were estimated to be 159(3) GPa and −3.6(6), respectively. A negative K0′ suggests the abnormal softening of the elastic modulus in monoclinic ZrO2 with compression. First-principles calculations supported present experimental results.

High pressure induced phase transformation through continuous topology evolution in zinc hydroxyfluoride synthesized via a hydrothermal strategy

Orthorhombic ZnOHF is synthesized via a hydrothermal strategy. Powder X-ray diffraction studies confirm that the prepared samples have a diaspore-type structure. According to the EDS analysis, the O/F ratio in equimolar proportion indicates the nearly perfect stoichiometry. The morphological features observed via SEM and TEM techniques reveal that the product is composed of micro/nanometer-scaled prism-like structures. The band gap estimated from UV–vis absorption measurements is 3.15 eV. The PL emission band is located at 470 nm. The compression behaviors of the as-prepared ZnOHF samples are investigated by using in situ high pressure angle dispersive synchrotron radiation X-ray diffraction techniques. The compression behaviors are characteristic of continuous topology evolution. The pressure-induced shearing reduces the symmetry of ZnOHF from the initial space group Pnma to its subgroup Pna21 in the pressure range of 14.2–19.8 GPa. The hints of a further phase transformation to the CdOHF-type structure at 30.7 GPa are also observed.

Synthesis of novel hydride Li3AlFeH8 at high temperature and pressure

Iron-containing complex hydrides are a fascinating class of materials for hydrogen storage applications because they consist of abundant iron and usually contains [FeH6]4− complexes, resulting in high hydrogen densities. In this study, we synthesized theoretically predicted Li3AlFeH8, which has the highest gravimetric hydrogen density of all transition metal complex hydrides, through a hydrogenation reaction of LiH, AlH3, and pure iron powder mixture under high pressure. The reaction process was observed in situ using a synchrotron radiation x-ray diffraction technique to clarify its reaction kinetics. The reaction temperature and pressure were changed to optimize reaction conditions for obtaining single phase Li3AlFeH8. Unfortunately, we did not obtain single phase Li3AlFeH8 because the reaction was slow. In addition, there were other phases with similar thermodynamic stabilities to that of Li3AlFeH8. Another novel hydride, LiAlFeH6, was found to be synthesized above 850 °C at 9 GPa.

Magnetic resonance study of exchange-biased Ni/NiO nanoparticles

Finite sized Ni/NiO nanoparticles (NPs) are prepared by oxidizing pure Ni-NPs in an ambient atmosphere with varying annealing time (tA). A synchrotron radiation x-ray diffraction technique was used to estimate the grain size, weight fraction and lattice parameters of Ni and NiO. The temperature (T) dependencies of effective g-factor and line-width of ferromagnetic resonance (FMR) spectra for a series of Ni/NiO NPs are determined. Three T-regions with different FMR behaviors T > 200 K, 200 > T > 130 K and T < 130 K are identified. In particular, for T < 200 K, the T-dependency of the g-factor reveals an evolution of exchange coupling between Ni and NiO due to the gradual oxidation of Ni NPs.

Magnetic field-induced changes of lattice parameters and thermal expansion behavior of the CoMnSi compound

The crystal structure of the CoMnSi compound during zero-field cooling and field cooling from room temperature down to 200 K was studied using the synchrotron radiation X-ray diffraction technique. The results show that the lattice parameters and thermal expansion behavior of the sample are changed by the applied magnetic fields. The lattice contracts along the a axis, but expands along the b and c axes. Due to enlarged and anisotropic changes under a magnetic field of 6 T, the lattice shows an invar-like behavior along all three axes. Critical interatomic distances and bond angles also show large changes under the influence of such a high magnetic field. These magnetic field-induced changes of the lattice are discussed with respect to their contributions to the large magnetocaloric effect of the CoMnSi compound.

Anomalous phase transition of InN nanowires under high pressure**Project supported by the National Natural Science Foundation of China (Grant Nos. 50772043, 51172087, and 11074089).

Uniform InN nanowires were studied under pressures up to 35.5 GPa by using in situ synchrotron radiation x-ray diffraction technique at room temperature. An anomalous phase transition behavior has been discovered. Contrary to the results in the literature, which indicated that InN undergoes a fully reversible phase transition from the wurtzite structure to the rocksalt type structure, the InN nanowires in this study unusually showed a partially irreversible phase transition. The released sample contained the metastable rocksalt phase as well as the starting wurtzite one. The experimental findings of this study also reveal the potentiality of high pressure techniques to synthesize InN nanomaterials with the metastable rocksalt type structure, in addition to the generally obtained zincblende type one.

Time-lapse synchrotron X-ray diffraction to monitor conservation coatings for heritage lead in atmospheres polluted with oak-emitted volatile organic compounds

We discuss the effectiveness of a lead tetradecanoate coating on lead to protect against harmful volatile organic compounds emitted from oak. The oak volatile organic compounds were characterized by GCMS and the major constituent was found to be acetic acid. Under the test conditions, the coating decreases the rate of corrosion by up to 75% compared to bare lead. The thickness of corrosion products on the sample was also calculated thus demonstrating the power of the time-lapse synchrotron radiation X-ray diffraction technique to deliver a quantitative estimate of the effectiveness of the coating.

Electrical resistivity of Ti–Zn mixed oxide thin films deposited by atomic layer deposition

Ti–Zn mixed oxide thin films, with thickness less than 50nm, were grown with atomic layer deposition (ALD) technique at low temperature (90°C) varying the composition. ALD is a powerful chemical technique to deposit thin films with thickness of few atomic layers. ALD oxide material growth is achieved by dosing sequentially the metal precursor and the oxidizing agent. Thanks to ALD nature of layer by layer growth it was possible to realize mixed metal, Ti and Zn, oxide thin films with controlled composition, simply by changing the number of cycles of each metal oxide layer. Structural and electrical properties of the prepared thin films were studied as a function of their composition. Synchrotron radiation X-ray diffraction technique was used to follow thin film crystallization during sample annealing, performed in situ. It was observed that the onset temperature of crystallization raises with Ti content, and sample structure was Zn2TiO4 phase. Electrical resistivity measurements were performed on crystalline samples, annealed at 600°C, revealing an increase in resistivity with Ti content.

Compositional study of prehistoric pigments (Carriqueo rock shelter, Argentina) by synchrotron radiation X-ray diffraction

In this work synchrotron radiation X-ray diffraction technique was successfully applied for the analysis of pigments found in excavation at Carriqueo rock shelter, Neuquén, Argentina. The pigment samples of orange, red, and brown shades were collected from different levels of this archaeological site and compared with a suspected source of provenance (La Oficina creek). X-ray diffraction patterns of several yellowish, reddish, and red pigments showed the presence of haematite, goethite, kaolinite, and quartz. The majority of Carriqueo collected samples belonged to the same group of the suspected source, having haematite and quartz as main crystalline phases. The results indicate that the raw material from La Oficina is the source of most of the pigments found at Carriqueo. The present work helps us to understand the strategy of supplying raw materials by human groups in the North Patagonia region.

Synchrotron radiation X-Ray diffraction in situ study of fine-grained minerals in shock veins of Suizhou meteorite

The synchrotron radiation X-ray diffraction technique developed for in situ study at high pressure and temperature has also been used to investigate microscopic mineral inclusions in ultra-high-pressure metamorphic rocks and deep-mantle samples. Present study added two more examples of successful utilization of synchrotron radiation X-ray diffraction technique for in situ investigations of fine-grained (0.5―30 μm in size) minerals in very thin shock melt veins of the Suizhou meteorite: (i) X-ray diffraction measurement of extremely small-sized vein matrix minerals, and (ii) identification of the micron-sized new mineral tuite embedded in the vein matrix. It has been revealed that the fine-grained vein matrix consists of well crystallized garnet, kama-cite and troilite, and the powder diffraction pattern consisting of 17 lines with d-values, intensities ( I ), relative intensities ( I / I o ) and Miller indices, as well as the cell parameters for the new mineral tuite has also been successfully obtained. The result of present investigations has enriched the content of dynamic high-pressure mineralogy and that of Earth’s mantle geochemistry.

Mineralogy of phyllosilicate-rich micrometeorites and comparison with Tagish Lake and Sayama meteorites

Four phyllosilicate-rich micrometeorites (MMs) were investigated by a synchrotron radiation X-ray diffraction technique and transmission electron microscopy. Three are saponite-rich MMs and one is a serpentine-rich one. In the saponite-rich MMs, we could not find serpentine, and vice versa in the serpentine-rich MM. In the saponite-rich MMs, major constituent minerals are saponite, Fe- and Ni-bearing sulfides, and magnetite. Two saponite-rich MMs contain fine-grained magnesiowüstite-rich aggregates. The aggregates consist of <50 nm polygonal magnesiowüstite coexisting with minor Fe sulfide grains. Their texture, chemical composition, and the result of heating experiments on matrix fragments of the Tagish Lake carbonaceous chondrite strongly suggest that these aggregates were formed by the breakdown of Mg- and Fe-rich carbonate grains when the MMs entered the Earth’s atmosphere. The estimated major mineral assemblage of the saponite-rich MMs before entering the Earth’s atmosphere is very similar to that of the Tagish Lake carbonate-rich lithology, and we suggest that the MMs and the meteorite were derived from similar asteroids. The major mineral assemblage and texture of the matrix of serpentine-rich MM are similar to the matrix of the Sayama CM2 chondrite that experienced heavy aqueous alteration. Chemical compositions of serpentine in the MM suggest that the degree of aqueous alteration of the MM is weaker than that of Sayama. In the MM, cronstedtite does not coexist with tochilinite, which is different from CM2 chondrites that experienced weak to moderate aqueous alteration. However, the possibility that the serpentine-rich MM was derived from the CM chondrite asteroid cannot be ruled out, because tochilinite can be preferentially decomposed during atmospheric entry heating due to its lower decomposition temperature than that of cronstedtite.

Determination of local strains in a monocrystalline turbine blade by microbeam X-ray diffraction with synchrotron radiation

X-ray peak profiles of the types {400} and {300} of monocrystalline nickel-based superalloy turbine blades were measured with a new microbeam synchrotron radiation X-ray diffraction technique. Under the coating of a turbine blade in the virgin state, a plastically deformed layer was found which is responsible for anomalous rafting. In a turbine blade subjected to an “accelerated mission test”, the phases γ and γ′ were found to be under elastic distortions arising from the superposition of counteracting internal stresses. It is concluded that the investigated section was under tensile creep load during service. In the regions near the surfaces, the lattice parameters of both γ and γ′ increase. The reason for this increase is the diffusion of Al from the NiAl coating into the bulk of the blade. Finally, the differences between the peak profiles measured with the microfocus technique and with a conventional diffractometer are discussed.

Structural aspects of dense solid halogens under high pressure studied by x-ray diffraction—Molecular dissociation and metallization

We have performed structural studies of solid bromine under ultrahigh pressures by using advanced synchrotron radiation X-ray diffraction techniques incorporated with a diamond-anvil high pressure cell. Reliable intensity measurements in its molecular phase up to 80 GPa, where it undergoes the molecular-to-monatomic phase transition (molecular dissociation), have enabled us to determine pressure dependence of molecular positions. By combining the previous results of iodine and chlorine, we have found an empirical scaling rule with respect to the crystal structure scaled with its intramolecular bond length for these three isostructural systems. By applying the Herzfeld criterion, we have also found a scaling rule for the metallization process prior to molecular dissociation.

Synchrotron X-ray study of monolayer krypton melting

The authors have studied the melting of commensurate monolayer krypton on graphite using very high-resolution synchrotron radiation X-ray diffraction techniques; a krypton particle size of 2300 AA is obtained. The melting transition appears to be second order at 112.9K with an order parameter exponent beta =0.065+or-0.015 and a broadening of Tc, sigma / approximately 0.0006 which we attribute to finite particle size. Although the broadening is much less than that obtained in coarser resolution experiments, the exponent beta agrees with those previous results.