Evolution Of Crystal Structure Research Articles

Spontaneous Compositional-Interfacial Co-Modification Engineering via Ion Exchange Reaction Between Perovskite and Electron-Transporting Layer for Exceptionally Long-Term Stability of Photovoltaics.

The long-term stability of perovskite solar cells (PSCs) is still challenging for commercialization and mainly linked to the life span of perovskite films. Herein, a spontaneous compositional-interfacial co-modification strategy is developed based on the ion exchange reaction by introducing ammonium hexafluorophosphate (NH4PF6) into antisolvent to form gradient structures through a simple one-step solvent engineering. With the assistance of the ion exchange reaction, NH4PF6 forms a multifunctional structure to protect perovskite films from both internal and external factors for the exceptionally long-term stability of photovoltaics. The reason for this is linked to the high hydrophobicity of NH4PF6 for preventing H2O invasion, suppressing ion migration by forming hydrogen bonding, and reducing perovskite defects. The resulting unencapsulated devices show exceptionally long-term stability under standardized the International Summit on Organic Photovoltaic Stability (ISOS) protocols, with over 94%, 81%, and 83% retained power conversion efficiencies after aging tests under N2 (ISOS-D-1I), ambient air (ISOS-D-1), and 85°C (ISOS-D-2I) for 14016, 2500, and 1248h, respectively. These performances compare well with the state-of-the-art stability of inverted PSCs. Further investigations are conducted to study the evolution of macroscopic morphology and microscopic crystal structure in aged perovskite films, aiming to provide evidence supporting the aforementioned improvements in stability.

Shish‐kebab structure evolution of HDPE/UHMWPE during hot drawing

AbstractUsing a solution‐mixing method, this research aimed to fabricate high‐density polyethylene (HDPE)/ultra‐high molecular weight polyethylene (UHMWPE) composite materials with uniform dispersion. By incorporating a small quantity of UHMWPE as a nucleating agent, additional contact points were introduced to enhance the crystallization rate of the HDPE matrix. Thermal stretching experiments were conducted on composite systems with varying UHMWPE contents and molecular weight additions at different temperatures. Elevating the stretching temperature was found to decrease the yield strain and yield strength, extend the stage of tensile plastic deformation, and diminish the overall mechanical properties of the composite material. Notably, stretching at temperatures ranging from 90 to 110°C accentuated the development of internal crystal orientation structures. Under low strain conditions, crystal slip was observed to be concentrated, with single crystals undergoing continuous stretching and breaking, resulting in a decrease in the long period. Conversely, at high strains, the induced formation of oriented lamellar structures was observed.Highlights Prepared HDPE/UHMWPE blends by UHMWPE with varying molecular weights. Analyzed the alterations in the HDPE/UHMWPE blends' internal crystal structure. Influence of UHMWPE addition, temperature on the evolution of crystal structure.

Modular slot-die coater for in situ grazing-incidence x-ray scattering experiments on thin films.

Multimodal in situ experiments during slot-die coating of thin films pioneer the way to kinetic studies on thin-film formation. They establish a powerful tool to understand and optimize the formation and properties of thin-film devices, e.g., solar cells, sensors, or LED films. Thin-film research benefits from time-resolved grazing-incidence wide- and small-angle x-ray scattering (GIWAXS/GISAXS) with a sub-second resolution to reveal the evolution of crystal structure, texture, and morphology during the deposition process. Simultaneously investigating optical properties by in situ photoluminescence measurements complements in-depth kinetic studies focusing on a comprehensive understanding of the triangular interdependency of processing, structure, and function for a roll-to-roll compatible, scalable thin-film deposition process. Here, we introduce a modular slot-die coater specially designed for in situ GIWAXS/GISAXS measurements and applicable to various ink systems. With a design for quick assembly, the slot-die coater permits the reproducible and comparable fabrication of thin films in the lab and at the synchrotron using the very same hardware components, as demonstrated in this work by experiments performed at Deutsches Elektronen-Synchrotron (DESY). Simultaneous to GIWAXS/GISAXS, photoluminescence measurements probe optoelectronic properties in situ during thin-film formation. An environmental chamber allows to control the atmosphere inside the coater. Modular construction and lightweight design make the coater mobile, easy to transport, quickly extendable, and adaptable to new beamline environments.

Comprehensive study of O2 and H2O interaction with La0.9Sr0.1ScO3–δ oxide

In this paper we study the processes of O2 and H2O interaction with La0.9Sr0.1ScO3−δ. Using high temperature neutron powder diffraction (HT-NPD), the evolution of crystal structure and water uptake was investigated in the temperature range 25–700 °C at 21.3 kPa in O2 and O2 + D2O atmospheres. The results of HT-NPD show the influence of the water uptake by La0.9Sr0.1ScO3–δ bulk on the thermal expansion of the material. The kinetics of oxygen surface exchange was studied using pulsed isotope exchange technique. The measurements were carried out in the temperature range 300−900 °C at pO2 = 5.1, 12.2 and 21.3 kPa in dry and humid (pH2O = 2.6 kPa) conditions. For the first time the physical model describing the kinetics of oxygen surface exchange between the mixture of oxygen and water in the gas phase and a solid oxide has been suggested. The model includes following steps: oxygen dissociative adsorption, oxygen incorporation, hydrogen surface diffusion, water adsorption and dissociation. The rate-determining step of the exchange is considered. The influence of O2 humidification on the oxygen surface exchange is discussed.

Cu/Fe-MOFs based on mixed ligands: Synthesis, crystal structure and electrocatalytic hydrogen evolution performance

Two new metal-organic framework complexes Cu-MOF (C28H16Cu2N6O9S2) and Fe-MOF (C28H17FeN6O9S2) were synthesized with 4-[5-(pyridin-4-yl)-[1,3]thiazolo[5,4-d] [1,3]thiazol-2-yl]pyridine (Py2TTz) and pyridine-2,6-dicarboxylic acid (DPA) as mixed ligands. The single crystal X-ray diffraction results displayed that Cu2+ coordinated with Py2TTz and DPA to form 3D network structure while Fe2+ coordinated only with DPA to form 2D laminar structure, in which Py2TTz interspersed between bilayer iron complexes. The presence of Py2TTz enlarged the pore size of Fe-MOF, increasing its Brunauer-Emmett-Teller (BET) surface area and specific surface area, while the 3D structure of Cu-MOF facilitated electron transport and mass transfer. As a result, the hydrogen evolution reaction (HER) performance of Cu-MOF was slightly higher than that of Fe-MOF. This work provided an interesting idea for the design and synthesis of inexpensive HER electrocatalysts.

Crystal structure evolution, bond characteristics and tunable microwave dielectric properties of (Ce1-xCax)(Nb1-xWx)O4 ceramics

Co-substitution of Ce3+ at the A-site and Nb5+ at the B-site by smaller Ca2+ and W6+ in (Ce1-xCax)(Nb1-xWx)O4 ceramics drives the structure from monoclinic fergusonite (x = 0.1 - 0.3) to tetragonal scheelite (x = 0.4). Adjusting the A-O and B-O bond characteristics could drastically tune the microwave dielectric properties. The εr decreased from 20.7 to 16.2, and the negative deviations between εr and εr(C-M) resulted from the rattling effect of Nb5+/W6+ cations in the octahedron along the b-axis direction. The τf varied from negative (−11 ppm/°C at x = 0.1) to positive (+87.8 ppm/°C at x = 0.4), mainly attributed to the rattling effect of Nb5+/W6+. Q×f increased from 21,006 to 45,025 GHz (x = 0.3) and then decreased to 36,563 GHZ (x = 0.4), accompanied by increasing packing fraction and decreasing Raman FWHM. The ceramic at x = 0.15 exhibited the optimum microwave dielectric properties of εr = 19.7, Q×f = 35,450 GHz, and τf = 0.8 ppm/°C.

The dynamic surface evolution of halide perovskites induced by external energy stimulation.

Tracking the dynamic surface evolution of metal halide perovskite is crucial for understanding the corresponding fundamental principles of photoelectric properties and intrinsic instability. However, due to the volatility elements and soft lattice nature of perovskites, several important dynamic behaviors remain unclear. Here, an ultra-high vacuum (UHV) interconnection system integrated by surface-sensitive probing techniques has been developed to investigate the freshly cleaved surface of CH3NH3PbBr3 in situ under given energy stimulation. On this basis, the detailed three-step chemical decomposition pathway of perovskites has been clarified. Meanwhile, the evolution of crystal structure from cubic phase to tetragonal phase on the perovskite surface has been revealed under energy stimulation. Accompanied by chemical composition and crystal structure evolution, electronic structure changes including energy level position, hole effective mass, and Rashba splitting have also been accurately determined. These findings provide a clear perspective on the physical origin of optoelectronic properties and the decomposition mechanism of perovskites.

Solid breeder material crystal structure evolution due to Li burn up–Loss of crystal stability

Solid breeder materials for fusion power plants are subjected to extreme conditions of radiation damage, high temperature and designed component burn-up. The loss of lattice stability of Li2TiO3 due to Li burn-up was investigated using first principles-based approaches to aid evaluation of upper limit of component lifetime. The lattice stability is analyzed using calculated phonon dispersion in the Li2TiO3 supercell, while Li burn-up is modeled by the introduction of Li-vacancies. It has been determined that the studied ceramic can be structurally stable up to ∼40% of Li atoms burn-up. At 50% burn-up, the negative frequency branch in the phonon dispersion spectrum appears indicating the loss of lattice dynamical stability. Moreover, the structure obtained by introduction of unstable frozen phonons with minima energy amplitude also results in a phonon dispersion with negative branches in the structure obtained. Therefore, the system completely loses stability when approximately half of Li atoms are consumed.

Time-resolved study of laser-induced phase separation in CsPb(IxBr1−x)3 perovskite under high pressure

Mixed-halide perovskites have attracted extensive interest with their broadly tunable bandgap and optoelectronic properties, which makes them ideal candidates for various solar cells and light-emitting diodes. However, the mixed-halide perovskites often encounter phase separation and degradation under light illumination, which prevents them from many optoelectronic applications. The study on the underlying mechanism and the controlling of the phase separation is crucial to improve the tailored properties for practical applications. Here, we report our systematical investigations of the time-resolved photoluminescence shift and crystal structure evolution on the nanocrystalline CsPb(IxBr1−x)3 perovskite under intense laser illumination and found the increasing contribution of bromine-rich phase over time. Furthermore, we subject the nanocrystalline CsPb(IxBr1−x)3 perovskite to a quasi-hydrostatic pressure environment and observed that the phase separation slows down quickly with increasing pressure and can be totally suppressed at a rather mild pressure below 0.2 GPa. These findings suggest the light-induced separation of the crystalline structure, and their optoelectronic properties can be largely suppressed, which provides a useful approach to overcome the problem caused by the intense light applications.

In situ self-transformation strategy toward zinc selenide electrode for lithium-ion capacitors

Conversion/alloying mechanism anode materials, featuring its higher theoretical capacity, have been deemed to one of the most potential candidates in the context of lithium ion capacitors (LICs). Nevertheless, the Li+ diffusion sluggish kinetics and severe volume variations during repeatedly lithiation/delithiation process further impede their application. Herein, an in situ self-transformation strategy is proposed to unlock the cyclic stability of electrode material. Multiple characterization techniques are adopted to unfold the electrode storage mechanism, the evolution of crystal structure, as well as the kinetics after reconstruction. The hexagonal wurtzite (WZ) in rGO-coupled ZnSe would be transformed spontaneously to cubic zinc-blende (ZB) phases upon the first electrochemical cycling with Li+. Consequently, the WZ-ZnSe@rGO electrode delivers dramatically cycling stability (451 mAh g−1 after 220 cycles at 0.1 A g−1). Additionally, we also prepare cubic m-ZB-ZnSe@rGO through physical mixing method, exhibiting high Li-storage capacity (468 mAh g−1 at 0.1 A g−1). This work suggests that in situ self-transformation strategy is feasible for creating high-performance electrode materials.

Intrinsic mechanism of Co/Mn elemental manipulation in enhancing the cycling stability of single-crystal ultrahigh-nickel layered cathodes

We synthesized single-crystal ultrahigh-nickel layered cathodes with manipulated Co/Mn doping to reveal the correlation between crystal structural evolution and performance. Our study emphasizes the importance of regulating the crystal structure evolution constructing high-performance cathodes.

In situ observation of thermal-driven structural transitions of a β-NaYF4 single nanoparticle aided with correlative cathodoluminescence electron microscopy.

NaYF4 systems have been widely studied as up-conversion host matrices, and their phase transitions are flexible and worth investigating in great detail. Herein, the evolution of morphology and crystal structure of a Eu3+-doped β-NaYF4 single nanoparticle heated in an air atmosphere was investigated using in situ transmission electron microscopy (TEM). The annealing process revealed that the hexagonal β-NaYF4 phase undergoes sequential transformations into high-temperature cubic phases at both 350 °C and 500 °C. The emission characteristics of Eu3+ in the single nanoparticle after heating treatment were also analyzed using Correlative Cathodoluminescence Electron Microscopy (CCLEM). The results of CCLEM suggest a gradual decrease followed by a subsequent increase in structural symmetry. A comprehensive spectroscopic and structural analysis encapsulates the entire transformation process as NaYF4 → YOF → Y2O3. In situ energy dispersive spectroscopy analyses (EDS) support this reaction process. The aforementioned technique yields correlative lattice-resolved TEM images and nanoscale spectroscopic information, which can be employed to assess the structure-function relationships on the nanoscale.

Ligand exchange induced crystal structure and morphology evolution of copper-tin-sulfur binary and ternary compounds.

In this manuscript, a simple one-pot heat-up method has been used to prepare multi-component copper-tin-sulfur nanomaterials, including binary Cu1.94S, ternary Cu4SnS4, and Cu1.94S/Cu4SnS4 nanocrystals by varying the reaction temperature, reaction time, and the type of copper source. Post-synthetic ligand exchange (LE) has further been introduced to replace the long-chain ligands originating from 1-dodecanethiol. It has been found that the LE process not only changes the surface ligands but also significantly affects the crystal structure and optical properties of nanocrystals. After LE, the crystal structures of Cu1.94S and Cu4SnS4 transformed to Cu7S4 and Cu3SnS4, respectively, with the Cu1.94S/Cu4SnS4 nanocrystals showing the same trend. This phenomenon could be ascribed to the loss of Cu+ originating from the strong complexation of Cu+ and ammonia with the formation of [Cu(NH3)n]2+ ions under aerobic conditions. Proton nuclear magnetic resonance (1H NMR) has been used to characterize the ligands on the surface before and after LE, which further demonstrated that the -SH was replaced during LE. Meanwhile, the band gaps of the obtained nanocrystals after LE show an obvious shift in the near-infrared region due to the evolution of crystal structures. This study will provide useful guidance for the LE of nanocrystals and the application of copper-based sulfide nanomaterials in optoelectronics and other fields.

Chemical composition-induced evolution of the structure, domain and electrical properties of Sm-doped (1 - x)Pb(Ni1/3Nb2/3)O3-xPbTiO3.

As the two typical basic binary solid solutions of the relaxor-PbTiO3 family, Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) has been widely investigated, whereas Pb(Ni1/3Nb2/3)O3-PbTiO3 (PNN-PT) has not. Here, 1.5 mol% Sm-doped (1 - x)Pb(Ni1/3Nb2/3)O3-xPbTiO3, (1 - x)PNN-xPT:0.015Sm with x = 0.33-0.39, ceramics have been prepared and the chemical composition-induced evolution of crystal structure, domain, and electrical properties investigated systematically. With increasing PT content, evolution of the rhombohedral-tetragonal structure was observed. A rhombohedral-tetragonal morphotropic phase boundary occurred around x = 0.36-0.37, which showed a peak piezoelectric property with piezoelectric constant d33 = 531 pC N-1 and planar electromechanical coupling factor kp = 0.37 at room temperature. At the same time, the x = 0.36 composition showed improved ferroelectric behavior with remanent polarization Pr = 13.4 μC cm-2 and coercive field Ec = 3.2 kV cm-1. Interestingly, different from its PMN-PT counterpart, there is no temperature-driven phase transition between room temperature and the Curie temperature for (1 - x)PNN-xPT:0.015Sm. These parameters indicated that the PNN-PT system is worthy of more attention and is a promising platform for further development of high-performance piezo/ferroelectric materials.

Experimental observation of two-dimensional phase in compressed FeF2

Iron difluoride (FeF2) has attracted considerable attention for its physical characteristics and practical applications, and its compression behaviors usually play a key role in the in-depth understanding of this compound. Since its high-pressure crystal structure evolution determining a more profound comprehension remains disputable, we carried out extensive experiments to focus on the pressure-induced structural phase transitions of FeF2. Through in situ high-pressure synchrotron x-ray diffraction measurements, we not only confirmed a reported high-pressure orthorhombic Pbca phase at 11 GPa but also identified an interesting two-dimensional structure with hexagonal close packed symmetry (P-3m1) that appears above 25 GPa at room temperature. Furthermore, the spontaneous strain fitting and electronic transport measurements suggest that its ambient rutile-type structure (P42/mnm) evolves into an orthorhombic structure (Pnnm) through a second-order phase transition at 5 GPa. These experimental results elaborate on the pressure-induced phase transitions of FeF2 on the order of P42/mnm → Pnnm → Pbca → P-3m1, shedding light on a rare three-dimensional to two-dimensional configuration transition in difluorides.

Coral-like CoSe2@N-doped carbon with a high initial coulombic efficiency as advanced anode materials for Na-ion batteries.

Na-ion batteries (NIBs) have attracted great interest as a possible technology for grid-scale energy storage for the past few years owing to the wide distribution, low cost and environmental friendliness of sodium resources and similar chemical mechanisms to those of established Li-ion batteries (LIBs). Nonetheless, the implementation of NIBs is seriously hindered because of their low rate capability and cycling stability. This is mainly because the large ionic size of Na+ can reduce the structural stability and cause sluggish reaction kinetics of electrode materials. Herein, three-dimensional nanoarchitectured coral-like CoSe2@N-doped carbon (CL-CoSe2@NC) was synthesized through solvothermal and selenizing techniques. As a result, CL-CoSe2@NC for NIBs at 2 A g-1 exhibits an ultrahigh specific capacity of 345.4 mA h g-1 after 2800 cycles and a superhigh initial coulombic efficiency (ICE) of 93.1%. Ex situ XRD, HRTEM, SAED and XPS were executed to study the crystal structure evolution between Na and CoSe2 during sodiation/de-sodiation processes. The aforementioned results indicate that the improved sodium storage property of CL-CoSe2@NC could be attributed to better electrode kinetics and a stable SEI film because of the 3D nanoarchitecture and the existence of the NC layer.

Thermochromism and thermal crystal structure evolution of YIn0.9Mn0.1O3

YIn1-x Mn x O3 is a newly discovered inorganic blue pigment whose vivid blue color results from MnO5 trigonal bipyramidal (TBP) polyhedra. Recently, it has been reported that commercial YIn1-x Mn x O3 powders exhibit a temperature-induced color change, i.e. thermochromism. In this study, we investigate the thermochromism and temperature-induced crystal structure evolution of synthetic YIn0.9Mn0.1O3 powders. We observe that a vivid blue color at RT gradually changed to a dark blue color with increasing temperature. This thermochromism is mainly attributed to a broadening of optical absorption bands in the visible and UV regions, and can also be contributed to by an enhancement of the UV absorption. Our crystal structure analysis using powder synchrotron X-ray diffraction data not only confirms the thermal expansion and enhanced thermal vibrations of oxygen, but also reveals a temperature-induced deformation of the TBP polyhedra. Based on these results, we discuss a possible mechanism for the thermochromism of the YIn0.9Mn0.1O3 system.

Research on Crystal Structure Evolution and Failure Mechanism during TSV-Metal Line Electromigration Process

The combined use of Through Silicon Via (TSV) and metal lines, referred to as TSV-metal lines, is an essential structure in three-dimensional integrated circuits. In-depth research into the electromigration failure mechanism of TSV and the microstructure evolution can serve as theoretical guidance for optimizing three-dimensional stacking. This article conducted electromigration experiments on TSV-metal line structural samples at current densities of 1.0 × 105 A/cm2, 5 × 105 A/cm2, and 1 × 106 A/cm2. Additionally, Electron Back Scattered Diffraction (EBSD) technology was employed to systematically investigate the microstructural evolution of the TSV-metal line structure profiles before and after the application of electrical testing. The results indicate that the current induces a change in the crystal orientation at the TSV-metal interface (TSV/metal interface) and the bottom metal line. This phenomenon notably depends on the initial angle between the grain orientation and the current flow direction. When the angle between the current direction and the grain orientations [001] and [010] is relatively large, the crystals are more likely to deviate in the direction where the angle between the grain orientation and the current is smaller. This is because, at this point, the current direction is precisely perpendicular to the <100> crystal plane family, where the atomic density is lowest, and the energy required for electron transport is minimal. Therefore, the current readily rotates in the direction of this crystal orientation. Before the electromigration tests, areas with a high level of misorientation were primarily concentrated at the TSV/metal interface and the corners of the TSV-metal line. However, these areas were found to be more prone to developing voids after the tests. It is conjectured that the high misorientation level leads to elevated stress gradients, which are the primary cause of cracking failures in the TSV-metal line. As the current density increases from 5 × 105 A/cm2 to 1 × 106 A/cm2, the electromigration failure phenomena in the TSV become even more severe.

Giant magnetocaloric effect for (Mn, Fe, V)2(P, Si) alloys with low hysteresis

The Fe2P type Mn–Fe–P–Si alloys exhibit a giant magneto-elastic first-order transition, but the large hysteresis limits their performance. Crystal structure evolution and magnetocaloric performance were investigated by varying the Mn and Fe contents at a constant V substitution of 0.02 in Fe2P-type (Mn1.17-xFe0.73-yV0.02) (P0.5Si0.5) (where x + y = 0.02). The V substitution of Fe content shows a larger reduction of hysteresis compared with the same substitution amount of Mn content. During magnetoelastic phase transition, V-substitution reduces the volume change and the volumetric stresses, providing a superior mechanical stability. Compound with the V substitution of Fe (y = 0.02) shows the best magnetocaloric effect with a low thermal hysteresis of 0.6 K. Our developed Mn1.17-xFe0.73-yV0.02P0.5Si0.5 alloys are excellent materials for room-temperature magnetic heat-pumping applications by using a permanent magnet.

Investigation of edge effect on wurtzite gallium nitride in nanoindentation using molecular dynamics simulation

In practical applications, block materials frequently experience edge collapse, yet our grasp of this phenomenon at the nanoscale remains limited. Understanding this is crucial, as nanoscale material behaviors can trigger intricate microscale effects that elude easy observation or comprehension at the macroscopic level. This work researched the edge effect of the wurtzite GaN with {0001} surface crystal orientation at different nanoindentation distances by molecular dynamics simulation. The results show that the GaN indentation edge effect is anisotropic. The atomic displacement directions prolonged [2–1–10], [–12–10], and [–1–120], which is hexagonal distributing, similar to the crystal structure. The dislocations are around the indenter and close to the upper surface, similar to the negative von Mises stress distributions. The closer the indenter is to the edge of the sample, the more atoms are extruded from the specimen edge, and the more serious the damage is to the edge generally. However, analysis of the mechanical response and phase transition shows that the damage to the edge can be weakened while the crystal structure is destroyed more severely at some specific locations of the indenter. This work reveals the evolution of GaN crystal structure under different nanoindentation distances and the mechanism of squeeze-out atoms from the edge at the atomic scale.