Crystal Phase Transition Research Articles

Evaluation of Zirconia Ceramic Processed by Digital Light 3D Printing Applicated as Solid-Electrolyte Sensor

Zirconia slurry aimed to apply in digital light process (DLP) printing technology were made of the 3 mol% yttrium oxide (Y2O3) stabilized micro-nano zirconium dioxide (3YSZ) powders. An overall mechanical strength can be obtained via a precise control of two-step sintering process. The results show that Y2O3 in 3YSZ would diffuses into the ceramic lattice, further stabilizing the metastable tetragonal zirconia (t-ZrO2) toughening phase in sub-micro sized grains with nearly 100% crystal phase transition ratio. The Vickers hardness of sintered ceramic parts reaches 12.94 ± 0.186 GPa. The fracture toughness (KIC) of sintered ceramics is 5.63 ± 0.015 MPa·m1/2. The propagation law of Vickers crack reveals the mechanism of strengthening and toughening of fine grains on matrix fracture toughness. Due to the uniform crystals also can make the corrosion better to construct a three-phase boundary sensitive process, the response of the T-ZrO2-SnO2 to 30 ppm NH3 is 15.7 mV which is 2 times more than the commercial ZrO2. A relative short response and recovery times of 6 s and 33 s can achieve with a good reproducibility of continuous response and recovery transients.

Heat capacity and thermal expansion of nanosized ferroelectric (NH4)2SO4 embedded in borosilicate glasses

The thermal properties of nanocomposites obtained by incorporating a ferroelectric (NH4)2SO4 (AS) into porous glasses (PG) was studied for the first time. X-ray diffraction studies showed a strong increase in the ratio of the size of nanocrystallites grown in glass matrices to pore size, dcryst/ dpore = 0.47→1.50→5.00, with a decrease in dpore = 320→46→7 nm. Calorimetric and dilatometric measurements showed a change from a first-order phase transition in AS single crystal to a second-order transformation in AS nanocrystallites. A restricted geometry also led to a significant decrease in the anomalous entropy in AS+PG samples compared to AS (J/mol∙K): 17.7 (AS)→12.4 (AS+PG320)→10.4 (AS+PG46)→8.1 (AS+PG7). A discussion of the nontrivial behavior of the phase transition temperature in embedded AS was carried out using the degree of PG filling, the ratio dcryst/dpore, texture, and the volumetric and linear baric coefficients for the bulk AS.

Effect of phospholipids on membrane characteristics and storage stability of liposomes

The membrane characteristics and storage stability of liposomes prepared by different phospholipids were investigated, including soybean phosphatidylcholine (SPC), egg yolk phosphatidylcholine (EPC) and hydrogenated soy phosphatidylcholine (HSPC). The mean vesicle size of HSPC liposomes was 437.8 nm, while the size of SPC and EPC liposomes were 112.3 and 121.3 nm, respectively. The AFM and TEM images demonstrated that SPC and EPC liposomes exhibited a more uniform distribution and greater membrane fluidity. The liposomes demonstrated different crystallization behavior and phase transition temperatures by XRD and DSC, respectively. Due to high saturated fatty acids content of HSPC, these liposomes displayed a tighter membrane packing as evident by FTIR and Raman spectra. The membrane hydrophobicity and micropolarity decreased with storage time. During storage, HSPC liposomes maintained a more compact membrane structure. HSPC liposomes were the most stable during storage as evident by significantly lower levels of lipid hydrolysis and oxidation.

Slow protein dynamics probed by time-resolved oscillation crystallography at room temperature.

The development of serial crystallography over the last decade at XFELs and synchrotrons has produced a renaissance in room-temperature macromolecular crystallography (RT-MX), and fostered many technical and methodological breakthroughs designed to study phenomena occurring in proteins on the picosecond-to-second timescale. However, there are components of protein dynamics that occur in much slower regimes, of which the study could readily benefit from state-of-the-art RT-MX. Here, the room-temperature structural study of the relaxation of a reaction intermediate at a synchrotron, exploiting a handful of single crystals, is described. The intermediate in question is formed in microseconds during the photoreaction of the LOV2 domain of phototropin 2 from Arabidopsis thaliana, which then decays in minutes. This work monitored its relaxation in the dark using a fast-readout EIGER X 4M detector to record several complete oscillation X-ray diffraction datasets, each of 1.2 s total exposure time, at different time points in the relaxation process. Coupled with in crystallo UV-Vis absorption spectroscopy, this RT-MX approach allowed the authors to follow the relaxation of the photoadduct, a thio-ether covalent bond between the chromophore and a cysteine residue. Unexpectedly, the return of the chromophore to its spectroscopic ground state is followed by medium-scale protein rearrangements that trigger a crystal phase transition and hinder the full recovery of the structural ground state of the protein. In addition to suggesting a hitherto unexpected role of a conserved tryptophan residue in the regulation of the photocycle of LOV2, this work provides a basis for performing routine time-resolved protein crystallography experiments at synchrotrons for phenomena occurring on the second-to-hour timescale.

Disorder-induced topological phase transition in HgCdTe crystals

Using the self-consistent Born approximation, we study a topological phase transition appearing in bulk HgCdTe crystals induced \emph{uncorrelated} disorder due to both randomly distributed impurities and fluctuations in Cd composition. By following the density-of-states evolution, we clearly demonstrate the topological phase transition, which can be understood in terms of the disorder-renormalized mass of Kane fermions. We find that the presence of heavy-hole band in HgCdTe crystals leads to the topological phase transition at much lower disorder strength than it is expected for conventional 3D topological insulators. Our theoretical results can be also applied to other narrow-gap zinc-blende semiconductors such as InAs, InSb and their ternary alloys InAsSb.

Self-Assembly of Ultrathin Nickel Oxysulfide for Reversible Gas Sensing at Room Temperature

Two-dimensional (2D) or ultrathin metal sulfides have been emerging candidates in developing high-performance gas sensors given their physisorption-dominated interaction with target gas molecules. Their oxysulfide derivatives, as intermediates between oxides and sulfides, were recently demonstrated to have fully reversible responses at room temperature and long-term device stability. In this work, we explored the micro-scale self-assembly of ultrathin nickel oxysulfide through the calcination of nickel sulfide in a controllable air environment. The thermal treatment resulted in the replacement of most S atoms in the Ni-S frameworks by O atoms, leading to the crystal phase transition from original hexagonal to orthorhombic coordination. In addition, the corresponding bandgap was slightly expanded by ~0.15 eV compared to that of pure nickel sulfide. Nickel oxysulfide exhibited a fully reversible response towards H2 at room temperature for concentrations ranging from 0.25% and 1%, without the implementation of external stimuli such as light excitation and voltage biasing. The maximum response factor of ~3.24% was obtained at 1% H2, which is at least one order larger than those of common industrial gases including CH4, CO2, and NO2. Such an impressive response was also highly stable for at least four consecutive cycles. This work further demonstrates the great potential of metal oxysulfides in room-temperature gas sensing.

Metal-organic framework-derived mixed-phase anatase/rutile TiO2 towards boosted lithium storage: Surface engineering and design strategy through crystal phase transition

The design and construction of electrodes with surface and interface structures bring new opportunities for high-performance lithium storage properties. Herein, we present a simple synthesis method to fabricate surface-amorphized anatase/rutile mixed-phase truncated octahedral TiO2 (TO-AR) structures with oxygen vacancy derived from metal-organic framework (MOF) with a temperature-controlled phase transition. Compared with single-phase TiO2, the mixed-phase TO-AR electrode shows higher specific capacity and better rate performance. Systematic experimental studies and theoretical calculations demonstrate that the abundant interface between anatase and rutile induced by the crystallographic phase transition provides efficient high-capacity Li+ storage and enhanced charge-transfer kinetics. Meanwhile, the amorphous surface and higher oxygen vacancy concentration improve the surface-induced capacitive properties. These results provide new insights into improving the electrochemical performance of metal-organic framework-derived anode materials in Li-ion batteries.

Structural Characterization and Dynamics of a Layered 2D Perovskite [NH3(CH2)5NH3]MnCl4 Crystal near Phase Transition Temperature

[NH3(CH2)5NH3]MnCl4 crystals are grown via slow evaporation, and the crystal undergoes a phase transition at 298 K (TC) according to differential scanning calorimetry, and the structures determined via X-ray diffraction at 173 and 333 K are orthorhombic systems in the space group Imma. These results differed slightly from those previously reported, and the reasons for this are analyzed. The thermal stability is relatively high, with a thermal decomposition temperature of approximately 570 K. The 1H spin-lattice relaxation times t1ρ exhibited very large variations, as indicated by the large thermal displacement around the 1H atoms, suggesting energy transfer at ~TC, even if no structural changes occurred. The influences of the chemical shifts of 1H of NH3 and short t1ρ of C1 adjacent to NH3 in cation are insignificant, indicating a minor change in the N−H⋯Cl hydrogen bond related to the coordination geometry of the MnCl6 octahedron. These properties will be make it a potential application for eco-friendly solar cells.

Full Composition Tuning of W1-xNbxSe2 Alloy Nanosheets to Promote the Electrocatalytic Hydrogen Evolution Reaction.

Composition modulation of transition metal dichalcogenides is an effective way to engineer their crystal/electronic structures for expanded applications. Here, fully composition-tuned W1-xNbxSe2 alloy nanosheets were produced via colloidal synthesis. These nanosheets ultimately exhibited a notable transition between WSe2 and NbSe2 hexagonal phases at x = 0.6. As x approaches 0.6, point doping is converted into cluster doping and eventually separated domains of WSe2 and NbSe2. Extensive density functional theory calculations predicted the composition-dependent crystal structures and phase transitions, consistently with the experiments. The electrocatalytic activity for the hydrogen evolution reaction (HER) in acidic electrolyte was significantly enhanced at x = 0.2, which was linked with the d-band center. The Gibbs free energy for the H adsorption at various basal and edge sites supported the enhanced HER performance of the metallic alloy nanosheets. We suggested that the dispersed doping structures of Nb atoms resulted in the best HER performance. Our findings highlight the significance of composition tuning in enhancing the catalytic activity of alloys.

Preparation and characteristics optimization of octadecanoic acid/octadecanol/expanded graphite based composite phase change materials for energy storage

The thermal energy storage (TES) based on latent heat technique with outstanding thermal performance is required to boost the development of the field thermal management application. Hence, this research proposes a solid-liquid composite phase change materials (CPCMs) based on octadecanoic acid (C18-acid), octadecanol (C18-OH) and expanded graphite (EG). The CPCMs structural and thermal properties were analyzed using the spectroscopy and calorimetry techniques. The X-ray diffractometer (XRD), Scanning electron microscope (SEM) and Fourier transformation infrared spectroscopy (FTIR) were utilized for the morphological and structural characterization of the CPCMs. Accordingly, the results revealed that the three components combined in the CPCMs were successfully mixed by physically combination. The CPCMs thermal performance was determined by using differential scanning calorimetry (DSC) and thermal conductivity analyzer (TCA) instruments. As a result, the CPCMs latent heats were in the area of 135.2 to 143.5 J/g in the melting process for the temperature range of 45.5 to 47 °C and −149.0 to −189.6 J/g during the crystallization phase transition in the temperature range of 37.1 to 37.8 °C. It is worth mentioning that the addition of several mass fractions (1 %, 3 %, 5 %, 7 % and 9 %) of EG in the binary C18-acid/C18-OH has significantly enhanced the CPCMs thermal conductivity from 0.066 W/(m·K) up to 3.38 W/(m·K), hence, leading to optimize the heat transfer rate in the CPCMs medium. Moreover, the thermal degradation and leakage experiments were performed to evaluate the CPCMs operating performance. Based on results, the solid-liquid CPCMs as prepared with great thermal properties is a suitable PCMs for the thermal energy management application.

Ferroelasticity in Organic–Inorganic Hybrid Perovskites

Molecular ferroelastics have received particular attention for potential applications in mechanical switches, shape memory, energy conversion, information processing, and solar cells, by taking advantages of their low-cost, light-weight, easy preparation, and mechanical flexibility. The unique structures of organic-inorganic hybrid perovskites have been considered to be a design platform for symmetry-breaking-associated order-disorder in lattice, thereby possessing great potential for ferroelastic phase transition. Herein, we review the research progress of organic-inorganic hybrid perovskite ferroelastics in recent years, focusing on the crystal structures, dimensions, phase transitions and ferroelastic properties. In view of the few reports on molecular-based hybrid ferroelastics, we look forward to the structural design strategies of molecular ferroelastic materials, as well as the opportunities and challenges faced by molecular-based hybrid ferroelastic materials in the future. This review will have positive guiding significance for the synthesis and future exploration of organic-inorganic hybrid molecular ferroelastics.

Phase transitions in flexible crystals of cocrystal solvate of caffeine

Phase transitions in flexible crystals of cocrystal solvate of caffeine

Piezoelectricity enhancement in graphene/polyvinylidene fluoride composites due to graphene-induced α → β crystal phase transition

Piezoelectric polymers represented by polyvinylidene fluoride (PVDF) possess many attractive attributes so they are widely used in electromechanical energy conversion devices. To further enhance the piezoelectric effect of PVDF, graphene and its derivatives have been added. A central issue is how the added graphene improves the piezoelectric properties of the graphene/PVDF composites. Starting from consideration of crystal phase transition from α to β phase in PVDF due to addition of graphene, we first introduce Cauchy’s cumulative probability function to characterize the evolution of β phase as a function of graphene content. Then, by considering the relationship between β phase and the dipole, and between the microscopic dipole moment and the macroscopic piezoelectric coefficient, a theory of piezoelectricity for the composite is obtained. The theory shows that the β phase increases slowly at low graphene content but the increase is very rapid as the graphene concentration approaches the percolation threshold, after which there is no significant growth. The piezoelectric coefficient also increases similarly until the percolation threshold, after which it starts to drop. When the graphene content is 0.11 vol%, the piezoelectric coefficient d33 increases from 22pC/N of pure PVDF to 39.73pC/N of graphene/PVDF composite, which is an 80.5% increase in d33. In addition, this theory is further extended and applied to the other nanoparticle-enhanced piezoelectric polymer composites. This crystal phase transition model serves to fill up the theoretical gap in piezoelectric enhancement in piezoelectric enhancement of PVDF by graphene.

Developing methods to study conformational changes in RNA crystals using a photocaged ligand

Crystallographic observation of structural changes in real time requires that those changes be uniform both spatially and temporally. A primary challenge with time-resolved ligand-mixing diffraction experiments is asynchrony caused by variable factors, such as efficiency of mixing, rate of diffusion, crystal size, and subsequently, conformational heterogeneity. One method of minimizing such variability is use of a photolabile caged ligand, which can fully saturate the crystal environment (spatially), and whose photoactivation can rapidly (temporally) trigger the reaction in a controlled manner. Our recently published results on a ligand-mixing experiment using time-resolved X-ray crystallography (TRX) with an X-ray free electron laser (XFEL) demonstrated that large conformational changes upon ligand binding resulted in a solid-to-solid phase transition (SSPT), while maintaining Bragg diffraction. Here we investigate this SSPT by polarized video microscopy (PVM) after light-triggered release of a photo-caged adenine (pcADE). In general, the mean transition times and transition widths of the SSPT were less dependent on crystal size than what was observed in previous PVM studies with direct ADE mixing. Instead, the photo-induced transition appears to be heavily influenced by the equilibrium between caged and uncaged ADE due to relatively low sample exposure and uncaging efficiency. Nevertheless, we successfully demonstrate a method for the characterization of phase transitions in RNA crystals that are inducible with a photocaged ligand. The transition data for three crystals of different sizes were then applied to kinetic analysis by fitting to the known four-state model associated with ligand-induced conformational changes, revealing an apparent concentration of uncaged ADE in crystal of 0.43–0.46 mM. These results provide further insight into approaches to study time-resolved ligand-induced conformational changes in crystals, and in particular, highlight the feasibility of triggering phase transitions using a light-inducible system. Developing such approaches may be paramount for the rapidly emerging field of time-resolved crystallography.

Front Cover: Structural Phase Transitions in Anthracene Crystals (ChemPlusChem 9/2022)

The cover picture shows arrangements of anthracene crystals: structural phase transitions in anthracene crystals have recently attracted much interest in a wide range of research areas in materials science. This Review discusses the engineering of anthracene, including its synthetic design, reactivities, and optical properties toward structural phase transitions of the crystals. More information can be found in the Review by S. Hayashi and co-workers.

Reversible disorder-order type structural phase transition of potassium dihydrogen phosphate bulk single crystals induced by dynamic shock waves

In this article, we report the reversible disorder-order type structural phase transition of potassium dihydrogen phosphate (KDP) bulk single crystal at dynamic shock pulses loaded conditions and the core results of the disorder-order type structural phase transitions have been authenticated by X-ray diffraction (XRD) and Raman spectroscopic results. In order to have further substantiation, we have also performed optical spectroscopic and microscopic analyses. As per the obtained data from the XRD, Raman and microscopic results, the control KDP crystal has the disordered type tetragonal structure whereas, at the 1st shocked condition, we observe a completely ordered tetragonal structure. Surprisingly, at the 2nd shocked condition, the disordered tetragonal structure has been retrieved. To the best of our knowledge, to date, this kind of reversible disorder-order type phase transition may be the first report on the research findings of KDP crystal.

Photonic Z2 Topological Anderson Insulators

That disorder can induce nontrivial topology is a surprising discovery in topological physics. As a typical example, Chern topological Anderson insulators (TAIs) have been realized in photonic systems, where the topological phases exist without symmetry protection. In this Letter, by taking transverse magnetic and transverse electric polarizations as pseudospin degrees of freedom, we theoretically propose a scheme to realize disorder-induced symmetry-protected topological phase transitions in two-dimensional photonic crystals with a combined time-reversal, mirror, and duality symmetry T_{f}=TM_{z}D. In particular, we demonstrate that the disorder-induced symmetry-protected topological phase persists even without pseudospin conservation, thereby realizing a photonic Z_{2} TAI, in contrast to a Z-classified quantum spin Hall (QSH) TAI with decoupled spins. By formulating a new scattering approach, we show that the topology of both the QSH and Z_{2} TAIs can be manifested by the accumulated spin rotations of the reflected waves from the photonic crystals. Using a transmission structure, we also illustrate the trivialization of a disordered QSH phase with an even integer topological index caused by spin coupling.

Crystal structure deformation and phase transition of AlScN thin films in whole Sc concentration range

This article reports lattice deformation and phase transition of AlScN thin films in the whole composition. AlScN films were deposited on Pt/Ta/SiO2/Si substrates by direct current magnetron reactive sputtering with Al and Sc targets. At Sc concentration up to 30%, AlScN has a wurtzite structure with piezoelectricity. Transition from a wurtzite phase to a two-phase mixture happens between 30% and 35% Sc concentration, and transition from a two-phase mixture to a cubic phase happens between 38% and 43% Sc concentration. The wurtzite structure gradually deforms with the decrease in lattice constant c from 16% to 35% Sc concentration. Lattice constant c at 38% Sc in the two-phase mixture region is larger than that of 35% Sc concentration. These increases mean that distortion of c axis for the wurtzite structure over 35% Sc concentration in the two-phase mixture region is considered to be released and/or eased due to the appearance of the cubic phase, and that Sc concentration of the wurtzite phase to be smaller and that of the cubic phase larger than the film composition measured by energy-dispersive x-ray spectroscopy and Rutherford backscattering spectroscopy. At higher Sc concentration up to 43%, the remained wurtzite phases are replaced by non-piezoelectric cubic phases, and the cubic structure approaches the rock-salt structure of ScN with a further increase in Sc concentration.

Suppression of phase-transition temperature in aluminium indium tungstate and aluminium indium molybdate

Aluminium indium tungstate (AlInW3O12) and aluminium indium molybdate (Al0.84In1.16Mo3O12) were synthesized by non-hydrolytic sol–gel chemistry, and their crystal structures, phase transition and thermal expansion behavior were studied using variable-temperature synchrotron powder diffraction. AlInW3O12 adopts an orthorhombic phase above 260 K and gradually transitions to a monoclinic polymorph below this temperature. Al0.84In1.16Mo3O12 also shows a gradual transition between the monoclinic and orthorhombic structures between 330 and 445 K. Both materials display much lower phase-transition temperatures than predicted on the basis of the parent compounds and Vegard's law. This suppression is attributed to the large size difference between Al3+ and In3+. Interestingly, both samples display positive thermal expansion along all unit-cell axes instead of the typically observed negative expansion of orthorhombic A 2 M 3O12 compositions.

Nonequilibrium phase transitions of a nematic liquid crystal under ac field-driven electroconvection.

We report on phase transitions between isotropic and nematic liquid crystal phases in nonequilibrium systems (NESs). ac field-driven electroconvection (EC) provides an NES, which can be well controlled by the voltage V and frequency f; it arises electrohydrodynamically at a threshold voltage V_{c}. In continuous cooling and heating processes with various rates R, the critical temperature T_{c} was determined at a critical time t_{c} for phase transitions. Moreover, the morphological and dynamical features in the phase transitions were examined using an electro-optical image processing method. In comparison with an equilibrium system (V=0), two typical turbulent ECs (i.e., NESs), which are called dynamic scattering mode 1 (DSM1 for V>V_{c}) and DSM2 (for V≫V_{c}), were examined to understand the nonequilibrium phase transitions. In particular, our results show that in high voltage-induced turbulence (i.e., DSM2), T_{c} can be determined effectively without considering R; this provides a possibility for a material technology application in nonequilibrium-based circumstances.