Crystal Lattice Research Articles

The Facile Construction of Anatase Titanium Dioxide Single Crystal Sheet-Connected Film with Observable Strong White Photoluminescence

Deposited by a reactive atmospheric pressure non-thermal TiCl4/O2/Ar plasma, anatase TiO2 single crystal sheet-connected film exhibits two large exposed {001} facets and a high concentration of oxygen defects. Strong white photoluminescence centered at 542 nm has been observed with naked eyes, whose internal quantum efficiency is 0.62, and whose intensity is comparable to that of commercial fluorescent lamp interior coatings. Based on the simulation results of a hybrid global–analytical model developed on this atmospheric pressure non-equilibrium plasma system, the mechanism of a self-confined growth of single crystal sheets was proposed. A high concentration of oxygen defects is in situ incorporated into the anatase crystal lattice without damaging its crystallographic orientation. This method opens a new way to construct 3D porous metal-oxide single crystal sheet-connected films with two exposing high energy surfaces and a large concentration of oxygen defects.

Achieving High-Temperature Phosphorescence by Organic Cocrystal Engineering.

Organic phosphors offer a promising alternative in optoelectronics, but their temperature-sensitive feature has restricted their applications in high-temperature scenarios, and the attainment of high-temperature phosphorescence (HTP) is still challenging. Herein, a series of organic cocrystal phosphors are constructed by supramolecular assembly with an ultralong emission lifetime of up to 2.16 s. Intriguingly, remarkable stabilization of triplet excitons can also be realized at elevated temperature, and green phosphorescence is still exhibited in solid state even up to 150 °C. From special molecular packing within the crystal lattice, it has been observed that the orientation of isolated water cluster and well-controlled molecular organization via multiple interactions can favor the structural rigidity of cocrystals more effectively to suppress the nonradiative transition, thus resulting in efficient room-temperature phosphorescence and unprecedented survival of HTP.

Achieving High‐Temperature Phosphorescence by Organic Cocrystal Engineering

AbstractOrganic phosphors offer a promising alternative in optoelectronics, but their temperature‐sensitive feature has restricted their applications in high‐temperature scenarios, and the attainment of high‐temperature phosphorescence (HTP) is still challenging. Herein, a series of organic cocrystal phosphors are constructed by supramolecular assembly with an ultralong emission lifetime of up to 2.16 s. Intriguingly, remarkable stabilization of triplet excitons can also be realized at elevated temperature, and green phosphorescence is still exhibited in solid state even up to 150 °C. From special molecular packing within the crystal lattice, it has been observed that the orientation of isolated water cluster and well‐controlled molecular organization via multiple interactions can favor the structural rigidity of cocrystals more effectively to suppress the nonradiative transition, thus resulting in efficient room‐temperature phosphorescence and unprecedented survival of HTP.

Antithermal Quenching Upconversion Luminescence via Suppressed Multiphonon Relaxation in Positive/Negative Thermal Expansion Core/Shell NaYF4:Yb/Ho@ScF3 Nanoparticles.

Thermal quenching (TQ) has been naturally entangling with luminescence since its discovery, and lattice vibration, which is characterized as multiphonon relaxation (MPR), plays a critical role. Considering that MPR may be suppressed under exterior pressure, we have designed a core/shell upconversion luminescence (UCL) system of α-NaYF4:Yb/Ln@ScF3 (Ln = Ho, Er, and Tm) with positive/negative thermal expansion behavior so that positive thermal expansion of the core will be restrained by negative thermal expansion of the shell when heated. This imposed pressure on the crystal lattice of the core suppresses MPR, reduces the amount of energy depleted by TQ, and eventually saves more energy for luminescing, so that anti-TQ or even thermally enhanced UCL is obtained.

Growth and physiochemical properties of semi organic ammonium pentaborate dihydrate single crystal

Abstract The slow evaporation technique was used to produce nonlinear optical ammonium pentaborate dihydrate (APBDH) single crystals. The crystal lattice parameters and structure of APBDH crystal was determined by single crystal X-ray diffraction (S-XRD) technique with the triclinic space group. The optical band gap of the grown crystal was determined using UV–Vis spectrophotometer. There is no absorption peak was observed in the entire visible region of the spectrum. The functional groups of the APBDH crystal were identified through Fourier transforms infrared (FTIR) and Fourier transform Raman (FR-Raman) analyses. The thermal decomposition and thermal stability of the grown crystal was measured using TG-DTA analyses. The laser damage threshold (LDT) analysis was used to know the ability to withstand the influence of laser on the grown crystal. Photoconductivity of the grown crystal was studied and its photocurrent and dark current behavior was examined. The surface morphology of the APBDH crystal was evaluated using HR-SEM analysis. The APBDH crystal was exhibited second harmonic generation behavior and its efficiency was calculated with different particle sizes.

Blue-Emitting Cs(Pb,Cd)Br3 Nanocrystals Resistant to Electric Field-Induced Ion Segregation.

High-performance solution-processed perovskite light-emitting diodes (PeLEDs) have emerged as a good alternative to the well-established technology of epitaxially grown AIIIBV semiconductor alloys. Colloidal cesium lead halide perovskite nanocrystals (CsPbX3 NCs) exhibit room-temperature excitonic emission that can be spectrally tuned across the entire visible range by varying the content of different halogens at the X-site. Therefore, they present a promising platform for full color display manufacturing. Engineering of highly efficient PeLEDs based on bromide and iodide perovskite NCs emitting green and red light, respectively, does not face major challenges except low operational stability of the devices. Meanwhile, mixed-halide counterparts demonstrating blue luminescence suffer from the electric field-induced phase separation (ion segregation) phenomenon described by the rearrangement (demixing) of mobile halide ions in the crystal lattice. This phenomenon results in an undesirable temporal redshift of the electroluminescence spectrum. However, to realize spectral tuning and, at the same time, address the issue of ion segregation less mobile Cd2+ ion could be introduced in the lattice at Pb2+-site that leads to the band gap opening. Herein, we report an original synthesis of CsPb0.88Cd0.12Br3 perovskite NCs and study their structural and optical properties, in particular electroluminescence. Multilayer PeLEDs based on the obtained NCs exhibit single-peak emission centered at 485 nm along with no noticeable change in the spectral line shape for 30 min which is a significant improvement of the device performance.

Impact of deposition voltage on the physical properties of rare earth element doped strontium sulphide for optoelectronic application

In this study, electrochemical deposition was used to synthesize SrS-doped zirconium materials at a varying voltage of deposition. The XRD result shows that SrS/Zr has a prominent peak intensity corresponding to 2theta values of 26.45o , 33.86o , 38.01o , and 51.49o . The crystal lattice is shown by the prominent peak intensity with higher 2theta degree values; the appearance of an unindexed peak is caused by the substrate utilized for the deposition. SrS surface morphology reveals a Clove-like surface with precipitate visible in the SrS micrograph; the large grain size on the surface of the substrate exhibits photon absorption but lacks any signs of pinholes. At the introduction of zirconium as a dopant to the SrS precursor, there was a drastic change in the precursor which is also noticed on the surface micrograph of the analyzed films. The films show a decrease in thickness from 129.14 to 120.09 nm and an increase in film resistivity from 1.24 x 109 to 1.29 x 109 ohm.m, which further led to a decrease in conductivity from 8.06 x 108 to 7.75 x 108 S/m. The impact of the deposition voltage on the reflectance reveals that lower voltage will stabilize the reflectance of SrS/Zr which will be useful for photovoltaic applications. SrS has an energy bandgap of 1.50 eV while SrS/Zr with bandgap energy of 2.00 – 2.50 eV.

Rare-Earth Ion Loss of Er- or Yb-Doped LiNbO3 Crystals Due to Mechanical Destructive Effect of High-Energy Ball Milling

Structural changes of Er- or Yb-ion doped LiNbO3 (LN) nanocrystals were studied in relation to the high-energy ball milling process. The evolution of the size of the particles and the formation of different phases were followed by dynamic light scattering and X-ray diffraction measurements, while the electronic transitions of rare-earth (RE) ions were investigated by absorption spectroscopy in the infrared spectral range. During the milling process, RE ions left the crystal lattice and an RE2O3 phase appeared to an increasing extent next to the LN. The change in the absorption spectra and the phases formed during the grinding process were found to be very similar for both investigated RE ions and were independent of their original concentration in the starting crystal samples. The extent of the RE loss was found to be 90% after 100 min of wet grinding.

Natural and synthetic plagioclases: Surface charge characterization and sorption of trivalent lanthanides (Eu) and actinides (Am, Cm)

The environmental fate of radiotoxic actinides may be controlled by their interactions with feldspars. Here, the sorption of trivalent minor actinides (Am, Cm) and their rare earth analog Eu onto synthetic pure Ca-feldspar (anorthite) and natural plagioclases of different Ca contents is investigated, covering ranges of [M3+] (52 nM–10 μM), solid-liquid ratios (1–3 g/L), pH (3–9), and ionic strengths (0.01–0.1 M NaCl) under both ambient and CO2-free conditions. As a first step to understand the uptake behavior of the heavy metals, the hitherto unknown surface charge and (de-)protonation reaction of Ca-feldspars is characterized. The zeta potential shows an unusual increase and charge reversal between pH 4 and 7 , which becomes more pronounced with increasing amounts of Ca in the crystal lattice and is likely connected to adsorption and/or surface precipitation of dissolved Al3+. Streaming potential measurements yield (de)protonation constants for anorthite surface sites of log K- = −6.94 ± 0.38 and log K+ = +6.84 ± 0.38. Batch sorption data shows strong immobilization of M3+ by plagioclases at mildly acidic and basic pH. Time-resolved laser fluorescence spectroscopy using Cm indicates the formation of an inner-sphere complex and its two hydrolyzed forms. The complex reactivity of dissolved Al3+ at the plagioclase-water interface severely complicated the development of a surface complexation model, emphasizing the need for additional research in this area. Our study highlights the importance of molecular-level studies to understand surface reactions and uncover unknown processes, which may have significant impact on the transport of (radiotoxic) contaminants in the geosphere.

Structural and resistivity properties of Fe1-xCoxSe single crystals grown by the molten salt method

A series of tetragonal Fe1-xCoxSe single crystals with a complete Co doping range (0 ≤ x ≤ 0.52) up to its solid solubility limit in FeSe have been grown by an eutectic AlCl3/KCl molten salt method. The typical lateral size of as-grown Fe1-xCoxSe single crystals is 1–5 mm. The chemical composition and homogeneity of the crystals was examined by both inductively coupled plasma atomic emission spectroscopy and energy dispersive spectrometer. X-ray diffraction analysis demonstrates that the crystal lattice parameters a and c are both linearly decreased with increasing Co doping level x. In the whole doping range, all the samples show metallic behaviour in contrast to a metal insulator transition of Cu-doped FeSe according to the resistivity measurements.

The characterisation of dental enamel using transmission Kikuchi diffraction in the scanning electron microscope combined with dynamic template matching

The remarkable physical properties of dental enamel can be largely attributed to the structure of the hydroxyapatite (HAp) crystallites on the sub-micrometre scale. Characterising the HAp microstructure is challenging, due to the nanoscale of individual crystallites and practical challenges associated with HAp examination using electron microscopy techniques. Conventional methods for enamel characterisation include imaging using transmission electron microscopy (TEM) or specialised beamline techniques, such as polarisation-dependent imaging contrast (PIC). These provide useful information at the necessary spatial resolution but are not able to measure the full crystallographic orientation of the HAp crystallites. Here we demonstrate the effectiveness of enamel analyses using transmission Kikuchi diffraction (TKD) in the scanning electron microscope, coupled with newly-developed pattern matching methods. The pattern matching approach, using dynamic template matching coupled with subsequent orientation refinement, enables robust indexing of even poor-quality TKD patterns, resulting in significantly improved data quality compared to conventional diffraction pattern indexing methods. The potential of this method for the analysis of nanocrystalline enamel structures is demonstrated by the characterisation of a human enamel TEM sample and the subsequent comparison of the results to high resolution TEM imaging. The TKD – pattern matching approach measures the full HAp crystallographic orientation enabling a quantitative measurement of not just the c-axis orientations, but also the extent of any rotation of the crystal lattice about the c-axis, between and within grains. Results presented here show how this additional information highlights potentially significant aspects of the HAp crystallite structure, including intra-crystallite distortion and the presence of multiple high angle boundaries between adjacent crystallites with rotations about the c-axis. These and other observations enable a more rigorous understanding of the relationship between HAp structures and the physical properties of dental enamel.

Impact of Substitutional Doping of Eu3+ on Optoelectronic Properties of BaMgSiO4 Phosphor Material: A Tunable Blue‐White Color‐Emitting Phosphor

The structure and the optical properties of the tridymite green color phosphor BaMgSiO4 :Eu are systematically examined. Due to the differing ion radii of Eu3+, Mg2+, Si4+, and the three different Ba 2+ sites in the crystal lattice, dopants can only replace the Ba2+ sites because the other sites are insufficiently large to hold the massive Eu3+. BaMgSiO4 is a promising candidate for inorganic photochromatic materials with excellent optical properties. It has attracted much attention in the world due to its applications in high‐density optical memory and light‐emitting diodes. Herein, the generalized gradient approximation and generalized gradient approximation plus Hubbard potential (GGA + U) are used to investigate the electronic structure and the entire optical properties of the parent and Eu‐doped BaMgSiO4, like dielectric function, refractive and extinction coefficients, the optical conductivity, reflectivity, and absorption spectra. It is found that the substitution of Eu ions reduces the energy bandgap of BaMgSiO4 and introduces the sub‐bands in between the valence and conduction bands. Findings show that the bandgap and optical characteristics of the BaMgSiO4 compound are described properly by the GGA + U method.

Third Harmonic Generation in Thin NbOI2 and TaOI2.

The niobium oxide dihalides have recently been identified as a new class of van der Waals materials exhibiting exceptionally large second-order nonlinear optical responses and robust in-plane ferroelectricity. In contrast to second-order nonlinear processes, third-order optical nonlinearities can arise irrespective of whether a crystal lattice is centrosymmetric. Here, we report third harmonic generation (THG) in two-dimensional (2D) transition metal oxide iodides, namely NbOI2 and TaOI2. We observe a comparable THG intensity from both materials. By benchmarking against THG from monolayer WS2, we deduce that the third-order susceptibility is approximately on the same order. THG resonances are revealed at different excitation wavelengths, likely due to enhancement by excitonic states and band edge resonances. The THG intensity increases for material thicknesses up to 30 nm, owing to weak interlayer coupling. After this threshold, it shows saturation or a decrease, due to optical interference effects. Our results establish niobium and tantalum oxide iodides as promising 2D materials for third-order nonlinear optics, with intrinsic in-plane ferroelectricity and thickness-tunable nonlinear efficiency.

Redox flow deionization using Prussian blue and functionalized ion exchange membrane for enhanced selective ion recovery

Flow electrode capacitive deionization (FCDI) is a newly developed water treatment technology that offers better performance than the original, solid electrode capacitive deionization (CDI). By eliminating the need for discharging process, FCDI provides much higher desalination capacity with a continuous desalination operation. Along with applications for salt removal, selective removal and recovery of specific ions are also prominent features of FCDI technology. Characteristics of electrodes and ion exchange membranes play a crucial role in controlling the selectivity of ions in an FCDI system. In this study, we demonstrated selective and continuous ion recovery by combining redox-active Prussian blue as flow electrodes and functionalized ion exchange membranes in FCDI configuration. Prussian blue selectively absorbs monovalent Na+ ions from Na+/Ca2+ mixtures through intercalation reaction, in which a smaller Stokes radius of Na+ ion is more favored to fit in the crystal lattice. Furthermore, such selectivity is much more enhanced through functionalization of a cation-exchange membrane (CEM) with polymer multilayers. A layer-by-layer method was used to deposit poly(allylamine hydrochloride) (PAH) and poly(styrene sulfonate) (PSS) on the CEM. Results showed that polymer multilayers changed the CEM from divalent to monovalent ion-affinity due to different ion sizes and charge density. The combination of Prussian blue and functionalized CEM raised the selectivity for sodium around 17 times compared to a control system (0.2 to 3.35). We believe that our approach can provide insight into various areas including resource production, recovery, removal of toxic ions, and material recycling using an FCDI system.

Development of new β Ti and Zr-based alloys in the Ta-(75-x)Ti-xZr system

The main objective of this study was to produce two new biomedical alloys, Ta-(75-x)Ti-xZr (x = 25, 50 wt%), and to carry out a detailed analysis of the crystal structures, phase composition, lattice parameters, hardness, and elastic modulus of the alloys under the influence of heat treatments. After melting (as-cast condition), the two alloys were subjected to two heat treatments carried out at a temperature of 1000 °C: one with slow cooling in the oven (SC) and the other rapidly cooled with ice water (RC). From the structural and microstructural characterizations (XRD, SEM, and Rietveld), it was observed that the Ta-(75-x)Ti-xZr produced are α+β type alloys. However, the Ta–25Ti–50Zr alloy contains a more significant amount of β phase due to the β stabilizing action of Zr combined with Ta as a typical β stabilizing element. Regarding the cooling after heat treatments, rapid cooling (RC) promoted the formation of the metastable α" phase, and heat treatment followed by slow cooling (SC) promoted the formation of the α+β phases. The alloys’ hardness, elastic modulus, and atomic packing factor (APF) were affected by changes in the α and α" phases fraction. The SC treatment increased APF, hardness, and elastic modulus, while the RC treatment decreased elastic modulus, optimizing it for biomedical applications.

Hydrothermally synthesized-nanoscale carbonated hydroxyapatite with calcium carbonates derived from green mussel shell wastes

A hydrothermal method for exploring the benefits of a low-cost calcium carbonate precursor generated by mineral carbonation of green mussel wastes was in the study for synthesizing carbonated hydroxyapatite at various temperatures. Two typical precipitated calcium carbonates identified include vaterite and calcite particles formed by previous direct mineral carbonation. The hydrothermal assisted solution at an initial pH of 5–6, containing calcium carbonate precursor and diammonium hydrogen phosphate with a Ca/P ratio of 1.67, was autoclaved for carbonated hydroxyapatite (CHA) growth for 24 h at 50, 70, 90, and 110 °C and then allowed to air cool naturally. The hydrothermally obtained powder was subjected to additional analytical evaluation, including XRD, FTIR, and SEM/EDX analysis, providing that the crystal structure, carbonate content, and lattice constants of the A- and B-type CHA formed by varying hydrothermal temperature agreed very well with the A- and B-type carbonated hydroxyapatite as reported in the literature. The hydrothermal process could produce more than 90 wt.% of hydroxyapatite nanoparticles (17–26 nm) with minor monetite and calcite. These experimental findings may aid in synthesizing A- and B-type CHA for medical applications such as bone and enamel.

Room-Temperature Anisotropic Actuation Driven by a Synergistic Order-Disorder and Displacive Phase Transition in a Ferroelectric Crystal.

Actuating materials convert different forms of energy into mechanical responses. To satisfy various application scenarios, they are desired to have rich categories, novel functionalities, clear structure-property relationships, fast responses, and, in particular, giant and reversible shape changes. Herein, we report a phase transition-driven ferroelectric crystal, (rac-3-HOPD)PbI3 (3-HOPD = 3-hydroxypiperidine cation), showing intriguingly large and anisotropic room-temperature actuating behaviors. The crystal consists of rigid one-dimensional [PbI3] anionic chains running along the a-axis and discrete disk-like cations loosely wrapping around the chains, leaving room for anisotropic shape changes in both the b- and c-axes. The shape change is switched by a ferroelectric phase transition occurring at around room temperature (294 K), driven by the exceptionally synergistic order-disorder and displacive phase transition. The rotation of the cations exerts internal pressure on the stacking structure to trigger an exceptionally large displacement of the inorganic chains, corresponding to a crystal lattice transformation with length changes of +24.6% and -17.5% along the b- and c-axis, respectively. Single crystal-based prototype devices of circuit switches and elevators have been fabricated by exploiting the unconventional negative temperature-dependent actuating behaviors. This work provides a new model for the development of multifunctional mechanically responsive materials.

The effects of additive agents on zinc and zinc–nickel alloys electrodeposited on steel substrates in acidic electrolytes

The influence of glycine, as a chelating agent, and triblock copolymer mixture of PPG-PEG-PPG and PEG1000, as a suppressor agent, on the deposition mechanisms of zinc and zinc-nickel alloys were studied by cyclic voltammetry (CV) and potentiometric electrochemical impedance spectroscopy (PEIS), using electrolyte solutions of chlorinated acid. Cyclic voltammetry measurements show that the composition of the electrolytic solution affects the voltammogram profiles. Complementary PEIS investigations allowed the electrodeposition mechanisms to be highlighted depending on the composition of the electrolytic solution. The electrodeposition of zinc, in the absence of additives, occurs in a single cathodic wave from the ZnCl3− species, whereas in the presence of glycine, a second more cathodic reduction wave is relative to the Zn(Gly)22+ species. The presence of the PPG-PEG-PPG and PEG1000 triblock copolymer induces a clear inhibition of the zinc reduction. Nevertheless, the zinc electrodeposition follows a three-dimensional instantaneous nucleation. The zinc electroplating mechanism involves a capacitive semi-circle at high frequency and two inductive loops at medium and low frequencies assigned to two adsorbed intermediates onto the substrate whatever the electrolyte composition. The presence of the polymer mixture affects the zinc reduction by increasing the charge-transfer resistance and the adsorption phenomena on the substrate. The electrodeposition of zinc-nickel alloys reveals a single reduction wave, from ZnCl3− and Ni(Gly)2+ species, and multiple anodic signals depending on the electrolytic composition, according to the presence of glycine to chelate the nickel species. The zinc-nickel electroplating was evidenced to be a multiple-step process with a three-dimensional instantaneous nucleation, including intermediate species adsorbed onto the substrate. The equivalent circuit proposed consists of two capacitive half-circles separated by an inductive loop for any electrolytic solution. However, the impedance spectra were affected by the presence of glycine by modifying the inductive loop reflecting the first adsorbed intermediate (Ni(I)ads). The morphology of zinc and zinc-nickel, with a nickel content between 14 and 19 wt%, is affected by the electrolyte composition, however with the same crystal lattice. The preferential orientation of the lattice was shown to depend on the additives present in the solution.

Symmetry-selective quasiparticle scattering and electric field tunability of the ZrSiS surface electronic structure

Three-dimensional Dirac semimetals with square-net non-symmorphic symmetry, such as ternary ZrXY (X = Si, Ge; Y = S, Se, Te) compounds, have attracted significant attention owing to the presence of topological nodal lines, loops, or networks in their bulk. Orbital symmetry plays a profound role in such materials as the different branches of the nodal dispersion can be distinguished by their distinct orbital symmetry eigenvalues. The presence of different eigenvalues suggests that scattering between states of different orbital symmetry may be strongly suppressed. Indeed, in ZrSiS, there has been no clear experimental evidence of quasiparticle scattering reported between states of different symmetry eigenvalues at small wave vector q⃗. Here we show, using quasiparticle interference, that atomic step-edges in the ZrSiS surface facilitate quasiparticle scattering between states of different symmetry eigenvalues. This symmetry eigenvalue mixing quasiparticle scattering is the first to be reported for ZrSiS and contrasts quasiparticle scattering with no mixing of symmetry eigenvalues, where the latter occurs with scatterers preserving the glide mirror symmetry of the crystal lattice, e.g. native point defects in ZrSiS. Finally, we show that the electronic structure of the ZrSiS surface, including its unique floating band surface state, can be tuned by a vertical electric field locally applied by the tip of a scanning tunneling microscope (STM), enabling control of a spin–orbit induced avoided crossing near the Fermi level by as much as 300%.

Thermoelastic modeling of cubic lattices from granular materials to atomic crystals

When a cubic lattice is confined by a surface layer, the effective thermoelastic properties can be tailored by the prestress produced by the surface. The thermal expansion coefficient, temperature derivative of elasticity, and the equation of state (EOS) of the solid depend on the potential of each bond and the lattice structure, which can be predicted by the recently developed singum model. This paper first uses a granular lattice confined by a spherical shell to demonstrate singum modeling of the thermoelastic behavior of the cubic lattices and then extends it to atomic crystal lattices by considering the surface tension and long-range interactions. Given the elasticity and the EOS of a cubic crystal, the interatomic potential can be inversely derived. As the bond length changes with thermal expansion and pressure, the singum model predicts the temperature- and pressure-dependent elasticity. Using the orientational average, isotropic elastic constants can be obtained for polycrystals. The case study of copper (Cu) demonstrates the versatility of the model for different cubic lattices and predicts the experimental results of pressure- and temperature-dependent elasticity. The singum model is general for different lattice types and EOS forms and provides clear physical and mechanical meanings to correlate the interatomic potential, EOS, and elasticity in the closed-form formulation, which is very useful in engineering design and analysis of metal structural members in fire, geothermal, and space applications without the needs of large-scale numerical simulations.