Crystal Growth & Design最新文献

Designing and realizing high-performance p-type transparent conductive oxide films represent a global materials challenge. Mg-doped CuCrO₂ delafossite has emerged as an ideal candidate for p-type transparent conductive oxides due to its balanced combination of favorable optical transmittance and electrical conductivity in the visible region. In this study, epitaxial CuCr_1–xMg_xO₂ (x = 0, 0.01, 0.03, 0.05, 0.07, 0.09) thin films were successfully fabricated on Al₂O₃ substrates using chemical solution deposition. We systematically investigated the effects of the Mg doping concentration on crystal structure, surface morphology, electrical transport properties, and optical transmittance. The results demonstrate that high-quality epitaxial growth was confirmed by X-ray diffraction (XRD) and φ-scan analysis. Mg doping synergistically regulates optoelectronic properties by introducing acceptor levels─resistivity decreased by orders of magnitude with increasing doping concentration, attributed to significantly enhanced hole carrier concentration. Concurrently, the optical bandgap progressively narrowed, with UV–vis–NIR spectroscopy confirming continuously tunable direct bandgap characteristics. This work elucidates the physical mechanism governing optoelectronic property modulation in epitaxial CuCr_1–xMg_xO₂ thin films, advancing both the development of epitaxial delafossite thin film fabrication techniques and further applications in transparent electronics.

While calcium carbonate is well known to exist in a range of different crystalline forms, including anhydrous polymorphs and hydrated phases, a new crystalline form─calcium carbonate hemihydrate (CCHH)─was reported in 2019 and has recently been observed in a biogenic material. The crystal structure of CCHH reported from diffraction studies is monoclinic, although a subsequent computational investigation suggested that an orthorhombic description of the structure may be more appropriate. Herein, we report experimental solid-state NMR characterization of CCHH, focused on solid-state ¹H NMR and ¹³C NMR measurements, including analysis of ¹H–¹³C heteronuclear correlation spectroscopy (HETCOR) and ¹³C chemical shift anisotropy (CSA) data, which reveals further insights into the structural and symmetry properties of this material. We demonstrate by means of DFT-GIPAW calculations that the monoclinic and orthorhombic descriptions of the crystal structure of CCHH are readily distinguishable on the basis of solid-state ¹H and ¹³C NMR data. Our experimental solid-state NMR measurements are shown to support the orthorhombic description of the crystal structure rather than the monoclinic description.

Two crystalline polymorphs of a conjugated organic fluorophore were obtained through separate synthetic protocols despite crystallizing under identical conditions. The unique polymorphs were confirmed by single-crystal X-ray diffraction. The two polymorphs had markedly different supramolecular packing. Thus, polymorph A was stabilized by directional C–H···N/S interactions with limited π overlap, while polymorph B assembled into extended π–π stacks and a denser network with short contacts. These structural differences resulted in distinct photophysics. Indeed, the emission quantum yield (Φ_fl) of Polymorph B was 4-fold lower along with multiexponential excited state kinetics compared to Polymorph A in addition to a 38 nm blue-shift in the emission. The metastable polymorph B could be converted to the thermodynamically stable Polymorph A by grinding the pristine crystal. Both intra- and supramolecular contacts could be leveraged to guide the crystal packing for modulating the emissive properties of the intrinsic fluorophores.

Precise regulation of metal cluster structures and luminescent properties is critical for the advancement of their practical applications. Copper clusters have garnered extensive attention due to their abundant, inexpensive, and excellent luminescent properties. However, their strong metallophilic interactions often restrict emissions to the red region, making it challenging to controllably tune their emission range─especially toward high-energy bands. In this work, we propose a counterion-induced strategy to modulate the structure and luminescence properties of copper clusters. By adjusting the size of counter cations, we induced varying degrees of distortion in Cu₅ anionic cluster structures and directed their crystallization into distinct assembly patterns, successfully obtaining four cluster-based luminescent materials. Theoretical calculations reveal that under the steric effects of counter cations, the four Cu₅ clusters exhibit different molecular configurations and intercluster interaction strengths, enabling broad-range emission wavelength modulation (546 → 687 nm). Notably, Cu₅-Pr-a and Cu₅-Et demonstrate unconventional high-energy emissions. This study provides a novel approach and experimental reference for the precise control of metal cluster structures and luminescent properties.

Poly(lactic acid) (PLA) porous materials hold great promise for biomedical applications such as tissue engineering and drug delivery. However, achieving precise control over their pore architecture remains challenging due to the complex interplay between phase separation and crystallization. This study investigates the temperature-directed competition among cocrystallization, homocrystallization, and stereocomplex (SC) crystallization in PLA/dimethylformamide (DMF) systems during thermally induced phase separation (TIPS). By quenching PLLA/PDLA solutions with varying ratios over a wide temperature range (−20 to 30 °C), we demonstrate that the final morphology, which ranges from three-dimensional nanofibrous networks to well-ordered lamellae or monodisperse microspheres, is intricately governed by the dominant crystallization pathway. At lower temperatures, the formation of PLA–DMF ε-complex crystals templates a nanofibrous structure upon solvent removal. In contrast, at elevated temperatures, SC crystallization is exclusively promoted in equimolar blends, resulting in coarse spherical particulates. Furthermore, the morphology and microstructure are found to influence the thermal stability and enzymatic hydrolysis rate of the PLA porous materials, without inducing cytotoxicity. These findings provide deeper insight into the crystallization-phase separation interplay in PLA systems and establish a versatile strategy for fabricating PLA-based materials with tailored morphologies to meet specific biomedical requirements.

The crystal growth of two families of lanthanide zirconium molybdates exhibiting luminescence properties is reported. Crystals of Ln₂Zr₃(MoO₄)₉ (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd) and Ln₂Zr₂(MoO₄)₇ (Ln = Tb, Dy) were obtained by the molten flux growth technique. Ln₂Zr(MoO₄)₅ (Ln = Ho, Er, Tm, Yb, Y) were synthesized by solid-state reactions. The compounds Ln₂Zr₃(MoO₄)₉ (Ln = La- Nd, Sm–Gd) crystallize in the space group R3̅c with lattice parameters of a = b = 9.85200(10)–9.78700(10), c = 59.1112(9)–57.9131(10) Å. The second class of compounds Ln₂Zr₂(MoO₄)₇ (Ln = Tb, Dy), crystallize in the space group C2/c with lattice parameters of a = 20.7457(4)–20.7015(4) Å, b = 9.8556(2)–9.8395(2) Å, c = 13.8424(3)–13.8261(2) Å, and β = 113.5210(10)–113.5440(10)°. The third class of compounds, Ln₂Zr(MoO₄)₅ (Ln = Ho, Er, Tm, Yb, Y), crystallizes in the space group Cmc2₁ with lattice parameters of a = 21.031(2)–20.824(4) Å, b = 9.7473(5)–9.6540(2) Å, and c = 9.7961(9)–9.l7420(2) Å. The structures consist of frameworks where LnO₉ and ZrO₆ polyhedra are connected with MoO₄ groups via corner-sharing. Solid-state reactions were used to make bulk polycrystalline samples for property measurements. Optical properties of Ce₂Zr₃(MoO₄)₉, Sm₂Zr₃(MoO₄)₉, Eu₂Zr₃(MoO₄)₉, and Tb₂Zr₂(MoO₄)₇ were investigated. In addition, the magnetic properties of Ce₂Zr₃(MoO₄)₉, Sm₂Zr₃(MoO₄)₉, Gd₂Zr₃(MoO₄)₉, and Tb₂Zr₂(MoO₄)₇ are reported.

Ionic liquids (ILs) represent an extensively studied class of materials. Nevertheless, their solid state has often been overlooked, leading to frequent knowledge gaps about their phase behavior or crystal structures that such materials may form. This work focuses on the development of a crystal structure prediction (CSP) scheme suitable for aprotic ILs, relying on quasi-random crystal structure generation, dispersion-corrected density functional theory (DFT-D)-based energy reranking, and quasi-harmonic phonon treatment. The interpretation of peculiar differences in the crystallizability of very similar ILs upon cooling of their melts is presented. The versatility of the computational protocol is validated for [emIm][MeSO₃], an IL known to be polymorphic. The current CSP identifies the [emIm][MeSO₃] polymorph that is thermodynamically stable in reality at the top of the stability ranking, both in terms of DFT-D refined lattice energies and quasi-harmonic Gibbs free energies. Several low-energy, high-entropy crystal structures are also proposed for [emIm][MeSO₃] as candidates for the remaining known polymorphs with yet unresolved crystal structures. Our CSP modeling explains the extraordinary reluctance of [emIm][EtSO₄] to crystallize due to its glassy shape of the polymorph landscape with no distinct global energy minimum crystal structure.

The edge-defined film-fed growth (EFG) method, as the core technology for growing high-quality gallium oxide (β-Ga₂O₃) single crystals, constitutes a complex system engineering. The precise control of thermal field distribution during crystal growth has emerged as one of the critical factors for enhancing crystal quality. Machine learning (ML) techniques have demonstrated tremendous potential in optimizing the thermal field design, particularly in predicting the influence of equipment dimensions on thermal field distribution. Centered on the application of ML in the thermal field design of β-Ga₂O₃, this paper proposes a prediction model based on equipment dimensions. A dataset containing 5000 sets of geometric parameters of equipment was constructed. A predictive model was established based on the machine learning Categorical Boosting (CatBoost) model, and explainable ML models were employed to analyze the relationship between equipment dimensions and thermal field distribution. Shapley additive explanation values were utilized to quantify the impact of inputs on outputs, thereby identifying the key indicators influencing the thermal field design in the EFG method. The optimal geometric configuration was obtained through multiobjective optimization, facilitating the growth of higher-quality β-Ga₂O₃ single crystals. Finally, the key indicator factors affecting the temperature gradient at the solid–liquid interface were verified through experiments.

Layered silicates can be versatile precursors for the preparation of porous materials. Their transformation into zeolites typically employs organic structure-directing agents and seed-assisted crystallization, as in interzeolite conversions. Several zeolite topologies have been synthesized using magadiite; however, the role of magadiite in these processes remains unclear. The recent resolution of the magadiite structure provides an opportunity to integrate and reinterpret existing knowledge on this topic. Here, we report an unusual conversion of the layered hydrous silicate magadiite into mordenite triggered solely by the external addition of aluminum to a precrystallized magadiite gel. Aluminum disperses in the solid, occupying distinct framework sites, while a reorganization of ring-building units occurs, resulting in a marked decrease in the amount of surface silanol/silanolate groups. This restructuring proceeds without evidence of amorphization, accompanied by a progressive increase in surface area and growth of morphologically prismatic mordenite particles in contact with the magadiite plate-like particles. This transformation of a dense pyknosil-like structure into an open zeolite framework exhibits features of solid-phase reorganization triggered by aluminum supplied from the solution. These findings introduce a seed- and OSDA-free route for converting layered silicates into zeolites, expanding the conceptual and synthetic space for tailored microporous materials.

Although the Microwave Plasma Chemical Vapor Deposition (MPCVD) method used for diamond growth has been studied for several decades, single crystal diamond as a semiconductor material substrate still faces the challenge of being unable to simultaneously achieve a high growth rate and high crystal quality. This study presents a combined simulation and experimental approach for the fabrication of 2 in. mosaic single crystal diamond using the MPCVD method. A multiphysics model incorporating electromagnetic, plasma, and heat transfer modules was developed to analyze the distributions of temperature, electron density, electric field, and reactive species during diamond growth. Based on simulation insights, a novel molybdenum substrate holder with circumferential grooves was designed to achieve a uniform temperature distribution, limiting lateral temperature variation to within 20 K across the substrate surface. The simulation predicted a peak growth rate of 13.6 μm/h at the center and an average rate of 12.2 μm/h over the central 1 in. region area, consistent with experimental observations. A total of 39 single crystal diamond substrates were arranged in a mosaic pattern and subjected to a multistep MPCVD growth process, followed by laser edge removal and mechanical polishing. High-resolution X-ray diffraction and Raman mapping confirmed high crystalline quality, with full width at half-maximum(FWHM) values of 128.10–169.50 arcsec in XRD and 2.43–2.70 cm^–1 in Raman spectra. The homoepitaxial regions exhibited superior crystal quality compared to lateral-epitaxial junctions, which exhibited mild stress concentration. This work establishes a scalable and quality-controllable pathway for producing large-area single crystal diamond wafers suitable for high-performance semiconductor devices.