Precursor Phase Research Articles

The role of fluocerite in the genesis of bastnäsite: mechanistic insights and transformation pathways.

Fluocerite is a rare earth element (REE) fluoride found as an accessory mineral in magmatic-hydrothermal REE ore deposits, including alkaline complexes and carbonatites, where it is often associated with REE-fluorocarbonates. This study investigates the crystallisation kinetics, mechanisms and energetics of fluocerite (REEF3) and its role as a precursor phase of bastnäsite, one of the key minerals used for the extraction of REE. Fluocerite was synthesized by reacting pure fluorite (CaF2) with La-, Ce- and Nd-bearing solutions at temperatures ranging from ambient to low hydrothermal (30-90 °C). The synthetic fluocerites were then placed in contact with Na2CO3 solutions at temperatures up to 200 °C. A combined approach using powder X-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy was used to determine the nature and quantify the crystallising solids. Our findings reveal a temperature-dependent fluorite-fluocerite transformation, with completion observed within 1 hour at 90 °C and extending to around 30 days at 30 °C. The rate of crystallisation decreases proportionally with the atomic number of the rare earth elements. On the other hand, the carbonation reaction of fluocerite exhibits a significantly slower rate, by ∼3 orders of magnitude, in comparison to the fluorite-fluocerite transformation, regardless of temperature conditions. The synthetic La, Ce and Nd fluocerites transformed into bastnäsite at all temperatures, also forming cerianite (CeO2) in the Ce-bearing experiments and metastable kozoite, NdCO3OH(orth), in the Nd-bearing experiments. Activation energies of fluocerite nucleation increase proportionally with the ionic radii of the REE (81 ± 6 (La); 84 ± 5 (Ce), 96 ± 10 (Nd) kJ mol-1), while the activation energies associated with fluocerite crystallisation are slightly higher for La (90 ± 12 kJ mol-1) and similar for Ce and Nd (76 ± 12 and 72 ± 8 kJ mol-1, respectively).

Impact of Rare Earth Elements on CaCO3 Crystallization: Insights into Kinetics, Mechanisms, and Crystal Morphology.

This study investigated the crystallization kinetics and mechanisms of calcium carbonate (CaCO3) in the presence of rare earth elements (REEs) including lanthanum (La), neodymium (Nd), and dysprosium (Dy). Through a comprehensive approach utilizing UV-vis spectrophotometry, powder X-ray diffraction, and high-resolution electron microscopy, we examined the effects of REEs on CaCO3 growth from solution at varying concentrations and combinations of REEs. Our findings highlight that even trace amounts of REEs significantly decelerate the rate of CaCO3 crystallization, also leading to alterations in crystal morphology and mechanisms of growth. The impact of REEs becomes more pronounced at higher concentrations and atomic mass, although the potential formation of poorly ordered REEs carbonate precursor phases can result in a decrease in the REE3+/Ca2+ ratio, influencing the crystallization rate of CaCO3. Vaterite and calcite were identified as the main crystallized polymorphs, with vaterite exhibiting distinct growth defects and calcite developing complex morphologies at higher REEs concentrations and an internal architecture suggesting a nonclassical growth route. We propose that REEs ions selectively adsorb onto different calcite surfaces, impeding growth on specific sites and resulting in intricate morphologies.

In situ study of the reaction phase A plus high-P clinoenstatite to forsterite plus water at reduced water activity

Abstract. We examined the reaction phase A plus high-P clinoenstatite to forsterite plus water (Reaction R1) by means of in situ X-ray diffraction measurements with the large volume press at the synchrotron PETRA III, Hamburg. Contrary to the study of Lathe et al. (2022), in which all experiments on Reaction (R1) were performed at a water activity of 1, the reversed experiments presented in this study were performed at reduced water activity with mole fractions of about XH2O= XCO2=0.5. The intention of this investigation was to test the observation made by Perrillat et al. (2005), which was that dehydration reactions are kinetically faster at reduced than under water-saturated conditions. The position of Reaction (R1) at the reduced conditions was determined by reversal brackets at 9.1 and 9.5 GPa (630 and 700 ∘C), at 9.7 and 10.0 GPa (725 and 700 ∘C), at 9.8 and 10.2 GPa (675 and 750 ∘C), and at 10.5 GPa (675 and 740 ∘C). Additionally, we performed two offline experiments with brackets at 10.0 and 10.6 GPa (750 and 700 ∘C, respectively) that are in agreement with the results of the in situ experiments. We do not observe any “intermediate” precursor phase in our experiments. The equilibrium of Reaction (R1) is shifted by about 100 ∘C to lower temperature compared to the results under water-saturated conditions. Thus, at a water activity (aH2O) below 1 the phase A plus clinoenstatite dehydration reaction can only occur in extremely cold subduction slabs. The kinetics of Reaction (R1) dehydration at reduced water activity is slower than that determined previously by Lathe et al. (2022) under water-saturated conditions. Thus, the above-mentioned hypothesis of Perrillat et al. (2005) could not be confirmed. However, in both of our studies on Reaction (R1), the newly formed dehydration product forsterite was of nanometer size, which supports earlier experimental observations, which is that product phases of dehydration reactions are generally very fine-grained and might promote the concept that intermediate-depth earthquakes in subduction zones are initiated by mechanical instabilities from extremely fine-grained materials formed during dehydration reactions.

Mega broadband photoresponsivity in degradation-controlled super-halide PF6 substituted Perovskite@graphene hybrid photodetectors

We present, probably for the first time, the use of super-halide PF6 as a substitution for iodine in the bulk precursor phase of FAPbI3 for stable perovskite@graphene photodetectors. Our novel approach confers improved stability of perovskite, as demonstrated by synchrotron-based time-dependent nano-X-ray Fluorescence mapping of iodine. We observed a predominantly high α-phase (with weaker δ and PbI2 phases) in the superior 10 % PF6-substituted perovskite, as revealed by synchrotron-based GIWAXS. Our FAPbI3-x(PF6)x@graphene photodetectors exhibited exceptional performance under power-dependent broadband illumination. In contrast to pure FAPbI3@graphene devices (x = 0), which showed time-dependent bi-directional photoresponse indicative of degradation, our 10 % PF6-substituted perovskite@graphene devices (x = 0.1) displayed unprecedented, positive, and stable photoresponsivity (∼1.01 × 106 A W−1), along with a high detectivity (D*) of 5 × 1014 Jones. Our devices also demonstrated remarkable sensitivity to signals from domestic appliances, exhibiting response times ranging from 93 to 101 ms. We model the photodetection mechanism using experimental band structure measurements to explain our results. Our findings suggest that our FAPbI3-x(PF6)x@graphene photodetectors hold great promise for a range of applications in the fields of optoelectronics and sensing. In addition, our findings can contribute to the development of more stable and efficient perovskite solar cells, thereby advancing the solar cell research field.

Evolution of kinetics and pore water composition during hydration of a CAC‐Calcite system by addition of Na5P3O10

AbstractIt was analysed how a low Na5P3O10 (STPP) concentration influences the hydration of a calcium aluminate cement. It is known that the hydration of a CAC‐Calcite system precipitates C2AHX as a precursor phase at 23°C during hydration before the formation of hemi‐ or monocarbonate and the additional formation of CAH10 and AH3. In our study the addition of 0.2 and 1.0 wt.% STPP (bwoc) to a CAC‐Calcite system at 23 °C and with a w/b of 0.33 was investigated and is compared with mixes without STPP addition. Heat flow calorimetry data showed that STPP accelerates the main reaction. Moreover, an additional heat flow event within the first 30 minutes was detected by STPP addition. However, from the results of QXRD analysis, crystalline hydrate phases are formed only during the main reaction. These are CAH10, C2AHX, AH3, hemicarbonate and monocarbonate. STPP shows an influence on the amount of crystalline C2AHX, otherwise, no difference in the qualitative phase content is observed. Gillmore‐Needle‐Testing (IMETER device) could observe an accelerated hardness development during the early heat flow event despite initially reduced viscosity. Pore water studies and thermodynamic modelling (PhreeqC) indicate the formation of an amorphous C‐P‐H phase during this early heat flow event.

Adsorption of Nickel Ions on the γ-Alumina Surface: Competitive Effect of Protons and Its Impact on Concentration Profiles.

Mesoporous γ-alumina is used as an adsorbent in the decontamination of water from heavy metals (e.g., nickel and cobalt) and as a support for heterogeneous catalysts prepared by impregnation. In these cases, alumina extrudates are in contact with aqueous solutions containing precursors of the active metal phase to be deposited. The proton concentration (or pH) in the metal solution in contact with alumina can impact the adsorption efficiency of decontamination processes and the activities of catalysts. Yet, it is difficult to quantify the effect of the pH inside the pores since protons are not detected by classical imaging techniques. In this article, the effect of protons on nickel adsorption on alumina is evaluated using a novel technique coupling liquid analysis (pH, conductivity, and UV/vis) and laser-induced breakdown spectroscopy (or LIBS) analysis of concentration gradients inside the solid. Both methods are in excellent agreement. The results show a slow diffusion of protons inside alumina pores (diffusion continues even after 940 min), yielding high proton concentration gradients. On the other hand, the nickel species penetrate the extrudates faster but are slowly displaced by protons under certain operating conditions. As a result, different metal concentration profiles are obtained, depending on the initial pH and contact time. These findings are interesting in catalysis since they prove the possibility of controlling the deposition of the active metal on catalysts by regulating the operating conditions of impregnation. For typical industrial impregnation times (a few minutes to 1 to 2 h), protons do not have enough time to deeply penetrate inside extrudates, so the initial pH of the metal solution will have nearly no effect on the metal distribution. Conversely, decontamination processes have much longer contact times; therefore, lower initial pH values should have negative impacts on the adsorption efficiency due to the protons displacing the adsorbed nickel.

Smoldering Multiple Myeloma Progressing to Active Multiple Myeloma Vs De-Novo Active Multiple Myeloma - a Comparison of Disease Characteristics, Organ Involvement and Outcomes in a Real-Life Multicenter Retrospective Cohort Study

Background Smoldering Multiple Myeloma (SMM) is an intermediate precursor phase in Multiple Myeloma (MM) evolution. SMM patients are monitored for progression to active disease, supposing such surveillance will identify myeloma-defining events (MDEs) early and consequently hasten treatment, prevent complications and improve outcomes. To what extent this approach is successful is not well established. We aimed to compare disease characteristics, end organ involvement and outcomes between SMM patients who progressed to active MM vs newly diagnosed MM (NDMM) patients. Methods We performed a two-center real-world case-control retrospective cohort study. Consecutive patients receiving first line treatment for MM after progressing from SMM were identified; each was matched by age and year of diagnosis (±2 years) to a patient first presenting as NDMM. SMM, MM, MDEs and response were defined by the International Myeloma Working Group (IMWG) criteria (2014, 2016); progression-free survival (PFS) and overall survival (OS) were calculated from active MM diagnosis. Data was extracted in 07/2023. Results We identified two cohorts of newly diagnosed MM patients, presented between 09/2008and 02/2023: Post SMM (P-SMM, N=57) and De novo MM patients (D-MM, N=57). Median follow up time was 38.6 months (IQR 23.3 - 72.7). There were no differences in baseline demographics between gender (p=.19), and median age: 73.4 (range 42 - 88) in the P-SMM group and 72.9 (range 42 - 92) in the D-MM (p=.75). Comparing MDEs using SLiM-CRAB criteria between groups, more patients in the D-MM group presented with hypercalcemia (p=.02) and lytic lesions (p=.03). Other domains were similar between groups: anemia (p=.68), renal failure (p=.59), FLC ≥100 (p=.76), % bone marrow plasma cells (BMPC) ≥ 60 (p=.11). D-MM patients had higher ISS/R-ISS at presentation: ISS ≥ II (30 vs 11, p=.004) and R-ISS ≥ II (31 vs 13, p=.002). Additional disease characteristics were balanced at diagnosis of active MM: heavy chain (p=.53), light chain type (p=.69), M-Protein level (p=.23), extra medullary disease (p=.14), Al amyloidosis (p=.13), and high-risk cytogenetics (p=.65). Bone involvement was more frequent in D-MM vs P-SMM patients, with significantly more pathological fractures (p=.006), bone pain (p=.001), and a detrimental bone disease (p=.001) (defined as combination of pathological fracture and/or ≥ 3 lytic lesions) (Figure 1B). Significantly higher rates of hospital admissions for upfront therapy initiation were seen in the D-MM group compared with P-SMM, 18 vs 7 (p=.008), as well as more potentially irreversible MDEs (pathological fractures and/or renal injury): 43 (p=.009) vs 31 (41.9%) respectively. Treatment patterns were balanced excluding bortezomib used more often in the D-MM (p=.009) and daratumumab in the P-SMM group (p=.03). Best response rates to upfront therapy were comparable between groups, (p=.71) as well as ≥ very good partial response (VGPR) rates (p=.88), 52.4% vs 47.6% in P-SMM and D-MM respectively. Frequency of skeletal imaging tests up-to 2-year period prior to active MM diagnosis were associated with lower rates of detrimental bone disease (p=.006). Despite the similar ≥ VGPR rates between cohorts, PFS was longer in the P-SMM group vs D-MM group, 39.6 vs 21.6 months, respectively (log-rank 0.01). A superior PFS in P-SMM group vs D-MM remained after correction for % BMPC at diagnosis (46.2% vs 58.8%, p=.03). OS was also longer, not reached vs 93.7 months (log-rank=.047) (Figure 1A). Conclusions Patients who develop active MM post SMM clinic surveillance presented with a lower disease burden, as well as reduced rates of detrimental bone disease and potentially irreversible MDEs. P-SMM patients had favorable PFS and OS rates. This may reflect effectiveness of SMM monitoring resulting in lower disease burden at time of treatment onset; favorable long-term outcomes may also be affected by variability in treatment patterns between groups. Another possible explanation is that patients with more indolent MM biology may have extended periods of precursor condition, hence increasing their likelihood to be diagnosed by incidental laboratory tests during their SMM phase.

Structural Characterization of Graphite Analogue BCx Synthesized Under Various Conditions and Its Application to Ti Intercalation.

A graphite-like material boron carbide (BCx) was synthesized under various heat treatment conditions and extensively characterized. First, we synthesized the BCx precursor phase by a single-step reaction using a mixed solution of BBr3 and C6H6. We confirmed that the precursor phase had a graphite-like structure with B-C chemical bonds, but its crystallinity was poor. To improve their crystallinity, we annealed the precursor sample at high temperature using a high-frequency furnace and determined the annealing condition. We also investigated the magnetic properties of BCx. The high-temperature annealing for the precursor phase yields the highest Pauli paramagnetic susceptibility χPauli, indicating the highest density of states at the Fermi level. Accordingly, the high-temperature treatment for the precursor phase is significant to improve its crystallinity and physical properties. In addition, we synthesized a Ti-intercalated material TiBC by using the same procedure as that for making the BCx precursor phase. The crystal structure can be indexed by the AlB2 structure, indicating that Ti atoms are intercalated between the BC layers. The χPauli value of TiBC is obtained to be 1 order of magnitude smaller than that of BCx, suggesting the compensation of hole carriers by electron doping through Ti intercalation into the BCx system.

Single-Cell RNA Sequencing Reveals Hypo-Responsiveness of T and NK Cells to Interferon Stimulation As an Immune Hallmark in Asymptomatic Waldenstrom's Macroglobulinemia

Introduction Waldenstrom macroglobulinemia (WM) is a rare, indolent non-Hodgkin lymphoplasmacytic lymphoma of the bone marrow (BM), characterized by monoclonal IgM protein production. WM is preceded by IgM monoclonal gammopathy of undetermined significance (IgM MGUS) and smoldering WM (SWM), which are clinically detectable but asymptomatic precursor phases (collectively referred to as asymptomatic WM; AWM). Recent work has revealed significant changes in the immune microenvironment of patients with overt WM, however, less is known about immune dysregulation in patients with early-stage disease. Methods We performed 5' single-cell RNA sequencing (scRNAseq) on BM immune cells from patients with AWM (n=28), healthy donors (HD, n=23), and patients with smoldering multiple myeloma (SMM) (n=27). We also performed an in vitro stimulation experiment using universal Type I interferon (IFN) and subsequent scRNAseq on bone marrow mononuclear cells (BMMCs) and peripheral blood mononuclear cells (PBMCs) from AWM (n=3) and HD (n=3). Results Overall, we annotated 210,019 immune cells, excluding normal B cells. Despite their early stage, AWM patients showed significantly altered BM immune cell composition, including increased proportions of CD56dim NK cells, CD8+ effector memory cells, and CD16 + Monocytes and decreased proportions of pro-inflammatory CD14 + monocytes and activated and interferon (IFN)-stimulated T and NK cells (q<0.2). Low-risk AWM presented similar changes in immune cell composition as intermediate- and high-risk AWM, implying that compositional alterations may be established early in the disease course. Notably, however, the proportion of Tregs was significantly increased in patients with SWM compared to IgM MGUS (p=0.04), suggesting that Tregs may play a role in disease progression. Next, we compared BM immune cell composition between patients with AWM and SMM. In both tumor types, patients showed significantly higher proportions of CD56dim NK cells and CD16 + monocytes compared to healthy donors. However, strikingly, a significant decrease in activated and IFN-stimulated T and NK cells was only observed in AWM, suggesting it may be a hallmark of disease. Comparison of BMMCs and PBMCs from patients with AWM following in vitro culture revealed that the lack of IFN-stimulated cells was systemic-in both BMMCs and PBMCs-although the effect was significantly more pronounced in BMMCs than PBMCs. Interestingly, while in vitro stimulation with Type I IFN resulted in the generation of IFN-stimulated T and NK cells in both HD and AWM, the levels of IFN stimulation did not entirely normalize, reproducing the gradient observed in the control samples without in vitro stimulation: AWM BM < AWM PB < HD BM. To test whether the observed defect was due to a lack of IFN in AWM, we next compared the gene expression profile of monocytes from AWM and HD, which revealed significantly higher activity of the IFN signature in monocytes from AWM compared to HD (p < 10 -5). This suggests that IFN levels in patients are at least not reduced. Collectively, these results indicate that T and NK cells from AWM are hypo-responsive to IFN stimulation, despite the presence of normal or possibly increased IFN in the BM microenvironment. Conclusion Our results indicate that despite the absence of symptoms, patients with AWM already have immune dysregulation in the BM, including the absence of IFN-stimulated T and NK cells, which may provide a rationale for therapeutic intervention. Previous studies have demonstrated clinical responses to therapeutic IFN administration, suggesting that novel formulations with improved therapeutic windows may have a role in treating patients with WM in the future.

Coherent lamellar intergrowth in alkali feldspar

A thermodynamic analysis of coherent lamellar intergrowth resulting from the exsolution of initially homogeneous alkali feldspar is presented. In contrast to earlier treatments, where the simplifying assumption of zero strain in the lamellar interfaces was used, our treatment is more general. The elastic stresses and strains associated with coherent lamellar intergrowth of Na-rich and K-rich alkali feldspar are calculated by minimising the overall elastic energy of the lamellar microstructure. At given pressure and temperature, the elastic energy depends on the volume proportions of the two lamellar types, and thus on the composition of the homogeneous precursor feldspar. As a consequence, there is no single coherent solvus for alkali feldspar, but coherent solvi are different for different compositions of the homogeneous precursor phase. Experimentally observed lamellar orientations agree with those predicted by minimising the strain energy on a set of all possible lamellar orientations.

ACP-Mediated Phase Transformation for Collagen Mineralization: A New Understanding of the Mechanism.

Despite significant efforts utilizing advanced technologies, the contentious debate surrounding the intricate mechanism underlying collagen fibril mineralization, particularly with regard to amorphous precursor infiltration and phase transformation, persists. This work proposes an amorphous calcium phosphate (ACP)-mediated pathway for collagen fibril mineralization and utilizing stochastic optical reconstruction microscopy technology, and has experimentally confirmed for the first time that the ACP nanoparticles can infiltrate inside collagen fibrils. Subsequently, the ACP-mediated phase transformation occurs within collagen fibrils to form HAP crystallites, and significantly enhances the mechanical properties of the mineralized collagen fibrils compared to those achieved by the calcium phosphate ion (CPI)-mediated mineralization and resembles the natural counterpart. Furthermore, demineralized dentin can be effectively remineralized through ACP-mediated mineralization, leading to complete restoration of its mechanical properties. This work provides a new paradigm of collagen mineralization via particle-mediated phase transformation, deepens the understanding of the mechanism behind the mineralization of collagen fibrils, and offers a new strategy for hard tissue repair.

“A fine wine, better with age”: Circular economy historical roots and influential publications: A bibliometric analysis using Reference Publication Year Spectroscopy (RPYS)

AbstractIn this study, we used the Reference Publication Year Spectroscopy (RPYS) method to explore the historical roots and influential publications of circular economy (CE) studies. Unlike traditional literature reviews, this method allows us to analyze frequently cited works over specified years, assisting in tracing the growth of research subjects over time and quantifying the impact of these citations. We reviewed over 8395 publications and 302,377 cited references, ranging from 1521 to 2021. Our study uncovered three distinct periods in the evolution of CE studies: (i) a precursor phase (1521–1988) that presented foundational yet indirectly related ideas; (ii) the “historical roots” (1989–2017) featuring seminal research during 12 notably influential years; and (iii) a recent period (2018–2021) characterized by other highly cited studies. Additionally, we identified several influential publications that have introduced innovative viewpoints and advocated for a systematic approach to CE, shaping the present direction of CE research. Our study not only provides essential context for future studies, helping scholars identify thematic gaps, but also frame their research within the existing body of knowledge, and contribute toward a comprehensive, multifaceted understanding of CE.

Evidence for liquid-liquid phase separation during the early stages of Mg-struvite formation.

The precipitation of struvite, a magnesium ammonium phosphate hexahydrate (MgNH4PO4 · 6H2O) mineral, from wastewater is a promising method for recovering phosphorous. While this process is commonly used in engineered environments, our understanding of the underlying mechanisms responsible for the formation of struvite crystals remains limited. Specifically, indirect evidence suggests the involvement of an amorphous precursor and the occurrence of multi-step processes in struvite formation, which would indicate non-classical paths of nucleation and crystallization. In this study, we use synchrotron-based in situ x-ray scattering complemented by cryogenic transmission electron microscopy to obtain new insights from the earliest stages of struvite formation. The holistic scattering data captured the structure of an entire assembly in a time-resolved manner. The structural features comprise the aqueous medium, the growing struvite crystals, and any potential heterogeneities or complex entities. By analysing the scattering data, we found that the onset of crystallization causes a perturbation in the structure of the surrounding aqueous medium. This perturbation is characterized by the occurrence and evolution of Ornstein-Zernike fluctuations on a scale of about 1nm, suggesting a non-classical nature of the system. We interpret this phenomenon as a liquid-liquid phase separation, which gives rise to the formation of the amorphous precursor phase preceding actual crystal growth of struvite. Our microscopy results confirm that the formation of Mg-struvite includes a short-lived amorphous phase, lasting >10s.

Varstrometry for Off-nucleus and Dual Subkiloparsec Active Galactic Nuclei (VODKA): Investigating the Nature of SDSS J0823+2418 at z = 1.81, A Likely Lensed Quasar

Dual quasars at small physical separations are an important precursor phase of galaxy mergers, ultimately leading to the coalescence of the two supermassive black holes. Starting from a sample of dual and/or lensed quasar candidates discovered using astrometric jitter in Gaia data, we present a pilot case study of one of the most promising yet puzzling candidate dual quasars at cosmic noon (z ∼ 1.8). Using multiwavelength imaging and spectroscopy from X-ray to radio, we test whether the SDSS J0823+2418 system is two individual quasars in a bound pair at separation ∼0.″64, or instead a single quasar being gravitationally lensed by a foreground galaxy. We find consistent flux ratios (∼1.25−1.45) between the two sources in optical, near-IR (NIR), UV, and radio, and thus similar spectral energy distributions, suggesting a strong-lensing scenario. However, differences in the radio spectral index, as well as changing X-ray fluxes, hint at either a dual quasar with otherwise nearly identical properties or perhaps lensing-based time lag of ∼3 days paired with intrinsic variability. We find with lens mass modeling that the relative NIR positions and magnitudes of the two quasars and a marginally detected central galaxy are consistent with strong lensing. Archival Sloan Digital Sky Survey spectra likewise suggest a foreground absorber via Mg ii absorption lines. We conclude that SDSS J0823+2418 is likely a lensed quasar, and therefore that the VODKA sample contains a population of these lensed systems (perhaps as high as 50%) as well as dual quasars.

Reduced Defect Density in MOCVD-Grown MoS2 by Manipulating the Precursor Phase.

Advancements in the synthesis of large-area, high-quality two-dimensional transition metal dichalcogenides such as MoS2 play a crucial role in the development of future electronic and optoelectronic devices. The presence of defects formed by sulfur vacancies in MoS2 results in low photoluminescence emission and imparts high n-type doping behavior, thus substantially affecting material quality. Herein, we report a new method in which single-phase (liquid) precursors are used for the metal-organic chemical vapor deposition (MOCVD) growth of a MoS2 film. Furthermore, we fabricated a high-performance photodetector (PD) and achieved improved photoresponsivity and faster photoresponse in the spectral range 405-637 nm compared to those of PDs fabricated by the conventional MOCVD method. In addition, the fabricated MoS2 thin film showed a threshold voltage shift in the positive gate bias direction owing to the reduced number of S vacancy defects in the MoS2 lattice. Thus, our method significantly improved the synthesis of monolayer MoS2 and can expand the application scope of high-quality, atomically thin materials in large-scale electronic and optoelectronic devices.

Microtwin evolution and grain boundary phase formation in iron-rich 2:17-type Sm-Co magnets: The effect of iron content

Iron-rich 2:17-type Sm-Co magnets are expected to possess a high energy product due to their elevated saturation magnetization. However, achieving high energy in manufactured magnets poses a challenge, and the mechanism by which the microstructure is affected by the iron content remains unclear. Here, we investigate the microstructure of 2:17-type Sm-Co magnets with varying iron contents in both single solid-solution precursors and aged magnets. Our study indicates that a higher iron content results in microtwin structures with a lower dislocation density in the 1:7H precursor phase, leading to an increased energy barrier and decreased driving force during the subsequent phase transformation. As a result, the 1:7H phase does not completely decompose, causing an increase in the intermediate phases. Furthermore, the impact of iron content on the 1:7H phase causes the aged magnets to have insufficient cell boundaries and massive grain boundary phases. Our study provides an understanding on the iron-rich 2:17-type Sm-Co magnets through the manipulation of the free energies and the defects in the solid-solution precursors.

Stability improvement of CH3NH3PbI3 hybrid perovskite through tin and chlorine doping

In recent years, the hybrid perovskite CH3NH3PbI3 has been widely studied because of its potential application in the fabrication of high efficiency solar cells. The main challenge is to avoid destabilization of this compound under working conditions. Indeed, the MAPbI3 begins to decompose into the precursor phases, a few hours or days after being formed. We reported a stability monitoring of doped compounds CH3NH3Pb0.9Sn0.1I2.8Cl0.2 and CH3NH3Pb0.75Sn0.25I2.5Cl0.5 obtained as films from solutions of the precursors in N-N dimethylformamide on chemically treated glass substrates. The monitoring was carried out using X-Ray diffraction and absorbance measurements in the UV-Vis region. The tetragonal symmetry initially determined for the three compounds, remains almost unaltered for CH3NH3Pb0.75Sn0.25I2.5Cl0.5 even after 600 days, under environmental conditions. The bandgap value for this doped perovskite is 1.44 eV.

Ageing evolution process of the [formula omitted]-phase in Al-Si-Cu-Mg alloys: Atomic-scale observations and first-principles calculations

This work characterizes the high temperature (above 200 °C) ageing process of the θ′ phase in Al-Si-Cu-Mg alloys by using atomic-resolution HAADF-STEM and first-principles calculations. By characterizing the morphology and coarsening growth process of the θP′ and θP1′ precursor, experimental observations suggest that the θP′ phase is based on GPI (Guinier-Preston I) growth expansion. With the ageing time increases and the atomic concentration changes, the Cu atoms on the outside of the θP′ phase rearrange to form the θP1′ phase. Subsequently, the θP2′ precursor phase is formed locally in the θP1′ phase as the Cu atoms gradually enter the θP1′ phase. Besides, it has been observed experimentally that the θP2′ precursor phase can be directly transformed into the θ′ phase without changing the morphology, structure and orientation relationships of the phase. Based on the experimental characterization and theoretical calculations of this work, we have proposed a novel ageing precipitation sequence: SSSS (Super Saturated Solid Solution)→GPI→θP′→θP1′→θP2′→θ′.

Robust and Manufacturable Lithium Lanthanum Titanate-Based Solid-State Electrolyte Thin Films Deposited in Open Air.

State-of-the-art solid-state electrolytes (SSEs) are limited in their energy density and processability based on thick, brittle pellets, which are generally hot pressed in vacuum over the course of several hours. We report on a high-throughput, open-air process for printable thin-film ceramic SSEs in a remarkable one-minute time frame using a lithium lanthanum titanium oxide (LLTO)-based SSE that we refer to as robust LLTO (R-LLTO). Powder XRD analysis revealed that the main phase of R-LLTO is polycrystalline LLTO, accompanied by selectively retained crystalline precursor phases. R-LLTO is highly dense and closely matched to the stoichiometry of LLTO with some heterogeneity throughout the film. A minimal presence of lithium carbonate is identified despite processing fully in ambient conditions. The LLTO films exhibit remarkable mechanical properties, demonstrating both flexibility with a low modulus of ∼35 GPa and a high fracture toughness of >2.0 . We attribute this mechanical robustness to several factors, including grain boundary strengthening, the presence of precursor crystalline phases, and a decrease in crystallinity or ordering caused by ultrafast processing. The creation of R-LLTO-a ceramic material with elastic properties that are closer to polymers with higher fracture toughness-enables new possibilities for the design of robust solid-state batteries.

Room temperature magnetron sputtering and laser annealing of ultrathin amorphous sulfur-rich MoSx films

Room temperature magnetron sputtering of an ultra-thin transition-metal dichalcogenide amorphous precursor and subsequent laser annealing-induced phase transformations were investigated for the synthesis of polycrystalline 2H-MoS2 semiconducting thin films. Radio frequency magnetron sputtering of a MoS3.6 target was used to produce amorphous precursors with S to Mo ratios greater than 2:1 on thermally annealed SiO2 substrates, glass, indium tin oxide coated glass, and amorphous boron-oxy-nitride. The influence of working pressure on the MoS2 and MoS3 interatomic bonding arrangements in amorphous MoSx films was explored with x-ray photoelectron spectroscopy. A 248 nm pulsed laser was used for annealing 1 cm2 sized areas of the amorphous precursor in an ambient atmosphere at fluences of 100–450 mJ for 1, 5, and 10 pulses to form a crystalline 2H-MoS2 phase. The role of laser fluence and substrate choice on phase transformation from the amorphous precursor to the 2H phase, as well as the competition between oxidation, elemental sulfur segregation, and ablation is discussed. Hall effect measurements confirmed p-type behavior of the produced semiconducting films and established mobility and charge carrier density characteristics of the laser-annealed films. The feasibility of scalable processing by combining sputtering from sulfur-rich targets and laser annealing for production of p-type 2H-MoS2 ultrathin films on various substrates is presented.