Sc Content Research Articles

Thermal Stability of the Ferroelectric Properties in 100 nm-Thick Al0.72Sc0.28N.

The discovery of ferroelectricity in aluminum scandium nitride (Al1-xScxN) opens technological perspectives for harsh environments and space-related memory applications, considering the high-temperature stability of piezoelectricity in aluminum nitride. The ferroelectric and material properties of 100 nm-thick Al0.72Sc0.28N are studied up to 873 K, combining both electrical and in situ X-ray diffraction measurements as well as transmission electron microscopy and energy-dispersive X-ray spectroscopy. The present work demonstrates that Al0.72Sc0.28N can achieve high switching polarization and tunable coercive fields in a 375 K temperature range from room temperature up to 673 K. The degradation of the ferroelectric properties in the capacitors is observed above this temperature. Reduction of the effective top electrode area and consequent oxidation of the Al0.72Sc0.28N film are mainly responsible for this degradation. A slight variation of the Sc concentration is quantified across grain boundaries, even though its impact on the ferroelectric properties cannot be isolated from those brought by the top electrode deterioration and Al0.72Sc0.28N oxidation. The Curie temperature of Al0.72Sc0.28N is confirmed to be above 873 K, thus corroborating the promising thermal stability of this ferroelectric material. The present results further support the future adoption of Al1-xScxN in memory technologies for harsh environments like applications in space missions.

Silesiaite, ideally Ca2Fe3+Sn(Si2O7)(Si2O6OH), a new species in the kristiansenite group: crystal chemistry and structure of holotype silesiaite from Szklarska Poręba, Poland, and Sc-free silesiaite from Häiviäntien, Finland

AbstractTwo silesiaite crystals, one from Szklarska Poręba, Poland (type locality), and the other from Häiviäntien, Finland, were studied with electron-probe microanalysis, Raman spectroscopy and single-crystal X-ray diffraction. The crystals have the following compositions normalised to 13 O2– + 1 (OH)– anions: Ca2.001(2)[(Sn1.105(6)Zr0.009(1))Σ1.114(Fe3+0.523(78)Sc0.185(62)Al0.070(14))Σ0.779(Fe2+0.065(12)Mn2+0.041(5)Mg0.003(3))Σ0.110]Σ2.003(Si3.997(2)O13OH), and Ca2.006(8)[(Sn1.110(18)Ti0.006(3))Σ1.107(Fe3+0.648(50)Al0.063(11))Σ0.710(Fe2+0.140(30)Mn2+0.011(3)Mg0.005(2))Σ0.155(Nb0.020(6)Ta0.011(3))Σ0.040]Σ2.009(Si3.991(14)O13OH), respectively. The structure of the crystals was refined in the triclinic system with unconventional space-group symmetry C1 to R1 = 2.02% and 3.56%, respectively. The unit cells were found to be a = 10.0080(2), b = 8.3622(1), c = 13.2994(2) Å, α = 89.987(1), β = 109.095(2), γ = 89.978(1)° and V = 1051.77(3) Å3 for silesiaite from Szklarska Poręba, and a = 9.9985(3), b = 8.3446(2), c = 13.2760(4) Å, α = 89.986(3), β = 109.122(2), γ = 90.020(2)° and V = 1046.55(5) Å3 for silesiaite from Häiviäntien. In both crystals, the Ca sites are occupied solely by calcium and Si sites by silicon atoms. Optimised occupancies of the four M sites indicated slightly different site fillings. In the Szklarska Poręba silesiaite, the M1 site is predominantly occupied by trivalent Fe + Sc and the M2–M4 sites by Sn. In contrast, in the Häiviäntien silesiaite, the M1–M3 sites are Sn-dominant, while Fe3+ predominantly occupies the M4 site. The differences can be considered a result of an evolution of the M1–M4 site occupancies following a decrease of the <M–O> distance. Among the minerals of the kristiansenite group, Sc-free silesiaite from the Häiviäntien pegmatite has the smallest average radius of M-site cations and a unit-cell volume that increases proportionally to the (Fe2+ ± Sc) content. The hydrogen atoms form moderate hydrogen bonds between disilicate groups (Si2O7 and Si2O6OH) linked in rows along [101], indicating the presence of one hydroxyl in the formula calculated for Z = 4. All three kristiansenite-group species, i.e. silesiaite, kozłowskiite and kristiansenite, are isostructural.

Scandium, yttrium, and lanthanide occurrence in Cantharellus cibarius and C. minor mushrooms

There is a dearth of data on rare earth elements (REE), yttrium and scandium in foods which extends also to baseline datasets for edible wild mushrooms, though this has started to change in the last decade. Concentrations and shale normalized patterns of REE and Y (REY) were studied by using inductively coupled plasma–quadrupole mass spectrometer in 22 pools (2235 specimens) of Cantharellus cibarius (Golden Chanterelle) collected in Poland and also a pool of C. minor (Small Chanterelle) (153 specimens) from Yunnan (Chinese Province). The total REY plus Sc varied in C. cibarius from 10 to 593 µg kg−1 dw whereas that for the Yunnan’s C. minor was 2072 µg kg−1 dw. C. minor from Yunnan has higher REY and Sc compared to the C. cibarius. Sc concentrations in twenty C. cibarius pools were below 1 µg kg−1 dw, but 17 and 27 µg kg−1 dw were detected at the other two sites and 66 µg kg−1 dw was detected in C. minor. The median Y content of C. cibarius and C. minor was 22 µg kg−1 dw and 200 µg kg−1 dw. The difference in REY and Sc concentrations and shale normalized patterns between mushrooms from Poland and Yunnan seems to reflect the regional difference in concentration and composition of these elements in the soil bedrock.

Incommensurate helimagnetic structure of Ba(Fe1−xScx)12O19 determined by single-crystal neutron diffraction

Sc-substituted hexagonal ferrite $\mathrm{Ba}{({\mathrm{Fe}}_{1\text{\ensuremath{-}}x}{\mathrm{Sc}}_{x})}_{12}{\mathrm{O}}_{19}$ has an incommensurate helimagnetic structure. However, the incommensurate helimagnetic structure has not been sufficiently determined, and the mechanism via which the helimagnetism develops has not been studied. Time-of-flight-Laue single-crystal neutron diffraction measurements were performed at 4--6 K on single-crystal samples of $\mathrm{Ba}{({\mathrm{Fe}}_{1\text{\ensuremath{-}}x}{\mathrm{Sc}}_{x})}_{12}{\mathrm{O}}_{19}$ having Sc concentrations of $x=0$, 0.128, 0.153, and 0.193. The incommensurate helimagnetic structure was determined by analyzing the magnitude and direction of the ${\mathrm{Fe}}^{3+}$ magnetic moments at the five Fe1--Fe5 sites ($2a, 4e, 4{f}_{1}, 4{f}_{2}$, and $12k$). The development mechanism of the helimagnetic structure was discussed from the standpoint of superexchange interaction. The crystal structure analyses revealed that the Sc substitution enabled two significant events, namely, the coordination changes of ${\mathrm{Fe}}^{3+}$ and ${\mathrm{Sc}}^{3+}$ at the $\mathrm{Fe}2(4e)$ site, resulting in the shortened bond distances of Fe2-O1 and the preferred substitution of ${\mathrm{Fe}}^{3+}$ at the $\mathrm{Fe}4(4{f}_{2})$ site with ${\mathrm{Sc}}^{3+}$. The magnetic structure analyses revealed that the helimagnetic structure of $\mathrm{Ba}{({\mathrm{Fe}}_{1\text{\ensuremath{-}}x}{\mathrm{Sc}}_{x})}_{12}{\mathrm{O}}_{19}$ is a cone type whose base is in the $ab$ plane and height is in the $c\text{\ensuremath{-}}\mathrm{axis}$ direction. The magnetic moments of $\mathrm{Fe}2(4e), \mathrm{Fe}4(4{f}_{2})$, and $\mathrm{Fe}5(12k)$ are aligned with distinct angles, leading to the helimagnetic structure of $\mathrm{Ba}{({\mathrm{Fe}}_{1\text{\ensuremath{-}}x}{\mathrm{Sc}}_{x})}_{12}{\mathrm{O}}_{19}$, and can be explained by assuming that there is an antiferromagnetic superexchange interaction ${J}_{5}$ between $\mathrm{Fe}2(4e)$ and $\mathrm{Fe}5(12k)$ that is negligible in the $x=0$ crystal. The shorter bond distance of Fe2-O1 in Sc-rich crystals revealed by the crystal structure analyses enhances the superexchange interaction ${J}_{5}$. However, the ${\mathrm{Sc}}^{3+}$ preference for $\mathrm{Fe}4(4{f}_{2})$ weakens ${J}_{3}$ and ${J}_{4}$. The relatively strong ${J}_{5}$ leads to competition among the three superexchange interactions, ${J}_{3}, {J}_{4}$, and ${J}_{5}$, resulting in the development of the helimagnetic structure. These findings facilitate the understanding of the essentials of the basic magnetic material $\mathrm{Ba}{\mathrm{Fe}}_{12}{\mathrm{O}}_{19}$.

Determination of scandium in ash and slag wastes and products of their processing by instrumental neutron activation analysis

Abstract Ash and slag waste accumulated throughout the world in appreciable amounts are, in essence, man-made deposits and are of interest as a potential source of critical elements, in particular Sc, as well as raw materials for obtaining construction materials. Coals from Siberia and the Far East are used as fuel at thermal power plants (TPPs) in the Primorsky Territory of Russia. These coals are characterized by a high Sc content. The content of Sc in the ash and slag wastes from landfills of six TPPs in Primorsky Krai was determined by neutron activation analysis with a Cf-252 radionuclide source. The Sc content ranged from 5.1 to 52.7 ppm. Average concentrations of Sc in ash and slag waste are 23.3 ppm. Verification of the INAA method was carried out by comparing with the ICP-MS data in reference materials (laterite and carbonatite scandium-containing ores). The possibility of using the Sc-46 isotope, produced by thermal neutron activation, as a radioactive tracer to assess the effectiveness of operations for Sc extraction and concentration is shown. Sc has been preconcentrated from the initial ash of the Primorsky thermal power plant by the precipitation method in the form of hydroxide, followed by separation from accompanying elements by dissolving the hydroxide in sodium hydroxide or hydrochloric acid. The possibility of concentrating Sc more than 4 times from the initial ash has been shown.

Chronic in-hive exposure to a field-relevant concentration of Closer™ SC (24% sulfoxaflor) insecticide altered immunological and physiological markers of honey bee foragers (Apis mellifera)

Chronic in-hive exposure to a field-relevant concentration of Closer™ SC (24% sulfoxaflor) insecticide altered immunological and physiological markers of honey bee foragers (Apis mellifera)

ДИАГНОСТКА СКРЫТОГО МАСТИТА ПУТЕМ ПОДСЧЕТА СОМАТИЧЕСКИХ КЛЕТОК В МОЛОКЕ КОРОВ

In this article, we present the course and results of scientific research aimed at calculation of the concentration of somatic cells in cow's milk to detect subclinical mastitis in individual farms of the Republic of Armenia. Comparison of somatic cell concentrations in milk from healthy and sick cows with subclinical mastitis, analysis and comparison of blood morphological parameters in sick and healthy animals has been implemented and the relationship between somatic cell concentration in milk and morphological abnormalities in sick cow blood has been identified. SC concentrations between 300 and 500 thousand/ml are indicative of mastitis risk. In this case, the type of reaction manifested was positive. It was found that the viscosity of the investigated solution "Somatic plus" + milk increases in proportion to the increasing concentration of somatic cells in the milk sample, which indicates subclinical mastitis. A study of the morphological parameters of blood in healthy and subclinical mastitis animals revealed some deviations from the reference values of blood parameters, leading to the conclusion that these changes in animals' blood are related to an increase in the number of milk's somatic cells. Increased leukocytes were found in sick animals' blood. This was followed by an increase in stab neutrophils, eosinophils, monocytes, lymphocytes, and ESR. As a result of all this, the body is experiencing inflammatory processes mobilizing its defensive mechanisms against pathogens.

GEOCHEMICAL AND MAGNETIC CHARACTERISTICS OF PLACER GOLD DEPOSITS FROM CENTRAL KALIMANTAN, INDONESIA

Massive tailings have resulted from the extensive use of placer deposits in Central Kalimantan, Indonesia, by artisanal and small-scale gold mining (ASGM) activities. Recently, the placer deposits and their tailings have been exploited for heavy minerals. In this study, geochemical and magnetic analyses were carried out on these deposits to identify the prospect of REE (rare earth element) exploration in the materials already collected by ASGM activities. Samples were collected from ten different locations. For each location, two different fractions were prepared for analyses, i.e. the heavy mineral (HM) fraction and the panned (M60) fraction. All HM and M60 samples were subjected to magnetic susceptibility measurements, but only representative samples were subjected to x-ray fluorescence (XRF) measurements (for Si, Ti, Fe, Zr, and Al) and to inductively coupled plasma-emission spectroscopy (ICP-OES) measurements (for Eu, Tb, Dy, and Sc). The results showed that the concentrations of major elements (Ti, Fe, Zr, and Al) vary significantly from deposits along one river to another, while the concentration of Si is rather similar. Compared to M60 samples, the HM samples have higher concentrations of Ti, Fe, Zr, Al, and Sc, implying that the sluice-box separation enhances the concentration of valuable minerals. Magnetic susceptibility is found to be correlated with Fe and Sc concentrations, confirming the potential use of magnetic measurements as a complementary tool for Fe and Sc exploitation in placer deposits. It is believed that both the source rocks and the sedimentary settings of these deposits determine whether certain elements (Sc, Fe, and Zr) are present or absent in Central Kalimantan placer deposits. The prospect of exploring and exploiting Sc in these placer deposits might augment the ASGM activities in Central Kalimantan.

Influence of scandium codoping on the stability of barium cerate electrolyte

Proton (H+) conducting electrolytes significantly outperform oxide ion (O2–) conducting electrolytes in terms of performance while also costing less to operate the cell. This makes them popular and potential electrolytes in future electrochemical devices such as intermediate temperature solid oxide fuel cells (IT-SOFCs). The standard solid-state reaction method has been utilized in the synthesis of scandium (Sc) co-doped barium zirconium cerate ceramics, BaCe0.8-xZr0.2ScxO3-δ. The powder X-ray diffraction spectra confirmed that the prepared samples are of single phase and have orthorhombic symmetry. The samples were analyzed for thermal stability by employing thermogravimetric analysis (TGA). All samples are stable up to 800 °C, according to TGA performed on dried and pre-hydrated samples—however, the samples under higher partial pressure of water exhibit lower degree of stability. Raman analysis was used to determine the stability of perovskite phase of the studied compositions both before and after TGA. This study showed that most initial phases either persisted or remained stable when the samples were treated at high vapor pressure. The thermal stability increased as the amount of Sc-substitution increased. Also, to investigate how the presence of grains and grain boundaries influenced the total resistance of samples with different Sc concentrations, complex impedance spectroscopy (CIS) was performed.

Serological and oncoinformatic analysis of HbA1c as a prognostic biomarker in screening the risks of different cancers among the male T2D patients of Bangladesh

Hemoglobin A1C (HBA1c) represents the average serological sugar status of T2D patients of the past three months, considered a clinically standard method of studying sugar metabolism. Overexpressing HbA1 can metabolically forecast the risk of different cancers among T2D patients. Based on this, the study aimed to analyze the impact of sugar metabolism in cancer development considering the overexpression of HbA1 as the prognostic biomarker of screening the risks of eight different cancers among the chronic male T2D patients of Bangladesh. Serological analysis of the concentrations of FBS, THABF, creatinine, SC, STGs, HDLC, and LDLC of the T2D patients was conducted in response to their individual HbA1c concentration. Afterward, HbA1 overexpression and promotor-methylation responsible for BLCA, BRCA, CHOL, COAD, LUAD, LUSC, PAAD, and PRAD cancers in the male T2D patients were profiled as the oncoinformatic screening, where the sample types used, individual cancer stages, racial-footprints, gender, age, nodal metastasis, p53-methylations, pancreatitis, diabetes status, smoking behaviors, and survivability status were studied. Finally, the genetic involvement of a group of genes responsible for genetic co-expression of HbA1, endophytic vesicle regulation, antioxidant regulation, and reactive oxygen species based-metabolic regulation in T2D males was identified and comprehensively discussed. The research revealed a significant correlation between BMI and FBS in both the patient and the control groups (p<0.0001). Besides, FBS, THABF, and creatinine were found significantly regulated with their respective HbA1c concentrations (p<0.0001) for each group. The SC, STGs, HDLC, and LDLC regulated ardently and equally for both groups (p<0.0001), while HbA1c ranged from 3.8-5.8% and 5.11-15.8%, for the controls and patients respectively. HbA1 was found interactive with diversified cancer-causing genes, while HbA1 was mostly downregulating with the progressing metastasis. To receive maximum benefits from using HbA1c in clinical profiling of cancer risks among chronic-male T2D patients in minimal time and expense further studies can be needed with a larger sample size.

A critical review of the occurrence of scandium and yttrium in mushrooms.

Scandium (Sc) and Yttrium (Y) along with the other rare earth elements (REE) are being increasingly extracted to meet the escalating demand for their use in modern high technology applications. Concern has been voiced that releases from this escalating usage may pollute environments, including the habitats of wild species of mushrooms, many of which are foraged and prized as foods. This review collates the scarce information on occurrence of these elements in wild mushrooms and also reviews soil substrate levels, including forested habitats. Sc and Y occurred at lower levels in mushrooms (<1.0-1000µgkg-1 dw for Sc and<1.8-1500µgkg-1 dw for Y) compared to the corresponding range for the sum of the lanthanides in the same species (16-8400µgkg-1 dw). The reported species showed considerably more variation in Y contents than Sc which show a narrow median distribution range (20-40µgkg-1 dw). Data allowing temporal examination was very limited but showed no increasing trend between the 1970s to 2019, nor were any geographical influences apparent. The study of the essentiality, toxicity or other effects of REE including Sc and Y at levels of current dietary intake are as yet undefined. High intake scenarios using the highest median concentrations of Sc and Y, resulted in daily intakes of 1.2 and 3.3μg respectively from 300g portions of mushroom meals. These could be considered as low unless future toxicological insights make these intake levels relevant.

Nanoscale compositional segregation in epitaxial AlScN on Si (111).

We report the growth of epitaxial wurtzite AlScN thin films on Si (111) substrates with a wide range of Sc concentrations using ultra-high vacuum reactive sputtering. Sc alloying in AlN enhances piezoelectricity and induces ferroelectricity, and epitaxial thin films facilitate systematic structure-based investigations of this important and emerging class of materials. Two main effects are observed as a function of increasing Sc concentration. First, increasing crystalline disorder is observed together with a structural transition from wurtzite to rocksalt at ∼30 at% Sc. Second, nanoscale compositional segregation consistent with spinodal decomposition occurs at intermediate compositions, before the wurtzite to rocksalt phase boundary is reached. Lamellar features arising from composition fluctuations are correlated with polarization domains in AlScN, suggesting that composition segregation can influence ferroelectric properties. The present results provide a route to the creation of single crystal AlScN films on Si (111), as well as a means for self-assembled composition modulation.

Ductility enhancement by activating non-basal slip in as-extruded Mg alloys with dilute Sc addition

This work systematically investigates the impact of the dilute Sc addition on microstructures and mechanical properties in Mg alloys. Electron back scattered diffraction, slip traces analysis, transmission electron microscopy, and visco-plastic self-consistent polycrystal constitutive (VPSC) modeling were performed to investigate the deformation mechanisms in the tensile testing, especially the activation of <c+a> slip. The results showed that as-solid solution samples only consisted of α-Mg phase. After extrusion, all samples exhibited a similar average grain size. With the increment of the Sc content, the ductility of the samples was significantly improved, which failure elongation (FL) of Mg-xSc (x = 0.3, 0.6, 0.9 wt.%) alloys improved from 14.4% to 24.8%. The yield strength of each alloy is similar, about 200 MPa. VPSC results indicated that the difference value of the initial slip resistance (τ0) between prismatic slip and basal slip decreases from 63 MPa to 49 MPa, and the difference value of τ0 between pyramidal slip and basal slip decreases from 72 MPa to 57 MPa. The VPSC and the two-beam diffraction results confirmed that the pyramidal <c+a> slip and prismatic <a> slip were activated in tensile testing. The quantitative analysis of the slip trace line verified that the volume of non-basal slip reached 49.5% when the Sc content increased to 0.9 wt.%. Therefore, the addition of Sc in solid solution increased the amount of pyramidal <c+a> and prismatic <a> dislocation activities during the deformation process, which was beneficial to coordinate the c-axis strain, and finally improved ductility of Mg alloy.

Electron effective masses of ScxAl1−xN and AlxGa1−xN from first-principles calculations of unfolded band structure

The electron effective masses of ScxAl1−xN and AlxGa1−xN, two of the most promising wide bandgap materials for power and RF electronic applications, have been calculated using the predictions of the density functional theory (DFT). More specifically, the unfolding technique has been adopted to extract the effective band structure of the two alloys under investigation. It has been found that the AlGaN effective masses m∗ approximately follow the Vegard law. On the contrary, due to the larger amount of disorder inside the crystal, the ScAlN shows a non-monotonic change of m∗ as a function of the Sc concentration, which requires the DFT calculations to be consistently performed for an accurate prediction. The ScAlN effective masses as a function of Sc content have been reported in the range 0≤x≤0.25 for the first time.

Raman Spectroscopy and Spectral Signatures of AlScN/Al2O3.

III-V solid solutions are sensitive to growth conditions due to their stochastic nature. The highly crystalline thin films require a profound understanding of the material properties and reliable means of their determination. In this work, we have investigated the Raman spectral fingerprint of Al1-xScxN thin films with Sc concentrations x = 0, 0.14, 0.17, 0.23, 0.32, and 0.41, grown on Al2O3(0001) substrates. The spectra show softening and broadening of the modes related to the dominant wurtzite phase with increasing Sc content, in agreement with the corresponding XRD results. We investigated the primary scattering mechanism responsible for the immense modes' linewidths by comparing the average grain sizes to the phonon correlation length, indicating that alloying augments the point defect density. The low-frequency Raman bands were attributed to the confined spherical acoustic modes in the co-forming ScN nanoparticles. Temperature-dependent Raman measurements enabled the temperature coefficient of the E2(high) mode to be determined for all Sc concentrations for the precise temperature monitoring in AlScN-based devices.

Geological setting and concentration of scandium in the Flatreef and eastern limb chromitites of the Bushveld Complex

Scandium is an important industrial metal for which demand is projected to increase in the future. Although many Sc deposits are secondary, Sc is scavenged by clinopyroxene during fractional crystallization of primary, mafic-ultramafic magmas. Sc may thus occur in sub-economic concentrations in mafic-ultramafic intrusions. In this work, we present new data on the concentration of Sc in the Bushveld Complex (BC) of South Africa. The eastern and western limbs of the BC are considered to be largely pristine, primary magmatic deposits, whereas the northern limb shows evidence of large-scale, localized crustal contamination. Samples from the primary magmatic cumulates of the eastern limb, from the mineralized Flatreef of the northern limb, and from the crustal-contaminated Footwall Assimilation Zone (FAZ) of the Flatreef were analysed for Sc. Despite the FAZ containing abundant clinopyroxene, interpreted to have recrystallized from the original cumulates in the presence of melted sedimentary rocks, no significant differences are seen in the concentration of Sc compared to other cumulate rocks of the BC containing less-abundant clinopyroxene. The concentration of Sc in the analysed samples is mainly controlled by mineralogy, with anorthosites, chromitites, and harzburgites containing under 20 ppm, and norites and pyroxenites containing 20-40 ppm. The parapyroxenites of the FAZ are less enriched in Sc than expected, suggesting that Sc may have been lost during alteration and recrystallization.

Design and 3D FEM Analysis of a Flexible Piezoelectric Micromechanical Ultrasonic Transducer Based on Sc-Doped AlN Film.

In this paper, a flexible piezoelectric micromachined ultrasonic transducer (PMUT) based on Scandium (Sc)-doped Aluminum Nitride (AlN) film was designed and modeled by the three-dimensional finite element method (3D-FEM). The resonant frequency of 218.1 kHz was reported. It was noticeable that a high effective electromechanical coupling coefficient (k2eff) of 1.45% was obtained when a combination of a flexible PI and a thin Si layer was used as the PMUT supporting structure layer. Compared with a pure Si supporting layer counterpart, the coupling coefficient had been improved by 110.68%. Additionally, the increase of Sc doping concentration in AlN film further enhanced the device electromechanical coupling coefficient and resulted in an improvement for transmitting/receiving sensitivity of the proposed flexible PMUT. When the doping concentration of Sc reached 30%, the emission sensitivity was as large as 1.721 μm/V, which was 2.86 times greater than that of conventional AlN film-based PMUT. The receiving sensitivity was found to be 2.11 V/KPa, which was as high as 1.23 times the performance of an undoped device. Furthermore, the bending simulation result showed that the proposed flexible PMUT device can maintain a good mechanical stability when the bending radius is greater than 1.5 mm. The simulation of sound field characteristics demonstrated that the flexible PMUT based on AlScN could receive stable sound pressure signals under the bending radius of 1.5 cm.

Research on Microstructure and Cracking Behavior of Al-6.2Zn-2Mg-xSc-xZr Alloy Fabricated by Selective Laser Melting

Selective laser melting (SLM) offers obvious advantages in the production of complex parts. However, the traditional 7xxx series aluminum alloy has a serious cracking tendency in the SLM process. Therefore, in order to analyze the microstructure and cracking mechanism, and obtain crack-free aluminum alloy fabricated by SLM, this paper studied the microstructure characteristics of as-deposited Al-6.2Zn-2Mg-xSc-xZr alloy with different Sc, Zr content, as well as the influence mechanism of Sc, Zr on cracking. The results show that with the increase of Sc and Zr content, the crack tendency and grain size decrease. When Sc and Zr content reach 0.6% and 0.36% respectively, cracks can no longer be observed in the as deposited alloy. The microstructure of the as deposited Al-6.2Zn-2Mg-0.6Sc-0.36Zr alloy consists of fine equiaxed and columnar crystals, in which Sc and Zr mainly exist in the aluminum matrix as solid solutions, and some exist in the form of Al3(Sc, Zr). The immediate reason for the absence of cracks is that the microstructure changes from coarse columnar grains to fine equiaxed-columnar grains when the content of Sc and Zr increases. The refined grain size may have the following beneficial effects: It helps with reducing the thickness of the liquid films. This will increase the tear sensitivity of the liquid film and the cracking tendency and therefore lowers the hot cracking tendency; And a refined grain size improves fracture roughness, leading to an enhanced cracking resistance. At the same time, the refinement of the grains will make the feeding channel of the grain boundary shorter and easy to feed, and the fine equiaxed grains can coordinate stress-strain during solidification more effectively than coarse columnar grains, which will decrease the cracking tendency.

The source and depositional environment of early Silurian iron formation in NW China: Constraints from element and isotope (Fe, C, O) geochemistry

Phanerozoic iron formations (IFs) provide a unique opportunity to understand both the contemporaneous chemical composition and redox state of seawater where they precipitated. However, the absence of detailed reports of Phanerozoic IFs inhibits a robust understanding of their depositional conditions and dominant Fe sources. Here, we describe a hematite- and siderite-rich IF from Kukeate hosted within lower Silurian submarine siliciclastic and carbonate sedimentary succession in NW China. The chemical composition of our analysed samples is dominated by high TFe2O3 and variable SiO2 contents, with low Al2O3, TiO2, Sc, Nb, Th, and Zr concentrations, indicating an authigenic origin. Distinct depletion in LREE relative to HREE, super-chondritic Y/Ho ratios, and slightly positive Gd anomalies, are diagnostic for derivation from surface seawater. The lack of strong positive Eu anomaly, along with coupled Fe and O isotopic characteristics for the hematite, point to a significant low-T hydrothermal input. Slightly negative to no Ce anomalies, weakly negative to mildly positive Eu anomalies, homogeneous δ56Fe values (near zero), and large positive δ13CV-PDB excursions, together suggest that there exists a dynamic redoxcline, which separated oxic surface water and ferruginous deeper water conditions, where dissolved Fe2+ in deep, reducing, Fe-rich hydrothermal fluids, was oxidized and precipitated as Fe(OH)3 in shallow oxygenated seawater, leading to the formation of hematite. Accordingly, the occurrence of Kukeate IF suggests intermittent ferruginous deeper water conditions during the early Silurian.

Scandium diffusion in forsterite: concentration dependence, inter-site reactions and the effect of trivalent cations on Fe diffusion

Diffusion of scandium (Sc) in synthetic forsterite (Mg2SiO4) was studied at 1400 °C at atmospheric pressure, in air. The Sc source was a powder of forsterite and protoenstatite (Mg2Si2O6) in order to buffer the silica activity, doped with various Sc contents, from ∼9 wt. ppm Sc to ∼8.5 wt% Sc2O3. The powder with the highest Sc content also contained thortveitite (Sc2Si2O7), which additionally buffers the activity of Sc2O3. All experiments were conducted for the same duration (550 h), but the length of the Sc diffusion profile (i.e. the distance over which the concentration decreased from the rim to core/background value) varied from ∼200 to 800 μm, with higher Sc concentrations associated with longer diffusion profiles. The geometry of Sc diffusion profiles also changes systematically with the Sc concentration – profiles with low Sc (<10 wt. ppm at the interface) have stepped shapes, those with medium Sc contents (80–400 wt. ppm at the interface) have near-linear profiles, while experiments with high Sc at the interface (>500 wt. ppm) show profiles with a shape that is approximately, but not exactly, describable by error function forms. Small but variable amounts of Fe contamination resulted in Fe diffusion profiles with interface concentrations of 80 to 1100 wt. ppm. The diffusivity of Fe, at these trace concentrations, appears to be a function of the concentration of Sc, rather than its own concentration, with the increased Sc concentration associated with an increase in Fe diffusivity of at least an order of magnitude. Similar behaviour is observed for other contaminants, Ni, Co, Mn and Li, at trace concentrations. Additionally, Al, present in the original forsterite crystal at the level of a few 10s of wt. ppm developed concentration profiles with a stepped form, broadly showing out-diffusion. The point along the profiles at which the Al concentration changes dramatically, coincides approximately with the end of the Sc profiles. Models are tested in which Sc diffusion is assumed to be concentration-dependent. In these models, the concentration-dependence is defined using the energy of binding between Sc3+ and M-site vacancy, and the diffusivity of the cation-vacancy pair. Such models are generally successful, but cannot fully describe the behaviour observed in these experiments. Rather, the diffusive behaviour of Sc and Al is better described by a model in which Sc3+ substitutes for Mg2+, charge balanced by vacancies (the Sc4/3[vac]2/3SiO4 substitution), and diffuses relatively rapidly in a concentration-dependent regime. Interaction of Sc with Al (present in the starting material) is proposed to lead to the formation of an MgScAlO4 component, upon which the diffusivity of Sc is drastically reduced. The model is capable of describing the majority of Sc and Al profiles observed. One experiment was hydroxylated following the diffusion anneal, revealing a multitude of defects supporting the suggestion that this system is more complex than simple concentration-dependent diffusion. Whilst these experiments were conducted in a simple system with lower Fe concentrations and higher fO2 than those typical of natural olivine, an example from a previous study (Cr diffusion in San Carlos olivine) shows that such complex behaviour may also be found in systems closer to natural conditions. The addition of Cr (∼2000 wt. ppm at the diffusion interface) appears to cause a ∼ 1 order of magnitude increase in the diffusivity of Fe-Mg, Ca and Ni relative to the published values conventionally used for diffusion chronometry.