Sm Contents Research Articles

Identification of optimal solid solution temperature for Sm2Co17-type permanent magnets with different Fe contents

It is confirmed that the solid solution temperature range to obtain optimal magnetic properties is different for the magnets with different Fe contents, and the correlation between magnetic properties and microstructures influenced by solid solution temperature (Ts) has been systematically studied. The optimal solid solution temperature range is 1413–1463 K for the Sm(CobalFe0.213 Cu0.073Zr0.024)7.6 magnet, which is higher than that of the Sm(CobalFe0.262Cu0.073Zr0.024)7.6 magnet (1403–1453 K), and the optimal Ts range is about 50 K for both of the magnets. The solid solution temperature range shifting toward relatively high temperature is due to the increase in a phase transition temperature. The magnet solution-treated at proper temperature exhibits 1:7H single phase, and intact cell structure and high Cu concentration (23.12 at%) in the cell boundary are found after aging process, which makes the magnet shows high intrinsic coercivity (Hcj) and magnetic field at knee-point (Hknee). At a lower solid solution temperature, the 2:17H, 1:5H and Zr-rich precipitation phases appear, which affects the cell structure, density of lamellar phase and Cu concentration in the cell boundary, leading to the reduced magnetic properties. However, at a higher solid solution temperature, there exist obviously light gray and dark regions with different Sm, Cu and Fe contents in scanning electron microscopy observation, and the magnet shows low pinning field in the two regions and incomplete cell structure, resulting in an inferior Hcj and Hknee.

Direct Sunlight Catalytic Decomposition of Organic Pollutants via Sm- and Ce-Doped BiFeO3 Nanopowder Synthesized by a Rapid Combustion Technique

In the development of photocatalytic processes towards waste water treatment, we have been long faced three foremost obstacles, including catalyst mass production, photon-energy cost and finally catalyst separation process after the treatment. In this study, such problems were addressed through the development of samarium and cerium-doped BiFeO3 (BFO) nanoparticles (NPs) (BixRExFeO3; RE = Sm, Ce, x = 0.00, 0.01, 0.03, 0.05;) employing a rapid solution combustion synthesis (SCS). This technique is greatly capable of large scale nanopowder production at low temperature. In the SCS procedure, different amount of oxidant-to-fuel (glycine-to-nitrate ion, Gly/NO3−) were investigated (Gly/NO3− = 0.2, 0.3, 0.37, 0.56, and 0.8). Moreover, a catalytic sunlight irradiation was employed to study the effect of Sm and Ce dopant contents on the photodegradation of benzene and methyl orange (MO) in the aqueous solution. The as-synthesized catalysts were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), UV–Visible diffuse reflectance spectroscopy (UV–Vis DRS) and Brunauer–Emmett–Teller (BET)/Barrett-Joyner Halenda (BJH) techniques. The band gap energy of BFO decreaed from 2.14 to 2.06 eV with the increase of Sm3+ contents while it increased up to 2.22 eV in the case of Ce-doped BFO. The solar decomposition of the organic pollutants demonstrated the superior performance of Bi1-xSmxFeO3 photocatalyst rather than using cerium in the BFO crystalline structure which is attributed to the increased surface area and visible light harvesting.

The effect of fluid-aided modification on the Sm-Nd and Th-Pb geochronology of monazite and bastnäsite: Implication for resolving complex isotopic age data in REE ore systems

Isotopic dating studies have revealed that many carbonatite-related REE ore systems have protracted and complex temporal evolution histories. The mechanisms that cause these complex dating results remain poorly understood. Here, we present an in-situ Sm-Nd and Th-Pb isotopic investigation of monazite and bastnäsite from a geologically-complicated deposit, the world-class Bayan Obo REE deposit of China, with the aim of defining the general mechanisms accounting for the protracted age spread observed in this and many other REE deposits.Monazite and bastnäsite are two principle REE ore minerals in the Bayan Obo deposit. Most of the studied monazite and bastnäsite grains have experienced fluid-aided modification. The modified grains have generally homogeneous Sm and Nd contents and Sm-Nd isotopic compositions, implying low mobility of Sm and Nd during the modification process. Thus, the Sm-Nd chronometer can be used to constrain the primary crystallization timing of the REE minerals at 1293 ± 48 Ma. However, altered REE minerals have apparent 208Pb-232Th ages (1248–261 Ma) that are variably younger than the primary crystallization age. In most samples, Th contents have no correlations with 208Pb-232Th ages, while Pb contents tend to decrease along with the younging trend of 208Pb-232Th ages. NanoSIMS mapping shows that 208Pb and 208Pb/232Th are heterogeneous, and irregularly distributed in the altered grains. Such results are indicative of variable Pb loss during the fluid-aided modification process. Thus, many Th-Pb ages represent partial isotopic resetting and, hence, are geologically meaningless. Completely reset ages cluster at 450–400 Ma or 280–260 Ma, representing two discrete episodes of post-ore hydrothermal activity. Small amounts of monazite and bastnäsite that were newly crystallized during these two overprinting episodes have initial Nd isotopic signatures approaching the time-evolved isotopic compositions of primary ores, which suggests insignificant REE input to the primary ores during these events. This study provides critical evidence to resolve complex dating results and disparate ore genesis models for the giant Bayan Obo deposit. Moreover, our results indicate the resistance of Sm-Nd isotopes, but the susceptibility of Th-(U)-Pb isotopes, to fluid-aided modification. Therefore, younger Th-U-Pb dates in geologically-complicated deposits should be treated with caution as they may represent partial resetting results and/or may not represent events of increased metal tenor.

Synthesis, Magnetic and Electrical Characteristics of Ba‐Sr Hexaferrites Substituted with Samarium, Chromium and Aluminum

AbstractA series of M‐type Ba−Sr hexaferrites of composition Ba0.20Sr0.80‐xSmxFe12‐y(Cr0.5Al0.5)yO19 (x=0.00–0.40; y=0.00–0.32) were prepared by solid‐state reaction route. XRD patterns reveals that there is a single magnetoplumbite phase in the hexaferrites with the substitutiom of Sm (0.00≤x≤0.20) and CrAl (0.00≤y≤0.16) contents, while for the hexaferrites containing Sm (x≥0.30) and CrAl (y≥0.24), impurity phase is detected in the structure. The remanence (Br) decreases with increasing substitution content of Sm (0.00≤x≤0.40) and CrAl (0.00≤y≤0.32). With the increase of substitution contents, the intrinsic coercivity (Hcj) increases, while the magnetic induction coercivity (Hcb) first increases, and then decreases. Br has a linear decreasing behavior with increasing temperature from 20 °C to 170 °C. Hcj raises linearly with increasing temperature from 20 °C to 170 °C. The average temperature coefficient of Br (αBr) basically remains constant with increasing substitution content of Sm (0.00≤x≤0.40) and CrAl (0.00≤y≤0.32). The average temperature coefficient of Hcj (αHcj) decreases with increasing substitution content of Sm (0.00≤x≤0.40) and CrAl (0.00≤y≤0.32). The electrical resitivity (ρ) decreases with increasing substitution content of Sm‐CrAl.

Overview of composition and technique process study on 2:17-type Sm–Co high-temperature permanent magnet

Sm–Co permanent magnets are widely used in aerospace equipments, tubes, sensors and hybrid electric vehicles due to their excellent magnetic properties at both room and high temperatures. Compared to that of Nd–Fe–B magnets, the capability of reliably operating at temperatures up to 500 °C is the biggest preponderance of Sm–Co permanent magnets. However, the reliable high-temperature magnetic properties are susceptible to composition and technique processes. So, appropriate composition and matched technique processes are prerequisites for good high-temperature magnetic properties. This review mainly emphasizes the influences of Sm, Fe, Cu and Zr contents and technique processes on development of high-temperature performance and discusses the controversial high-temperature coercivity mechanism of 2:17-type high-temperature Sm–Co magnets.

Evaluation of the surface water quality in the Kebir-Rhumel catchment area (northeast Algeria) using biotic indices and physico-chemical analyses.

Assessing the water quality of the Kebir-Rhumel watershed by the use of benthic macroinvertebrates and physico-chemical analysis is the aim of this work. Thirteen physicochemical parameters and macroinvertebrates fauna were collected monthly in 15 stations located along the catchment area in the two principal wadis: El Kebir and Rhumel. Canonical correspondence analysis was used to study the relationships between physico-chemical parameters and macroinvertebrates. Biotic indices Biological Monitoring Working Party (BMWP'), Global Biological Normalized Index (IBGN), EPT index (Ephemeroptera, Plecoptera, Trichoptera), and %EPT/Chironomidae, based on benthic macroinvertebrates, have been applied in assessing the biological water quality. According to the results, a majority of the physicochemical parameters measured during the study period show spatial heterogeneity (Kruskal-Wallis, P value < 0.05), indicating that Rhumel wadi is more polluted compared with El Kebir wadi; the NO2-, NO3-, PO4-3, Cl-, and SM contents are very high consequences of human and industrial anthropogenic actions. Canonical correspondence analysis has shown that the environmental parameters measured during this study influence the dynamics of macroinvertebrates, and the polluo-resistant taxa (Chironomidae) predominate in sites very rich in organic matter with low oxygen conditions. Sensitive taxa have a vulnerability to pollution. The biotic indices used confirm the diagnosis of the physicochemical analysis demonstrating a very degraded quality at Rhumel wadi. The EPT index and %EPT/Chironomidae results are closer to the scores of the BMWP' index.

Evolution of Mineral Composition during Eclogite Metamorphism in the Belomorian Mobile Belt: Data from Vichennaya Luda Island

The detailed mineralogical-geochemical study of eclogites and their retrograde products (amphibolites in a rim of eclogite boudin) from Vichennaya Luda Island (Keret Archipelago, White Sea) revealed systematic variations in major-, trace and rare-earth element composition of rock-forming minerals, which should be taken into account in geochronological and thermobarometric studies. Garnets from garnet–amphibole interlayers in the eclogites demonstrate a prograde zoning. In addition, garnet rims differ from their cores in a “hump-like” REE pattern owing to the elevated Sm, Eu, Gd and Dy contents and a negative slope of HREE pattern, as well as in an increase of Sm/Nd and a decrease of Lu/Hf ratio. It has been established that the eclogites contain clinopyroxene with depleted (to chondritic level) REE content, a positive Eu anomaly, and lowered Ti, V, Cr, Y, Zr, and Hf contents. Based on these geochemical features, the Cpx can be ascribed to relict that have preserved during peak eclogite metamorphism. Amphiboles in amphibolite rim of boudin differ sharply from amphiboles in eclogite in the lowered contents of LREE and some HREE. In addition to almost a two-fold decrease of Ti content in the eclogite–amphibolite sequence, amphiboles demonstrate a significant decrease of V, Sr, Y, Nb, and Hf contents. All biotites have sinusoidal REE pattern, which is typical of minerals formed through fluid-induced disequilibrium processes. Biotite from eclogites has higher Ti content and elevated contents of REE, Nb, V, Cr, Ba, and Hf as compared to biotites from the amphibolization rim. The eclogites and amphibolites developed after them are similar in major, trace, and rare-earth element composition.

Comparison of the Thermal Conductivity of Sm-Containing AZ31 and ZK30 Alloys

Magnesium alloys with different Sm contents, with research focus on ZK30 and AZ31, were prepared and their microstructures and thermal conductivities were investigated. Results of microstructure analysis showed that Sm element in the as-cast ZK series of magnesium alloys was mainly distributed along the grain boundaries in the form of (Mg, Zn)3Sm rare-earth phase. However, Sm element in AZ series of magnesium alloys was distributed over the grains and at grain boundaries in form of Al2Sm phase. The Al2Sm phase at the core acted as a nucleus to refine the grain of AZ series of magnesium alloys. The grain size of the as-extruded magnesium alloys was obviously smaller than that of the as-cast magnesium alloys. Moreover, the crushed secondary phases were arranged along the direction of extrusion. Results showed that thermal conductivity of magnesium alloys could be improved by increasing Sm content. Thermal conductivities of ZK series of magnesium alloys were obviously higher than those of AZ series of magnesium alloys. This was mainly attributed to the significantly smaller lattice distortion of ZK series of magnesium alloys compared to that of AZ series of magnesium alloys.

Investigations on microstructures, mechanical and corrosion properties of Mg-5.5Zn-0.8Zr alloys with Sm addition

The microstructure, mechanical and corrosion properties of as-cast Mg-5.5Zn-0.8Zr (ZK60) alloys with varying Sm contents were investigated. The microstructures of the ZK60 alloy mainly consisted of α-Mg grains and Mg7Zn3 particles in common. Addition of Sm to ZK60 alloy resulted in the formation of Mg41Sm5 and (Mg, Zn)3Sm phases, which changed the number, morphology and distribution of the second phase of the alloy, resulting in finer, more homogeneous grains and improved mechanical properties. The ultimate tensile strength (UTS), yield strength (YS) and elongation (EL) of the ZK60-0.8Sm alloy were increased by 19.8%, 25.3% and 31.7%, compared to those of ZK60 alloy, from 162 to 194 MPa, 74.4 to 93.2 MPa and from 6.0% to 7.9%, respectively. The corrosion mode of Sm-containing ZK60 alloys changed from serious local corrosion to uniform corrosion, and the corrosion resistance was improved. When the content of Sm was 1.6 wt%, the corrosion rate of the alloy was 1.7102 g · cm−2 · h−1, which was only 89% of the corrosion rate of ZK60 alloy. The improvement of the properties of ZK60-xSm alloys was attributed mainly to the interaction of solid solution strengthening, fine grain strengthening and precipitation strengthening.

English

The present work is focused on investigating the effect of rare earth ion on structural, magnetic and transport properties of (Cu0.5Zn0.5Fe2-x)SmxO4[x = 0.00, 0.05 and 0.10] ferrites which were prepared by solid state reaction technique at 1100°C for 3 h. The X-ray diffraction analysis revealed that rare earth free sample shows formulation of single phase cubic spinel structure with no extra peak whereas Sm substituted Cu-Zn ferrite samples show additional peaks that correspond to a secondary orthoferrite phase. Lattice parameter, bulk density, X-ray density and porosity of the studied samples are increased with Sm substituted ions. Lattice parameter of both series are slightly decrease with increase Sm content. The initial permeability decreases with increasing Sm ions in ferrite. Quality factor signifies the merit of the material from the application point of view. The dielectric constant was found to decrease continuously with increasing frequency and remain almost constant at higher frequency range. The dielectric behavior of the experimental ferrite samples can be explained on the basis of the mechanism of the dielectric polarization and conduction process. The saturation magnetization decreases with increasing rare earth Sm contents. Key words: Solid state reaction technique, sintering temperature, quality factor, dielectric polarization.

Isotope Systematics and Age of Authigenic Minerals in Shales of the Upper Riphean Inzer Formation, South Urals

Clay subfractions (SFs) with particles size of 2–5, 0.6–2.0, 0.3–0.6, 0.2–0.3, and 0.1–0.2 μm of two shale samples (Upper Riphean Inzer Formation, South Urals) are studied using transmission electron microscopy, X-ray diffractometry (XRD), and U–Pb, Sm–Nd, Rb–Sr, and K–Ar methods. The SFs are composed of low-temperature 1Md illite; quartz, chlorite, and 2M1 illite are observed only in some coarse SFs. Irrespective of the size, the clay particles are equant. The standardized illite crystallinity indices (CIS) of all SFs are typical of the dia(cata)genesis zone. The CIS value increases, the I002/I001 ratio of XRD patterns decreases, and the K content and K/Rb ratio increase with decreasing particle size of the SFs from 2–5 to 0.1–0.2 μm. Leaching with 1N HCl and 1N NH4OAc and U–Pb, Sm–Nd, and Rb–Sr analysis of untreated SFs, leachate, and residue allowed us to study the isotope systematic of mixing in mobile and silicate material of shales. The 208U/204Pb and 87Rb/86Sr ratios of leachates are lower and the 147Sm/144Nd ratio is higher than those of residues. The leachates are also characterized by less radiogenic Pb and Sr and more radiogenic Nd relative to residues. With decreasing size of SF particles, the U, Pb, Sm, Nd, and Sr contents of leachates gently decrease and the Rb content increases. The 87Rb/86Sr and 87Sr/86Sr ratios of leachates of fine SFs are significantly higher, whereas their 238U/204Pb ratio is lower in comparison with coarse SFs. What is more, the data points of residues of various SFs occur along the mixing lines in the 87Rb/86Sr‒87Sr/86Sr and 1/86Sr‒87Sr/86Sr plots. The data points of corresponding leachates also form linear trends in 238U/204Pb‒206Pb/204Pb, 206Pb/204Pb‒207Pb/204Pb, 147Sm/144Nd‒143Nd/144Nd, and 87Rb/86Sr‒87Sr/86Sr coordinates. Apparent Rb–Sr ages calculated from slopes of “inner isochrons” (“leachochrons”) as well as K-Ar ages gradually decrease from 835–836 and 721–773 Ma, respectively, for SFs of 2–5 μm and to 572‒580 and 555‒580 Ma, respectively, for SFs of 0.1–0.2 μm. Thus, the XRD and isotopic data indicate that both clay and mobile shale constituents are mixtures at least of two components, and the silicate phase contains authigenic illites of various ages. First-generation illite abundant in the coarse SFs of 2–5 μm and 0.6–2.0 μm was formed immediately after the deposition of the Inzer sediments and its age of 803–836 Ma is consistent with stratigraphic age of the Inzer Formation. The formation of this illite was facilitated either by lithostatic burial or intense horizontal fluid flow caused by tectonic inversion in the eastern regions of the Uralian paleobasin. The age of the second-generation illite is 572–580 Ma; it was formed as a result of vertical movements or renovation of the composition of the pore fluids during deformations and metamorphism of the South Urals related to the evolution of the Beloretsk metamorphic complex.

Sm-mediated dielectric characteristics and tunable magneto-electric coefficient of 0.5Bi1-xSmxFe0.95Mn0.05O3-0.5PbTiO3 composites

Magneto-electric multiferroic composites have gained a lot of interest these days mainly due to extensive potential of coupling between ferroelectric and magnetic orders. In this work, we present a series of 0.5Bi1-xSmxFe0.95Mn0.05O3 − 0.5PbTiO3 (x = 0.00, 0.03, 0.06, 0.09, 0.12 and 0.15) composites, prepared by sol-gel auto-combustion and solid state reaction method to explore the tunability of magneto-electric coefficient. X-ray diffraction confirmed the rhombohedraly distorted cubic perovskite and tetragonal structures of BiFeO3 and PbTiO3, respectively. Ferroelectric loops showed that leakage current can be tuned and reduced by Sm-doping. Magnetic analysis showed switching of antiferromagnetic behaviour into weak ferromagnetic behaviour. Saturation and remanent magnetization were also calculated exhibiting an increasing trend with increasing Sm contents. Synthesized composites showed the non-linear frequency dependent dielectric response which was explained on the basis of Maxwell Wagner theory. Time varying conductivity was probed on the basis of polaron mechanism. The optimized composite reveal an enhanced magneto-electric coupling as compared to that of pure BiFeO3 which makes them feasible for the fabrication of multifunctional devices.

Synthesis, characterisation and investigation of enhanced photocatalytic activity of Sm&lt;SUP align="right"&gt;+3&lt;/SUP&gt;, Ni&lt;SUP align="right"&gt;+2&lt;/SUP&gt; co-doped TiO&lt;SUB align="right"&gt;2 nanoparticles on the degradation of azo dyes in visible region

Pure and samarium-nickel co-doped TiO2 nanoparticles with different Sm contents were synthesised by sol-gel method. The synthesised nanoparticles were characterised using different techniques. It is revealed from experimental results that the doping of TiO2 with samarium and nickel not only increase the surface area of mesoporous TiO2 but also decrease the particle size (17.0 nm to 8.01 nm by increasing Sm+3 contents). Diffuse-reflectance spectroscopic studies showed the slight red shift in band-gap transitions and appearance of the new absorption band in the visible region (719 nm) caused by Ni+2 and Sm+3 doping. The photocatalytic degradation of azo dyes (Reactive Red-195 and Reactive Black-08) was carried out in visible region using modified TiO2 at different pH values. Results revealed that 99% of RR-195 and 75.33% RB-08 were degraded after 10-20 minutes of irradiation. Maximum degradation was achieved in case of nanoparticles co-doped with 5% Ni and 3% Sm.

Evolution of Magnetic Anisotropy With Sm Contents in Sm–Co Thin Films

In this paper, the evolution of magnetic anisotropy as a function of Sm contents in buffer-free Sm-Co thin films grown by molecular beam epitaxy is investigated. From the soft magnetic Sm <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">17</sub> phase, the anisotropy evolves to the hard magnetic SmCo <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> phase with a distinct perpendicular anisotropy and a maximum magnetic anisotropy energy of 1.67 MJ/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> as measured by torque magnetometry at 300 K. For SmCo <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> , a saturation magnetization of 845 emu/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , close to the bulk single crystal value is achieved, while a squareness ratio close to unity is measured in the hysteresis curve perpendicular to the film plane. Previously grown YCo <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> and CeCo <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> thin films with perpendicular anisotropy show a considerably reduced uniaxial anisotropy as well as a reduced squareness ratio as compared to SmCo <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> . These results demonstrate that the magnetic parameters of rare earth-cobalt thin films can be adapted according to the requirements of applications such as magnetic recording.

Modification of the Sm–Nd isotopic system in garnet induced by retrogressive fluids

AbstractGarnet, as a major constitutive mineral of eclogite, is important for Sm–Nd dating of eclogite due to its high Sm/Nd ratio and its stability during retrogression. However, a comprehensive study of the petrography, mineral chemistry, garnet water content, and Sm–Nd isotopic composition of eclogites from the Bixiling massif, Central Dabie Zone (CDZ), reveals significant modification of the Sm–Nd isotopic system in garnet as a result of retrogression. This problem constitutes a challenge for Sm–Nd dating of the Bixiling eclogites, with the Sm–Nd isochron ages of 218 ± 4 to 210 ± 9 Ma reported in the literature being younger than 226 ± 3 Ma, which is the generally accepted peak metamorphic age of the CDZ. Petrographic analysis reveals heterogeneity in colour within single fractured garnet grains. There are light‐pink garnet (Grt‐P) and red garnet (Grt‐R) types that possess distinct chemical compositions. Compared to Grt‐P, Grt‐R has higher Fe and andradrite contents but lower Al and grossular contents. Grt‐P also has lower water contents (15–35 ppm) than Grt‐R (34–65 ppm), which, together with the spatial association between Grt‐R and fractures, suggests that the colour change is related to fluid alteration. Grt‐P is an ultra‐high‐pressure (UHP) mineral, and Grt‐R is the product of the interaction between Grt‐P and a fluid during retrogression. Moreover, Grt‐R features lower Sm and Nd contents but higher Sm/Nd ratios than Grt‐P. The Sm–Nd isochrons defined by UHP minerals (Grt‐P+Omp+Rt or Grt‐P+Cpx+WR) from three eclogite samples yield consistent ages of 226.0 ± 3.8 Ma, 225.0 ± 3.9 Ma and 226.2 ± 6.9 Ma, which are identical to the peak metamorphic age of 226 ± 3 Ma for the CDZ. The retrogressed garnet (i.e., Grt‐R), omphacite and rutile, together define a pseudoisochron with younger ages of 218.9 ± 5.9 to 202.8 ± 4.8 Ma, which are geologically meaningless. The increase in the Sm/Nd ratio with constant or lower 143Nd/144Nd ratios during the transformation of Grt‐P to Grt‐R was probably the cause of these younger ages.

Fabrication and properties of high B value [Mn1.56Co0.96Ni0.48O4]1−x[SrMnO3]x (0 ≤ x ≤ 0.5) spinel–perovskite composite NTC films

The [Mn1.56Co0.96Ni0.48O4]1−x[SrMnO3]x ((MCN)1−x(SM)x, 0 ≤ x ≤ 0.5) ceramic thin composite films were grown on SiO2/Si (100) substrates by the chemical solution deposition (CSD) method. The results of X-ray diffraction showed that the (MCN)1−x(SM)x (0 < x ≤ 0.5) films were a resemblance of the spinel–perovskite composite structure. The field emission scanning electron microscope analyses presented a considerable improvement in relative density with the increasing of the SM contents. In particular, the thermal constant of (MCN)1−x(SM)x ceramic film increased from 3289 to 5390 K with the increasing of the SM contents (x) from 0 to 0.5. This feature was attributed to the increase in the grain boundary resistance and the increase in Mn3+/Mn4+ pairs as the SM contents increased. From the spectroscopic ellipsometer spectroscopy results, it was found that the (MCN)0.5(SM)0.5 film had the biggest refractive index n value of 2.36 at 1.5 eV and a strong absorption peak at 4.0 eV. The sensitivity of MCN spinel ceramic film was enhanced by the compounding of SM. It was a significant disposition in the study of negative temperature coefficient thermistors.

Microstructure and magnetic characterization of the Sm-CoMn co-substituted SrCaM hexagonal ferrites

A series of Sm-CoMn substituted hexagonal ferrites with chemical composition of Sr0.85-xCa0.15SmxFe12-y(Co0.5Mn0.5)yO19 (0.00 ≤ x ≤ 0.60, (0.00 ≤ y ≤ 0.50) were synthesized by the solid-state reaction method. Microstructure and magnetic properties of the hexaferrites have been investigated by the X-ray diffraction, field emission scanning electron microscopy and a permanent magnetic measuring system. A single magnetoplumbite phase is exhibited in the hexaferrites with the substitutiom of Sm (0.00 ≤ x ≤ 0.12) and CoMn (0.00 ≤ y ≤ 0.10) contents. For the hexaferrites containing Sm (x ≥ 0.24) and CoMn (y ≥ 0.20), impurity phases are observed in the structure. The FESEM micrographs exhibit that the hexaferrites with different Sm-CoMn contents have formed hexagonal structures and the grain size of the hexaferrites remains unchanged with increasing Sm-CoMn content. The remanence (Br), Hk/Hcj ratios, and maximum energy product [(BH)max] decrease with increasing Sm-CoMn content (0.00 ≤ x ≤ 0.60, (0.00 ≤ y ≤ 0.50). Instrinsic coercivity (Hcj) and magnetic induction coercivity (Hcb) increase with increasing Sm-CoMn content (0.00 ≤ x ≤ 0.12, 0.00 ≤ y ≤ 0.10), and then decrease with increasing Sm-CoMn content (0.12 ≤ x ≤ 0.36, 0.10 ≤ y ≤ 0.30), while for the hexaferrites with Sm (x ≥ 0.36) and CoMn (y ≥ 0.30), with increasing Sm-CoMn content, Hcj increases and Hcb decreases.

Geochronology and geochemistry of mafic dykes in the Helanshan complex: Implications for Mesozoic tectonics in the North China Craton

The Helanshan tectonic belt (HTB) is a major tectonic divide between the Alxa and Ordos blocks in the North China Craton. The geochronology and petrogenesis of the mafic dykes in the northern HTB are keys to understanding the tectonic evolution of this belt. The mafic dykes, intruded into the Neoarchean–Paleoproterozoic metamorphic basement, are mainly composed of diabase with a mineral assemblage of plagioclase (45%–60%), pyroxene (25%–35%), minor quartz and Fe–Ti oxides. The LA-ICPMS U–Pb analysis of zircon grains from representative dykes yield a weighted mean age of 206 ± 1.9 Ma, which represents the crystallization age of the dyke. The diabases show high contents of Fe2O3T (11.88–17.55 wt.%), low contents of SiO2 (45.65–50.95 wt.%) and MgO (3.31–5.50 wt.%) with low Mg# (=100 × MgO/(MgO + FeO) atomic ration) of 33–44. They are characterized by enrichment of light rare earth elements (LREEs) and large ion lithophile elements (LILEs) (e.g., Rb, Ba and Pb), and slight depletion of high field strength elements (HFSEs). These features suggest that the magma has undergone extensive fractionation of olivine and pyroxene but only minor crustal contamination during its evolution. Their high Sm contents and La/Sm ratios, and low Sm/Yb ratios indicate that magma from which the dykes formed was derived from low degree (about 5%) partial melting of an enriched garnet + spinel lherzolite mantle source. Together with regional geology, these geochemical and geochronological data suggest that the mafic dykes in the HTB were formed in an intracontinental extensional setting during the late Triassic.

Effect of samarium doping on structural, optical and magnetic properties of vertically aligned ZnO nanorod arrays

Samarium doped vertically aligned one dimensional ZnO nanorod (NR) arrays were grown by vapor phase transport (VPT) method through vapor solid (VS) growth process. Influence of different concentrations (0% to 8%) of Sm (all Sm contents in the paper are in mass fraction) on the ZnO NR arrays were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), photoluminescence (PL), Raman spectroscopy and vibrating sample magnetometry (VSM) techniques, respectively. X-ray diffraction studies revealed that the ZnO NR arrays were perfectly oriented along (002) crystallographic orientation with wurtzite crystal structure. Photoluminescence results showed an increase in oxygen vacancies due to increase in Sm doping. M-H curves revealed enhanced ferromagnetic behavior, and the magnetic moment values were 0.45, 0.363, 1.694, 3.613 and 2.197 emu/cm3 for (0–8%) Sm doped ZnO NR arrays respectively. The curve revealed that paramagnetic behavior was observed for undoped ZnO NR arrays and on increasing the Sm dopant to 4%, paramagnetic switched to ferromagnetic behavior.

Hydrothermal synthesis of Sm-doped Bi2MoO6 and its high photocatalytic performance for the degradation of Rhodamine B

Serials Sm doped Bi2MoO6 photocatalyts with different Sm contents (xSm-Bi2MoO6, x% = 0.0%, 0.4%, 0.6%, 0.8%, 1.0%, 1.2%) were prepared via hydrothermal method to improve the photocatalytic performance of pure Bi2MoO6. The samples are characterized by XRD, XPS, SEM, TEM, HRTEM, and PL techniques. It indicates that Sm3+ ions were successfully doped into Bi2MoO6, and the band gap value was gradually decreased with Sm dopant concentration increasing. The photocatalytic activity of Sm-doped Bi2MoO6 photocatalyst was significantly affected by the Sm doping content. Compared to pure Bi2MoO6, the Sm-doped Bi2MoO6 samples exhibited much higher photocatalytic activity and 0.8% Sm-doped Bi2MoO6 shows the highest RhB photodegradation rate, being 89% in 50 min under visible light irradiation. The improved photocatalytic activity of Sm-doped Bi2MoO6 could be attributed to the enhanced visible light absorption, narrower band gaps and higher separation rate of electron-hole pairs derived from Sm trapping photogenerated electrons. But the phase structure, special surface areas and morphology have little effects on the higher photocatalytic activity of Sm-doped Bi2MoO6.