Sm Content Research Articles

Normal and inverse magnetocaloric effect and short-range ferromagnetic interaction in (Pr,Sm)0.5Sr0.5MnO3 phase separated manganite

The dependence of critical phenomenon on disorder induced by R/A-site cational size mismatch in polycrystalline manganite Pr0.5-xSmxSr0.5MnO3 (x = 0.25) has been investigated by means of bulk magnetization M (H, T) in the vicinity of the ferromagnetic-paramagnetic phase-transition. The critical exponents characterizing this second order phase transition, have been obtained using different methods such as modified Arrott plot, Kouvel-Fisher plot, critical isotherm analysis and field dependence of magnetocaloric effect. Moreover, the self-consistency and reliability of obtained critical exponents are verified by the Widom scaling law and scaling equations. We demonstrate that at x = 0.25 doping level, the β value match well with those theoretically predicted for the 3D-Heisenberg model, while the γ value is close to that expected for the 3D-Ising model. This suggests that the presence of R/A-site disorder in the system must be taken into account to fully describe the magnetism of phase separated manganites. Hence, the short-range ferromagnetic originates from phase inhomogeneity and evolves with addition of disorder depending on Sm content. Moreover, this sample also shows a coexistence of normal and inverse magnetocaloric effect.

Phase relations of the (Pr1−xSmx)2Fe14B system

ABSTRACTThe phase relations in the (Pr1−xSmx)2Fe14B system in a whole concentration range have been studied by means of X-ray powder diffraction (XRD), differential thermal analysis (DTA) and scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS). The XRD patterns of the (Pr1−xSmx)2Fe14B samples have been refined by Rietveld method. These results reveal that all the alloys (Pr1−xSmx)2Fe14B are similar to the end member of the investigated system Pr2Fe14B with tetragonal structure (space group P42/mnm). The continuous solid solutions were formed in this system. The normalized lattice parameters and unit cell volumes of (Pr1−xSmx)2Fe14B solid solutions decrease linearly with x ranging from 0 to 1.0. The DTA measurements show that the peritectic temperature of (Pr1−xSmx)2Fe14B increases with increasing Sm content and no metastable phases are detected. Based on the DTA data, SEM–EDS and XRD results, the vertical section of Pr2Fe14B–Sm2Fe14B in the Pr–Sm–Fe–B system has been constructed.

Ferroelectric and Dielectric Behavior of Samarium-Substituted Bi4Ti3O12 Nanomaterials Synthesized by Gel Combustion Method

Samarium (Sm) substituted bismuth titanate (Bi4Ti3O12, BT) nanoparticles with compositions of Bi4−xSmxTi3O12 (BSmT) (where x = 0.0, 0.25, 0.50, 0.75, 1.0) were prepared by using the gel combustion method. X-ray diffraction pattern of prepared nanoparticles confirmed that all the BSmT compositions were of the single phase orthorhombic structure with the space group of B2ab. The dielectric loss at 100 Hz varied from 0.0925 to 0.056 with an increase in Samarium content. Dielectric loss confirmed the lower leakage current of BSmT nanoparticles. The ferroelectric behavior of BSmT nanoparticles showed that the Bi3.50Sm0.50Ti3O12 had good ferroelectric property and also had minimum leakage current. The increase of coercive field (Ec) and the increase of remnant polarizations (Pr) were pronounced with the increase in Sm content confirming to the fact that the substitution of Sm3+ had improved the ferroelectric properties of BT.

Structure evolution and piezoelectric properties across the morphotropic phase boundary of Sm-substituted BiFeO3 ceramics

The evolution of structure, ferroelectric, and piezoelectric properties in Bi1−xSmxFe0.99Ti0.01O3 ceramics was extensively investigated within the entire morphotropic phase boundary region with 0 ≤ x ≤ 0.20. A sequential phase transition of R3c-Pna21-Pbnm with increasing Sm content was revealed by Rietveld refinement of the X-ray diffraction data together with the macroscopic ferroelectric measurements. Both ferroelectric and piezoelectric properties showed a great enhancement in the vicinity of the R3c/Pna21 (polar-to-polar) phase boundary, which should be caused by the field-induced phase transition between these two phases. Such field-induced phase transition might be essentially accompanied by a change of magnetic state, which indicated a way of controlling magnetism by means of electric field.

Crystallographic features in the vicinity of the morphotropic phase boundary in the multiferroic material Bi1-xSmxFeO3

ABSTRACTThe multiferroic material Bi1-xSmxFeO3 shows ferroelectric and antiferromagnetic properties in the ground state of the Bi-rich side. When the Sm content increases from x = 0 in BiFeO3, the (ferroelectric-R3c → paraelectric-Pnma) state change occurs around x = 0.14. According to the previous studies on Bi1-xSmxFeO3, the state boundary between the R3c and Pnma states can be identified as a morphotropic phase boundary (MPB), which is nearly parallel to the temperature axis in the state diagram. The notable feature of Bi1-xSmxFeO3 is that a remarkable piezoelectric response was also found near the MPB. However, the origin of the remarkable response has not been understood sufficiently. In this study, thus, the crystallographic features in the vicinity of the MPB have been examined by x-ray powder diffraction and transmission electron microscopy. It was confirmed that the R3c and Pnma states were present for 0 ≤ x ≤ 0.15 and for 0.16 ≤ x ≤ 0.30, respectively. In addition to these states, there also existed the PbZrO3-type state around x = 0.15, which was identified as a modulated structure. Based on the analysis of the modulated structure, furthermore, it was suggested that the PbZrO3-type state could be regarded as a 2q state, which is characterized by two transverse modulation waves with k1 = [1/2 0 0]o and k2 = [0 1/2 0]o in the orthorhombic-Pnma notation.

Phase diagram of the Nd2Fe14B–Sm2Fe14B pseudo-binary system

The phase relations in the (1−x)Nd2Fe14B–xSm2Fe14B system over the whole concentration range have been studied by means of X-ray powder diffraction (XRD), differential thermal analysis (DTA) and scanning electron microscopy with energy-dispersive X-ray spectroscopy. Crystal structure parameters for all studied compositions of (Nd1−xSmx)2Fe14B have been determined by full-profile Rietveld refinements. These results revealed that all intermediate alloys of (Nd1−xSmx)2Fe14B are similar to the end member of the investigated system, Nd2Fe14B, with a tetragonal structure (space groupP42/mnm). The formation of continuous solid solutions has been found in this system. The normalized lattice parameters and unit-cell volumes of (Nd1−xSmx)2Fe14B solid solutions decrease linearly with increasing Sm content. The DTA measurements show that the melting temperature of (Nd1−xSmx)2Fe14B increases linearly with increasing Sm content and no metastable phases were detected. Based on the DTA data and XRD results, a tentative phase diagram for the pseudo-binary system Nd2Fe14B–Sm2Fe14B has been constructed.

Formation of the C-type Orbital-Ordered State in the Simple Perovskite Manganite Sr1-xSmxMnO3

ABSTRACTThe simple perovskite manganite Sr1-xSmxMnO3 (SSMO) has been reported to have a highly-correlated electronic system for eg-electrons in a Mn ion. According to the previous studies, the C-type orbital-ordered (COO) state with the I4/mcm symmetry was found to be formed from the disordered-cubic (DC) state on cooling. The feature of the COO state is that its crystal structure involves both the Jahn-Teller distortion to orbital ordering and the R25-type rotational displacement of oxygen octahedra. Because of the involvement of both the distortion and the displacement, their competition should be expected in the formation of the COO state. However, the detailed features of the competition have not been understood yet. Thus, the crystallographic features of the COO state in SSMO have been examined by x-ray powder diffraction and transmission electron microscopy. It was found that, when the Sm content increased from x = 0 at room temperature, the DC state changed into the COO state with the tetragonal symmetry around x = 0.13. The notable feature of the COO state is that the state is characterized by a nanometer-scaled banded structure consisting of an alternating array of two tetragonal bands. One tetragonal band consisted of the COO state involving both the Jahn-Teller distortion and the R25-type rotational displacement. But, there was only the latter displacement in the other, the state of which could be identified as a disordered tetragonal (DT) state. Based on this, it is understood that the COO-state formation from the DC state should take place via the appearance of the DT state, which may involve fluctuations of the C-type orbital ordering.

HDL-sphingomyelin reduction after weight loss by an energy-restricted diet is associated with the improvement of lipid profile, blood pressure, and decrease of insulin resistance in overweight/obese patients

BackgroundSphingomyelin (SM) diminishes the fluidity of the surface monolayer of high-density lipoproteins (HDL), affecting their intravascular metabolism and antiatherogenic properties. Since overweight is associated with an altered HDL structure, weight loss may result in changes in HDL subclasses, particularly in their SM content. Therefore, we determined the plasma SM concentrations associated to both total HDL and HDL subclasses after weight loss in obese patients. MethodsFifty overweight patients, 40 women and 10 men, aged 38.6±6.4 y, were given an energy-restricted diet according to their sex, age, and height. No physical activity was prescribed. Plasma SM concentrations of HDL subclasses were determined by a gel surface method developed for this study. Cholesterol of HDL subclasses was also determined by enzymatic methods performed on a gel surface. ResultsMean weight lost was 3.5±0.4kg after 6weeks of dietary intervention. As expected, insulin resistance and blood pressure decreased whereas lipid profile improved, except for HDL-cholesterol. SM in plasma and in all HDL subclasses significantly decreased after intervention. The magnitude of HDL-SM reduction was statistically associated with the amelioration of the components of the metabolic syndrome; the reduction of BMI explained the decrement of HDL-SM in a multivariate analysis. ConclusionHDL-SM decreased after weight loss by an energy-restricted diet. Further, the association of this decrement with the improvement of blood pressure, lipid profile and the decrease of insulin resistance, was statistically significant; all HDL subclasses were similarly affected. Whether a reduction in HDL-SM contributes to the cardiovascular benefits of weight loss remains to be elucidated.

Doping level effect on the luminescence efficiency of Sm<SUP align="right">3+</SUP>-doped BaWO<SUB align="right">4 phosphors prepared by sol-gel process

The Sm-doped BaWO4 phosphor powders with Sm content of 0-7.5 at.% were fabricated with a sol-gel method. X-ray diffraction analysis, scanning electron microscopy, and photoluminescence spectra analysis were used to characterise the microstructural and photoluminescence efficiency. The effect of Sm doping level was studied. A granular particle morphology and decreased nanoscale average particles size with increasing Sm-doping level were observed. The matrix showed weak violet-blue emission. The Sm3+ in the BaWO4 matrix showed red emission that is obviously stronger than violet-blue emission of the matrix. A maximal doping level of Sm3+ cation was observed for a highest emission efficiency of Sm3+ cation.

STUDY OF STRUCTURAL AND DIELECTRIC PROPERTIES OF PZT CERAMICS MODIFIED BY SM ION SUBSTITUTION

The Effect of Sm substitution on the structural and dielectric properties of Pb1−xSmx(Zr0.4Ti0.6)1−x/4 O3 (PSZT) (x = 0.00, 0.04, 0.08 and 0.12) composition prepared from mixed oxide method at high temperature were synthesized. The formation of single – phase compounds were confirmed by XRD studies which were found to be in tetragonal phase at room temperature The dielectric constant, tangent loss, and transition temperature of PSZT as a function of temperature at selected frequencies has exhibited that maximum or peak are strongly dependent on Sm content. When the temperature of PSZT samples is increased above transition temperature, dielectric constant begins to decrease obeying Curie – Weiss law. The Conduction process was found to be mixed type. The variation of dielectric constant and tangent loss with temperature at selected frequencies exhibit their phase transition above room temperature.

Effects of Sm on microstructure and corrosion resistance of hot-extruded AZ61 magnesium alloys

Abstract

Effect of samarium doping on the physical properties of chemically sprayed titanium dioxide thin films

Titanium dioxide (TiO2) thin films were doped with samarium ion at different concentration ratios (y = ([Sm3+]/[Ti4+]) in the range of 0–1 at. % by a step of 0.25 at. %) and deposited on glass substrates, using a spray pyrolysis technique. Samples were characterized using X-ray diffraction (XRD), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), and photoluminescence spectroscopy, with a special emphasis on the evolution of their physic-chemical properties as a function of their Sm doping ratio. Typically, a decrease in the crystalline quality of the anatase phase is observed when the nominal Sm content increases from 0.25 to 1 at. %. A change of photoluminescence behavior of the titania films is also evidenced when the Sm content increases. Wemple-Di Domenico single oscillator model was applied in order to study the dispersion parameters as a function of Sm doping ratio.

Structural and Luminescence Properties of Sm(3+) Doped TTB -Type BaTa2O6 Ceramic Phosphors.

Pure and 0.5 to 10mole% Sm(3+) doped TTB (tetragonal tungsten bronze)-type BaTa2O6 ceramic phosphor was produced by the solid state reaction method which performed at 1425°C for 20h. XRD and SEM analysis indicated single TTB phase for undoped and 0.5 to 10mole% Sm(3+) doped BaTa2O6 structures. SEM also showed that the BaTa2O6 grain size decreased with the increasing content of Sm(3+). Optical analysis indicated significant emissions in the visible spectral region as green (λ = 562.7nm) and orange-reddish (λ = 597.1nm). The emission intensity increased with the increasing doping concentration up to 2.5mole%, and then decreased due to the concentration quenching effect.

Deposition of Sm2O3-doped CeO2 layers using the MOCVD method

Sm2O3-doped CeO2 layers were synthesized on the inner surfaces of tube shaped quartz glass substrates using the MOCVD method. Ce(tmhd)4 and Sm(tmhd)3 were used as precursors. Argon and air were the carrier gases. Air was also a source of oxygen, necessary for the elimination of carbon (a solid by-product of the reactant pyrolysis). The molar content of Sm(tmhd)3 in the reactant mixture was: 0.1; 0.2; 0.3. The temperature of the synthesis was maintained at 600–800°C. Such a low synthesis temperature made possible the deposition of amorphous and nanocrystalline layers. The higher the synthesis temperature, the greater the content of the crystalline phase and the larger the crystallites.The obtained layers were analysed by the scanning electron microscopy combined with the EDS and X-ray analyses.This work is a part of research on amorphous and nanocrystalline composite electrolyte CeO2+Sm2O3/ZrO2+Y2O3 for solid oxide fuel cells (SOFC).

A Highly Effective Catalyst of Sm-MnOx for the NH3-SCR of NOx at Low Temperature: Promotional Role of Sm and Its Catalytic Performance

Sm-Mn mixed oxide catalysts prepared by the coprecipitation method were developed, and their catalytic activities were tested for the selective catalytic reduction (SCR) of NO with ammonia at low temperature. The results showed that the amount of Sm markedly influenced the activity of the MnOx catalyst for SCR, that the activity of the Sm-Mn mixed oxide catalyst exhibited a volcano-type tendency with an increase in the Sm content, and that the appropriate mole ratio of Sm to Mn in the catalyst was 0.1. In addition, the presence of Sm in the MnOx catalyst can obviously enhance both water and sulfur dioxide resistances. The effect of Sm on the physiochemical properties of the Sm-MnOx catalyst were investigated by XRD, low-temperature N2 adsorption, XPS, and FE-SEM techniques. The results showed that the presence of Sm in the Sm-MnOx catalyst can restrain the crystallization of MnOx and increase its surface area and the relative content of both Mn4+ and surface oxygen (OS) on the surface of the Sm-MnOx catal...

Thermoelectric Properties of Bi2-xSmxCa2Co2Oy (x = 0.00, 0.01, 0.02, 0.03)

In this paper, the polycrystalline samples of Bi2-xSmxCa2Co2Oy (x = 0.00, 0.01, 0.02, 0.03) were prepared using conventional solid state reaction method. The X-ray Diffraction (XRD) results showed that all samples were found to be single phase. The lattice parameters of Bi2-xSmxCa2Co2Oy samples and relative densities decreased slightly with increase in Sm content, whereas the β angle decreased with the increasing x content. The decrease of the corresponds to the increasing Sm content. The Seebeck coefficient and resistivity increased with increasing Sm content. The substitution of trivalent Sm3+ for trivalent Bi3+ may decrease the hole concentration and mobility of the system, which also can lead to an increase in the Seebeck coefficient and resistivity. The Sm substitution for Bi leads to a decrease in the size of particle, which increased the scattering of charge carriers across grain boundaries. Among all the samples, Bi1.97Sm0.03 Ca2Co2Oy exhibited the highest power factor of 5.4 × 10−5 Wm−1K−2 at 752 K. These results suggest that the Sm is an effective substitution element for improving the thermoelectric properties of Bi2Ca2Co2Oy.

Site selectivity of Sm3+ ions in BaBi4−xSmxTi4O15 ceramics and its influence on electrical properties

Samarium (Sm) substitution in BaBi4−xSmxTi4O15 for (x=0.00–0.50) is investigated. Raman spectroscopy reveals preferential substitution of Sm3+ for Bi3+ at the A-site up to x=0.20 in the perovskite block, and shows improvement in electrical properties. Beyond x=0.20, partial incorporation of Sm3+ into the (Bi2O2)2+ layers leads to cationic disorder and a decrease in octahedral distortion resulting in poor dielectric and ferroelectric properties. The un-deviated “rigid layer” mode at 54cm−1 up to x=0.20 confirms stability of Bi3+ in the (Bi2O2)2+ layers over the Bi3+ in the perovskite layers. Reduced electrical conductivity, low dielectric losses and improved ferroelectric polarization are seen for an optimum Sm content of x = 0.20.

Magnetocaloric effect in (La1−xSmx)0.67Pb0.33MnO3 (0 ≤ x ≤ 0.3) manganites near room temperature

We present an investigation on structure, magnetic and magnetocaloric properties of the perovskite manganites (La1−xSmx)0.67Pb0.33MnO3 (x = 0, 0.1, 0.2, 0.3) synthesized by sol–gel technique. The XRD patterns show that all synthesized samples have reflections typical of the perovskite structure with orthorhombic symmetry. Thermomagnetic measurements showed that all the samples display a paramagnetic–ferromagnetic transition with decreasing temperature. The Curie temperature decreases with increasing Sm content from 358 K for x = 0–286 K for x = 0.3. We determined the isothermal magnetic entropy changes of all the samples from the magnetization measurements and furthermore measured the adiabatic temperature change of the sample for x = 0.3 directly. The results showed that the adiabatic temperature change, determined using together the entropy change and the specific heat and the value obtained by direct temperature change measurements both give 1.3 K for a magnetic field change of 3 T at about 280 K. We also measured the cyclic adiabatic temperature-change of the sample and the results indicate that the sample undergoes a reversible temperature-change on field-cycling which is essential for magnetic refrigeration.

Preparation of pure and Sm-doped Na0.5Bi0.5TiO3 nanosized powders by sol–gel method and their electrical properties

The sol–gel method was applied to synthesize Na0.5Bi0.5TiO3 (NBT) sols and ceramic powders by using glycol as solvent and the optimized condition was determined. The optimized preparation parameters were selected as follows: reaction temperature = 20 °C, pH of sol system = 3.5, nNBT:nglycol (mol) = 1:12, drying temperature = 150 °C, annealing temperature = 350 °C and calcination temperature = 700 °C. In this condition, the prepared powders show pure perovskite phase and good crystalline structure with uniform size about 50 nm, and their resistivity was 3.71 × 106 Ω m at room temperature. Then, Sm-doped Na0.5Bi0.5TiO3 ceramic powders were also prepared by using the sol–gel method, and the changes in constitution, structure, and electrical properties before and after Sm-doping were characterized. The resistivity of modified NBT powders was distinctly decreased after Sm-doping. With an increase in Sm content, the resistivity first increases and then decreases, and its lowest value was 2.41 × 105 Ω m with 0.5 at% Sm content. The dielectric properties of modified NBT powders were also improved by Sm-doping, which reveals a higher dielectric constant, stable dielectric constant curve and dielectric loss curve with an increase in frequency. XRD and SEM analyses demonstrate that there are no new phases appearing in Sm-doped specimens, but the cell parameters have changed and grain size has increased, which would be devoted to the enhancement of the electrical properties.

Effect of Composition on Structural and Magnetic Properties of Nanocrystalline Ferrite Li0.5Sm x Fe2.5–x O4

The effect of Sm content Li0.5Sm x Fe2.5–x O4 (x = 0, 0.05, 0.1, and 0.2) and sintering temperature on the phase evolution, microstructure, and bulk magnetic properties of lithium ferrite prepared by mechanical alloying is investigated. XRD results of pure samples confirmed that the single ferrite phase is formed after sintering at 800°C; however, increasing of samarium content led to the formation of secondary phase (SmFeO3) and enhanced intensity. The bulk magnetic properties decreased with increase Sm content and increased with sintering temperatures. Single-phase ferrites Li0.5Sm x Fe2.5–x O4 were produced by sintering of sample at 800°C, which is lower than the temperature associated with the conventional ceramic procedure.