Increasing Sm Content Research Articles

Effects of Sm on the grain refinement, microstructures and mechanical properties of AZ31 magnesium alloy

The effects of samarium (Sm) on the grain refinement, microstructures and mechanical properties of as-cast AZ31 (Mg–3Al–1Zn–0.3Mn) magnesium (Mg) alloy have been investigated. Very serious grain coarsening happens when Sm content is between 0.16% and 1.18%. This is due to both the reactions between Al and Sm which reduce the constitutional undercooling effect and the lack of Al2Sm heterogeneous nuclei. However, excellent grain refinement effect is achieved at Sm content above 2.17%, which is because the in-situ formed Al2Sm particles significantly promote heterogeneous nucleation. The main phases in AZ31–xSm alloys include α-Mg, β-Mg17Al12, Al11Sm3 and Al2Sm. The Mg17Al12 phase is gradually suppressed by the increase in Sm content, and the Al2Sm is present at a higher Sm content. Because of grain refinement strengthening and secondary phase strengthening effects, the room temperature tensile property of AZ31–3.13Sm alloy has the optimal value of YS78.7MPa–UTS216.7MPa-EL13.6%.

Structure and permanent magnetic properties of SmFex (x=3–8) melt spun ribbons during heat treatment

Compounds with the composition SmFex (x=3–8) were prepared by melt spun method at a velocity of 40 m/s and subsequent annealing at temperature between 600–1000 °C. The crystal structures of the as-quenched and as annealed powders were investigated by XRD methods with following Rietveld analysis. The glass forming ability could be enhanced by the increase of Sm content to x≤5. Metastable Sm5Fe17-type structure existed when 3≤x≤5 and temperature was lower than 800 °C. SmFe2-type structure could be stable up to 1000 °C when x>3 and temperature was under 800 °C. The content of SmFe2-type decreased with the increase of x value and increased with temperature lower than 800 °C, from which SmFe2-type started to bring the transition to SmFe3-type. As for Sm5Fe17-type compounds with x=3.4, the highest coercivity of 33.6 kOe could be obtained under a velocity of 30 m/s and heat treated under 700 °C×1 h.

Magnetostrictive properties of amorphous SmCo thin films with imprinted anisotropy

We examine the magnetostriction in amorphous SmCo thin films with a composition in the range 4--27 at. % Sm. The magnetostriction increases significantly with increasing Sm content but is small compared to terbium-based ferromagnetic compounds, despite the large imprinted anisotropy. The magnetostriction and anisotropy both increase approximately linearly as the temperature is reduced. The magnetoelastic energy is found to be far smaller than the anisotropy energy so the magnetoelastic atomic displacements during growth cannot be the origin of the imprinted anisotropy. The anisotropy is only slightly altered by the application of large tensile stresses, indicating that the local strain fields involved in magnetostriction are not equivalent to the global strain produced by mechanical bending.

Samarium and Yttrium Codoped BaCeO3 Proton Conductor with Improved Sinterability and Higher Electrical Conductivity

Acceptor-doped barium cerate is considered as one of the state-of-the-art high temperature proton conductors (HTPCs), and the proton conductivity of such HTPCs is heavily dependent on the dopant. In this work, a codoping strategy is employed to improve the electrical conductivity and sinterability of BaCeO3-based HTPC. BaCe0.8Sm(x)Y(0.2-x)O(3-δ) (0 ≤ x ≤ 0.2) powders are synthesized by a typical citrate-nitrate combustion method. The XRD and Raman spectra reveal all the compounds have an orthorhombic perovskite structure. The effects of Sm and/or Y doping on the sinterability and electrical conductivity under different atmospheres are carefully investigated. The SEM results of the sintered BaCe0.8Sm(x)Y(0.2-x)O(3-δ) pellets indicate a significant sintering enhancement with increasing Sm concentration. BaCe0.8Sm0.1Y0.1O(3-δ) exhibits the highest electrical conductivity in hydrogen among the BaCe0.8Sm(x)Y(0.2-x)O(3-δ) pellets. Anode-supported BaCe0.8Sm0.1Y0.1O(3-δ) electrolyte membranes are also fabricated via a drop-coating process, and the corresponding single cell exhibits desirable power performance and durability at low temperatures. The results demonstrate that BaCe0.8Sm0.1Y0.1O(3-δ) is a promising proton conductor with high conductivity and sufficient sinterability for proton-conducting solid oxide fuel cells operating at reduced temperatures.

Dielectric dispersion and energy band gap of Bi1.5−xSmxZn0.92Nb1.5O6.92 solid solution

The optical transmittance and reflectance spectra of samarium doped bismuth–zinc–niobium-oxide (BZN) pyrochlore ceramics are investigated in the wavelength range of 200–1050nm (200–1500THz). The Sm content in the Bi1.5−xSmxZn0.92Nb1.5O6.92 solid solution significantly alters the optical properties. Therefore, increasing the Sm doping ratio from x=0.10 to x=0.13 decreased the indirect forbidden energy band gap from 3.60 to 3.05eV. In addition, above 350THz, increasing the Sm content decreases the dielectric constant values and alters the dielectric dispersion parameters. The dielectric spectra which were evaluated in the frequency range of 200–1500THz reflected a sharp decrease in the dielectric constant with increasing frequency down to 358THz. The spectra reflected a resonance peak at this frequency. Such resonance spectrum is promising for technological applications as it is close to the illumination of 870nm IR lasers that are used in optical communications. The calculated oscillator (Eo) and dispersion (Ed) energies near that critical range (375–425THz) reflected an increase in both Eo and Ed with increasing Sm content.

Effect of Sm-substitution on structural, electrical and magnetic properties of BiFeO3

Samarium-modified bismuth ferrites (i.e., Bi1−xSmxFeO3 (BSFO; x = 0, 0.05, 0.15, 0.25) were synthesized in a single-phase by a solid-state reaction method. Preliminary x-ray structural analysis suggested that crystal structure of the material is rhombohedral for x = 0.0, 0.05, 0.15 and orthorhombic for x = 0.25 composition. The surface morphology and textures of the pellet samples, recorded by scanning electron microscope at room temperature, show uniform distribution of the different size of plate- and rod-shaped grains on the surface of the samples. The grain size generally decreases with increase of Sm-content in BSFO. Detailed studies of permittivity and impedance parameters of the samples in a wide frequency range (1 kHz — 1 MHz) at different temperatures (30°C–450°C) provide many new and interesting results about relaxation processes. Room temperature magnetic hysteresis loops revealed that the spontaneous magnetization increases due to structural distortion and partial destruction of spiral spin structure caused by the substitution of Sm in BiFeO3. Enhancement in magneto-electric coupling coefficient of BFO was observed with increase of Sm in BSFO.

Ce1–xSmxO2–δ-attapulgite nanocomposites: synthesis via simple microwave approach and investigation of its catalytic activity

Ce1–xSmxO2–δ-attapulgite (ATP) nanocomposites were successfully prepared via a facile microwave approach. This was a facile and rapid process requiring only low power of microwave irradiation (160 W). The catalytic performance of the Ce1–xSmxO2–δ-ATP nanocomposites with different Sm contents for degradation of methylene blue (MB) was systematically evaluated. The Ce1–xSmxO2–δ-ATP nanocomposites showed enhanced catalytic activities compared with pure CeO2/ATP. Specifically, the catalytic activities of Ce1–xSmxO2–δ-ATP nanocomposites increased with increase in Sm content from x=0.0 to 0.3. The introduction of an optimal amount of Sm3+ into CeO2 contributed to the formation of structure defects and electronic defects in the oxide lattice, which could increase concentration of oxygen vacancies. However, further increasing Sm content to x=0.4 induced the formation of more agglomerates, leading to decreased catalytic activity. It was believed that this facile, rapid microwave-assisted strategy was scalable and could be applied to synthesize other nanocomposites for different applications.

Study of A-Site Disorder Dependent Structural, Magnetic, and Magnetocaloric Properties in La0.7-xSmxCa0.3MnO3 Manganites

We report studies on the magnetocaloric effect of samarium doped lanthanum manganites with different Sm-concentrations. Polycrystalline La0.7-xSmxCa0.30MnO3 (0≤x≤0.3) samples were prepared using the conventional solid-state reaction method with phase purity and structure confirmed using X-ray diffraction. Temperature dependent magnetization measurements and Arrott analysis reveal first order ferromagnetic transition in parent sample and second order ferromagnetic transition in doped sample with Curie temperature decreasing progressively with increasing Sm concentration from ∼182 K for x = 0.05 to 109 K for x = 0.30. A large magnetic entropy change (∼1.75 J kg-1 K-1 at 0.5 T) has been observed in La0.7Ca0.3MnO3 sample, and is greatly suppressed as a function of disorder caused by Sm doping. This is ascribed to the gradual loss of first-order ferromagnetic transition. This investigation suggests that La0.7-xSmxCa0.30MnO3 compounds can be used as a potential magnetic refrigerating material with wide range of temperature.

Effects of Sm content on thermal stability of Sm2Co17 sintered magnets

Influence of Sm content on thermal stability of Sm2Co17 sintered magnets has been investigated. It is found that the temperature coefficients of remanence (α) first decrease, runs through a minimum, then starts to increases with increasing Sm content. During the sintering process, liquid phase (SmCo1.7) is beneficial to densification of the magnets. A substitution of Co for Fe in Sm-Co sintered magnets has been proved to decrease the α and improve the thermal stability of these materials.

Phase transition and electric field induced strain properties in Sm modified lead zirconate stannate titanate based antiferroelectric ceramics

The effect of Sm addition on the crystal structures and electrical properties of Pb1−3x/2Smx(Zr0.63Sn0.26Ti0.11)O3 ceramics were investigated in this work. X-ray diffraction analysis showed that with increasing Sm content from 0.005 to 0.03, the phase structure of the specimens underwent transition from ferroelectric (FE) to antiferroelectric (AFE) state due to the substitution of Sm3+ with smaller ion radius for Pb2+ decreasing the tolerance factor of the ceramics. In addition, it was observed that with the improvement of Sm3+ content, the strain of the specimens first increased and then decreased, and the largest value of 0.735% was obtained in the sample with x = 0.015 near AFE/FE phase boundary at the measuring frequency 1 Hz. This is because the reversal of the domains, which produces the strain, is more consummate in this composition. Further, the strain at different frequencies was nearly the same at high electric field, which was attributed to that the electric field applied to the sample was so large that the reorientation of the domains could finish in all measuring frequencies. Both a high strain level and a relatively good frequency stability in the specimen with x = 0.015 make a potential candidate for actuators applications over a wide-frequency working range.

Effect of Sm on the Microstructure and Mechanical Property of Mg-xSm-0.4Zn-0.3Zr Alloys

The effect of Sm content (2, 4, 6, 8wt.%) on the microstructures and mechanic properties of gravity casting Mg-xSm-0.4Zn-0.3Zr alloys were investigated. The results showed that the cast alloy mainly consists of α-Mg matrix and Mg41Sm5 phase distributed at the grain boundaries, and the amount of the second phase increased with the rise of Sm content. After the solution treatment (T4), the second phase disappeared, however small amount of cuboid-like phase were found inside the grain, and its volume fraction also increases with the rise of Sm content. It is found in the age hardening curves of the alloys at 175, 200, and 225 °C that the alloys with various components almost showed the same trend of age hardening. While the higher the Sm content, the harder the alloy. With the Sm content increases, the yield strength (TYS) of cast alloys (F state) were obviously improved, however the tensile strength (UTS) became lower because of the quick drop of the elongation. The elongations of solid solution (T4) and aging (T6) alloy became lower, while the yield strength and tensile strength increased at first and then decreased. The optimized component is Mg-4Sm-0.4Zn-0.3Zr, which the mechanic properties at T6 state are: TYS=131MPa; UTS=261MPa; δ=6.8%.

Characterization of A-site deficient samarium doped barium titanate

Ba1−xSm2x/3TiO3 (0.00≤x≤0.10, in a step of 0.02) ceramics have been prepared through solid state reaction route. Structural studies (XRD, FTIR, Raman) suggested a tetragonal symmetry of all the prepared ceramics and a decrease in tetragonality with increase in Sm content. Rietveld refinement technique has been employed to investigate the details of crystal structure and was found to be tetragonal at room temperature with space group P4mm. Photoluminescence study confirmed formation of shallow defects. The prepared materials are found to show photoemission in the violet, blue and green zone. Optical band gap values calculated from UV-visual diffuse reflectance spectra showed a decreasing trend in band gap values with increase in samarium concentration. Disk shaped pellets were prepared using PVA as binder. Scanning electron microscopy showed a drastic decrease in grain size on doping than undoped barium titanate. A regular increase in the grain size with increase in Sm content in the doped compositions is observed. Dielectric studies were performed over a wide temperature range from 15K to 600K at different frequencies. Normal ferroelectric character was obtained for all the compositions. A gradual decrease in the Curie temperature was noticed with increase in samarium content. P∼E hysteresis loops showed a domain pinning effect which increased successively resulting in a decrease in the values of remnant polarization and coercive fields.

Microstructure and properties of Sm-substituted BiFeO3 ceramics

Bi1−xSmxFeO3 (x=0.00−0.15) ceramics were synthesized by sol-gel technique with rapid liquid phase sintering process to study the effects of samarium (Sm) substitution on their microstructure and properties. X-ray diffraction (XRD) and Raman studies showed that the structure of BiFeO3 was changed from rhombohedral to orthorhombic at the samarium substitution concentration about x=0.10. The SEM investigation suggested that the Sm substitution hindered the grain growth. Magnetic measurements showed that all the samples studied had a weak ferromagnetism, and the ferromagnetic property of BiFeO3 was improved by Sm substitution due to the suppressed or broken cycloid spin structure caused by the changes in the crystalline structure and size effect. The leakage current was found to be reduced with increasing Sm concentration. The dielectric and ferroelectric measurements showed that dielectric constant, dielectric loss and ferroelectric properties were strongly dependent on the Sm content, Sm substitution could significantly improve the dielectric constant, remnant polarization and decrease the dielectric loss due to the significant decrease of the electric leakage of the samples.

Dielectric properties of Sm-doped CaCu3Ti4O12 ceramics

The effects of Sm substitution on structure, dielectric properties and conductivity of CaCu3Ti4O12 ceramics were investigated. Ca1−xSmxCu3Ti4O12 (x=0.0%, 0.5%, 1.0%) ceramics were synthesized by the solid-state reaction method. Single phase crystal of the ceramics with space group Im3 was obtained. With increasing Sm content, the dielectric loss of Ca1−xSmxCu3Ti4O12 ceramics improved but the dielectric constant also decreased significantly, with both the low- and high-temperature dielectric relaxations suppressed.

Performance of double-perovskite Sr2−xSmxMgMoO6−δ as solid-oxide fuel-cell anodes

Double-perovskite Sr2−xSmxMgMoO6−δ (SSMM, 0≤x≤0.8) is investigated as a possible anode material for solid-oxide fuel cells on La0.9Sr0.1Ga0.8Mg0.2O3−δ (LSGM) electrolytes. Single-phase SSMM samples with 0≤x≤0.4 are prepared. At x≥0.6, a small amount of SrMoO4 and Sm2O3 impurities are observed. The Mg/Mo ordering in SSMM decreases with increasing Sm content. Substitution of Sm for Sr significantly improves the electrical conductivity of SSMM. At x=0.6, the sample yields the highest conductivity, with values reaching 16Scm−1 in H2 at 800°C. The maximum power densities of single cells achieved with x=0.0, 0.2, 0.4, 0.6, and 0.8 anodes on a 300μm-thick LSGM electrolyte are 693, 770, 860, 907, and 672mWcm−2, respectively, in H2 at 850°C. The SSMM sample with x=0.4 is considered as the best anode candidate because of the impurity formation seen in x≥0.6 samples. The x=0.4 sample not only has a thermal-expansion coefficient closer to that of the LSGM electrolyte but also exhibits good electrochemical performance and stability in commercial city gas containing H2S, where the maximum power density achieved is 726mWcm−2 at 850°C.

Infrared spectra study of Nd 1.85−xR xCe 0.15CuO 4±δ ( R = Gd and Sm) single crystals

The X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectra, and resistivity ρ are measured on Nd 1.85− xR x Ce 0.15CuO 4± δ ( R = Gd and Sm) single crystals. From the XRD and FTIR spectra studies, the lattice constant c are found to decrease faster for Gd doping than that for Sm doping with increasing doping concentration x. Upon Gd doping, all the transmission peaks shift to high frequency but nearly unchanged with increasing Sm doping content. The volume of the unit cell observed through XRD and FTIR spectra decreases faster for Gd doping than that for Sm doping. Furthermore, for Gd doping the superconducting T c decreases rapidly with increasing the doping concentration, while the T c decreases slowly for Sm doping with increasing Sm content, which is found to be very well consistent with the evolution of the volume of the unit cell for two series.

Influence of Sm-substitution on structure and electromagnetic properties of Ba 3− xSm xCo 2Fe 24O 41 powders

Sm-substituted barium hexaferrites, Ba 3− x Sm x Co 2Fe 24O 41 ( x=0–0.25), were prepared by a conventional ceramic sintering method. The microstructure, complex permittivity, complex permeability and static magnetic properties of the samples were studied using powder X-ray diffraction, field emission scanning electron microscopy, vector network analyzer and vibrating sample magnetometry. The results reveal that by introducing a relatively small amount of Sm 3+ instead of Ba 2+ an important modification of both structure and high-frequency electromagnetic properties can be obtained. Doping of Sm 3+ suppressed the grain growth and gave rise to a decrease of the grain size. As the Sm content increases, the static magnetic properties continuously increase. The real part and imaginary part of complex permittivity initially increase with Sm content, and then decreases when x>0.10. The imaginary part of complex permeability decreases after Sm 3+ is doped. There is no obvious change in the real part of the complex permeability for different Sm contents. The reasons are discussed using electromagnetic theory.

Effects of particle size and composition on coercivity of Sm–Co nanoparticles prepared by surfactant-assisted ball milling

The SmCox (x=3.5, 4, 5, 6, 8.5, and 10) magnetic nanoparticles with different composition have been prepared by surfactant-assisted ball milling technique. By controlling the settle-down time and the centrifugation conditions, the SmCox nanoparticles with different particle size and narrow size distribution were successfully obtained. It was observed that the SmCo nanoparticles become unstable with increasing Sm content. It was also observed that the coercivity of the SmCox nanoparticles increases with Co content and particle size, indicating a complex effect of the particle size and composition on magnetic hardening of the hard magnetic nanoparticles.

Preparing different phases of Mg-Li-Sm alloys by molten salt electrolysis in LiCl-KCl-MgCl 2-SmCl 3 melts

Different phases of Mg-Li-Sm alloys were prepared by galvanostatic electrolysis in LiCl-KCl-MgCl 2-SmCl 3 melts at 670 °C. The electrolysis process and phase control of Mg-Li-Sm alloys were studied. The microstructures of α, α+β, β phases of Mg-Li-Sm alloys were characterized by X-ray diffraction (XRD) and optical microscope (OM). Analysis of scanning electron microscopy (SEM) and EDS mapping analysis showed that Mg distributed homogeneously in Mg-Li-Sm alloys. EDS result showed that the distribution of Sm was more at grain boundaries than within the grains. Inductively coupled plasma (ICP) analyses of the samples obtained by electrolysis showed that the chemical compositions of Mg-Li-Sm alloys were consistent with the phase structures of XRD patterns, and the lithium and samarium contents in Mg-Li-Sm alloys could be controlled by the electrolysis time and concentrations of SmCl 3. Effect of Sm on corrosion property of Mg-12Li alloy was studied. The corrosion resistance of the alloy improved firstly and then worsened with the increase of Sm content. The optimum Sm content was about 0.7 wt.%.

Effects of Sm substitution on microwave dielectric properties of Ba 4La 9.33(Ti 0.95Zr 0.05) 18O 54 ceramics

Sm substitution for La was investigated for the modification of Ba 4La 9.33(Ti 0.95Zr 0.05) 18O 54 ceramics. A single-phase solid solution with tungstenbronze-like structure formed in the whole range of y values in Ba 4(La 1− y Sm y ) 9.33(Ti 0.95Zr 0.05) 18O 54 ceramics. As Sm content increased, there was a constriction of the b-axis and c-axis, and decrease in the cell volume. The Qf value did not obey the mixing rules and it varied nonlinearly with composition y. Small levels of Sm substitution improved the Qf value with a decrease of dielectric constant. The temperature coefficient of resonant frequency varied from positive to negative and decreased continuously with the increase of Sm content. A near zero τ f value (−2.38 × 10 −6/°C) was obtained at the composition of y = 0.7.