Gd Substitution Effects on the Magnetic Properties of the Pr1−x Gd x Co4Si Compounds

The crystal structure and magnetic properties of single phase Pr_1?x Gd _x Co₄Si compounds with x=0,0.2,0.4,0.6,0.8, and 1.0 have been investigated. X-ray analysis reveals that the compounds crystallize as a single phase having the hexagonal CaCu₅-type structure with the space group P6/mmm. The substitution of Gd for Pr causes a linear decrease of the unit-cell parameters a and c, and the unit-cell volume V. Magnetic measurements indicate that all samples are ordered magnetically below the Curie temperature. The saturation magnetization at 4.2 K decreases upon the Gd substitution up to x=0.6, and then increases.     

The Effect of Cadmium Substitution on the Superconducting Properties of Tl1−x Cd x Ba2Ca2Cu3O9−δ Compound

In order to study how Cd substitution for Tl changes, the superconducting properties of Tl_1?x Cd _x Ba₂Ca₂Cu₃O_9?δ compound with x=0, 0.1, 0.2 and 0.3. We have prepared samples with Cd in place of Tl by the solid state reaction method. It has been found that the increase of the Cd concentrations of all samples produced increases the transition temperature from 113 to 123 K and changes the mass density ρ _m, C/a and volume fraction V _Ph(1223).. XRD shows that the partial substitution of Tl with Cd is helpful to form the superconducting 1223 phase (TlBa₂Ca₂Cu₃O_9?δ ). It has been shown that samples mainly contain tetragonal phase 1223 with a few additional mixed 1212 and 1201 phases.     

Thermal Properties of La1−x A x CoO3 (A = Ca and Ba)

The thermal properties of La_1?x A _x CoO₃ (A = Ca, Ba and 0.0≤x≤0.3) for temperature (1 K≤T≤300 K) have been investigated using the Modified Rigid ion model (MRIM) with pair wise interionic interaction potential. The temperature dependent (1 K≤T≤300 K) variation of specific heat and thermal expansion for La_1?x A _x CoO₃ (A = Ca, Ba and 0.0≤x≤0.3) has presented proper interpretation of the experimental data. Also the effect of lattice distortions on the thermal properties of these perovskite cobaltates has been studied by an atomistic approach. In addition, the results on the cohesive energy (?), molecular force constant (f), Reststrahlen frequency (υ), Debye temperature (θ _D ) and Gruneisen parameter (γ) are also discussed.     

Effect of electropulsing on the precipitation of NbC x N1−x from austenite phase

The precipitation of NbC _x N_1?x significantly affects the high-temperature mechanical properties of Nb microalloyed steel. The control of the precipitation behaviour of NbC _x N_1?x is the key, especially the nucleation and precipitation from Nb solid solution. We explore to use electropulsing to promote the precipitation of NbC _x N_1?x through thermodynamic model, chemical phase analysis, XRD and TEM. The modelling research show that electropulsing intensity significantly promotes the nucleation of NbC _x N_1?x in austenite phase. The higher the electropulsing temperature is, the better the promotion effect is. The chemical phase analysis and XRD investigation results show that electropulsing can increase the amount of precipitation of NbC _x N_1?x by 50% at 950°C compared to the precipitation without electropulsing.     

Effect of Pr and Ca Substitution on the (La1−x−u Pr x Ca u )(Ba1.5Sr0.5)Cu3O y Superconductors

In the fully oxygenated single phase (La_1–x–u Pr _x Ca _u )(Ba_1.5Sr_0.5)Cu₃O _y (0x1.00, 0u0.20) system, if u=0, the z-coordinate of the Ba site, z(Ba), and d _Ba–bp (distance between the Ba site and the basal plane) are lowered by increasing the amount of Pr in the (La_1–x Pr _x )(Ba_1.5Sr_0.5)Cu₃O _y series. On the contrary, if u0, z(Ba) and d _Ba–bp are raised by increasing the amount of Ca ion in the (La_1–x–u Pr _x Ca _u )(Ba_1.5Sr_0.5)Cu₃O _y (0x0.30, 0u0.20) series. Linear relationships are found between z(Ba), d _Ba–bp and the oxygen stoichiometry (y). T _c and p _sh (the hole concentration in CuO₂ layers) increase with increasing the angle of Cu(2)-Ba-Cu(2). Relative positions of the Cu(2) and Ba sites are important in determining the T _c of these 123 compounds.     

Effect of Composition Variations on Electrical and Optical Properties of La1−x (Ca, Sr) x MnO3 Thin Films

Thin films of La _0.67 Ca _0.33 MnO ₃₊ (d 200 nm) grown at 750° C on MgO(100) substrates by pulsed laser deposition were annealed in various oxygen atmospheres. The LaF ₃ , CaF ₂ and Mn overlayers (d 5-10 nm) have been evaporated onto the films in order to saturate the compound by La, Ca or Mn during subsequent annealing at 900° C in air. Further, the pulsed injection CVD method has been utilized to prepare series of La _1–x Sr _x MnO ₃ films with x = 0÷0.5 on LaAlO ₃ (100). The effect of composition variations on electrical resistivity and magnetoresistance of the films as well as on their optical transmission and reflection spectra in the energy range between 0.2 and 4.0 eV has been investigated.     

Effect of Trace Sc and Zr on the Mechanical Properties and Microstructure of A1 Alloy 2618

1. IntroductionAluminum alloy for aircraft industry is requiredto maintain microstructure stabilityt strength andtoughness at temperatures ranging from 100 to 200'Cor even higher. Some rapidly solidified powder metallurgy (RS/PM) experimental alloys, such as ALFe-VSi alloyt have good mechanical properties up to 300'C.But the alloys produced by rapid solidiflcation processing tend to be relatively more costly and moredifficult to prepare than wrought materials fabricatedfrom ingots[1]. Acc…     

Low-temperature properties of pseudoternary R(Rh1−x Ir x )4B4 (R=Ho and Dy) systems

Pseudoternary Ho(Rh_1–x Ir_x)₄B₄ and Dy(Rh_1–x Ir_x)₄B₄ systems were investigated with respect to the interplay between superconductivity (SC) and long-range magnetic ordering by means of specific heat (C) and upper critical magnetic field (H _c2) measurements. For Ho(Rh_1–x Ir_x)₄B₄ withx0.2 and Dy(Rh_1–x Ir_x)₄B₄ withx0.15, ferromagnetic (FM) ordering, reminiscent of spin-1/2 mean-field theory, was observed. In particular, FM ordering in Ho(Rh_1–x Ir_x)₄B₄ with 0.07x0.2 was found to destroy SC at a second critical temperatureT _c2 below the superconducting transition temperatureT _c, and was accompanied by a spike-shaped feature inC atT _c2. Coexistence of antiferromagnetic (AFM) ordering with SC was observed in both systems for 0.2x0.7. The compounds withx0.5 exhibited Néel temperaturesT _N that were smaller thanT _c and enhanced values ofH _c2 belowT _N. TheT _c andT _N undergo an abrupt decrease and increase, respectively, nearx0.5, and then cross atx0.6, above whichT _N>T _c. For Ho(Rh_1–x Ir_x)₄B₄ with 0.275x0.4, two different AFM transitions were detected in a double-peak feature inC.     

Thermal Diffusivity of La1−x Sr x MnO3 (x < 0.3)

Perovskite manganites are interesting because of their colossal magnetoresistance. In this work high resolution thermal diffusivity measurements of La_1–x Sr _x MnO₃ (0 x 0.3) single crystals in the temperature range from 250 to 400 K are presented. A photopyroelectric device in the standard back configuration has been used. The thermal diffusivity through second-order magnetic phase transitions, as well as through first- and second-order structural phase transitions has been measured. The critical parameters of the sample with x = 0.3 at the ferromagnetic-to-paramagnetic transition have been obtained, and are close to the values predicted by the Ising model.     

The Effect of Annealing Temperature on the Magnetic Properties of Mn x Co1?x Fe2O4 Ferrites Nanoparticles

Mn _x Co_1?x Fe₂O₄ ferrites compounds (0??x??0.6) have been synthesized by a glycol-thermal method from high-purity metals chlorides. Single phase spinel structure of the nanoparticles has been confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. The diameters of the as-prepared powders were estimated from XRD and TEM and were found to be in the range: 7 to 13?nm. Room temperature magnetizations were obtained using a vibrating sample magnetometer (VSM) on the as-prepared samples and on samples annealed at 500 and 700?°C. The variation of coercive fields, saturation and remnant magnetizations as a function of composition (x) and grain size have been investigated. ⁵⁷Co M?ssbauer spectra for as-prepared samples were also measured at different temperatures (27, 100, and 200?°C). Significant changes in magnetization properties and M?ssbauer parameters are observed across the composition range studied. The variation of coercive fields and saturation magnetizations appear to critically depend on the particle sizes as the compounds evolve from single domain to multidomain structure.     

Effect of Fe Substitution on the Structural,Magnetic and Magnetocaloric Properties of Pr0.6La0.1Mg0.3Mn1−x Fe x O3 (0≤x≤0.3) Perovskite Manganites Prepared by Sol Gel Method

Studies of the structural, magnetic, and magnetocaloric properties of polycrystalline Pr_0.6La_0.1Mg_0.3Mn_1?x Fe _x O₃ (0≤x≤0.3) perovskite manganites were carried out. The compounds were synthesized using the sol–gel method. X-Ray diffraction (XRD) analysis using Rietveld refinement shows that all our compounds crystallize in the orthorhombic structure with the Pnma space group. The surface morphology and elemental analysis of both samples were carried out by scanning electron microscopy (SEM) and the energy dispersive X-ray technique (EDX), respectively. Magnetization measurements versus temperature under magnetic applied field of 0.05 T showed that all our investigated samples display a ferromagnetic-paramagnetic transition. The substitution of Mn by Fe leads to an increase of the Curie temperature T _C from 64 K for x=0 to 380 K for x=0.3. The Arrott plots show that the phase transition is of second order. A large magnetic entropy change |ΔS _M | deduced from isothermal magnetization curves has been recorded in the parent compound Pr_0.6La_0.1Mg_0.3MnO₃ reaching a maximum of 0.79 J/kg K under a magnetic applied field of 2 T close to T _C . Our results on magnetocaloric properties suggest that the Pr_0.6La_0.1Mg_0.3MnO₃ compound is attractive as a possible refrigerant for low temperature magnetic refrigeration.     

Elastic and Thermal Properties of Double Doped Orthovanadate: Eu1−x (La0.254Y0.746) x VO3

We present the effect of A-site double doping (La_0.254Y_0.746) on elastic and thermal properties of EuVO₃ in a wide doping range (0≤x≤1), using a modified rigid ion model (MRIM). Various lattice distortions and their relation to bulk modulus has been investigated systematically. The effect of the lattice distortions on thermodynamic properties of Eu_1?x (La_0.25Y_0.74) _x VO₃ has been explored by an atomistic approach. The computed results emphasize that the Debye temperature decreases while the specific heat increases with increase in doping concentration (x). The computed temperature dependent (1 K≤T≤300 K) specific heat trends are in accordance with the corresponding experimental data at various compositions. Future scope of MRIM has also been discussed.     

Effect of CuO on the sintering and dielectric characteristics of (Ba1−x Sr x ) (Ti0.9Zr0.1)O3 ceramics

In order to lower the temperature required to density (Ba_1–x Sr _x ) (Ti_0.9Zr_0.1) O₃ (BSTZ-series) and to avoid the formation of a low dielectric constant phase, copper oxide is added as liquidphase promotor after BSTZ-series are calcined. Thea-axis lattice constant at room temperature elongates with both increasing amount of CuO added and higher sintering temperature, while thec-axis lattice constant elongates only slightly under the same condition. The dielectric constant increases with sintering temperature. However, for different amounts of CuO added, the dielectric constant increases with increasing amount of CuO at lower sintering temperatures (below 1100°C). When a higher sintering temperature is used (above 1200°C), the dielectric constant reaches a maximum at 1 wt % CuO added, and decreases slightly on further addition of CuO.     

Effect of Al content on the performance of Cu(In1−x Al x )S2 synthesized by hydrothermal solution processing

Al doped CuInS₂ (CIS) material was prepared by a low cost and non vacuum wet chemical process. The effect of aluminum concentrations on the crystal structure, morphology, percentage composition, and band gap of Cu(In_{1? x} Al _x )S₂ were investigated. The X-ray diffraction (XRD) shows that the size of crystal grains decreased with the increase of Al concentrations. Scanning electron microscope presents the size of particles is gradually become smaller with Al concentrations increase. The reason for these phenomenons is Al concentrations cause the solution to a colloidal state. Binding between ions and grains growing together gradually become harder in a colloidal solution. In situ XRD tests show that CIS perform exceptional thermal stability below 798 K but decomposed to Cu₂S and In₂S₃ at the temperature higher than 798 K. Results of energy dispersive X-ray analysis (EDAX) show the nearly stoichiometry composition of Cu(In_{1? x} Al _x )S₂ which matched well with the ratio of the precursor solution. The transmission spectra show that spectral transmittance decrease with decreasing contents of Al. The band gap of Cu(In_{1? x} Al _x )S₂ is continuously tuned in a range of 1.56–1.92 eV as Al/(Al + In) content ratio varied from 0 to 0.3. Finally, the mechanism of Al concentration on the properties of Cu(In_{1? x} Al _x )S₂ was discussed briefly.     

Magnetic and Magnetocaloric Properties of Laves Phase Dy1−x Gd x (Co1−x Ni x )2 Solid Solutions

We report magnetic and magnetocaloric properties of the polycrystalline series of Dy_1?x Gd _x (Co_1?x Ni _x )₂ (x=0.1, 0.2, 0.3, 0.4 and 0.5) solid solutions. The samples were characterized by powder X-ray diffraction patterns taken at room temperature and revealed that all the Dy_1?x Gd _x (Co_1?x Ni _x )₂ solid solutions consist of the C15 cubic Laves phase MgCu₂ type structure and a small amount of DyCo₃ and Dy₂O₃ impurity phases. Magnetic measurements showed that the samples undergoes a second-order type phase transition at T _C<130 K, from paramagnetic to ferromagnetic state. Heat capacity measurements have been performed for all solid solutions and allowed us to determine the Debye temperature. The magnetocaloric effect has been studied by means of specific heat measurements in magnetic field 0.42, 1 and 2 T. The GdNi₂ substitution effect on magnetic and magnetocaloric properties will be discussed.     

Effect of Ce Substitution on the Magnetoresistivity and Flux Pinning Energy of the Bi2Sr2Ca1−x Ce x Cu2O8+δ Superconductors

In this study, the effect of Ce doping on the properties of Bi₂Sr₂Ca_1?x Ce _x Cu₂O_8+δ ceramic superconductors, with x=0.0, 0.01, 0.05, 0.1, and 0.25, has been investigated. Samples’ precursors were prepared using the conventional solid state method and subsequently textured using the Laser Floating Zone technique. The magnetoresistance measurements were studied under various applied magnetic fields. The activation energies, irreversibility fields (H _irr ), upper critical fields (H _c2) and coherence lengths at 0 K (ξ(0)) were calculated from the resistivity versus temperature (ρ–T) curves, under DC magnetic fields up to 5 T. The thermally activated flux flow model has been applied in order to calculate the flux pinning energies. The results indicated that H _c2(0) varied from 416.19 to 115 T and the flux pinning energies varied from 1.46 to 0.042 eV at 0 T.     

Mechanical Alloying Effect on the Structure of Fe-Al-(Si) Alloy

The mechanical alloying effects on the structures of Fe71.3AI28.4(CeO2)0.3 and Fe73.3AI9.8-Si,e.e(CeO2)0.3 samples have been investigated mainly by Mossbauer spectroscopy and X-ray diffraction. It is found that with the increase of milling time, a substituting disordered a-Fe solution is formed gradually and almost completed after milled for 72 h. Further increasing milling time causes the atomic rearrangement within the powders. Correspondingly' the average lattice parameter and average crystalline size change until 72 h and remain constant after 72 h. The addition of Si leads to the higher disordered degree reflected in the smaller average hyperfine field and larger mean Square deviation.