Phase Homogeneity and Crystal Structure of Sb88Te12 Synthesized by Melt-quench Method

Phase homogeneity and crystal structure of Sb88Te12 alloy synthesized by melt-quench method have been analyzed using X-ray diffraction(XRD) and Raman spectroscopy.Rietveld refinement of crystal structure of Sb88Te12 has revealed the formation of Sb8Te3 and Sb phases respectively with 11R and A7 structures(space group is R3m).Phase fractions of the phases Sb8Te3 and Sb have been determined to be 44.44% and 55.56% respectively.Raman spectrum of Sb88Te12 has showed a highest intensity peak at 156 cm-1 and another peak at 151.1 cm-1,which correspond to A 1g modes of Sb8Te3 and element Sb,respectively.Analysis of Raman spectrum has substantiated the results obtained from structure refinement regarding the presence of two different phases.     

Microstructure and melting properties of Ag–Cu–In intermediate-temperature brazing alloys

The microstructure and melting properties of ternary Ag–Cu–In intermediate-temperature alloys(400–600 °C) prepared by electric arc melting were investigated in this work. The melting properties, phase compositions, microstructure and hardness were characterized by differential scanning calorimetry(DSC), X-ray diffraction(XRD), scanning electron microscopy(SEM)and micro-hardness tester, respectively. The results show that the melting properties, phase compositions, microstructure and hardness of Ag–Cu–In brazing alloys are substantially different when adding different levels of indium. Indium element could effectively reduce the melting temperatures of(Ag–Cu28)–x In alloys, and the melting temperatures of(Ag–Cu28)–25In alloy are located at 497.86 and 617.48 °C. When the indium content varies from 5 wt% and 10 wt%, the dominant phases in the alloys are Ag-rich and Cu-rich phases, and their granular crystals are smaller than 0.5 lm. When the indium content is higher than 15 wt%, the phase compositions of the alloy are Ag4 In and Cu11In9, and the microstructure exhibits dendritic crystals with a uniform distribution. The hardness of(Ag–Cu28)–x In alloy decreases first and then increases with the content of indium increasing, and the highest hardness of(Ag–Cu28)–25In alloy is HV 266.0.     

Microstructure of phases in a Cu–Zr alloy

The morphology and crystallography of phases in the Cu-0.12% Zr alloy were investigated by scanning electron microscope(SEM), transmission electron microscope(TEM), and high-resolution transmission electron microscope(HRTEM). The results show that the as-cast microstructure of Cu–Zr alloy is mainly Cu matrix and eutectic structure which consist of Cu and Cu5Zr phases with a fine lamellar structure. The disk-shaped and plateliked Cu5Zr phases with fcc structure are found in the matrix, in which habit plane is parallel to {111}a plane of the matrix.Between the copper matrix and Cu5Zr phase,there exists an orientation relationship of [112]a|| [011]Cu5Zr;(111)a||(111)Cu5Zr. The space structure model of Cu5Zr phase can be established.     

Synthesis and Characterization of CdO–SnO_2 Nanocomposites Prepared by Hydrothermal Method

In this work,(1-x)CdO–x SnO_2 nanocomposites(B 0.15) have been synthesized via hydrothermal route. The structural study reveals that CdO nanostructures possess crystalline phase and cubic structure. The CdO–SnO_2 nanocomposites possess both cubic and orthorhombic structure with good crystallinity. The crystallite size in the nanocomposites was found to be in the range of 9.6–19.6 nm. Field emission scanning electronic microscopy and highresolution tunnelling microscopy analysis confirm the presence of both cubic and orthorhombic structures which is also confirmed from X-ray diffraction studies. Fourier transform infrared spectroscopy(FTIR) studies confirm that CdO–SnO_2 nanocomposites possess the characteristics band of both CdO and SnO_2 nanostructures. The UV–visible absorption studies confirm that the optical absorption band in CdO–SnO_2 nanocomposites possesses both blue and red shift as compared to that of CdO nanostructures. Photoluminescence spectroscopy studies reveal the appearance of strong emission peak at 513,469 and 369 nm corresponding to green, blue and violet emission spectrum, respectively, in CdO–SnO_2 nanocomposites.The FTIR studies confirm the presence of hydroxyl and water functional group due to atmospheric water vapours and chemical bonding in CdO and CdO–SnO_2 nanocomposites. Raman spectroscopy confirms the presence of Raman bands of both CdO and SnO_2 phases in the CdO–SnO_2 nanocomposites.     

Phase fraction evolution in hot working of a two-phase titanium alloy: experiment and modeling

In the present work, the coupled effects of initial structure and processing parameters on microstructure of a two-phase titanium alloy were investigated to predict the microstructural evolution in multiple hot working. It is found that microstructure with different constituent phases can be obtained by regulating the initial structure and hot working conditions. The variation of deformation degree and cooling rate can change the morphology of the constituent phases, but do not alter the phase fraction. The phase transformation during heating and holding determines the phase fraction for a certain initial structure. β-α-βtransformation occurs during heating and holding.β to αtransformation leads to a significant increase in content and size of lamellar α. The α to β transformation occurs simultaneously in equiaxed α and lamellar α. The thickness of lamellar a increases with temperature, which is caused by the vanishing of fine α lamellae due to phase transformation and coarsening by termination migration. By assuming a quasi-equilibrium phase transformation in heating and holding,a modeling approach is proposed for predicting microstructural evolution. The three stages of phase transformation are modeled separately and combined to predict the variation of phase fraction with temperature.Model predictions agree well with the experimental results.     

Structure and intrinsic magnetic properties of Sm_(1-x)Pr_xCo_5(x=0–0.6) compounds

In this work, the effects of Pr content on the structure and intrinsic magnetic properties of Sm_(1-x)Pr_xCo_5(x = 0–0.6) compounds prepared by induction melting were systematically investigated by scanning electron microscopy(SEM), X-ray diffraction(XRD), and magnetic measurements. Microstructural observation and chemical composition analysis show that Sm_(1-x)Pr_xCo_5 compounds are composed of(Sm, Pr)Co(1:5) phase and(Sm, Pr)-rich grain boundary phase. XRD results show that all the Sm_(1-x)Pr_xCo_5 compounds have a(Sm, Pr)_1Co_5 main phase with the hexagonal CaCu_5-type crystal structure and the(Sm, Pr)_2Co_7 impurity phase. In addition, the detailed research shows that the lattice constants(a, c) and unit volume(V) are all enlarged with the increases in Pr content. According to the magnetic measurements, as the Pr content increases to larger than 0.4, both the Curie temperature(T_C) and the anisotropy field(H_A) of all the Prdoped compounds decrease rapidly. Meanwhile, the magnetization of Sm_(1-x)Pr_xCo_5 compounds at applied field of 14 T(M_(14 T)) are observably improved with Pr doping content of x0.3. Among them, Sm_(0.6)Pr_(0.4)Co_5 compound exhibits slightly lower H_Aand T_C, but much higher M_(14 T) than those of the binary SmCo_5, indicating that doping of proper Pr content into SmCo_5 compound can optimize the intrinsic magnetic properties. As a result, the optimal intrinsic magnetic properties of H_A= 29.11 T,T_C= 989 K, and M_(14 T)= 102.31 mA·m~2·g-1are obtained in Sm_(0.6)Pr_(0.4)Co_5 compound.     

TEM STUDIES OF THE W PHASE AND ITS ORDERED W'PHASE IN RARE EARTH Mg ALLOYS

By means of transmission electron microscopy(TEM),the W phase and its ordered W'phase in as-cast Mg-Zn-Zr-Y system alloys were studied.The W phase,which distributes alongthe grain boundaries in the form of a lamellar eutectoid with Mg,is of FCC structure with α=0.865 nm.The W'phase,which is an ordered structure of the W phase with α=2.055 nm,was found in the alloy with lower Y content.The W and W'phases have a simple orientationrelationship of(100)_W//(100)_(W'),(010)_W//(010)_(W'),and(001)_W//(001)_W;but they do nothave an orientation relationship with the α-Mg matrix.The results of convergent electroncliffractions(CBD)on these phases show that their point group is m3m and that the space group isFm3m.     

1:13 phase formation mechanism and first-order magnetic transition strengthening characteristics in (La,Ce)Fe_(13–x)Si_x alloys

The effects of the introduction of Ce to La_(1-x)Ce_xFe_(11.5)Si_(1.5) alloys on 1:13 phase formation mechanism,the first-order magnetic phase transition strengthening characteristics,and magnetocaloric property were studied,respectively.The results show that the formation mechanisms of 1:13 and La Fe Si phases in La_(1-x)Ce_xFe_(11.5)Si_(1.5) alloys are the same as those of Ce_2Fe_(17) and CeFe_2 phases in Ce–Fe binary system,respectively.The substitution of Ce in 1:13 phase which is limited can make the first-order magnetic phase transition characteristics strengthen,which can make thermal and magnetic hysteresis increase,the temperature interval of temperatureinduced phase transition decrease,and the critical magnetic field of field-induced magnetic phase transition(HC)increase,respectively.Owing to the lattice shrink of 1:13phase with the increase in Ce content,the Curie temperatures(TC) show a linear decrease.The maximum change in magnetic entropy gradually increases due to the decrease in temperature interval of temperature-induced phase transition,but the relative cooling capacities are all about80 Jákg-1at magnetic field of 2 T.     

PREPARATION OF NANO-CRYSTALLINE Fe-Cu THIN FILMS AND THEIR MAGNETIC PROPERTIES

Fe-Cu thin films of 0.2μm in thickness with different Cu contents were prepared by using r.f. magnetron sputtering onto glass substrate. The effect of sputtering param-eters, including Ar gas pressure and input rf power, on the structure and magnetic properties was investigated. It was found that when the power is lower than 70 W, the structure of the films remained single bcc-Fe phase with Cu solubility of up to 50at.%. TEM observations for the bcc-Fe phase showed that the grain size was in the nanometer range of less than 20nm. The coercivity of Fe-Cu films was largely affected by not only Ar gas pressure but also rf power, and reached about 2.5Oe in the pressure of 0.67-6.67Pa and in the power of less than WOW. In addition, saturation magnetization, with Cu content less than 60at. %, was about proportional to the con-tent of bcc-Fe. When Cu content was at 60at.%, however, saturation magnetization was much smaller than its calculation value.     

Phase selection and performance of Mg–Cu–Y amorphous composite with different Mg/Cu ratios

In this article, Mg–Cu–Y alloys with two different Mg/Cu ratios(in at%) were prepared using a watercooled copper mold. Scanning electron microscopy and X-ray diffraction were applied to analyze the microstructure and phase composition. Moreover, corrosion resistance and wear resistance were studied systematically. The results show that both Mg65 Cu25 Y10 and Mg60 Cu30 Y10 alloys could form a composition of crystalline and amorphous phases. Although the microstructure of Mg65 Cu25 Y10 consists of an amorphous phase and a-Mg, Mg2 Cu, and Cu2 Y crystalline phases, the microstructure of Mg60 Cu30 Y10 alloy mainly consists of the amorphous phase and a-Mg, Mg2 Cu. With reducing Mg/Cu ratio, the alloys have better corrosion resistance and wear resistance. The mechanism has also been discussed in detail.     

First-Principles Investigation on Phase Stability,Elastic and Magnetic Properties of Boron Doping in Ni-Mn-Ti Alloy

The all-d-metal Ni-Mn-Ti Heusler alloy has giant elastocaloric effect and excellent mechanical properties, which is different from the conventional Ni-Mn-based Heusler alloys. In this work, the preferred site occupation, phase stability, martensitic transformation, magnetic properties, and electronic structure of the B-doped Ni₂Mn_1.5Ti_0.5 alloys are systematically investigated by the first-principles calculations. The results show that B atoms preferentially occupy the octahedral interstitial. The doped B atoms tend to exist in the (Ni₂Mn_1.5Ti_0.5)_1-xB_x (x = 0.03, 0.06, 0.09) alloy in the form of aggregation distribution, and the martensitic transformation temperature decreases with the increase in the B content. For octahedral interstitial doping, the toughness and plasticity of the (Ni₂Mn_1.5Ti_0.5)_1-xB_x alloys decrease, but the strength and rigidity are greatly enhanced. This is because a small part of the d-d hybridization in ternary Ni-Mn-Ti alloy is replaced by the p-d hybridization in Ni-Mn-Ti-B alloy.     

Reduced Annealing Time and Enhanced Magnetocaloric Effect of La(Fe,Al)13 Alloy by La-nonstoichiometry and Si-doping

LaFe_13-xM_x (M = Si, Al) alloys are promising for use in magnetic refrigeration. However, they require long annealing time (30 days) in order to optimize the magnetocaloric properties. Research has shown that the addition of extra La in off-stoichiometric alloys can greatly shorten the annealing time. Therefore, the purpose of this study is to investigate the influence of the extra addition of La on the annealing properties of a new off-stoichiometric La_1.7Fe_11.6Al_1.4-xSi_x (x = 0, 0.1, 0.4) alloys. It was demonstrated that after a 36h annealing time, a large volume fraction of 1:13 magnetocaloric phase was obtained for all alloys. Further microstructural analysis of the off-stoichiometric La_1.7Fe_11.6Al_1.4-xSi_x alloys revealed a facet-like grain morphology. The La_1.7Fe_11.6Al_1.4 and La_1.7Fe_11.6Al₁Si_0.4 alloys were shown to contain large 1:13 phase precipitates separated in a La-rich matrix, while the La_1.7Fe_11.6Al_1.3Si_0.1 alloy had a continuous 1:13 phase matrix with a fine dispersion of La-rich precipitates throughout. When the magnetic field varied between 0 and 2 T, the corresponding magnetic entropy change and relative cooling capacity for the La_1.7Fe_11.6Al_1.3Si_0.1 specimen were determined as 4.58 J/kg K and 173.6 J/kg, respectively. More importantly, the La_1.7Fe_11.6Al_1.3Si_0.1 alloy displayed only a slight volume change when the meta-magnetic phase transition occurred, which is promising for cyclic use.     

Phase Stability,Magnetic Properties,and Martensitic Transformation of Ni2−xMn1+x+ySn1−y Heusler Alloy with Excess Mn by First-Principles Calculations

The phase stability, magnetic properties, martensitic transformation, and electronic properties of the Ni_2−xMn_1+x+ySn_1−y system with excess Mn have been systematically investigated by the first-principles calculations. Results indicate that the excess Mn atoms will directly occupy the sublattices of Ni (Mn_Ni) or Sn (Mn_Sn). The formation energy (E_f) of the austenite has a relationship with the Mn content: E_f = 135.27(1 + x + y) − 293.01, that is, the phase stability of the austenite decreases gradually with the increase in Mn content. According to the results of the formation energy of austenite, there is an antiparallel arrangement of the magnetic moment between the excess and normal Mn atoms in the Ni_2−xMn_1+x+ySn_1−y (x = 0 or y = 0) system, while the magnetic moment direction of the normal Mn atoms arranges antiparallel to that of Mn_Ni atoms and parallel to that of Mn_Sn atoms in the Ni_2−xMn_1+x+ySn_1−y (x, y ≠ 0) system. The martensitic transformation occurs in some Ni_2−xMn_1+x+ySn_1−y (x, y ≠ 0) alloys with large magnetic moments of ferrimagnetic austenite. Besides, the valence electrons tend to distribute around the Ni or Mn_Ni atoms and mainly bond with the normal Mn atoms. The results of this work can lay a theoretical foundation for further development of the Ni_2−xMn_1+x+ySn_1−y system as the potential ferromagnetic shape memory alloys.     

Formation and Relative Stabilities of Core-Shelled L12-Phase Nano-structures in Dilute Al-Sc-Er Alloys

First-principles thermodynamic calculations were carried out at the interface level for understanding the precipitation of coherent L1₂-phase nano-structures in dilute Al-Sc-Er alloys. All energetics, relevant to bulk substitution, interface formation, interfacial coherent strain and segregation, were calculated and used to evaluate the nucleation and relative stabilities of various possible L1₂ nano-structures. Only matrix-dissolved solute Er (or Sc) can substitute Sc (or Er) in L1₂-Al₃Sc (or Al₃Er). The inter-substitution between L1₂-Al₃Sc and Al₃Er is not energy feasible. Ternary L1₂-Al₃(Er_xSc_1-x) precipitates tend to form the Al₃Er-core and Al₃Sc-shell structure with a sharp core/shell interface. Three possible formation mechanisms were proposed and examined. The effects of Er/Sc ratio and aging temperature on the relative stabilities of L1₂-phase nano-structures in Al were also discussed.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Multiferroic Consequence of Porous (BiFeO_3)_x–(BiCrO_3)_(1-x) Composite Thin Films by Novel Sol–Gel Method

In this work, we have presented a spin-coating method to produce thin films started with pure BiCrO_3(BCO) and ended up with BiFeO_3(BFO) by increasing x values in the(BiFeO_3)_x–(BiCrO_3)_(1-x)composites. All the produced thin films have been crystallized at the annealing temperatures of 400 °C for 0.5 h. The XRD and EDAX spectrums give insight that the two crystal phases related to BCO and BFO stayed together within the thin film matrices. SEM analysis showed that the prepared composite had macroporous morphology with interconnected pores and its width(size) decreased with increasing x values. The strong correlations are observed among the microstructure, dielectric, ferroelectric, ferromagnetic properties and Fe concentration. Among all composites, the composition of 0.75 shows an attractive magnetization, polarization, switching and improved dielectric behaviors at room temperature. Significant increase in the multiferroic characteristics of 0.75 composition is due to arise of lower leakage current by causing reduction in oxygen vacancy density, and enhancement of super-exchange magnetic interaction between Fe~(3+) and Cr~(3+) at BFO/BCO interface layers. Our result shows that the thin layer on Pt(111)/Ti/SiO_2/Si substrate possesses simultaneously improved ferroelectric and ferromagnetic properties which make an inaccessible potential application for nonvolatile ferroelectric memories.     

Gamma-phase influence on shape memory properties in Ni-Mn-Co-Ga-Gd high-temperature shape memory alloys

The effect of γ-phase on two-way shape memory effect(TWSME) of polycrystalline Ni_(56)Mn_(25-x)Co_xGa_(18.9)Gd_(0.1) alloys was investigated. The results show that an appropriate amount of ductile γ-phase significantly enhances the TWSME. The largest TWSME of 1.4% without training is observed in Ni_(56)Mn_(21)Co_4Ga_(18.9)Gd_(0.1) alloy, and this value is increased to 2.0% after thermomechanical training. The as-trained TWSME decays over the first five thermal cycles and then reaches a stable value as the number of cycles further increasing. Only the degradation of 0.2% is observed after 100 thermal cycles. The better TWSME and thermal stability are ascribed to the stable extra stress field formed by the plastically deformed γ-phase.     

Crystal structures and structural relationships of KFe2(SeO2OH)(SeO3)3 and SrCo2(SeO2OH)2(SeO3)2

The new phases KFe₂(SeO₂OH)(SeO₃)₃ and SrCo₂(SeO₂OH)₂(SeO₃)₂ have been synthesized under low-hydrothermal conditions and their structures were determined by single-crystal X-ray methods. Both compounds are monoclinic; KFe₂(SeO₂OH)(SeO₃)₃: space group P2, A = 9.983(4), B = 5.270(1), C = 10.614(4) Å, β = 97.42(2)°, V = 553.7 ų, Z = 2; SrCo₂(SeO₂OH)₂(SeO₃)₂: space group P2ln, A = 14.984(2), B = 5.286(1), C = 13.790(2) Å, β = 94.72(1)°, V = 1088.5 ų , Z = 4. The refinements converged to R-values of 2.9 and 3.6% respectively.

The atomic arrangement in KFe₂(SeO₂OH)(SeO₃)₃ and SrCo₂(SeO₂OH)₂(SeO₃)₂ is based on isolated MO₆ octahedra (M = Fe³⁺, Co²⁺), which are corner-linked via trigonal pyramidal selenite groups to a framework structure. Interstitials are occupied by potassium or strontium atoms in ten- or eight-coordination respectively, and by the lone-pair electrons of the Se⁴⁺ atoms. Both compounds are not isotypic but are closely related and may be interpreted as different distortions of an idealized structure type in space group P2/m, which was modelled for a theoretical compound SrFe₂(SeO₃)₄ by distance least squares refinement (program ).     

Enhanced Thermochemical H_2 Production on Ca-Doped Lanthanum Manganite Perovskites Through Optimizing the Dopant Level and Re-oxidation Temperature

Perovskite material is one of the promising classes of redox catalysts for hydrogen production through two-step thermochemical H20 splitting. Herein, an analogue of La_(1-x)Ca_xMnO_3 perovskite was systematically investigated as a catalyst for thermochemical H2 evolution. The Ca doping level(x = 0.2, 0.4, 0.6, 0.8) and re-oxidation temperature were comprehensively optimized for the improvement of catalytic performance. According to our experimental results, La_(0.6)-Ca_(0.4)MnO_3 perovskite displayed the highest yield of H2 at the re-oxidation temperature of 900℃ and the obtained H2 production was-10 times higher than that of the benchmark ceria catalyst under the same experimental condition. More importantly, La_(0.6)Ca_(0.4)MnO_3 perovskite catalyst exhibited impressive cyclic stability in repetitive O_2 and H_2 test.     

Ba4In2−x(CO3)1+xO6−2.5x and Ba4In0.8Cu1.6(CO3)0.6O6.2—new indium oxycarbonates closely related to n=3 Ruddlesden–Popper phases

Investigations of phase relations in the Ba-rich part of the In₂O₃–BaO(CO₂)–CuO pseudo-ternary system at 900 °C have revealed the existence of new indium–copper oxycarbonate – Ba₄In_0.8Cu_1.6(CO₃)_0.6O_6.2. Rietveld refinement of the X-ray powder diffraction data combined with infrared studies gives evidence that this phase is a oxycarbonate crystallising in the tetragonal structure (space group I4/mmm) with unit cell parameters: a=4.0349(1) Å and c=29.8408(15) Å. In the binary part of the In₂O₃–BaO(CO₂) system we have identified the occurrence of Ba₄In_2−x(CO₃)_1+xO_6−2.5x oxycarbonate solid solution showing a crystal structure also described by I4/mmm space group, but with the unit cell parameters: a=4.1669(1) Å and c=29.3841(11) Å for x=1. The existence range of this phase, −0.153<x<0.4, includes chemical compositions of earlier found phases: Ba₅In_2+xO_8+0.5x with 0≤x≤0.45 (known as the -solid solution), as well as the binary Ba₄In₂O₇ phase. The crystal structures of both new oxycarbonates are isomorphic and related to n=3 member of the Ruddlesden–Popper family.