Journal of Alloys and Compounds

Published by Elsevier
Online ISSN: 0925-8388
Publications
Article
The elastic, piezoelectric, and dielectric properties of [001](c) and [011](c) poled 0.33Pb(In(1/2)Nb(1/2))O(3)-0.38Pb(Mg(1/3)Nb(2/3))O(3)-0.29PbTiO(3) single crystals have been fully characterized at room temperature, and the temperature and frequency dependence of the dielectric susceptibility ε(33) were also measured. The depoling temperature of this crystal is more than 20 °C higher than that of the corresponding binary 0.71Pb(Mg(1/3)Nb(2/3))O(3)-0.29PbTiO(3) system. From the measured P-E hysteresis loops, the coercive fields along [001](c) and [011](c) directions have been determined to be 6.0 kV/cm and 6.6 kV/cm, respectively, which indicate that these domain engineered ternary relaxor-based ferroelectric single crystals are excellent candidates for high-power applications.
 
Article
The influence of temperature on electric-field-induced domain switching of [0 0 1]c oriented 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-0.3PT) single crystal has been studied. The piezoelectric properties of PMN-0.3PT single crystal change drastically at one critical field at 30 °C and two critical fields at 90 °C corresponding to electric-field-induced domain switching. The domain structures were studied by polarizing light microscopy on the [100]c surface under the electric field applied along [001]c direction. The PMN-0.3PT single crystal exhibits a rapid increase in piezoresponse at 100 V/mm, which is related to R-MA phase transformation. At 90°C, the M and T0 0 1 phases coexist at 100 V/mm, while T001 mono-domain appears at 300 V/mm. The domain switching process here can be identified as (T100 or T010) → M → T001. The experimental results show that the phase state and domain structures of the crystal are closely related to the piezoelectric behaviors.
 
Article
Two new compounds, Cd1.16Zn2.34(AsO4)1.5(HAsO4)(H2AsO4)0.5 (1) and Cd0.74Mg2.76(AsO4)1.5(HAsO4)(H2AsO4)0.5 (2), have been prepared hydrothermally. Their crystal structures consist of chains of edge-sharing M1O4(OH0.5)2, M1aO4(OH0.5)2, M2O5(OH0.5), and M2aO5(OH0.5) octahedra (M1, M1a = Zn, Cd; M2, M2a = Zn for 1, and M1, M1a = Mg, Cd; M2, M2a = Mg for 2) that are stacked parallel to (1 0 1) and are connected by the [(AsO4)0.5(AsO3(OH))0.5]2.5- and [(AsO4)0.5(AsO2(OH)2)0.5]2- tetrahedra. These chains produce two types of channels parallel to the c-axis. Cd atoms are located in channels 2, while in channels 1 are situated hydrogen atoms of OH groups. The infrared spectra clearly show the presence of broad O-H stretching and bending vibrations centred at 3236, 2392 1575 and 1396 cm-1 in (1), and 3210, 2379 1602 and 1310 cm-1 in (2). The O-H stretching frequency is in good agreement with O⋯O distances. Furthermore, structural characteristics of compounds with similar alluaudite-like structures were discussed.
 
Article
The paper presents new calorimetric data on the excess heat capacity and vibrational entropy of mixing of Pt-Rh and Ag-Pd alloys. The results of the latter alloy are compared to those obtained by calculations using the density functional theory. The extent of the excess vibrational entropy of mixing of these binaries and of some already investigated binary mixtures is related to the differences of the end-member volumes and the end-member bulk moduli. These quantities are used to roughly represent the changes of the bond length and stiffness in the substituted and substituent polyhedra due to compositional changes, which are assumed to be the important factors for the non-ideal vibrational behaviour in solid solutions.
 
Conference Paper
Concern for line current harmonics in commercial and industrial systems has increased greatly in recent years. The Canadian Standards Association Senior Part II Committees directed that a method for measuring these harmonic currents be developed so that Part II Standards could set appropriate limits. The results of this mandate is Standard C232.2 #0.16. Measurement of Harmonic Contents. This document is described. Attention is given to the test procedure, the measurement circuit, and the supply source
 
Conference Paper
The traditional method of evaluating and calibrating health physics instruments is to use a calibrator that consists of a single high-activity gamma radiation level desired for testing. To have accurate radiation intensities inside the calibrator cavity, the attenuator must be designed from precise absorption calculations. The authors report calculations made to determine the thickness of tungsten alloy metal required for specific attenuation. These calculations include the buildup contribution by secondary scattering radiation, and they are compared to values calculated with the buildup factor omitted.< >
 
Conference Paper
Summary form only given. Nuclear waste isotopes can be transmuted to less-hazardous by forms bombardment with thermal neutrons, which in turn can be produced by stopping of high-energy protons in an appropriate target. Various vessels are required to contain the target material (a liquid or solid high-atomic weight metal or alloy), a moderator (D<sub>2</sub>O), and the nuclear waste slurry. Vessel materials nearest the target will be subjected to a high flux of both fast spallation neutrons and thermal neutrons, while at the outer vessel the radiation environment is characterized by a lower flux of predominantly thermal neutrons. Key materials issues include the nature of displacement damage events from the high-energy neutrons, and the effect of impurities (particularly helium and hydrogen) formed during spallation and thermal neutron capture
 
Conference Paper
Radon progeny are ubiquitous in plutonium facility workplace atmospheres, which often must be continuously monitored for the presence of low concentrations of transuranic contaminants. The alpha decay energy of the <sup>218</sup>Po and <sup>212</sup>Bi (6 MeV) radon and thoron daughters is sufficiently close to the alpha energies of important actinides such as <sup>239</sup>Pu (5.15 MeV) and <sup>241 </sup>Am (5.5 MeV) that considerable interference in the process of detection can result. A novel approach to suppressing the contributions of these background alpha-emitters to the transuranic count based on selective removal of high diffusion mobility size particles containing radon daughters has been developed. Laboratory investigations of several factors of determining the performance of such an approach have been completed, and a prototype continuous air monitor has been successfully built and tested incorporating a screened inlet
 
Conference Paper
Electronic structures and densities of states of the following alkaline-earth metal silicides have been calculated using the first-principle pseudopotential method, Mg<sub>2</sub>Si, BaSi<sub>2</sub>, Ca<sub>2</sub>Si and Sr<sub>2</sub>Si. Energetics of these in their equilibrium structures in comparison with other hypothetical structures (i.e. Ca<sub>2</sub>Si-type Mg<sub>2</sub>Si and Mg<sub>2</sub>Si-type Ca<sub>2</sub>Si) are also considered to clarify the structural change of alkaline-earth metal silicides with the promotion to the heavier elements. The semiconducting behaviors of these could be predicted though the energy band gaps calculated were about 40% of the actual measured values. Energetics of the non-stoichiometry and the atomic site of dopants for Mg<sub>2</sub>Si are also discussed.
 
Conference Paper
Summary form only given. The electronics of the 13000 photomultipliers of the high-resolution ZEUS calorimeter is described. It consists of pulse-shapers 10-MHz-5-μs analog delay lines, analog buffers, multiplexers, and VME-ADC (analog-to-digital converter) cards. Digital signal processors on the ADC cards apply correction constants and reconstruct charge and time from the digitized voltage samples. The system achieves a dynamic range of 16.5 b and a time resolution below 1 ns
 
Conference Paper
Summary form only given. Lawrence Livermore National Laboratory is developing an automated nuclear material pyrochemical processing system that synthesizes technology advances in robotics, remote and automated control, material and component hardening, and crucible furnaces. The system will increase productivity and yield, and reduce risks and routine exposures for operators. Design constraints have included the hostile environments, nuclear material and robot safety criteria, adaptation of commercial robotics, and extreme seismic spectra, and need to show significant improvements over current practice. The results to data are a working tilt-pour furnace in a developmental glovebox presently incorporating a modified commercial gantry robot
 
Conference Paper
A microprocessor-based multivariable controller incorporating state feedback as well as feedforward control for fast regulation and stability of a current source inverter-fed induction motor (CSI-IM) drive is presented. The design of the state feedback controller is based on the industrial regulator theory together with the pole-placement technique applied on a linearized d - q axes state-space model of the drive and includes a reduced-order observer to estimate the inaccessible states such as d - q axes rotor currents. A feedforward control in terms of reference and disturbance inputs has been added to the feedback controller-observer to obtain faster dynamic response. The controller is implemented in real-time using an Intel 8085 microprocessor kit. The hardware and software aspects of the controller are discussed, and test results are presented and compared with digital simulation results for step changes in references and load torque. Typical results show the possible improvement in response with the addition of feedforward control
 
Conference Paper
Summary form only given. Measurements have been made on 4-mm-diameter gas proportional straw tubes with lengths up to 1 m, operating with a gas mixture tailored for both efficient X-ray detection and high-rate operation. Using a new high-bandwidth shaping amplifier, which has an impulse response of about 3.5 ns full width at half maximum (FWHM), a clear picture of signal reflections from the end of anode wire has been obtained. Electronic noise levels resulting from the various modes of anode wire termination, and the lowest signal levels that can be used to satisfy high-rate operation and efficient particle or transition radiation photon detection have been determined
 
Article
A new series of rare earth solid solutions of YxNd2−xW3O12 (x = 0.0–1.0, 1.6–2.0) were successfully synthesized by the solid-state method and studied by X-ray and neutron powder diffractions. The samples were found to crystallize in monoclinic with space group C2/c for x = 0.0–1.0 and in orthorhombic with space group Pnca for x = 1.6–2.0. Thermal properties of YxNd2−xW3O12 (x = 0.25 and 1.90) were studied with high-temperature XRD. It was found that the thermal behaviors of YxNd2−xW3O12 depend not only strongly on their structures, but also on their compositions. Positive thermal expansions of compound Y0.25Nd1.75W3O12 are found to be anisotropic along the three crystallographic axis, where a-axis expands in the 25–200 °C range but contracts in the 200–800 °C range, while b- and c-axes show expansion in the whole temperature range. Negative thermal expansion coefficient of Y1.9Nd0.1W3O12 was calculated to be −17.9 × 10−6 K−1 from 200 to 1000 °C, comparing to −20.9 × 10−6 K−1 of Y2W3O12.
 
Article
The TiCr2−xVx compounds with 0.0≤x≤1.2 series have been synthesised and characterised by X-ray powder diffraction. X-Ray qualitative and quantitative phase analysis has been carried out on the as-cast alloys using the Rietveld method. The refinements of the structure shows that the materials crystallise either in the hexagonal or in the cubic Laves phase type for low V contents. For x>0.6, the system is found of b.c.c.-type structure only. The pressure–composition–temperature (P–C–T) isotherms measured at 298 K show that the as-cast alloys absorb large amounts of hydrogen, from 4 to 5.2 H/f.u. The P–C–T diagrams reveal also the presence of a relatively flat plateau, and a large hysterisis effect, and correspondingly the hydride cannot be completely dehydrogenated.
 
Article
The n-CdS1−xSex thin films of variable composition have been deposited on amorphous glass and FTO-coated glass substrate by simple and cost effective spray pyrolysis technique. The various deposition parameters have been optimized by using photoelectrochemical technique. The structural, surface morphological, compositional, optical and electrical properties have been studied. The X-ray diffraction studies indicated that all the films are polycrystalline in nature with hexagonal structure irrespective of the composition. The lattice parameters ‘a’ and ‘c’ vary from 4.1034 to 4.2615 Å and 6.6664 to 6.9243 Å respectively with change in composition parameter from x = 0.0 to x = 1.0. Polycrystalline texture with nearly smooth surface and clearly defined grains has been observed for all samples from scanning electron microscopy (SEM). EDAX studies confirmed that CdS1−xSex films have approximately same stoichiometry both initially and finally. The absorption coefficient ‘α’ is of the order of 104 cm−1. The optical absorption studies reveal that direct allowed transition with band gap energy between 2.44 and 1.74 eV. It is found that resistivity of the films decreased with increase in ‘x’ up to 0.8 and further it increases for x = 1.0. Semiconducting behavior has been observed from resistivity measurements.
 
Article
Applying a solution – based combustion process, Ag-doped LaFeO3 orthoferrites were synthesized. The samples were characterized by multiple techniques to establish structure – property relationships. Specifically, for structural characterization, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), Fourier transmission infrared spectroscopy (FTIR), Thermo-gravimetric analysis (TGA), and X-ray photoelectron microscopy (XPS) were carried out. For properties, squid magnetometer measurements (for magnetic properties), titrations (for chemical analysis), and diffuse reflectance (for optical band gap properties) measurements were carried out to elucidate structure–property relationship.
 
Article
We report DC isothermal magnetization, global critical current density (JC), Intra-grain critical current density (JCintra) and resistive upper critical field (Bc2) of polycrystalline Y1-xCaxBa2Cu3O7-{\delta} (YBCO); x = 0.00, 0.05, 0.10, 0.15, 0.20 and 0.25. Ca doping at Y sites in YBCO superconductor results in flux pinning property, which can enhance the critical current density and upper critical fields. JC and JCintra are experimentally calculated through DC isothermal magnetization measurement (M-H), employing the well known Bean's critical model. It is observed that both type of current densities (global and intra) enhance with lower doped (5%) samples and can be accounted in terms of reaching maximum of pinning centers and improved grain couplings nature. The upper critical field (Bc2) increases with Ca content being consistent with enhanced grain coupling nature of doped samples.
 
Article
Polycrystalline samples of (Na1−yMy)xCo2O4 (M=K, Sr, Y, Nd, Sm and Yb; y=0.01∼0.35) were prepared by a solid state reaction method. In this study, in order to improve the thermoelectric properties of NaxCo2O4, the effects of partial substitution of other metals for Na on the thermoelectric properties of NaxCo2O4 from room temperature to 1073 K were investigated. For M=Sr, the thermoelectric power and the electrical resistivity increased, and the electronic and lattice contribution to the thermal conductivity decreased compared to the non-substituted sample. These effects suggest that the carrier density was reduced by the substitution of Sr for Na. As a result, the figure of merit of the sample for M=Sr was improved. On the other hand, for other samples in spite of the increase in the electrical resistivity, the thermoelectric power decreased. These results are anomalous effects, which cannot be described merely by a change of the carrier density. For all samples, except for M=Y, the lattice contribution to the thermal conductivity decreased and for all samples, except for M=K, the electronic contribution slightly decreased.
 
Article
We prepared Zn1−xBixO (0 ≤ x ≤ 0.02) thermoelectric materials using the tape casting method and then studied their thermoelectric properties. The electrical conductivity of Zn1−xBixO decreased with an increase in Bi2O3 content. The Seebeck coefficient values were negative over the entire temperature range (600–800 °C), i.e., an n-type conduction. The highest absolute value of the Seebeck coefficient (484 μV K−1) was obtained for Zn0.9975Bi0.0025O at 800 °C. We obtained a significantly enhanced thermoelectric power factor by adding Bi2O3. The highest power factor (3.06 × 10−4 Wm−1 K−2) was obtained for Zn0.9975Bi0.0025O at 800 °C. This value was about six times higher than that of Bi2O3-free ZnO (0.54 × 10−4 Wm−1 K−2) at 800 °C.
 
Article
In this paper the effect of concentration of KOH solution containing 0.02 M borohydride on the electrochemical properties of Ml(NiCoAl)5 hydrogen storage alloys, including the high rate dischargeability, exchange current density I0, limiting current density IL, and diffusion of hydrogen in the hydride, by means of linear polarization, anodic polarization, cathodic polarization, and electrochemical impedance spectroscopy, was studied in detail. The results show that high rate dischargeability, the exchange current density i0, and limiting current density IL increase, and the anodic and cathodic polarization decrease with the increase in concentration of KOH. The size of a semicircle of electrochemical impedance spectroscopy decreased with increase in concentration of KOH, which indicates that the diffusion coefficient of hydrogen increases. Within the range of the experimentation, it can be concluded that the higher the concentration of KOH, the better the electrochemical properties of Ml(NiCoAl)5 hydrogen storage alloys.
 
Article
0.96(Na,K)(Nb0.9Ta0.1)O3–0.04LiSbO3 powders in the orthorhombic phase were synthesized in the molten salt KCl at a low temperature 800 °C. It was revealed that K+ in the molten salt tended to substitute Na+ in the A-sites and the final product 0.96(Na0.29K0.71)(Nb0.9Ta0.1)O3–0.04LiSbO3 was synthesized from the nominal composition 0.96(Na0.5K0.5)(Nb0.9Ta0.1)O3–0.04LiSbO3. The dense ceramics under pressureless were obtained by sintering in the air. The ceramics exhibited high piezoelectric constant d33 of 239 pC/N and good remnant polarization Pr of 30.79 μC/cm2 with coercive electric field Ec of 2.01 kV/mm. And leakage current was reduced by muffling the ceramics with the as-prepared powders during the sintering process.
 
Article
The amorphous Mg1−xLaxNi (x=0, 0.05, 0.10) alloys (a-Mg1−xLaxNi) were prepared by mechanical alloying (MA). Electrochemical properties of the alloy electrodes were characterized, the results showed that the specimens had large electrochemical discharge capacities at room temperature. The X-ray diffraction (XRD) results showed that the amorphous Mg1−xLaxNi alloys decomposed into the crystalline Mg2NiH4 and Ni phases as the increase in electrochemical cycle number of the samples, which was the main reason for the discharge capacity losses of the electrodes. The cyclic life and differential thermal analysis (DTA) results showed that partially replacing Mg by appropriate amounts of La leads to an improvement of cyclic stability due to an increase of the thermal stability. In addition, the SEM analysis results showed that the replacement of Mg by La could prevent the MgNi alloy from a decrease in particle size. Over all, the amorphous Mg0.95La0.05Ni alloy showed the best electrochemical properties.
 
Article
Three compositions of SrO doped LaCrO3 (LSC) namely La1−xSrxCrO3 (x=0.05, 0.15 and 0.30) were synthesized by a novel microwave assisted technique and the thermodynamic activity of SrO (aSrO) in LSC for the three compositions was measured as a function of temperature over the range 890–1100 K by employing a solid electrolyte emf technique with SrF2 as the electrolyte. The reference electrode used for all the galvanic cells was SrZrO3,ZrO2,SrF2,O2/Pt. The SrO potential, ΔGSrO and aSrO for the solid solutions were computed and these values were used to evaluate the compatibility of LSC with the other components of solid oxide fuel cells. The ΔGSrO for these compositions could be represented as −131.6+0.05047T for 0.05 LSC, −85.2+0.01124T for 0.15 LSC and −66.7+0.00339T for 0.30 LSC in terms of kJ mol−1. The SrO potential thus seem to increase with increasing SrO content as expected.
 
Article
The effects of ZnO additive on the microstructures, the phase formation and the microwave dielectric properties of MgTiO3–CaTiO3 ceramics were investigated. The sintering temperature of ZnO-doped 0.95MgTiO3–0.05CaTiO3 ceramics can be lowered to 1300 °C due to the liquid phase effect. Formation of second phase MgTi2O5 can be effectively restrained through the addition of ZnO. The microwave dielectric properties are found strongly correlated with the sintering temperature as well as the amount of ZnO addition. At 1300 °C, 0.95MgTiO3–0.05CaTiO3 ceramics with 1 wt% ZnO addition possesses a dielectric constant ɛr of 20, a Q × f value of 65,000 (at 7 GHz) and a τf value of −5.8 ppm/°C. In comparison with pure 0.95MgTiO3–0.05CaTiO3 ceramics, the doped sample shows not only a 16% loss reduction but also a lower sintering temperature. That makes it a very promising material to replace the present one for GPS patch antennas.
 
Article
This report discusses the latest performance data for X-ray waveguides applied in the production of hard X-ray micro-spots. It is possible to compress an X-ray radiation beam in a thin film waveguide in one direction down to the level of about 0.1 μm, a value which has not been achieved routinely with any other device. A gain factor of about 5 could be achieved in this case for a photon energy of 17 keV. The thin film waveguides were found to provide increasing transmission from 11 keV to 25 keV. As the exiting beam is not only of small size but also highly coherent and divergent it can be used in a number of microscopic techniques: e.g. micro-diffraction, micro-fluorescence, Gabor-holography, phase contrast microscopy.
 
Article
Phase transformation of solid solution (Ti–50Ni)1−xCx (x = 0.1, 0.5 at.%) alloys have been studied by using differential scanning calorimetry, physical property measurement system and optical microscope. The transformation temperature decreases due to the existence of titanium carbide (TiC) particles compared with that of near-equiatomic Ti–Ni shape memory alloy. The resistivity vs. temperature curves show hysteresis. Thermoelastic martensitic transformation occurred in two alloys despite the difference in TiC content. Nevertheless, the resistivity results show different martensitic transformation routes. A one-step B2 → B19′ transformation occurred in the low TiC content alloy and an R transformation appeared in another alloy, suggesting that the martensitic transformation routes depended on the TiC content. The cumulative effect of the TiC particles causes the local stress field and lattice distortion to restrain the transformation of the B19′. On the other hand, the TiC content has an effect on the temperature coefficient of electrical resistivity (TCR) of alloys. The Ti–Ni–0.5C alloy shows a negative TCR in the range 100–300 K during which transformation occurs. Another alloy shows the opposite result. The cause of the negative TCR is briefly discussed.
 
Article
La1−xNdxMgAl11O19 (x = 0, 0.1, 0.2) ceramic powders were synthesized by chemical-coprecipitation and calcination method, and were then pressureless-sintered at 1700 °C for 10 h in air to fabricate dense bulk materials. La1−xNdxMgAl11O19 ceramics were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The thermal expansion coefficients (TECs) and thermal diffusivity coefficients of La1−xNdxMgAl11O19 ceramics were studied with a high-temperature dilatometer and a laser flash diffusivity technique from room temperature up to 1200 °C. La1−xNdxMgAl11O19 (x = 0, 0.1, 0.2) ceramics exhibited a defect magnetoplumbite structure. The TECs of LaMgAl11O19 and La0.8Nd0.2MgAl11O19 are 8.49 × 10−6 K−1 and 8.58 × 10−6 K−1 at 1200 °C, respectively. The thermal conductivity of La1−xNdxMgAl11O19 (x = 0, 0.1, 0.2) ceramics locates in the range of 2.62–3.87 W m−1 K−1 from room temperature to 1200 °C.
 
Article
A sintered polycrystalline sample of Ag1−xPb18SbTe20 (x = 0, 0.1, 0.3) was prepared by a solid-state reaction. The electrical resistivity and Seebeck coefficient were measured from room temperature to about 800 K. The electrical resistivity of Ag1−xPb18SbTe20 (x = 0, 0.1, 0.3) decreases with increasing Ag content. The values of the electrical resistivity are of the order of 10−4 Ω m. The Seebeck coefficient of Ag1Pb18SbTe20 is positive up to 420 K, however, it changes to negative from 420 to 800 K. The absolute value of the Seebeck coefficient of Ag1−xPb18SbTe20 (x = 0.1, 0.3) at 373 K is 404 and 320 μV K−1, respectively, which is twice as high as that of state-of-the-art thermoelectric materials.
 
Article
The solid solution NdMn2−xFexGe2 (x < 1.4) was studied by means of X-ray powder diffraction, magnetic measurements and neutron diffraction study. A typical SmMn2Ge2-like behaviour is observed for x = 0.425. The magnetic structures of NdMn1.6Fe0.4Ge2, NdMn1.4Fe0.6Ge2 and NdMn1.1Fe0.9Ge2 have been determined between 2 and 300 K. The results lead to the construction of a partial x-T magnetic phase diagram. Results of both NdMn2−xFexGe2 and LaMn2−xFexGe2 solid solutions are compared, and the effects of Mn substitution on the in-plane magnetic couplings are discussed. The effects of iron substitution on the interplane magnetic couplings are examined. A slight increase of the critical dMn−Mn distance is observed. In NdMn1.1Fe0.9Ge2, the onset of antiferromagnetism seems to be correlated to a large decrease of the GeGe separation.
 
Article
The series of Nb-poor Finemet-type alloys Fe73.5Si13.5B9Cu1Nb3−xAlx (x = 0, 0.1, 0.2, 0.4, 0.8 and 1.6) were prepared by partial substitution of Nb by Al and then were annealed at different temperatures under hydrogen protection. The effect of Al content as well as the annealing conditions on permeability spectra is discussed. It is found that (1) the initial permeabilities of the samples containing Al are greater than that of the samples without Al after isothermally annealing except for those annealed at 813 and 833 K, (2) the initial permeability (annealed at 793 K) of those containing a moderate amount of Al (x = 0.1, 0.2, 0.4 and 0.8) are the greatest compared with those annealed at other temperatures, and (3) besides the Debye-type relaxation a new relaxation peak appears in μ″–f curves and shows a tendency moving towards higher frequency with the increase of applied field amplitude, which is explained by using the domain wall motion theory in this paper. It is concluded that the initial permeability and relaxation permeability can be improved by moderate substitution of Nb by Al in Finemet type alloys and the initial permeability is dependent on the annealing temperatures. This research provides an innovative method for fabricating higher permeability soft magnetic materials at low cost; meanwhile, it is also significant in academic research.
 
Article
(1 − x)[0.82Bi0.5Na0.5TiO3–0.18Bi0.5K0.5TiO3]–xBiFeO3 lead-free piezoelectric ceramics (abbreviated as BNKT–BFx with x varying from 0 to 0.10 mol) were prepared by solid-state reaction process. Variation of the microstructure and piezoelectric properties of BNKT–BFx ceramics with BF content was investigated. The results indicated that the piezoelectric constant d33, the planar electromechanical coupling factor kp and mechanical quality factor Qm varied with the BF amount. X-ray diffraction (XRD) analysis showed that the incorporated BF diffused into BNKT lattice to form a solid solution. Scanning electron microscope (SEM) also indicated that BF in high amount affected the microstructure. The morphotropic phase boundary (MPB) with rhombohedral and tetragonal coexistence for the ceramics lies in the range of x = 0–0.06 in (1 − x)BNKT–xBF system. The optimum values of d33 and kp are 122 pC/N and 0.317 at x = 0.04.
 
Article
The intermetallic compound formation between Sn–8.5Zn–0.5Ag–0.1Al–xGa lead-free solders and Cu substrate under aging was investigated for the Ga contents of 0.05% and 2%. The investigation was conducted by dipping Cu in the solder. The results of investigation indicated that the intermetallic compounds formed were Al4.2Cu3.2Zn0.7, Cu5Zn8, CuZn5 and AgZn3 at the interface in the as-dipped stage. The aging treatment at 150 °C convents the AlCuZn and CuZn5 compound to Cu5Zn8. The Cu6Sn5 compound was formed closing to the Cu substrate after aging for 1000 h. The AgZn3 was decomposed and Ag dissolves in Cu5Zn8 after aging for 500 h. Addition of Ga into the solder also increases the thickness of Cu5Zn8 compound. Long time aging results in the formation of voids and consequently cracks between IMC and solder.
 
Article
A fluorborate bath being suitable for the continuous electrodeposition system was used to deposit Ni1−xFex (0.1 < x < 0.75) alloys. The obtained alloys were smooth, bright and flexible. The effects of pH, temperature, iron content in electrolytes and current density on alloy composition and plating current efficiency were investigated. The analysis of XRD of Ni1−xFex alloys was used to explore the relationship between alloy composition and crystal structures. The surface morphology of alloys was observed using scanning electron microscopy (SEM).
 
Article
Laves phases of composition Zr(Cr1−xMx)2 with M = Mn, Fe, Co, Ni, Cu and 0 < x < 0.2 have been synthesized with the hexagonal C14- and/or cubic C15-type structures. By X-ray and neutron diffraction we have determined the structures of the alloys and in particular the sites for the 3d metal substitution. The position of the hydrogen atoms in the structures and the occupation of the different sites of the hydrides have been determined. Purity and quality of polycrystalline alloys have been checked by using electron microscopy scanning and energy-dispersive X-ray techniques. The effects of the MCr substitution have been studied for phase stability, maximum hydrogen content and hydrogen site stability and analysed in view of applications as electrodes in H-M batteries.
 
Article
Systematic studies of the hydriding behavior of LaNi5−xSnx alloys with tin contents in the range 0.20<x<0.25 have revealed changes in the pressure–composition–temperature (P–C–T) isotherms measured after heating the hydrides above 450 K. Some loss in reversible capacity was observed along with reductions in the plateau pressures and hysteresis ratios while the slopes of the plateaus became greater. These changes are indications of degradation processes and increased disorder within the alloy structure. Additional experiments were performed for long periods (i.e. >1000 h) at elevated temperatures and hydrogen pressure to produce further degradation in the P–C–T isotherms. The impact of alloy composition on the isotherms has been determined. The crystal lattice properties of the alloys before and after hydrogen reactions have been studied using high-resolution X-ray powder diffraction with synchrotron radiation. Changes in these X-ray diffraction patterns are correlated to various structural modifications resulting from hydride formation and degradation.
 
Article
Systematic phase studies on the system YbSe-Yb2Se3 revealed besides the two terminal compounds three intermediate phases Yb0.91Se, Yb0.83Se and Yb0.75Se, all of them without significant phase width, which is characteristic for the so-called room temperature equilibrium. Lattice parameters are given for all phases. Structure determinations from X-ray powder diffraction data have been carried out for Yb0.91Se  Yb7.24Se8 as well as for YbSe for comparison. The superstructure of Yb0.91Se is halite related (NaCl type) with ordering of vacancies in the cationic sublattice and partial ordering of Yb2+ and Yb3+. Therefore the ideal formula of the mixed valence compound is Yb7Se8  □1Yb52+Yb23+Se82−. The actual phase Yb0.91Se has additional ytterbium statistically distributed over the sites of vacancies. The change in the Yb-Se distance of 2.966 Å in YbSe to 2.830 and 2.938 Å in Yb7.24Se8 definitely proves the simultaneous appearance of Yb2+ and Yb3+, both octahedrally coordinated.
 
Article
It has previously been established that adding 0.2 wt.% Zn into a Sn–3Ag–0.5Cu–0.5Ce alloy improves the mechanical properties and eliminates the problem of rapid whisker growth. However, no detailed studies have been conducted on electromigration behavior of Sn–3Ag–0.5Cu–0.5Ce–0.2Zn alloy. The electromigration damage in solder joints of Sn–3Ag–0.5Cu and Sn–3Ag–0.5Cu–0.5Ce–0.2Zn with Ag/Cu pads and Au/Ni(P)/Cu pads was studied after current stressing at room temperature with an average current density of 3.1 × 104 A/cm2. With additions of 0.5 wt.% Ce and 0.2 wt.% Zn, the electromigration processes of Sn–Ag–Cu solder joints were accelerated due to refinement of the solder matrix when joint temperature was around 80 °C. Since Ni is more resistant than Cu to diffusion driven by electron flow, solder joints of both alloys (Sn–3Ag–0.5Cu and Sn–3Ag–0.5Cu–0.5Ce–0.2Zn) with Au/Ni(P)/Cu pads possess longer current-stressing lifetimes than those with Ag/Cu pads.
 
Article
SrBi2−xLaxNb2O9 (x = 0, 0.05, 0.1, 0.2 and 0.35) ceramics were prepared by a conventional solid-state reaction method. Their structure and dielectric properties were investigated. X-ray diffraction analysis showed that single-phase layered perovskites were obtained. A relaxor like transition was observed in SrBi2−xLaxNb2O9 with x = 0.2 and 0.35. For the specimens with x = 0.05 and 0.1, a relaxation-type dielectric loss peak was observed in the temperature range of 30–150 °C. The temperature of the maximum dielectric constant Tm decreases linearly with increasing La content. The degree of frequency dispersion ΔTm, which is the Tm difference between 10 kHz and 1 MHz, increases from 0 °C for x = 0–7 °C for x = 0.35. However, when x = 0.1, ΔTm equals −1 °C, which might be attributed to oxygen-vacancy-induced dielectric relaxation. In addition, La substitution results in a decrease in both remanent polarization and coercive field.
 
Article
The crystal structures occurring in the ζ-region of the Mn–N phase diagram were investigated by X-ray and high temperature neutron diffraction within a range of compositions MnNy with 0.39<y<0.48. The ζ-region consists of several phases all based on an hcp arrangement of Mn. They differ by their arrangements of N atoms on the octahedral sites. A high temperature ‘γ-type’ phase of defect anti-NiAs type, ahcp×ahcp×chcp, space group P63/mmc, is disordered with respect to nitrogen. Three long-range nitrogen ordered superstructure phases exist: (1) an ‘ε-type’ superstructure, observed below 570 K for MnN0.388 and MnN0.421 with 31/2ahcp×31/2ahcp×chcp with respect to an hcp unit cell. Powder diffraction data can be equally well described in P6322, P312 or ; (2) a ‘ζ-type’ superstructure, observed below about 870 K for MnN0.457 and MnN0.472 with anti-α-PbO2 type structure with 2ahcp×31/2ahcp×chcp, space group Pbna; (3) a ‘β-type’ superstructure observed above 870 K for MnN0.484 with anti-CaCl2 type superstructure, ahcp×31/2ahcp×chcp, space group Pmnn. These findings require a revision of the Mn–N phase diagram that is, up to now, presented with only one single ζ-phase in the literature.
 
Article
Mg–5Al–0.3Mn–2Nd alloy was prepared by metal mould casting. The as-cast ingot was homogenized, and then hot-rolled with total thickness reduction of 63%. Further annealing treatment was carried out on the hot-rolled sample. Microstructure and mechanical properties of the studied alloy in as-cast, hot-rolled and annealed states were investigated. Results showed that main phases of the as-cast sample were composed of α-Mg, Al2Nd, Mg17Al12 and Al11Nd3. While for the hot-rolled and annealed samples, no Mg17Al12 phase was detected. Average grain size of the as-cast sample was about 90 μm. After hot rolling, average grain size was greatly refined to about 20 μm. Furthermore, the long acicular Al11Nd3 phase broke into many small sections. Tensile test results showed that ultimate tensile strength and yield strength of the hot-rolled sample were 340 MPa and 240 MPa, respectively. Compared with those of the as-cast sample, they were enhanced by 47.8% and 269% correspondingly. However, elongation greatly decreased to 9%. Through annealing treatment, elongation recovered to more than 24% again.Research highlights▶ Hot rolling was carried out on Mg–5Al–0.3Mn–2Nd alloy. ▶ Basal texture was obtained for the hot-rolled sample. ▶ Grain size was refined and mechanical properties were enhanced by hot rolling. ▶ Hot-rolled alloy demonstrated good thermal stability.
 
Article
The growth behavior of intermetallic layer with or without adding 0.3 wt% Ni into the Sn–0.7Cu solder was studied during the wetting reaction on Cu-substrate and thereafter in solid-state aging condition. The Cu-solder reaction couple was prepared at 255, 275 and 295 °C for 10 s. The samples reacted at 255 °C were then isothermally aged for 2–14 days at 150 °C. The reaction species formed for the Sn–0.7Cu/Cu and Sn–0.7Cu–0.3Ni/Cu soldering systems were Cu6Sn5 and (CuNi)6Sn5, respectively. The thickness of the intermetallic compounds formed at the solder/Cu interfaces and also in the bulk of both solders increased with the increase of reaction temperature. It was found that Ni-containing Sn–0.7Cu solder exhibited lower growth of intermetallic layer during wetting and in the early stage of aging and eventually exceeded the intermetallic layer thickness of Sn–0.7Cu/Cu soldering system after 6 days of aging. As the aging time proceeds, a non-uniform intermetallic layer growth tendency was observed for the case of Sn–0.7Cu–0.3Ni solder. The growth behavior of intermetallic layer during aging for both solders followed the diffusion-controlled mechanism. The intermetallic layer growth rate constants for Sn–0.7Cu and Sn–0.7Cu–0.3Ni solders were calculated as 1.41 × 10−17 and 1.89 × 10−17 m2/s, respectively which indicated that adding 0.3 wt% Ni with Sn–0.7Cu solder contributed to the higher growth of intermetallic layer during aging.
 
Article
Results of X-ray, neutron diffraction, magnetization and Mössbauer measurements with circularly polarised beam on polycrystalline samples of the ternary intermetallic alloys UFe4−xAl8+x with x in the range (−0.4, 0.4) are presented. The alloys crystallise in the structure of ThMn12 type, belonging to the space group I4/mmm (no. 139). X-ray and neutron diffraction confirmed the phase homogeneity of all samples but that one with 4−x=4.4. Monochromatic Circularly Polarised Mössbauer Source (MCPMS) measurements reveal spin-canted magnetic structures in randomly oriented powders exposed to a field of 1 T at T=12 K. Magnetization measurements in an external field of 0.01 T allowed disclosing ferromagnetic-like behaviour vs. temperature and quite dissimilar magnetization and hysteresis curves against the fields in the alloys of interest.
 
Article
The dielectric properties and the microstructures of 0.6Ba(Co1/3Nb2/3)O3–0.4Ba(Ni1/3Nb2/3)O3 ceramics with CuO additions (0.25–1 wt%) prepared with conventional solid-state route have been investigated. It is found that 0.6Ba(Co1/3Nb2/3)O3–0.4Ba(Ni1/3Nb2/3)O3 ceramics can be sintered at 1270 °C due to the sintering aid of CuO addition. At 1270 °C, 0.6Ba(Co1/3Nb2/3)O3–0.4Ba(Ni1/3Nb2/3)O3 ceramics with 0.5 wt% CuO addition possesses a dielectric constant (ɛr) of 32.5, a Q × f value of 82,000 (9 GHz) and a temperature coefficients of resonant frequency (τf) of −21.2 ppm/°C. The CuO-doped 0.6Ba(Co1/3Nb2/3)O3–0.4Ba(Ni1/3Nb2/3)O3 ceramics can find applications in microwave devices requiring low sintering temperature.
 
Article
The ternary Sn–Cu–Co system eutectic composition was obtained by means of CALPHAD (CALculation of PHAse Diagram) methodology and it was found to be 0.4% Co and 0.7% Cu (wt%) with a melting point of 224 °C. The tensile behavior of this alloy was investigated at different strain rates (10−5, 10−4 and 10−3 s−1) and compared to both Sn–37Pb and Sn–4.0Ag–0.5Cu. The Sn–4.0Ag–0.5Cu alloy depicts the highest ultimate tensile strength (UTS) followed by the Sn–37P and finally the Sn–0.7Cu–0.4Co system. The elastic modulus was also higher for the Sn–4.0Ag–0.5Cu followed by the Sn–0.7Cu–0.4Co and last the Sn–37Pb. The microstructure of the Sn–0.7Cu–0.4Co alloy is composed of two types of intermetallic phases, (Cu,Co)6Sn5 and (Co,Cu)Sn2 dispersed in a Sn-rich matrix. The microstructure of this alloy proved to be very stable, after aging at 150 °C for 24 h. The eutectic Sn–0.7Cu–0.4Co solder alloy can therefore be a very good alternative for the SAC alloys for surface mount technology applications.
 
Article
The interfacial reaction and morphology change of intermetallic compound (IMC) between the Sn–0.4 wt.% Cu solder and two different kinds of substrates (Cu and electroless nickel-immersion gold (ENIG)) during reflow at 255 °C for up to 60 min were studied. Until the reaction time of 1 min, only Cu6Sn5 IMC was formed on the Cu substrate. After reflow for 5 min, the solder/Cu interface exhibited a duplex structure of Cu6Sn5 and Cu3Sn. According to the top view observation, the Cu6Sn5 IMC formed on the Cu substrate had a well-known morphology of a round or scallop shape. In the case of the ENIG substrate, the reaction between molten Sn–0.4Cu solder and electroless Ni–P layer resulted in the formation of a (Ni,Cu)3Sn4 layer at the interface. Until the reaction time of 10 min (Ni,Cu)3Sn4 IMC layer was formed and attached well on the electroless Ni substrate. And, the Cu content in the (Ni,Cu)3Sn4 IMC layer increased with increasing reaction time. From the top view micrograph of the interface, it was known that three types (needle-type, boomerang-type and chunk-type) of (Ni,Cu)3Sn4 IMC were formed. Also, P-rich Ni (Ni3P) and Ni–Sn–P layers were observed between IMC layer and electroless Ni–P layer. On the other hand, the reaction for 60 min resulted in the formation of two IMCs, a relatively thin and continuous (Ni,Cu)3Sn4 and a relatively big discontinuous (Cu,Ni)6Sn5, at the interface. After reflow for 60 min, the electroless Ni–P layer in some parts of the sample was completely consumed by reaction between molten solder and substrate.
 
Article
Mg–4Al–0.4Mn–xPr (x = 1, 2, 4 and 6 wt.%) magnesium alloys were prepared successfully by the high-pressure die-casting technique. The microstructures, mechanical properties, corrosion behavior as well as strengthening mechanism were investigated. The die-cast alloys were mainly composed of small equiaxed dendrites and the matrix. The fine rigid skin region was related to the high cooling rate and the aggregation of alloying elements, such as Pr. With the Pr content increasing, the α-Mg grain sizes were reduced gradually and the amounts of the Al2Pr phase and Al11Pr3 phase which mainly concentrated along the grain boundaries were increased and the relative volume ratio of above two phases was changed. Considering the performance-price ratio, the Pr content added around 4 wt.% was suitable to obtain the optimal mechanical properties which can keep well until 200 °C as well as good corrosion resistance. The outstanding mechanical properties were mainly attributed to the rigid casting surface layer, grain refinement, grain boundary strengthening obtained by an amount of precipitates as well as solid solution strengthening.
 
Article
The precipitation sequence in a Mg–10Gd–3Y–0.4Zr (wt.%) alloy during isothermal ageing at 250 °C has been investigated using transmission electron microscopy. It is found that the precipitation sequence involves super-saturated solid solution (S.S.S.S.) → β″(D019) → β′(cbco) → β1(fcc) → β(fcc), which is similar to that of WE54 alloy but different from previously reported three-stage sequence: S.S.S.S. → β″(D019) → β′(cbco) → β (bcc). The metastable β′ phase, which plays an important role for the age hardening of the alloy, has a shape of convex lens and is very thermally stable at 250 °C. Formation of β1 phase appears to take place via an in situ transformation from a decomposed β′ phase.
 
Article
Sm2(Fe1−xGax)17 (x = 0–0.5) compounds were prepared by arc melting. X-ray diffraction patterns showed that all compounds were single phase with rhombohedral Th2Zn17-type structure. X-ray diffraction patterns of the aligned samples showed that the alloys with x = 0.15, 0.20 and 0.25 have uniaxial anisotropy at room temperature. The spin reorientation transition temperatures were measured by a superconducting quantum interference device (SQUID) and a magnetic balance. A tentative phase diagram was constructed. The substitution of Ga for Fe leads to an increase in the reorientation temperature and the lattice constants. The Curie temperature increases with the Ga concentration, and achieves a maximum at x = 0.2, then decreases. The saturation magnetization decreases monotonically with Ga concentration. The coupling constants ATT and ART were derived using a mean molecular field model. ATT reaches a maximum at x = 0.3 and then decreases with x, but ART is almost unchanged with varying x.
 
Article
High pressure hydrides of V0.995C0.005 were thermally cycled between β2- and γ-phases hydrides for potential use in cryocoolers/heat pumps for space applications. The effect of addition of carbon to vanadium, on the plateau enthalpies of the high pressure β2 + γ region is minimal. This is in contrast to the calculated plateau enthalpies for low pressure (α + β1) mixed phases which showed a noticeable lowering of the values. Thermal cycling between β2-and γ-phase hydrides increased the absorption pressures but desorption pressure did not change significantly and the free energy loss due to hysteresis also increased. Hydriding of the alloy with prior cold-work increased the pressure hysteresis significantly and lowered the hydrogen capacity. In contrast to the alloy without any prior straining (as-cast), desorption pressure of the alloy with prior cold-work also decreased significantly. Microstrains, 〈ɛ2〉1/2, in the β2-phase lattice of the thermally cycled hydrides decreased after 778 cycles and the domain sizes increased. However, in the γ-phase, both the microstrains and the domain sizes decreased after thermal cycling indicating no particle size effect. The dehydrogenated α-phase after 778 thermal cycles also showed residual microstrains in the lattice, similar to those observed in intermetallic hydrides. The effect of thermal cycling (up to 4000 cycles between β2- and γ-phases) and cold working on absorption/desorption pressures, hydrogen storage capacity, microstrains, long-range strains, and domain sizes of β2- and γ-phase hydrides of V0.995C0.005 alloys are presented.
 
Top-cited authors
Jacques Huot
  • Université du Québec à Trois-Rivières
Shinsuke Yamanaka
  • Osaka University
Rachel Schulz
  • Hebrew University of Jerusalem
Etsuo Akiba
  • Kyushu University
Ken Kurosaki
  • Osaka University