Journal of Alloys and Compounds

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.

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.

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.

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.

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

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.< >

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 (D₂O), 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

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 ²¹⁸Po and ²¹²Bi (6 MeV) radon and thoron daughters is sufficiently close to the alpha energies of important actinides such as ²³⁹Pu (5.15 MeV) and ²⁴¹Am (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

Electronic structures and densities of states of the following alkaline-earth metal silicides have been calculated using the first-principle pseudopotential method, Mg₂Si, BaSi₂, Ca₂Si and Sr₂Si. Energetics of these in their equilibrium structures in comparison with other hypothetical structures (i.e. Ca₂Si-type Mg₂Si and Mg₂Si-type Ca₂Si) 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 Mg₂Si are also discussed.

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

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

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

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.