bluuebunny/crossref_metadata_2025 huggingface dataset:
Void Formation in Neutronand Ion-Irradiated Copper and Nickel
Authors: Shimomura Y. , Mukouda I.
Published: April 2011

In copper which was irradiated by fission neutrons at 300°C in a temperature controlled rig to 0.0003 dpa with the damage production rate of 6 × 10−5 dpa/hr, the number of voids exceeds the number of gas atoms of hydrogen and helium which were generated by the transmutation reaction. The number density of voids was almost the same in as-received and gas-atomremoved copper which was neutron irradiated to 0.0003 dpa. These results suggest that voids can be formed by clustering of only vacancies. In 5 MeV Ni-ion irradiated copper, voids could not be observed in specimens which were irradiated between 200°C and 450°C from 0. 1 dpa to 30 dpa with the damage production rate of 6 dpa/hr. Voids were observed only in copper which was Ni-ion irradiated at 500°C. The difference of void formation on neutron-irradiation and ionirradiation is discussed. It is concluded that the production rate of damage is an important factor on the void formation in irradiated metals.
Plasticity and Microstructure of Irradiated Pd
Authors: Baluc N. , Dai Y. , Victoria M.
Published: April 2011

Single crystalline specimens of pure Pd have been irradiated at ambient temperature with 590 MeV protons to doses ranging between 10−4 and 10−1 dpa. Tensile deformation experiments revealed that irradiation induces hardening and embrittlement, while scanning (SEM) and transmission electron microscopy (TEM) observations showed that plastic deformation of specimens irradiated to a dose ≥ 10−2 dpa is strongly localized and yields the creation of slip bands at the macroscopic scale and of defect-free channels at the microscopic level.
Isotopic Tailoring to Optimize Studies for Radiation Resistance in Fusion Materials: Small Specimen Technology Development
Authors: Ohnuki S. , Shiba K. , Kohno Y. , Kohyama A. , Robertson J. P. , Hamilton M. L. , Gelles D. S.
Published: April 2011

Single variable experiments are being conducted to study effects of H/He/dpa on properties based on isotopically tailored alloys. 54Fe has been used to prepare an isotopically tailored duplicate of the commercial steel F82H, and a small number of TEM disks have been irradiated in order to study radiation embrittlement. From single disk specimens, mechanical properties were obtained using a shear punch technique that produces a 1 mm blank from the 3 mm disk, and microstructural information was obtained from the 1 mm blanks thinned to electron transparency.
Effective Interactions Approach to Phase Stability in Alloys Under Irradiation
Authors: Enrique Raúl A. , Bellon Pascal
Published: April 2011

Phase stability in alloys under irradiation is studied considering effective thermodynamic potentials. A simple kinetic model of a binary alloy with phase separation is investigated. Time evolution in the alloy results from two competing dynamics: thermal diffusion, and irradiation induced ballistic exchanges. The dynamical (steady state) phase diagram is evaluated exactly performing Kinetic Monte Carlo simulations. The solution is then com- pared to two theoretical frameworks: the effective quasi-interactions model as proposed by Vaks and Kamishenko, and the effective free energy model as proposed by Martin. New developments of these models are proposed to allow for quantitative comparisons. Both theoretical frameworks yield fairly good approximations to the dynamical phase diagram.
Md Investigation of Thermal Spike Effects on Defect Production and Disordering by Displacement Cascades in Nl3AL
Authors: Gao F. , Bacon D. J.
Published: April 2011

Molecular dynamics (MD) simulations are used to obtain detailed information on defect production and disordering produced in the primary cascade state of radiation damage in Ni3AI as a function of irradiation temperature, Tirr Although the number of Frenkel pairs decreases with increasing Tirr, the size of interstitial clusters and the interstitial clustering fraction increase with Tirr. The number of antisites defects per cascade increases by about 20% as Tir increases from 100 to 600K, and then by about 90% from 600 to 900K due to the increase in the intensity and lifetime of the thermal spike. The average size of disordered zones at different Tir, is compared with experimental transmission electron microscopy data and the results are in reasonable agreement. The long-range order parameter in the cascade region is found to be consistent with values obtained experimentally on Ni3A1 irradiated by ions to a similar dose. The chemical short-range order parameter is about 0.6 over the whole range of Tirr, considered, suggesting that the cascade core retains some short-range order at high temperature due to local reordering.
Ceramic SFF by Direct and Indirect Stereolithography
Authors: Chu Gabriel T-M. , Brady G. Allen , Miao Weiguo , Halloran John W.
Published: April 2011

Direct ceramic stereolithography (SLA) is done using UV-curable suspensions of powders in acrylates in a conventional SLA machine. Hydroxyapatite prototypes for bone tissue scaffolds are built from Image-Based Design files, featuring an interior architecture of void passages. Complex alumina objects are built as digital sculptures. Piezoelectric ceramic actuators from PZT, which are difficult to photocure, are built using indirect stereolithography, where SLAbuilt epoxy molds are used to form a thermal-cured suspension of PZT powders. We report on the thermal-curing behavior of the suspensions, and the fundamentals of part building.
A Review of Robocasting Technology
Authors: Cesarano Joseph
Published: April 2011

Robocasting is a freeform fabrication technique for dense ceramics and composites that is based on layer-wise deposition of highly loaded colloidal slurries. The process is essentially binderless with less than 1% organics and parts can be fabricated, dried, and completely sintered in less than 24 hours. This review will highlight materials developments for structural applications and modelling of slurry flow. Fabrication of preforms for alumina / metal composites will be discussed as well as techniques for multimaterial deposition in both graded structures and discrete placement of fugitive materials.
New Process and Materials Developments in 3-Dimensional Printing, 3DP™
Authors: Uhland S. A. , Holman R. K. , Cima M. J. , Sachs E. , Enokido Y.
Published: April 2011

The Three-Dimensional Printing (3DP™) process has been modified to incorporate colloidal science for the fabrication of fine ceramic parts. Complex shaped alumina and silicon nitride components have been formed directly from 3-dimensional CAD files using submicron powders. Parts were built using a sequential layering process of the ceramic slurry followed by ink jet printing of a binder system. A well dispersed slurry and optimized printing parameters are required to form a uniform powder bed with a high green density. Liquid-powder bed interactions affect the geometry and internal structure of the component. The redispersion of the unprinted powder bed is critical in order to retrieve the printed components. The slurry and powder bed chemistry are the major factors controlling powder bed redispersion. The process is generic and can be readily adapted for new materials systems. Our research is currently focused on the fabrication of dielectric RF filters. Preliminary results have demonstrated the ability to successfully fabricate cylindrical RF resonators.
Enhanced Infrared Absorptance of Polyethylene Terephthalate via Inorganic Particulate Additives
Authors: Maiorino L. A. , Meyers K. S. , Speyer R. F.
Published: April 2011

Amorphous carbon and infrared absorbing glass particulate additives to polyethlene terephthalate increased its infrared absorptance. Significantly lower volume concentrations of carbon were required for a given absorptance increase; however, test bars with glass additive concentrations displaying ˜90% absorptances were largely aesthetically unaltered. Carbon additions to produce the same infrared absorptance resulted in nearly opaque test bars. Heat transfer calculations showed preform heatup time could be reduced from 1 s to 0.6 s with glass particle additions
Cold Spray Direct Fabrication – High Rate, Solid State, Material Consolidation
Authors: Smith M. F. , Brockmann J. E. , Dykhuizen R. C. , Gilmore D. L. , Neiser R. A. , Roemer T. J.
Published: April 2011

Direct fabrication of metal near-net shapes from a computer model typically involves melting and solidification, which can cause high residual stresses, undesirable phases, poor microstructures, rough surface finishes, warpage, and other problems. This paper describes a new technology, still under development, that might be used to directly fabricate solid, near-fulldensity, free-form shapes of many metals, and even some composite materials, at or near room temperature without melting and solidification. In this process, tentatively called Cold Spray Direct Fabrication (CSDF), powder particles in a supersonic jet of compressed gas impact a solid surface with sufficient energy to cause plastic deformation and consolidation with the underlying material by a process thought to be analogous to explosive welding. Material deposition by cold spray methods has already been successfully demonstrated by several investigators. This paper presents results of an experimental study to investigate the effects of selected process variables on cold spray particle velocities. In addition, a key technical barrier to the CSDF concept is focusing the spray stream down to dimensions that would permit a useful level of part detail, while still providing practical build rates. This paper presents results of initial research to develop an aerodynamic lens that may provide the required particle stream focusing.
Atomic Displacement Parameters: A Useful Tool in the Search for New Thermoelectric Materials?
Authors: Sales B. C. , Chakoumakos B. C. , Mandrus D. , Sharp J. W. , Dilley N. R. , Maple M. B.
Published: April 2011

The atomic displacement parameters (ADPs) measure the mean-square displacement amplitude of an atom about its equilibrium position in a crystal. It is demonstrated that the ADPs can be used to identify crystalline solids with unusually low lattice thermal conductivties. A low lattice thermal conductivity is essential in the design of thermoelectric materials with improved efficiencies.The atomic displacement parameters (ADPs) have been measured using powder neutron diffraction as a function of temperature for several clathrate-like compounds (RxCo4-yFeySb12, where R= La, Ce, Yb or TI, x=0.22, 0.8, 1, y=0, 1;Tl2SnTe5 and Tl2GeTe5). The ADP data show that in each of the compounds one of the atoms is weakly bound and “rattles” within its atomic cage. This atomic “rattling” severely reduces the ability of these crystals to conduct heat and in some cases the lattice thermal conductivity approaches the theoretical minimum value. In many clathrate-like compounds, the ADP can also be used to estimate the Einstein frequency of the “rattler”, and to predict the existence of localized vibrational modes.
Thermoelectric Properties of Mixed Rhenium Chalcogenides Re6Te15-x Sex (0 ≤ × ≤ 8)
Authors: Dalafave S. Kilibarda , Ziegler J. , Mcallister H.
Published: April 2011

Reported are the temperature dependencies of the thermoelectric power and electrical resistivity of mixed rhenium chalcogenides Re6Te15-x,Sex (0 ≤ x ≤ 8) in the range 90–420 K. Influence of the partial chalcogen exchange on thermoelectric properties of these compounds is discussed. The samples are prepared by sintering elemental powders inside evacuated and sealed quartz ampoules at 1150 K for 170 hours. X-ray analysis reveals an orthorhombic lattice for samples with x < 8 and a tetragonal lattice for the Re6Te7Se8. sample. The lattice parameters and the unit cell volume decrease with increasing selenium concentration.

The measurements indicate p-type semiconducting behavior for all samples. The presence of the energy gap is observed at higher temperatures (T ≥ 180–220 K) for all x. Data suggest hopping conduction at lower temperatures. Room temperature resistivities increase non-linearly from 6.9 to 20.4 Ω m with the increasing selenium content. Initially, the thermoelectric power a increases with temperature for all samples, with the fastest increase in Re6Se8 Te7 and the slowest in Re6Te15. The temperature at which a reaches maximum decreases with the increasing Se content. Above this temperature, a decreases uniformly as the temperature increases, the slowest increase being for Re6Se8Te7 and the fastest for Re6Te15. Such α(T) dependence is also discussed. The temperature dependence of the power factor, α2/ρ, is presented. Comparison of ρ, α, and the power factor in Re6SexTe15-x with currently used state-of-the-art materials is given.
The Nanofabrication of Quantum Wires for the Next Generation of Thermoelectrics
Authors: Demske D. L. , Price J. L. , Guardala N. A. , Lindsey N. , Barkyoumb J. H. , Sharma J. , Kang H. H. , Salamanca-Riba L.
Published: April 2011

The fabrication of a thermoelectric nanocomposite material consisting of nanometer scale bismuth (Bi) wires embedded in a porous mica template host is discussed in detail. In fabricating the mica templates, a positive ion accelerator is employed to irradiate 10 μm thick mica sheets with collimated beams of 15 MeV carbon ions at fluence levels of 1.5 × 1013 ions/cm2. The normally incident beam generates latent nuclear damage tracks in the direction oriented perpendicularly to the mica basal plane. Atomic Force Microscope (AFM) pictures of etched tracks verify that we have fabricated porous templates containing arrays of channels with densities up to 1013/cm2 and diameters as small as 5 nanometers, thus providing pores having an aspect ratio of about 2000:1. Scanning electron micrographs of 50 nm diameter tracks show that these are parallel channels with smooth, non-tapered walls. In addition, to fabricate the wires we have developed a solution-electrodeposition process employing a PC processor-driven potentiostatic/galvanostatic system. Currently, we are electrochemically embedding 10 μm long Bi wires through the nanochannel templates. The potentiostatic electrodeposition behavior of these wires is described. Current-voltage waveforms confirm that the wires are electrically uninterrupted through the mica template. Transmission electron micrographs (TEM) show these wires are single crystals, of well-defined orientation with diameters down to 50 Å. We observe bundles of 80 Å wires with a packing density of about 109/cm2. Energy Dispersive X-ray Spectroscopy (EDS) has corroborated the presence of Bi in the nanochannels. The observation of the bismuth crystal orientation in the porous mica template is examined.
Boundary Effects in Thin-Film Thermoelectrics
Authors: Bartkowiak M. , Mahan G. D.
Published: April 2011

Equations describing the resistances to the transport of heat and electricity through boundaries of thin-film thermoelectrics are derived. We show that these boundary resistances obey a boundary form of the Wiedemann-Franz law and cause a new type of thermal instability for short thermoelectric devices. We consider boundary thermal resistances both for phonons (Kapitza resistance) and for electrons, the contact electrical resistance at the junctions, and the boundary thermoelectric effects. It is shown that the Kapitza resistance causes reduction of the effective thermal conductivity of the system only if the electron and phonon subsystems are out of equilibrium. In this case, the thermoelectric figure of merit Z can be increased by reducing the thickness of the film. The electrical contact resistance at the junctions is shown to degrade the performance of the device. However, according to the boundary Wiedemann-Franz law, electrical contact resistance is accompanied by a thermal boundary resistance for the electron subsystem, which can cause an additional enhancement of Z. In some cases, this can lead to a device with ZT as high as 3 at room temperatures.
Preparation and Properties of Porous Bismuth Films
Authors: Shen W. -N. , Dunn B. , Ragot F. , Goorsky M. S. , Moore C. D. , Chen G. , Gronsky R. , Fuller-Mora W. W. , Gillespie D. J. , Ehrlich A. C.
Published: April 2011

The use of chemical solution routes to form inorganic thin films is a relatively new method which represents an alternative to vapor phase routes. The present study involves the use of a chemical solution route, the decomposition of metal carboxylates, to prepare bismuth thin films of controlled porosity. Such morphologies offer the opportunity to disrupt phonon transport without greatly affecting electrical conductivity and bismuth represents a well known system in which to investigate these effects. Porous bismuth thin films have been prepared using bismuth 2-ethylhexanoate (Bi[OOCCH(C2H5)C4H9]3) as the precursor in a solvent of 2-methyl- 1-propanol. The solution is deposited on glass, Kapton, silicon, alumina or magnesia substrates by spin coating and heated to between 250 – 300°C in hydrogen. Heat treatment temperature and time are important for controlling film microstructure as both pore volume (25 to 50%) and preferred orientation depend upon heat treatment conditions. Bismuth films (62 nm thick) with 32% porosity exhibit conductivities in the range of 150 S/cm with Seebeck coefficients comparable to that of bulk materials.
Physical Properties Of Single-Phase Skutterudite Thin-Films (CoSb3 and IrSb3)
Authors: Caylor J. C. , Stacy A. M. , Sands T. , Gronsky R.
Published: April 2011

Bulk skutterudite phases based on the CoAs3 structure have yielded compositions with a high thermoelectric figure-of-merit (“ZT”) through the use of doping and substitutional alloying. It is postulated that further enhancements in ZT may be attained in artificially structured skutterudites by engineering the microstructure to enhance carrier mobility while suppressing the phonon component of the thermal conductivity. In this work the growth and properties of singlephase CoSb3 and IrSb3 skutterudite thin films are reported. The films are synthesized by pulsed laser deposition (PLD) where the crystallinity can be controlled by the deposition temperature. Powder X-ray diffraction (PXRD), Transmission electron microscopy (TEM) and Rutherford- Back Scattering (RBS) were used to probe phase, structure, morphology and stoichiometry of the films as functions of growth parameters and substrate type. A substrate temperature of 250°C was found to be optimal for the deposition of the skutterudites from stoichiometric targets. Above this temperature the film is depleted of antimony due to its high vapor pressure eventually reaching a composition where the skutterudite structure is no longer stable. However, when films are grown from antimony-rich targets the substrate temperature can be increased to at least 350°C while maintaining the skutterudite phase. In addition, adhesion properties of the films are explored in terms of the growth mode and substrate interaction. Finally, preliminary room temperature electrical and thermal measurements are reported.
Experimental Study of the Effect of the Quantum Well Structures on the Thermoelectric Figure of Merit in Si/Si1-xGex System
Authors: Sun X. , Liu J. , Cronin S. B. , Wang K. L. , Chen G. , Koga T. , Dresselhaus M. S.
Published: April 2011

In bulk form, Si1-xGex is a promising thermoelectric material for high temperature applications. In this paper, we report results from an experimental study as well as theoretical modeling of the quantum confinement effect on the enhancement of the thermoelectric figure of merit. Si/Si1-xGex, multiple quantum well structures are fabricated using molecular beam epitaxy (MBE) on SOI (Silicon-on-Insulator) substrates in order to eliminate substrate effects, especially on the Seebeck coefficient. A method to eliminate the influence of the buffer layer on the thermoelectric characterization is presented. An enhancement of the thermoelectric figure of merit within the quantum well over the bulk value is observed.
Observed Properties and Electronic Structure of RNiSb Compounds (R = Ho, Er, Tm, Yb and Y). Potential Thermoelectric Materials
Authors: Sportouch S. , Larson P. , Bastea M. , Brazist P. , Ireland J. , Kannewurf C. R. , Mahanti S. D. , Uher C. , Kanatzidis M. G.
Published: April 2011

The RNiSb compounds (R=Ho, Er, Tm, Yb and Y) and some selected solid solution members such as (Zr1-xErx)Ni(Sn1-xSbx) and ErNiSb1-xPnx (Pn=As, Sb, Bi) have been studied. They all crystallize in the MgAgAs structure type, which can be considered as a NaCI structure type in which half of the interstitial tetrahedral sites are occupied by Ni atoms. The measured values of the Seebeck coefficients, at room temperature, are positive for RNiSb (R=Ho, Er, Yb and Y) compounds and ErNiSb1-xPnx (Pn=As, Sb, Bi) solid solutions, but for (Zr1-xErx)Ni(Sn1-xSbx) members vary from negative to positive values when 0 < x < 1. Some of these compounds show metallic conductivity while others exhibit thermally activated charge transport. Solid solutions of these materials have lower thermal conductivities than the pure members, RNiSb (R=Ho, Er, Yb and Y) and ZrNiSn. The electronic structures of RNiSb compounds, where R is Y, La, Lu, and Yb, have been studied with density functional theory. The results of the calculations for these systems, except for the Yb compound, indicate narrow gap semiconductors with large effective masses near the conduction band extrema. The Yb system is expected to show heavy fermion characteristics.
Theoretical Calculation of the Vibrational modes in Ge46 Clathrate and Related MxGayGe46-y Type Clathrates
Authors: Dong Jianjun , Sankey Otto F. , Demkov A. A. , Ramachandran Ganesh K. , Gryko Jan , McMillan Paul , Windl Wolfgang
Published: April 2011

We have calculated theoretically the vibrational modes of the type-I Ge46 clathrate and some related Zintl phase structures MxGayGe46-y using ab initio density functional theory. The vibrational modes of pure Ge46 (without guest species) are compared to the MxGayGe46-y structures, and it is found that small metal atoms (e.g. Na) have vanishing restoring force in the large cage, while the larger alkali-earth metal Ba has a restoring force constant less than 10% of that of the a framework atom. This makes them ideal “rattler” systems.
The Effect of A Graded in Profile on the Figure of Merit of PbTe
Authors: Dashevsky Z. , Shusterman S. , Horowitz A. , Dariel M. P.
Published: April 2011

The present study was aimed at demonstrating the possibility of producing a graded charge carrier concentration in a PbTe crystal by taking advantage of the concentration profile that is set up by the diffusion of In from an external source. Doping by indium generates deep impurity levels lying close to the edge of the conduction band. The Fermi level pinning effect and the electron population of the In impurity levels, which reduces the minority carrier concentration at elevated temperature, significantly improve the thermoelectric behavior of the resulting material. The penetration profiles of In, originating from an external gaseous or liquid source, were determined using Seebeck coefficient measurements in p- and n-type PbTe crystals. In the p-type crystal, the Seebeck coefficient changed sign as the In concentration induced a change from p-type to n-type character. The thermovoltage of a PbTe crystal in which an In concentration profile, generated by In diffiusing from a gaseous source had been established, was determined in the 50 to 430 °C temperature range. The constant Seebeck coefficient that was observed over the whole temperature range provides the experimental support for the underlying premises of this study.
Flux Synthesis of New Multinary Bismuth Chalcogenides and their Thermoelectric Properties
Authors: Chung Duck-Young , Choi Kyoung-Shin , Brazis Paul W. , Kannewurf Carl R. , Kanatzidis Mercouri G.
Published: April 2011

We present the synthesis and structure of the new chalcogenide compounds, Rb0.5Bi1.83Te3, APb2Bi3Te7 (A = Cs, Rb), K1.25Pb3.50Bi7.25Se15 and A1+xPb4−2xSb7+xSe15 (A = K, Rb). The layered structures of the first two telluride compounds are related to each other in a very interesting fashion. These compounds are n-type metallic conductors and solid solutions with Se and Sb have also been synthesized. K1.25Pb3.50Bi7.25Se15 and its Sb analogs have a complex three-dimensional structure composed of NaCl- and Bi2Te3-type building units. The thermal stability, melting behavior, electrical conductivity and thermopower of these compounds are reported.
Mechanical properties of SU-8
Authors: Mcaleavey A. , Coles G. , Edwards R. L. , Sharpe W. N.
Published: April 2011

An existing test system for recording the stress-strain curves of metal microspecimens has been used to measure the strength of the ultrathick photoresist SU-8. The microspecimens are 3 mm long with a gage section 0.2 mm wide. The SU-8-25 specimens were 0.08 mm thick with an average strength of nearly 120 MPa, and the SU-8-50 specimens were 0.125 or 0.145 mm thick with an average strength of 130 MPa. Measurements of Young's modulus proved difficult, but a preliminary value of 3 GPa was obtained.
Characterization of Transparent Conducting Pulsed Laser Deposited Films in the Indium Zinc Oxide System
Authors: Rougier A. , Naghavi N. , Marcel C. , Portemer F. , Dupont L. , Guéry C. , Tarascon J.M.
Published: April 2011

Thin films of indium zinc oxide so called IZO were prepared with pulsed laser deposition. It was found that the crystalline structure, the composition and the morphology of the films as well as the optical and electrical properties were quite sensitive to the deposition conditions namely to the temperature and oxygen pressure. The crystallinity of the ZnkIn2O3+k (k from 1 to 5) thin films increases as the substrate temperature increases. An average transmittance of 85 % in the visible region was obtained for any k values. Optical measurements show a continuous decrease of the band gap as the zinc amount increases. The highest conductivity reported is for the ZnIn2O4, thin films deposited at 300 °C (σ = 1.2 103 S/cm). Increasing the amount of Zn (i.e. k value) was found to result in a conductivity decrease. Finally, a good correlation between the electric mobility and the optical mobility is obtained.
A Neutron Diffraction Study of Co2Ru1-xMnxO4 Spinels
Authors: Mandrus D. , Keppens V. , Chakoumakos B. C. , Granroth G. E. , Nagler S. E.
Published: April 2011

Powder neutron diffraction and magnetization measurements are presented on the Co2Ru1-xMnxO4 system. In these materials the tetrahedral (A) sites are occupied by Co2+ (S = 3/2) ions, and the octahedral (B) sites are jointly occupied by Co3+ (low spin, S = 0), Ru3+ (low spin, S = 1/2), and Mn3+ (S = 2) ions. The measurements reveal that Co2RuO4 undergoes a spin-glass transition, Co2MnO4 is a collinear ferrimagnet, and that Co2Ru0.5Mn0.5O4 undergoes an unusual magnetic double transition. Triple-axis measurements indicate that the lower temperature transition in Co2Ru0.5Mn0.5O4 is characterized by the onset of diffuse scattering and the emergence of short-range order. The Co2Ru1-xMnxO4 series appears to be well-suited for studying the coexistence of long- and short-range magnetic order.
Plutonium Pyrochemical Salts Oxidation Using Vanadium Oxide
Authors: Smith Donna M. , Neu Mary P. , Garcia Eduardo , Dole Vonda R.
Published: April 2011

This paper presents results from the oxidation of PuCl3 with two-thirds, one, and two equivalents of V2O5 and the oxidation of Pu° with two and three equivalents of V2O5. All of the PuCl3 reactions were successful in that little or no starting materials remained and the major plutonium reaction product was PuO2. There is no evidence that V is reduced to V(II) or V°. According to powder XRD analysis, the bottom layers of all three reactions are identical, the middle layers contain different phases, and phases in the top layer of the oxidation with one equivalent of V2O5 is contained in the top layer from the oxidation with two-thirds equivalent of V2O5. The Pu° oxidations are more complex than the PuCl3 oxidations. More unreacted Pu° remains in the reaction using three equivalents of V2O5 than the reaction using two equivalents of V2O5. The lack of predictability of these reactions may be a result of the source of Pu° used in our experiments. The presence of soluble Pu(III) and the relative absence of PuO2 in all the Pu° reactions suggests V2O5 does not oxidize Pu° to Pu(IV) under these conditions. Chlorine is detected in the off-gas of the Pu° oxidations, indicating the salt matrix participates in the reaction.
The Bismuth-Barium Oxides
Authors: Müller K. , Meen J.K. , Elthon D.
Published: April 2011

Phase relations have been determined for the Bi-Ba oxide pseudobinary up to 50 cat % Ba in 1 atm of oxygen at 640°-1000°C. The low-temperature α-Bi2O3 polymorph does not dissolve appreciable BaO. All other phases in the system have significant ranges of solution. The δ-Bi2O3 polymorph, stable from 730°C to 825°C is an end-member of a face-centered cubic solid solution (FCCss) that dissolves up to 2.7 % Ba. Ba-saturated FCCss and Bi-saturated rhombohedral (ß) solid solution (6.3 % Ba) melt at a eutectic at 753 °C. Less Bi is needed to saturate the ß phase at lower temperatures so α-Bi2O3 coexists with a ß phase containing 11.5 % Ba at 646°C.

The amount of Ba required to saturate the ß phase depends less strongly on temperature. Ba-saturated ß phase contains 19 % Ba at 700°C. These ß materials are in equilibrium with an oxide near Bi3BaO5.5 that undergoes two polymorphic transformations: low-temperature cubic (<700°C); orthorhombic (700-730°C); high-temperature cubic (Cht). There is a eutectic between the ß and Cht, at 775±6°C. At T<700°C, 26.5 % Ba saturates the latter but it can take in up to 29.5 % Ba (at 812°C). At T<815°C the coexisting phase is BiBaO3. A tetragonal (T) phase forms by reaction of Ch, and BiBaO3 and has ~35% BaO at 815°C. The composition span of T widens as temperature increases. Cht, melts incongruently at 820°C to a liquid and T with 29.8 % Ba. Above that temperature the Bi-saturated and Ba-saturated T phases both become more Ba-rich as temperature is elevated. T melts incongruently to liquid and BiBaO3.

The δ-Bi2O3 and ß, both anion conductors, have structures based on that of fluorite. The other oxides have perovskite-like structures. Half of the Bi in BiBaO3 is pentavalent and half is trivalent. The other oxides appear to have all their Bi in the 3+ state.
Synthesis of Na1-xLnxNbO3(Ln=La, Nd, Sm, Gd) and their Structures and Electrical Properties
Authors: Sugimoto Wataru , Naito Masahiro , Sugahara Yoshiyuki , Kuroda Kazuyuki
Published: April 2011

Polycrystalline samples of Na1-xLnxNbO3(Ln=La, Nd, Sm, Gd) were synthesized by solid-state reactions. Reduced niobates were obtained as single-phase perovskites forx=0.05 and 0.1 when Ln=La and Nd andx=0.05 when Ln=Sm. The Gd-substituted samples could not be prepared under the synthetic conditions studied. Compositional analysis of the products revealed a slight amount of sodium loss during synthesis. The structural parameters obtained from Rietveld analysis revealed an increase in unit-cell volume. All of the obtained samples showed semiconducting behavior. Similar semiconducting behavior was observed for the same x value, suggesting the weak influence of the different Ln species to the electrical properties.
Melting Relations of Bi2O3-SrO-CaO-CuO Superconductors at Various Oxygen Fugacities
Authors: Styve Vance J. , Geny Joel , Meen James K. , Elthon Don
Published: April 2011

In an effort to synthesize monophasic superconducting oxides in the quaternary system Bi2O3-SrO-CaO-CuO two studies have been conducted. The melting relations of superconducting oxides Bi2Sr2CaCu2O8 (Bi-2212) and Bi2Sr2Ca2Cu3O10 (Bi-2223) have been experimentally investigated separately at various oxygen fugacities {f(O2)} from I to 3. 10-4 bar at 1 atm total pressure. Several interesting properties of the system have been found with respect to this portion of the quaternary; the modal proportions of liquid produced at the solidus depend on the oxygen fugacity. The amount of liquid produced at the Bi-2212 solidus reached a maximum of approximately 75% at f(O2) = 0.1 bar, Bi-2223's maximum proportion of liquid formed at the solidus continues to increase up to the lowest oxygen fugacity f(O2) = 0.01 bar studied. CaO (with a small amount of dissolved SrO) is the liquidus phase over the entire range of f(O2) for both compositions. (Sr,Ca)2CuO3 is the second phase to crystallize at high f(O2) but, as f(O2) decreases, its primary phase volume shifts for Bi-2212, and Bi2(Ca,Sr)3O6 is the second phase to form. (Sr,Ca)14Cu24O41 exhibited liquidus relationship only in high oxygen fugacities. Only Bi-2212 melts to assemblages that include bismuth-bearing crystalline phases. Bi9(Ca,Sr)16Ox is stable only at high oxygen fugacities and Bi2(Ca,Sr)3O6 is only stable at the lower values. At the lowest oxygen fugacities, Bi-2212 liquids crystallize (SrCa)CuO2 at a higher temperature than (SrCa)2CuO3 and no (Sr,Ca)CuO2 was found in Bi-2223 bulk compositions. These variations apply constraints on the positions of the univariant and invariant phase equilibria and these constraints are described.
207PB NMR and Monte Carlo Studies of Ionic Solid Solutions
Authors: Kye Young-Sik , Herreros Bruno , Harbison Gerard S.
Published: April 2011

Lead, strontium and barium nitrates, like the titanates of the same cations, form a continuous set of solid solutions. 207Pb NMR spectra of mixed crystals of lead/strontium nitrate and lead/barium nitrate each show up to 13 lines, arising from lead ions with from zero to twelve Pb2+ nearest-neighbor cations replaced by Sr2+ or Ba2+. In the case of (Pb,Sr)(NO3)2 these shifted lines are further split by the multiplicity of inequivalent nearest-neighbor replacements. The average shift per Sr2+ ion is 21.8 ppm; that for Ba2+ is smaller. Using Monte Carlo/Metropolis calculations, the intensities of the resonances can be fit to statistical models of Pb2+ and Sr2+ ion distributions, and used to probe the microenergetics of solid solution formation. The data can be satisfactorily fit by distributions in which the cations are slightly clustered, with like pairs of nearest neighbors being favored by 120 J/mol over unlike pairs. Interestingly, this finding is inconsistent with the conventional interpretation of powder diffraction results for the mixed crystals, where the dependence of lattice parameter on composition shows a slight positive curvature, generally held to indicate a favorable interaction between unlike ions.
Energetics of Nitridophosphates PON and “LiNaPON Glasses”
Authors: Tessier F. , Le Sauze A. , Marchand R. , Navrotsky A.
Published: April 2011

Structural analogies have been demonstrated between the β-cristobalite, α-quartz and moganite phases of PON and its isoelectronic analog SiO2. Whereas the energetics of silica are well established, no data exist for the energetics of formation of nitridophosphates. High temperature solution calorimetry was used to determine the energetics of PON samples and a series of “LiNaPON oxynitride” glasses. Enthalpies of formation were measured as -371.71 ± 4.45 kJ/mol and -356.14 ± 3.98 for β-cristobalite and amorphous PON respectively and as -961.88 ± 3.86 kJ/mol for a 9 wt% nitrogen containing LiNaPON glass. These values constitute the first set of energetics data necessary to achieve further thermodynamic studies on nitridophosphates.
Novel Polar Intermetallic π-Systems along the Zintl Border
Authors: Guloy Arnold M. , Xu Zhihong
Published: April 2011

Studies have shown that complex Zintl phases exhibit a rich diversity of crystal structures. These have also revealed a remarkable success of the Zintl concept in rationalizing stoichiometry, crystal structure and chemical bonding of many main group intermetallics. Still there are unresolved questions about the usefulness of the concept in explaining structure-property relationships in intermetallics near the Zintl border, and as a rational tool in designing new materials. Limitations of the concept are represented by violations often associated with “electron-deficient” phases that contain Group 13 metalloids. Recent investigations on “electron-deficient” Zintl phases containing post transition metals have led to the synthesis of a number of novel inorganic-intermetallic π-systems. Since unique structures and properties are already apparent in normal Zintl phases, it is anticipated that the exploratory synthesis and characterization of conjugated and multiple-bonded inorganic systems will produce not only unusual crystal chemistry but interesting physical properties as well. We report on new complex Zintl phases that include the semiconducting SrCa2In2Ge - which features [In2Ge]6- chains and represents a novel inorganic conjugated π-system analogous to a polyallyl chain with In-In double bonds, and Ca5In9Sn6 - which contains In trimers, [In3]5- analogous and isoelectronic with the aromatic cyclopropenium cation, [C3H3]+. These unusual materials, Zintl π-systems, represent a promising class of electronic materials with a range of potential applications.
Synthesis and Characterization of A New Weak Ferromagnet: Fe(II) Ethylene-BIS-(Phosphonates)
Authors: Bellitto C. , Federici F. , Mahmoud M.R. , Ibrahim S.A.
Published: April 2011

Iron(II)-ethylene-bis-(phosphonates), Fe2[O3P-(CH2)2-PO3]·2H2O was synthesized by reaction of [FeSO4]·7H2O and the corresponding ethylene-bis-(phosphonic acid) and it was characterized by X-ray powder diffraction, thermogravimetry, UV-visible and infrared spectroscopy, and the magnetic properties were studied by a SQUID magnetometer. The metal-ion is in the d6 high-spin electronic configuration and it appears to have an octahedral coordination. The thermal variation of the d.c. magnetic susceptibility of Fe2[O3P-(CH2)2-PO3]·2H2O follows the Curie-Weiss law, with a negative Weiss constant of θ =-55K. Below 100K, the susceptibility increases until a peak at TN=24K is observed, and this is associated to the three-dimensional antiferromagnetic order. Below 24K, Fe2[O3P-(CH2)2-PO3]·2H2O behaves as a “weak” ferromagnet and it represents an example of an unusual kind of molecular-based magnetic materials, having a finite zero-field magnetization.
Preparation of SiC-Diamond Nanocomposites
Authors: Gierlotka S. , Ekimov E. , Palosz B. , Stel'makh S. , Pielaszek R. , Witek A. , Grzanka E. , Presz A. , Boysen H. , Bismayer U.
Published: April 2011

Compacts of composites SiC-diamond were made by infiltration of Si into nanocrystalline diamond powders in a toroid-type press under the pressure of 7.7 GPa at 1300 °C. In-situ high pressure diffraction studies of these processes were performed in MAX80 cubic anvil press at a pressure of 8.5 GPa in temperatures up to 1800°C in HASYLAB at DESY, Hamburg, Germany. Sintering was performed for (i) pure nanocrystalline diamond powders, (ii) a mixture of nanocrystalline powders of diamond and nanocrystalline SiC, (iii) a mixture of nanocrystalline diamond with microcrystalline Si powders and (iv) compacts of nanocrystalline diamond infiltrated by Si. The SiC-diamond composites obtained by infiltration of Si have best physical properties: hardness similar to conventional diamond compacts (approximately 50 GPa), highest density 3.35 g cm-3 and uniform nanocrystalline microstructure.
Gradually Varying Intermediate Valence of Fe in La1-xCaxFeO3
Authors: Li Jiangong
Published: April 2011

The isomer shift of La1-xCaxFeO3 decreases gradually from the value for trivalent iron to that for tetravalent iron, as the Ca content x increases from 0 to 1. This indicates that iron in La1-xCaxFeO3 has an intermediate valence state. The intermediate valence state of iron increases gradually from trivalence to tetravalence. This can be interpreted as being due to electron delocalization among iron ions on identical octahedral sites. The Mossbauer spectra at various temperatures of La0.5Ca0.5FeO3 and their theoretical treatment show that electron delocalization slows down with decreasing temperature.
The Structure Directing Role of Cations in the Synthesis of Low Silica LTL Zeolites
Authors: Burton A. , Lobo R. F.
Published: April 2011

The structure and extraframework cations of dehydrated zeolites (Ba,K)-G,L (Si/Al=1) and (Ba,Li)-G,L (Si/Al=1) are characterized by powder neutron diffraction. The results provide direct evidence of the similar structure directing roles which barium and potassium play in the syntheses of zeolites with the LTL topology.
A - and B - Site Order in (Na1/2La1/2)(Mg1/3Ta2/3)O3 Perovskites
Authors: Dupont L. , Chai L. , Davies P.K.
Published: April 2011

The “1:2” family of A2+(B2+1/3B+5+2/3)O3 (e.g. B2+ = Mg, Ni, Zn; B5+ = Nb, Ta) mixed metal perovskites typically adopt a 1:2 layered ordered structure when A = Ba and Sr, and a 1:1 ordered doubled perovskite structure for A = Pb. To understand the stability of the cation order in these systems and explore how the different cation correlations affect their dielectric and ferroelectric properties, the response of several members of this family of perovskites to a series of chemical substitutions and thermal treatments have been explored. In this paper we present results for a system where the divalent A cation is replaced by a 1:1 mixture of Na+ and La3+. At all temperatures this substitution stabilizes 1:1 B-site ordering. Below ~ 950°C an additional ordering reaction occurs on the A sub-lattice with Na and La occupying alternate layers along the c axis. The formation of different orientational variants of the A-site ordered phase produces a twinned nano-domain structure which in turn perturbs the length-scale, but not the symmetry, of the order on the B-site lattice. The presence of (Na1/2La1/2) on the A-site is apparently effective in destabilizing the 1:2 layering of the B-site cations observed in alkaline earth systems, possibly through unfavorable local charge imbalances.
Low-Temperature Multistep Topotactic Routes to New Mixed-Valence Perovskites
Authors: Lalena J.N. , McIntyre R.A. , Cushing B.L. , Thomas K.A. , Heintz J.L. , Seip C.T. , O'Connor C.J. , Wiley J.B.
Published: April 2011

Multistep topotactic routes are exploited to introduce mixed-valency into mixed-metal oxides at low temperatures (≤ 350°C). A new set of single- and triple-layered perovskites, Na1-x-yCax/2LaTiO4and Na2-x+yCax/2La2Ti3O10, respectively, has been prepared by a combination of ion exchange and reductive intercalation. The single-layer series are metastable compounds. The magnetic and electronic behavior of the triple-layer titanate is consistent with Anderson localization effects, while those of the single-layer materials are more complex; samples demonstrate “Hurd-like” conductivity and an unusual magnetic response. The details of the synthesis and characterization of these materials are presented and their magnetic and electronic behavior discussed.
Ambient temperature synthesis of polycrystalline thin films of lithium cobalt oxide with controlled crystallites† orientations
Authors: Goldner R.B. , Zerigian P. , Liu T.Y. , Clay N. , Vereda F. , Haas T.E.
Published: April 2011

Polycrystalline thin films of lithium cobalt oxide (nominally LiCo02) have been deposited by a process which we have named, ion beam directed assembly (IBDA). It is similar to ion assisted deposition (IAD) or ion beam assisted deposition (IBAD), but the major difference is that in IBDA the ion beam directs, via the vector momenta of the ions, rather than merely assists, the growth. Hence, we also term the process directed assembly to distinguish it from self assembly. Also, in directed assembly the ions may or may not become an integral part of the film's composition.

In this paper we wish to show that the IBDA process may be capable of controlling microstructure, e.g., in the case of polycrystalline films, control the orientations of the crystallites. For LiCoO2 we have observed this in two ways - by X-ray analysis, and electrochemically, by lithium diffusivity measurements. In particular, we have observed increased lithium diffusivities (≥ 10−8 cm 2/s) in IBDA deposited films as compared to that found for rf sputter deposited films (z 10−10 cm2/s). In addition, the coulometric titration characteristics of an IBDA deposited Lil−yCoO2 are very similar to those of sputtered deposited films (for lithium extraction/insertion, y ≤0.5, and for quasi-equilibrium voltages up to 4.2 volts).
Resonant Raman Characterization of Polyparaphenylene Based Carbon Materials
Authors: Marucci A. , Brown S. D. M. , Pimenta M. A. , Matthews M. J. , Dresselhaus M. S. , Endo M.
Published: April 2011

The structure of the polymer polyparaphenylene (PPP), heat-treated at temperatures (THT) between 650°C≤ THT ≤750°C and prepared according to either the Kovacic or the Yamamoto methods, is studied by the resonant Raman technique using five laser excitation energies Elaer in the range 1.92–3.05 eV. The resonant Raman analysis allows identification of the benzenoid and quinoid forms of PPP as well as the amorphous material associated with the onset of the carbonization process. The results enable us to follow the evolution of the PPP polymer with heat-treatment temperature and to determine the differences between the materials prepared using the two different methods.
Electrical and Esr Studies of Lithium Manganese Oxide Spinels
Authors: Julien C. , Gendron F. , Ziolkiewicz S. , Nazri G.A.
Published: April 2011

We report electrical properties of the lithium manganospinel LiMn2 O 4 and its delithiated/lithiated forms, Li1−x−∂Mn2−∂O4 with 0.0≤x≤0.4 and 0.00≤∂0.18. The electrical conductivity has been determined from d.c. measurements as a function of temperature and lithium content in the host lattice. LiMn2O4 exhibits a phase transition in the vicinity of 280 K, which disappears in the lithium-rich samples. Electrical data are analysed using the model of small-polaron transport. ESR spectroscopy has been applied to identify the singular structural features. Investigations as a function of temperature show a reliable determination of the modifications in the cationic sublattice and of the lithium overstoichiometry. The hopping conductivity mechanism between the Mn3+ and Mn4+ sites gives a coherent explanation for the observed ESR signal of cyclotron resonance.
Physical Properties of Lithium-Cobalt Oxides Grown by Laser Ablation
Authors: Escobar-Alarcon L. , Haro-Poniatowski E. , Jimenez-Jarquin J. , Massot M. , Julien C.
Published: April 2011

We have studied the growth and the physical properties of LiCoO2 films as a function of formation conditions, i.e., substrate temperature and partial oxygen pressure. These films were grown on various substrates by the laser ablation technique using a Nd:YAG laser at 100 MW/cm2 power density. LiCoO2 films were characterized by XRD, SEM, and vibrational spectroscopy. The synthesized compounds show high homogeneity in composition and in particle dimension. The main advantage of this method is the less time needed for the reaction to occur completely. Raman scattering spectroscopy provides information on the local environment of cations.