bluuebunny/crossref_metadata_2025_split huggingface dataset:
High Temperature Thermoelectric Properties of Boron Carbide
Authors: Aselage T. L. 
Published: March 2011

ABSTRACTBoron carbides are refractory solids with potential for application as very high temperature p-type thermoelectrics in power conversion applications. The thermoelectric properties of boron carbides are unconventional. In particular, the electrical conductivity is consistent with the thermally activated hopping of a high density (≈ 1021/cm3) of bipolarons; the Seebeck coefficient is anomalously large and increases with increasing temperature; and the thermal conductivity is surprisingly low. In this paper, these unusual properties and their relationship to the unusual structure and bonding present in boron carbides are reviewed. Finally, the potential for utilization of boron carbides at very high temperatures (up to 2200°C) and for preparing n-type materials is discussed.
Review of Lead-Telluride Bonding Concepts
Authors: Elsner Norbert B. 
Published: March 2011

ABSTRACTOver the past few years, there has been a trend to use thermoelectrics for generating power from waste heat or coupling the thermoelectrics with fossil fuel driven appliances or Diesel engines to make them more efficient and/or independent of outside power. PbTe based alloys are being considered for some of these applications. Presented below are some of the techniques that have been pursued in making electrical contacts. Because PbTe can be used up to ∼ 600°C, these alloys offer more efficiency than the (Bi,Sb)2 (SeTe)3 based alloys which are only useful to <300° C. Unfortunately, at these h~gher temperatures, the PbTe based alloys need to be encapsulated to prevent oxidation. This latter step is not addressed in this paper, but can significantly add to the price of a PbTe generator.
Thermoelectric Properties of Single Crystal Alloys Bi8Sb32Te60, Bi9Sb31Te60and Bi10Sb30Te60Grown by the T.H.M. Method
Authors: Caillat T. , Carle M. , Fleurial J. P. , Scherrer H. , Scherrer S. 
Published: March 2011

ABSTRACTIt has been reported that high figures of merit could be achieved on bismuth telluride grown by T.H.M. (Travelling Heater Method). Further improvements could be obtained for the p-type materials by studying solid solutions formed by bismuth telluride and antimony telluride.A good knowledge of the ternary phase diagram is necessary to obtain homogeneous ingots by T.H.M..We present the results of the determination of ternary phase diagram (Bi-Sb-Te). The equilibrium data between liquid and solid alloys Bi8Sb32Te60, Bi9Sb31Te60and Bi10Sb30Te60are also reported and it allows their elaboration by T.H.M..Thermoelectric characterization of ternary samples is carried out as a function of stoichiometric deviations. Measurements of electrical and thermal conductivities as well as Seebeck coefficient were done at room temperature for the Bi8Sb32Te60, Bi9Sb31Te60and Bi10Sb30Te60alloys.The values of the figure of merit remain interesting for the alloys studied and a maximum value of 3.2 10−3K−1is reached for the Bi9Sb31Te60alloy.
Properties of Bi-Te-Sb Single Crzystals Grown by the Czochralski Method for Thermoelectric Cooling
Authors: Anatychuk Lukyan I. , Klim Vladimip A. , Kshevetsky Stanislav A. 
Published: March 2011

ABSTRACTMaterials based on Bi.Te, Se, Sb and produced by pressing, extrusion or zone recrystalization are used usually for the thermoelectric cooling. But by Czochralski method materiales have been far less grown. Researches on growing of monocrystalline ingots on the base of combinations Bi-Se-Te and Bi-Sb-Te have been done by [1,2]. The same researches have been made at our Institute.
Thermoelectric Power Studies on La2-xSrxNiO4-δ
Authors: Liu C.-J. , Sánchez M. G. , Cowan D. O. 
Published: March 2011

ABSTRACTThermoelectric power (S) has been measured on La2-xSrxNiO4-δ. Both nonmetallic (0.5 < × < 1.0) and metallic materials (1.1 ≤ × ≤ 1. 5) have been investigated between 80 and 310 K. The sign of S changes from negative to positive between 150 and 220 K for both metallic and nonmetallic samples. The position at which the curve crosses from negative to positive depends upon the composition (x). For example, when × = 1.15 (metallic conductivity) S changes from negative to positive at about 220 K. However, if this sample is heated to 1000° C under argon, the material becomes nonmetallic and the sign of S remains positive between 80 and 310 K. These results may indicate that more than one type of carrier is involved. The absolute magnitude of S at 300 K decreases with × for 0.5 ≤ × ≤ 1.15 and then increases with × for 1.15 ≤ × ≤ 1.5. In the heavily doped material where S becomes more negative with increasing doping, the thermoelectric power strongly indicates that electrons and not holes are the majority carriers.
Radiation Defect Study in the P-Type Copper Seleind
Authors: Marchuk N. D. , Dolgolenko A. P. 
Published: March 2011

ABSTRACTP-Cu2-δ Se(δ=0.025) samples, self-doped through a departure from the stoichiometry(po= 4.8·1020) and cadmium-doped up to a concentration po= 5.6·1020cm−3 were studied in the course of their irradiation in a reactor up to a fluance of -6·1020 n·cm−2 of fast neutrons at a temperature of -500-550° C. The dependence of the resistivity and thermo-emf on the fast neutron fluence is described in terms of the theory of effective medium and representation of defect clusters as dielectric inclusions in a conducting matrix of p-Cu2Se(Cd) and p-Cu2_δSe samples.Defect clusters of a mean radius of -27 Å are shown to appear not only because of scattering of the fast pile neutrons on copper and selenium atoms, but also due to a nuclear reaction 112Cd(n,γ)114Cd on thermal neutrons with an efficiency of 3.43 cm−1. Increase of the conductivity in the process of the reactor irradiation of p-Cu2-δSe at small fluences of fast neutrons and appearance of a whitish deposit of selenium on the surface of samples after high fluences of fast neutrons were observed.
Is there a Lower Limit to the Thermal Conductivity of Solids?
Authors: Cahill David G. , Pohl R. O. 
Published: March 2011

ABSTRACTThe thermal conductivity of various systematically disordered crystals has been measured. It has been found that the lowest thermal conductivity above ∼100 K that can be achieved is equal to that of the amorphous phase. This experimentally observed lower limit of the thermal conductivity can be described with a model proposed by Einstein in which the elastic energy propagates in a random walk among the atoms which are vibrating with random phases, and which is called the minimum thermal conductivity. This heat transport mechanism resembles somewhat that commonly accepted in liquids.
A New Method for Thermal Diffusivity Measurements in Metals Utilizing the Thermo-Electric Effect
Authors: Shai Isaac , Laor Uri , Gilad Ilan 
Published: March 2011

ABSTRACTA new method for the measurement of the thermal diffusivity in metals, using transient conditions, is demonstrated. This method is using the principle of superposition of thermal loads. Only time measurements are required, and no accurate temperature and heat flow rate measurements are needed. The method utilizes the Seebeck effect for the measurement of the time dependence of the temperature. A solution of the heat transfer equation for the model pertinent to the described method is derived, and results obtained for several materials are presented.
Thermal Conductivity of N-Type Si-Ge
Authors: Klfmens Paul G. 
Published: March 2011

ABSTRACTThe lattice thermal conductivity of 80-20 Si-Ge is treated theoretically for the case of the Fermi energy positioned for optimum figure of merit. The spectral distribution of the lattice conductivity is limited by anharmonic interactions, by the randomness of the Si-Ge lattice and, at low frequencies, by the interaction with free carriers and neutral donors. The two latter processes dominate over grain boundary scattering. The spectral conductivity is sharply peaked around 0.1 of the Debye frequency. A further reduction in lattice conductivity can be obtained by small insulating inclusions. This is partially offset by a reduction in electronic conductivity, but results in some improvement in the figure of merit.
A Model for the High Temperature Transport Properties of Heavily Doped P-Type Silicon-Germanium Alloys
Authors: Vining Cronin B. 
Published: March 2011

ABSTRACTA model is presented for the high temperature transport properties of large grain size, heavily doped p-type silicon-germanium alloys. Good agreement with experiment (±10%) is found by considering acoustic phonon and ionized impurity scattering for holes and phonon-phonon, point defect and hole-phonon scattering for phonons. Phonon scattering by holes is found to be substantially weaker than phonon scattering by electrons, which accounts for the larger thermal conductivity values of ptype silicon-germanium alloys compared to similarly doped n-type silicongermanium alloys. The relatively weak scattering of long-wavelength phonons by holes raises the possibility that p-type silicon-germanium alloys may be improved for thermoelectric applications by the addition of an additional phonon scattering mechanism which is effective on intermediate and long-wavelength phonons. Calculations indicate improvements in the thermoelectric figure of merit up to 40% may be possible by incorporating several volume percent of 20 Å radius inclusions into p-type silicon-germanium alloys.
Enhanced Third Order Nonlinearity in Macrocyclic Compounds
Authors: Hosoda Masahiro , Wada Tatsuo , Garito Anthony F. , Sasabe Hiroyuki 
Published: March 2011

ABSTRACTThe third-order nonlinear optical susceptibilities χ(3)1111(-3ω; ω, ω, ω) of macrocyclic compounds such as phthalocyanines and porphyrins are determined for the vacuum deposited and spin coated thin films by optical third-harmonic generation measurements at a wavelength of 1907 nm. The enhancements of the χ(3) values are discussed in terms of the central metal substitution, molecular stacking, extended ring size and number of χ-electrons. We firstly describe the results of extended porphyrin systems with 26 delocalized π-electrons.
Poly(Vinyl Ethers) as Nonlinear Optical Materials, Shg in Corona Poled Polymer Films
Authors: S'heeren♦ Gert , Vanermen Guy , Samyn Celeste , Beylen Marcel Van , Persoons Andre 
Published: March 2011

ABSTRACTNew poly(vinyl ethers) with pendant groups exhibiting nonlinear optical properties were synthesized: 4-cyano and 4-nitro-4'-(alkoxy) azobenzene substituted poly(vinyl ethyl ether), copolymers and 4-dicyano or 4-cyano-4-carbomethoxyvi-nyl-4'-(alkoxy)benzene substituted poly(vinyl ethyl ether). Films spincoated from these polymers were poled by a positive corona discharge just above their T9 (as measured by DSC). The second order susceptibilities of tne films were derived from full-angle Maker fringe patterns at 1064 nm. Susceptibilities x(2) zzz as high as 23×10−9 esu were measured.
The Nonlinear Optical Properties of Polyacetylene within the Intermediate Exciton Formalism
Authors: Yaron David , Silbey Robert 
Published: March 2011

ABSTRACTWithin the Singles-CI approximation, the perturbation theory expression for γ (the non-resonant third-order nonlinear optical susceptibility) contains a class of terms which correspond to (i) the creation of an s-type exciton (ii) a transition to a p-type exciton, and (iii) a return to the ground state through an s-type exciton. The contribution of these terms to γ is considered in the limit of an infinite chain of polyacetylene. The infinite chain limit is obtained by considering a ring of polyacetylene and allowing the ring size to go to infinity. The limit is approached using three methods, each of which reveals a different characteristic length of the system. The form of the excitons is found to be independent of ring size for rings which are larger than the size of the exciton.
Linear and Nonlinear Optical Properties of Processable Polymeric Materials
Authors: Kaino Toshikuni , Tomaru Satoru , Kurihara Takashi , Amano Michiyuki 
Published: March 2011

ABSTRACTLinear and nonlinear optical (NLO) polymeric materials with good processabilities are discussed. An azo-dye substituted copolymer (3RNO2, nitro-terminated diazo dye) are investigated. The polymer film was found to be transparent and attenuation loss was less than 2 dB/cm. The χ(3) of 3RNo2 reaches 5×10−11 esu in the near-resonant region. With polymers where the dye molecules are introduced into the polymer backbone (a main chain polymer), a χ(3) larger than 10−11 esu is obtained even in a monoazo dye introduced polymer. A new molecular crystal, symmetrically substituted benzylidene-aniline compound, SBAC for short, are also successfully polymerized (introduced into a polymer main chain) and their χ(3) values are revealed to be around 1010 esu in the near-resonant wavelength region. The optical transmission of these polymers is also investigated and revealed to be around 2 dB/cm. With poly(arylene vinylene), a certain population of χ-conjugation length will induce enhancement of the resonant χ(3) of the polymers. The polymer can be used to fabricate channel waveguides with the photo-bleaching technique.
Synthesis, Characterization, and Processing of Organic Nlo Polymers
Authors: Druy Mark A. , Glatkowski Paul J. , Burzynski Ryszard 
Published: March 2011

ABSTRACTThe research described in part in this manuscript is a multi disciplinary effort to target key applications and material and processing requirements for these third order nonlinear optical polymers. It discusses the synthesis, characterization, and processing of nonlinear optical properties of polyimides which have been tailored for nonlinear optical activity.
Third-Order Nonlinear Optical Properties of Phthalocyanines
Authors: Shirk James S. , Undle J. R. , Flom Steven R. , Bartoli F. J. , Snow Arthur W. 
Published: March 2011

ABSTRACTThis paper discusses the third-order nonlinear optical (NLO) properties of substituted phthalocyanines measured by time-resolved degenerate four-wave mixing at 1064 nm. The study explores optical pumping as a mechanism contributing to a large third-order optical nonlinearity in one member of this interesting class of NLO materials, PbPc(CP)4.
Third Order Nonlinear Optical Responses of Metallophthalocyanines in Films and Solutions
Authors: Reeves Roger J. , Powell Richard C. , Ford Warren T. , Chang Young H. , Zhu Weiming 
Published: March 2011

ABSTRACTDihydrogen, copper, platinum, and lead octakis(2-ethylhexyloxy)phthalocyanines (Pc's) were studied in polystyrene films at 532 nm and in chloroform solutions at 1064 nm by picosecond degenerate four wave mixing. Resonant χ(3) values of Pc's at 532 nm (a local minimum in the absorption spectrum) at a time coincident with the 20 psec pump pulses were as high as 104 times that of CS2 by extrapolation of the response from 1 wt % PtPc in polystyrene film to a value for pure PtPc. Delay of the probe pulse as long as 3 nsec revealed acoustic responses stronger than the fast electronic responses. The films showed the expected quadratic dependence of the instantaneous reflectivity on incident intensity only for a decade of magnitude of intensity, 100–1000 MW/cm2, with the output saturating at higher intensities. Excited state absorption at 532 nm was detected in the film samples by pulse-probe spectroscopy and was shown to be a factor in the saturation observed in the NLO signals. Nonresonant χ(3) values at 1064 nm were as high as 120 times that of CS2 from measured responses of 1 wt % chloroform solutions of Pc's. Time delay of the probe revealed both fast electronic and slower acoustic responses at 1064 nm too.
Third-Order Nonlinear Optical Properties of a Series of Systematically Designed Conjugated Rigid-Rod Polyquinolines
Authors: Agrawal Ashwini K. , Jenekhe Samson A. , Vanherzeele Herman , Meth Jeffrey S. 
Published: March 2011

ABSTRACTThe third-order nonlinear optical properties of thin films of two series of conjugated rigid-rod polyquinolines, exemplified by poly(2, 2'-(l, 4-phenylene)-6, 6'-bis(4-phenyl quinoline)) (PPPQ, 2d) and poly(2, 7-(l, 4-phenylene)-4, 9-diphenyl-l, 6-anthrazoline) (PPDA, 3d), were investigated by third harmonic generation spectroscopy. Of the nine polyquinolines with diverse backbone structures, PPPQ has the largest optical nonlinearity with a χ(3) (-3ω; ω, ω, ω) value of 3.2 × 10−12 esu and 3.3 × 10−11 esu in the off-resonant and three-photon resonant regions, respectively. A comparison of the nonresonant χ(3) of the series of nine systematically derived polyquinolines showed that a scaling law of the form χ(3) ∼ (λmax)v ∼ Eg-v does not hold; in fact, the nonresonant χ(3) was essentially independent of the optical bandgap. These results suggest that structure-χ(3) propeny relationships in polymers cannot be inferred from those of oligomers and model compounds.
A New Organic Crystal---MHBA for Potential Diode Laser Second-Harmonic Generation
Authors: Jiang Minhua , Tao Xutang , Yuan Duorong , Zhang Nan , Shao Zongshu 
Published: March 2011

ABSTRACTThis paper reports a potential new organic crystal materials MHBA whose cut-off wavelength is 370nm and powder SHG intensity is 30 times higher than that of Urea. The crystal structure, single crystal growth, linear and nonlinear optical properties of MHBA are reported in detail. MHBA crystal belongs to monoclinic system; space group is P21, and the unit cell parameters are: a=14.057Å, b=7.875Å, c=15.037Å and β=115.45°. The nonlinear susceptibilities are: d11=25.0d36KDP, d12=10d36KDP, d13=33.3d36KDP and d14=8.3d36KDP.
Quadratic Nonlinear Optical Properties of Polymeric Organic Materials.
Authors: Cheng L.-T. , Foss R. P. , Meredith G. R. , Tam W. , Zumsteg F. C. 
Published: March 2011

ABSTRACTWe discuss our rational approach to incorporate optically nonlinear molecules into polymeric and cross-linked materials through the use of isocyanate-hydroxy coupling chemistry. Thin film fabrication, optical loss, poling, second harmonic generation, and electro-optic properties are discussed.
Synthesis of Fullerols as Polyhydroxylated Fullerene Derivatives
Authors: Chiang Long Y. , Upasani Ravi , Swirczewski John W. , Creegan Kathy 
Published: March 2011

ABSTRACTwe outline three methods for the preparation of fullerols as polyhydroxylated fullerene derivatives through the reaction of fullerenes with electrophilic reagents. The synthetic methodology includes a sequence of reactions using an aqueous acid chemistry, the epoxidation reaction, or the interesting nitronium chemistry as an key approach for the conversion of fullerenes to fullerols. The structure of fullerols was characterized and proposed to consist of at least 13 hydroxy functional moieties incorporating both hydroxy and hemi-ketal as parts of the structural components.
Functionalizing Fullerenes Through Cycloaddition Reactions
Authors: Malhotra Ripudaman , Narang Subhash C. , Nigam Asutosh , Ganapathiappan S. , Ventura Susanna , Satyam Apparao , Bhardawaj Tilak , Lorents Donald C. 
Published: March 2011

ABSTRACTWe have explored several cycloaddition reactions as a general approach for preparing fullerene derivatives. In view of their electron-deficient nature, they are expected to participate as dienophiles rather than dienes in cycloadditions. This behavior is exemplified in their reactions with sulfur trioxide, diphenylisobenzofuran, and the nitrone from cyclohexanone and N-methyl-hydroxylamine. Fullerenes also formed adducts with maleic anhydride, although in this case the nature of the adduct is not clear. While changes in physical properties such as solubility or IR spectra clearly indicated formation of adducts, mass spectral analysis of diese and many other fullerene derivatives often showed ions due to fullerenes; thus confirmatory evidence for the derivatives was not available from mass spectrometry.
Structures and Properties of C60 & C70 Thin Films Fabricated by Organic MBE
Authors: Tanigaki K. , Ichihsdhi T. , Ebbesen T. W. , Kuroshima S. , Iijima S. , Hiura H. , Takahashi H. 
Published: March 2011

ABSTRACTThe C60/C70 thin film crystals have been fabricated on the (001) surface of alkali halide substrates, KC1, KBr, and NaCl, and their structures have been studied. The crystal structure analyses by TEM show that the hexagonal closed packing (hep) with lattice parameters of a=10.0 Å and c=16.3 Å and the face-centered cubic (fee) with a=14.2 Å coexist in the C60 thin film crystals. The C70 thin film crystals show an expanded lattice constant of a=10.5 Å from the view perpendicular to the stacking plane. The ratio of hep to fee is dependent on the kind of the substrates and on the substrate temperatures during the crystal growth. The observed reversible change in the Raman spectrum of the C60 thin films implies a rotational molecular motion in the thin film crystals.
Electronic Structure of Carbon Fibers based on C60
Authors: Saito Riichiro , Fujita Mitsutaka , Dresselhaus G. , Dresselhaus M. S. 
Published: March 2011

ABSTRACTThe electronic structures of some possible carbon fibers nucleated from the hemisphere of a bucky ball are presented. A one-dimensional electronic energy band structure model of such carbon fibers, having not only a principal rotational axis but also fibers with screw axes, can be derived by folding the two-dimensional energy bands of graphite. By considering the variation of the fiber diameter and helicity within a simple tight binding model calculation, we show that 1/3 of the fibers are metallic and 2/3 are semiconducting. The effect of adding multiple tubule layers is considered.
Electronic Structure of Fullerene Tubules
Authors: Mintmire J. W. , Robertson D. H. , Dunlap B. I. , Mowrey R. C. , Brenner D. W. , White C. T. 
Published: March 2011

ABSTRACTRecent reports suggest that graphitic tubules with diameters on the order of fullerene diameters have been synthesized. Such small-diameter tubules should have electronic properties related to those of two-dimensional graphite. We demonstrate by comparison with results from a first-principles, self-consistent, all-electron Gaussian-orbital based local-density functional approach that an all-valence tight-binding model can be expected to give a reasonable description of the electronic states of these tubules. In analyzing both high-symmetry tubules and lower-symmetry chiral tubules, we see that a relatively high carrier density could be expected for many of these structures.
Photoelectron Spectra of C60H36 and C60H60
Authors: Dunlap B. I. , Mintmire J. W. , Robertson D. H. , Brenner D. W. , Mowrey R. C. , White C. T. 
Published: March 2011

ABSTRACTWe have calculated the electronic structure of icosahedrai C60H60 and tetrahedral C60H60 via an all-electron Gaussian-orbital based local-density functional approach. The one-electron wavefunctions and eigenvalues have been used in a first-order time-dependent perturbation theoretic calculation of the spherically averaged X-ray and ultraviolet pho-toemission cross-sections for these molecules.
Synthesis of AC60-Para-Xylylene Copolymer
Authors: Loy Douglas A. , Assink Roger A. 
Published: March 2011

ABSTRACTThe preparation and purification of macroscopic quantities of buckminsterfullerenes [1] or buckyballs has ignited an explosion of research into their physical and chemical properties, and a variety of strategies for preparing new fullerene-based materials. Free radical synthesis is an appealing approach for forming polymeric fullerene materials. We report a polymeric fullerene material prepared by reacting pure C60 with xylylene from the thermolysis of paracyclophane. Addition of xylylene to a purple solution of C60 in toluene solution at -78 °C resulted in an olive-green solution from which an insoluble brown powder precipitated upon warming to room temperature. Analyses of the powder by solid state 13C MAS NMR, IR, and thermal gravimetric analysis are consistent with C60-xylylene copolymer.