Doping

Distribution by Scientific Domains
Distribution within Polymers and Materials Science

Kinds of Doping

  • n-type doping
  • nitrogen doping
  • p-type doping
  • transfer doping

  • Terms modified by Doping

  • doping agent
  • doping concentration
  • doping content
  • doping control
  • doping control analysis
  • doping density
  • doping effect
  • doping level

  • Selected Abstracts


    Characterization of pure and doped potassium hydrogen tartrate single crystals grown in silica gel

    CRYSTAL RESEARCH AND TECHNOLOGY, Issue 5 2009
    I. Quasim
    Abstract Growth of pure-, sodium- and lithium- doped potassium hydrogen tartrate single crystals by gel technique is reported. Growth conditions conducive for the growth of single crystals are worked out. The crystals are characterized by using powder XRD, SEM, FTIR, AES, EDAX, CH analysis and thermoanalytical techniques. The stoichiometric composition for the grown crystals are established as KHC4H4O6.H2O, (K)0.98(Na)0.02.H2O and (K)0.94(Li)0.06HC4H4O6.H2O. Doping of sodium and lithium in the pure potassium hydrogen tartrate single crystals is found to influence the size, perfection, morphology, crystal structure and the thermal stability of crystals. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    SDS-PAGE of recombinant and endogenous erythropoietins: benefits and limitations of the method for application in doping control

    DRUG TESTING AND ANALYSIS, Issue 1 2009
    Christian Reichel
    Abstract Doping of athletes with recombinant and genetically modified erythropoietins (EPO) is currently detected by isoelectric focusing (IEF). The application of these drugs leads to a significant change in the isoform profile of endogenous urinary erythropoietin (uhEPO). Dynepo, MIRCERA, biosimilars with variable IEF-profiles as well as active urines and effort urines have made additional testing strategies necessary. The new generation of small molecule EPO-receptor stimulating agents like Hematide will also challenge the analytical concept of detecting the abuse of erythropoiesis stimulating agents (ESA). By determining their apparent molecular masses with SDS-PAGE a clear differentiation between endogenous and exogenous substances also concerning new EPO modifications is possible. Due to the orthogonal character of IEF- and SDS-PAGE both methods complement each other. The additional benefits of SDS-PAGE especially in relation to active and effort urines as well as the detection of Dynepo were investigated. Due to significant differences between the apparent molecular masses of uhEPO/serum EPO (shEPO) and recombinant, genetically or chemically modified erythropoietins the presence of active or effort urines was easily revealed. The characteristic band shape and apparent molecular mass of Dynepo on SDS-PAGE additionally evidenced the presence of this substance in urine. A protocol for the detection of EPO-doping in serum and plasma by SDS-PAGE was developed. Blood appears to be the ideal matrix for detecting all forms ESA-doping in the future. Copyright © 2009 John Wiley & Sons, Ltd. [source]


    Enhancement of Anodic Response for DMSO at Ruthenium Oxide Film Electrodes as a Result of Doping with Iron(III)

    ELECTROANALYSIS, Issue 2 2003
    Brett
    Abstract The oxidation of dimethyl sulfoxide (DMSO) to dimethyl sulfone (DMSO2) is representative of numerous anodic oxygen-transfer reactions of organosulfur compounds that suffer from slow kinetics at noble metal electrodes. Anodic voltammetric data for DMSO are examined at various RuO2 -film electrodes prepared by thermal deposition on titanium substrates. The response for DMSO is slightly larger at RuO2 films prepared in a flame as compared with films prepared in a furnace; however, temperature is more easily controlled in the furnace. Doping of the RuO2 films with Fe(III) further improves the sensitivity of anodic response for DMSO. Optimal response is obtained at an Fe(III)-doped RuO2 -film electrode prepared using a deposition solution of 50,mM RuCl3 and 10,mM FeCl3 in a 1,:,1 mixture of isopropanol and 12,M HCl at an annealing temperature of 450,°C. The Levich plot (i vs. ,1/2) and Koutecky-Levich plot (1/i vs. 1/,1/2) of amperometric data for the oxidation of DMSO at an Fe(III)-doped RuO2 -film electrode configured as a rotated disk are consistent with an anodic response controlled by mass-transport processes at low rotational velocities. Flow injection data demonstrate that Fe(III)-doped RuO2 -film electrodes exhibit detection capability for methionine and cysteine in addition to DMSO. Detection limits for 100-,L injections of the three compounds are ca. 3.2×10,4,mM, i.e., ca. 32,pmol. [source]


    EuIII -Doping of Lamellar Bilayer and Amorphous Mono-Amide Cross-Linked Alkyl/Siloxane Hybrids

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2010
    Silvia C. Nunes
    Abstract Two structurally different but chemically similar families of alkyl/siloxane mono-amidosil hosts, represented by m-A(x) [where x = 14 or 8 represents the number of CH2 groups of the pendant alkyl chains directly bonded to the carbonyl group of the amide cross-link] have been doped with a wide range of concentrations of Eu(CF3SO3)3. Mono-amidosils m-A(x)nEu(CF3SO3)3 with n,,,10 (where n is the molar ratio of carbonyl groups per Eu3+ ion) have been analyzed. The m-A(8)nEu(CF3SO3)3 mono-amidosils are transparent and amorphous films, in which the alkyl chains adopt gauche conformations. In contrast, the m-A(14)nEu(CF3SO3)3 mono-amidosils are solid powders; here the lamellar bilayer hierarchical structure of m-A(14) coexists with a new lamellar phase in which the Eu3+ ions are bonded to carbonyl oxygen atoms of the amide groups. At n = 10 the hydrogen-bonded associations formed are highly ordered and considerably stronger than those found in the less concentrated hybrids and in the nondoped matrices. "Free" and weakly coordinated triflate ions occur in all the mono-amidosil samples. The hybrids are white light emitters (maximum quantum yield: 0.08,±,0.01), presenting a broad emission band in the blue/purplish-blue spectral region (ascribed to the hybrid host) superimposed on the 5D0,7F0,4 Eu3+ intra-4f6 transitions. Two Eu3+ local coordination sites (named A and B) have been discerned in both systems. Site A is attributed to weakly coordinated Eu3+/CF3SO3, ion pairs, whereas site B involves Eu3+ coordination to the oxygen atoms of the C=O groups, of the CF3SO3, ions and of the water molecules. For site B, the long-range order of the hybrid host induces distinct features in the energy of the 5D0,7F0,4 transitions, the 5D0 lifetime and the degree of covalency of the Eu3+,first-ligand bonds. [source]


    Controllable Molecular Doping and Charge Transport in Solution-Processed Polymer Semiconducting Layers

    ADVANCED FUNCTIONAL MATERIALS, Issue 12 2009
    Yuan Zhang
    Abstract Here, controlled p-type doping of poly(2-methoxy-5-(2,-ethylhexyloxy)- p -phenylene vinylene) (MEH-PPV) deposited from solution using tetrafluoro-tetracyanoquinodimethane (F4-TCNQ) as a dopant is presented. By using a co-solvent, aggregation in solution can be prevented and doped films can be deposited. Upon doping the current,voltage characteristics of MEH-PPV-based hole-only devices are increased by several orders of magnitude and a clear Ohmic behavior is observed at low bias. Taking the density dependence of the hole mobility into account the free hole concentration due to doping can be derived. It is found that a molar doping ratio of 1 F4-TCNQ dopant per 600 repeat units of MEH-PPV leads to a free carrier density of 4,×,1022,m,3. Neglecting the density-dependent mobility would lead to an overestimation of the free hole density by an order of magnitude. The free hole densities are further confirmed by impedance measurements on Schottky diodes based on F4-TCNQ doped MEH-PPV and a silver electrode. [source]


    Doping of Conjugated Polythiophenes with Alkyl Silanes

    ADVANCED FUNCTIONAL MATERIALS, Issue 12 2009
    Chi Yueh Kao
    Abstract A strong modification of the electronic properties of solution-processable conjugated polythiophenes by self-assembled silane molecules is reported. Upon bulk doping with hydrolized fluoroalkyl trichlorosilane, the electrical conductivity of ultrathin polythiophene films increases by up to six orders of magnitude, reaching record values for polythiophenes: (1.1,±,0.1),×,103,S cm,1 for poly(2,5-bis(3-tetradecylthiophen -2-yl)thieno[3,2- b]thiophene) (PBTTT) and 50,±,20,S cm,1 for poly(3-hexyl)thiophene (P3HT). Interband optical absorption of the polymers in the doped state is drastically reduced, making these highly conductive films transparent in the visible range. The dopants within the porous polymer matrix are partially crosslinked via a silane self-polymerization mechanism that makes the samples very stable in vacuum and nonpolar environments. The mechanism of SAM-induced conductivity is believed to be based on protonic doping by the free silanol groups available within the partially crosslinked SAM network incorporated in the polythiophene structure. The SAM-doped polythiophenes exhibit an intrinsic sensing effect: a drastic and reversible change in conductivity in response to ambient polar molecules, which is believed to be due to the interaction of the silanol groups with polar analytes. The reported electronic effects point to a new attractive route for doping conjugated polymers with potential applications in transparent conductors and molecular sensors. [source]


    Doping of the Metal Oxide Nanostructure and its Influence in Organic Electronics

    ADVANCED FUNCTIONAL MATERIALS, Issue 8 2009
    Mi-Hyae Park
    Abstract Synthesizing metal oxides through the sol,gel process provides a convenient way for forming a nanostructured layer in wide band gap semiconductors. In this paper, a unique method of introducing dopants into the metal oxide semiconductor is presented. The doped TiO2 is prepared by adding a Cs2CO3 solution to a nanocrystalline TiO2 solution that is synthesized via a non-hydrolytic sol,gel process. The properties of the TiO2:Cs layer are investigated and the results show stable nanostructure morphology. In addition to providing morphological stability, Cs in TiO2 also gives rise to a more desirable work function for charge transport in organic electronics. Polymer solar cells based on the poly(3-hexylthiophene) (P3HT): methanofullerene (PC70BM) system with the addition of a TiO2:Cs interfacial layer exhibit excellent characteristics with a power conversion efficiency of up to 4.2%. The improved device performance is attributed to an improved polymer/metal contact, more efficient electron extraction, and better hole blocking properties. The effectiveness of this unique functionality also extends to polymer light emitting devices, where a lower driving voltage, improved efficiency, and extended lifetime are demonstrated. [source]


    Aliovalent Doping for Improved Battery Performance: Aliovalent Substitutions in Olivine Lithium Iron Phosphate and Impact on Structure and Properties (Adv. Funct.

    ADVANCED FUNCTIONAL MATERIALS, Issue 7 2009
    Mater.
    Lithium metal phosphate olivines have emerged as important storage electrodes in batteries for electric vehicles and other applications addressing global issues of energy supply and climate change. On page 1060, Meethong et al. use controlled aliovalent solute doping to tailor the defect and atomic structure in olivines, and demonstrate the resulting impact on physical and electrochemical properties. [source]


    Enhanced Photorefractivity of Poly(N -vinylcarbazole)-Based Composites through Electric-Field Treatments and Ionic Liquid Doping

    ADVANCED FUNCTIONAL MATERIALS, Issue 3 2009
    José A. Quintana
    Abstract It is shown that the photorefractive (PR) performance of polymer composites based on poly(N -vinylcarbazole) can be improved when samples are subjected to an electric field for a certain time, i.e. conditioned, previous to the PR characterization. It is also found that for conditioned samples the addition of an organic ionic liquid to the PR composition allows to obtain PR effect without the need of using a sensitizer. The typical electric field treatment time at room temperature and at a field of 20,V µm,1 is 20,min. This procedure leads to a decrease of dark conductivity and an increase of photoconductivity, and consequently an increase of conductivity contrast. This results in higher PR two-beam-coupling gain coefficients and shorter response times, particularly at low fields. Dependencies of the process dynamics on impurities, applied field strength, temperature and the presence of an organic ionic liquid are examined in detail. It is remarkable the significant increase of the PR gain coefficients, and more drastically of the net gain coefficients, observed at low fields (<55,V µm,1), when an ionic organic liquid such as benzalkonium chloride is added to unsensitized conditioned PR composites. These findings open a new route to improve the PR performance, not only of PVK-based composites, but also of other types of organic materials, the main advantage being that no sensitizer is needed. [source]


    Surface-Transfer Doping of Organic Semiconductors Using Functionalized Self-Assembled Monolayers,

    ADVANCED FUNCTIONAL MATERIALS, Issue 8 2007
    W. Chen
    Abstract Controlling charge doping in organic semiconductors represents one of the key challenges in organic electronics that needs to be solved in order to optimize charge transport in organic devices. Charge transfer or charge separation at the molecule/substrate interface can be used to dope the semiconductor (substrate) surface or the active molecular layers close to the interface, and this process is referred to as surface-transfer doping. By modifying the Au(111) substrate with self-assembled monolayers (SAMs) of aromatic thiols with strong electron-withdrawing trifluoromethyl (CF3) functional groups, significant electron transfer from the active organic layers (copper(II) phthalocyanine; CuPc) to the underlying CF3 -SAM near the interface is clearly observed by synchrotron photoemission spectroscopy. The electron transfer at the CuPc/CF3 -SAM interface leads to an electron accumulation layer in CF3 -SAM and a depletion layer in CuPc, thereby achieving p-type doping of the CuPc layers close to the interface. In contrast, methyl (CH3)-terminated SAMs do not display significant electron transfer behavior at the CuPc/CH3 -SAM interface, suggesting that these effects can be generalized to other organic-SAM interfaces. Angular-dependent near-edge X-ray absorption fine structure (NEXAFS) measurements reveal that CuPc molecules adopt a standing-up configuration on both SAMs, suggesting that interface charge transfer has a negligible effect on the molecular orientation of CuPc on various SAMs. [source]


    n-Type Doping of Organic Thin Films Using Cationic Dyes,

    ADVANCED FUNCTIONAL MATERIALS, Issue 3 2004
    A. Werner
    Abstract We present an approach to stable n-type doping of organic matrices using organic dopants. In order to circumvent stability limitations inherent to strong organic donors, we produce the donor from a stable precursor compound in situ. As an example, the cationic dye pyronin B chloride is studied as a dopant in a 1,4,5,8-naphthalene tetracarboxylic dianhydride (NTCDA) matrix. Conductivities of up to 1.9,×,10,4,S,cm,1 are obtained for doped NTCDA, two orders of magnitude higher than the conductivity of NTCDA doped with bis(ethylenedithio)-tetrathiafulvalene as investigated previously, and four orders of magnitude higher than nominally undoped NTCDA films. Field-effect measurements are used to prove n-type conduction and to study the doping effect further. The findings are interpreted using a model of transport in disordered solids using a recently published model. Combined FTIR, UV-vis, and mass spectroscopy investigations suggest the formation of leuco pyronin B during sublimation of pyronin B chloride. [source]


    Dilute Doping, Defects, and Ferromagnetism in Metal Oxide Systems

    ADVANCED MATERIALS, Issue 29 2010
    Satishchandra B. Ogale
    Over the past decade intensive research efforts have been carried out by researchers around the globe on exploring the effects of dilute doping of magnetic impurities on the physical properties of functional non-magnetic metal oxides such as TiO2 and ZnO. This effort is aimed at inducing spin functionality (magnetism, spin polarization) and thereby novel magneto-transport and magneto-optic effects in such oxides. After an early excitement and in spite of some very promising results reported in the literature, this field of diluted magnetic semiconducting oxides (DMSO) has continued to be dogged by concerns regarding uniformity of dopant incorporation, the possibilities of secondary ferromagnetic phases, and contamination issues. The rather sensitive dependence of magnetism of the DMSO systems on growth methods and conditions has led to interesting questions regarding the specific role played by defects in the attendant phenomena. Indeed, it has also led to the rapid re-emergence of the field of defect ferromagnetism. Many theoretical studies have contributed to the analysis of diverse experimental observations in this field and in some cases to the predictions of new systems and scenarios. In this review an attempt is made to capture the scope and spirit of this effort highlighting the successes, concerns, and questions. [source]


    Syntheses, structures, and supramolecular properties of giant ,-expanded macrocyclic oligothiophenes

    HETEROATOM CHEMISTRY, Issue 5 2007
    Masahiko Iyoda
    Fully conjugated ,-expanded macrocyclic oligothiophenes with 60,-, 90,-, 120,-, 150,-, and 180,-electron systems (1,5) were synthesized using modified McMurry coupling reaction as a key step. Compound 1 was converted into macrocyclic oligo(2,5-thienylene-ethynylene) 6 using bromination-dehydrobromination procedure. X-ray analysis of 1 revealed a unique molecular and packing structure, reflecting a round, planar shape with nanoscale inner cavity. Interestingly, 2 and 3 self-aggregate in the solid state to form nanowires. The structure of fibrous aggregates was established by scanning electron microscopic and atomic force microscopic analyses. Compounds 1,6 exhibit multi-step reversible redox behavior with fairly low first oxidation potentials, reflecting their cyclic conjugation. Doping of 1,3 with iodine gives semiconductors owing to their ,-donor properties and ,,, stacking ability. © 2007 Wiley Periodicals, Inc. 18:460,466, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20337 [source]


    Nanoparticle-Dispersed Liquid Crystals Fabricated by Sputter Doping

    ADVANCED MATERIALS, Issue 5 2010
    Hiroyuki Yoshida
    A simple and robust method to prepare nanoparticle-dispersed liquid crystals is demonstrated. Highly dispersed gold nanoparticle,liquid crystal suspensions are fabricated by simply sputter doping the gold target on the host liquid crystal (see figure). The existence of the nanoparticles is supported by optical extinction measurements, polarization optical microscopy, and transmission electron microscopy. An improvement in the electro-optic response, namely, a decrease in the threshold voltage, is also demonstrated in twist nematic devices fabricated using the nanoparticle-dispersed liquid crystal. [source]


    Ground-State Interaction and Electrical Doping of Fluorinated C60 in Conjugated Polymers

    ADVANCED MATERIALS, Issue 44 2009
    Olga Solomeshch
    C60F36 is reported to be an efficient dopant for conjugated polymers. Its fluorine atoms induce a large shift in the energy levels with respect to C60. Its role as a dopant is studied by examining the charge transfer formed with the commonly used polymer, P3HT. [source]


    Impurity Doping in Silicon Nanowires

    ADVANCED MATERIALS, Issue 27 2009
    Naoki Fukata
    Abstract Silicon nanowires (SiNWs) have considerable potential to assist the realization of next-generation metal-oxide semiconductor field-effect transistors (MOSFETs) with vertical structures. Impurity doping and its control is a key technique in the creation of SiNW devices, which renders it necessary to develop characterization methods for dopant atoms in SiNWs. In this Research News, we described how the states of the dopant atoms boron and phosphorus can be detected. [source]


    GaN Nanofibers based on Electrospinning: Facile Synthesis, Controlled Assembly, Precise Doping, and Application as High Performance UV Photodetector,

    ADVANCED MATERIALS, Issue 2 2009
    Hui Wu
    Nitride nanofibers have been synthesized based on a simple electrospinning technique for the first time. No catalysts or templates are needed in this new synthetic method. Highly oriented GaN nanofiber arrays, as well as a high-performance UV photodetector based on single GaN nanofiber assembled FET devices, can be facilely fabricated using this technique. Precise doping of other elements into the GaN nanofibers is easy by this solution-based synthetic method. [source]


    Controlling Electrical Properties of Conjugated Polymers via a Solution-Based p-Type Doping,

    ADVANCED MATERIALS, Issue 17 2008
    Keng-Hoong Yim
    Tetrafluoro-tetracyano-quinodimethane (F4TCNQ) is used to p-dope conjugated polymers with a wide range of the HOMO levels via co-blending in a common organic solvent. Doping results in several orders of magnitude increase in the bulk conductivity and hole-current with reduced turn-on voltage. The effectiveness of doping increases as the HOMO level of the polymer becomes smaller. [source]


    Amphoteric Phosphorus Doping for Stable p-Type ZnO,

    ADVANCED MATERIALS, Issue 20 2007
    A. Allenic
    The role of dislocations in stable p-type phosphorus-doped ZnO epitaxial films is investigated. It is shown that good p-type conductivity is always associated with a considerable increase in the density of dislocations, which can aid the formation of shallow complex acceptors and provide sinks for native donors. [source]


    Improved Hydrogen Storage Properties of Ti-Doped Sodium Alanate Using Titanium Nanoparticles as Doping Agents,

    ADVANCED MATERIALS, Issue 12 2003
    B. Bogdanovi
    By using nanosized doping agents, the properties of Ti-catalyzed NaAlH4 storage systems are considerably improved. Hydrogenation,dehydrogenation cyclic testing shows that with nanosized TiN dopants, storage capacities of 5 wt.-% H2 could be achieved. Doping with nanosized Ti brought hydrogenation times close to those required for practical applications, combined with high capacity (4.5 wt.-% H2, see Figure). [source]


    Synthesis and characterization of new unsaturated polyesters containing cyclopentapyrazoline moiety in the main chain

    JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010
    Ismail A. Alkskas
    Abstract 3-p -Hydroxyphenyl-6- p -hydroxybenzylidene cyclopentapyrazoline (III) and 3-vanillyl-7-vanillylidene cyclopentapyrazoline (IV) were used as new starting materials for preparing new unsaturated polyesters. The polyesters were prepared by reacting (III) or (IV) with adipoyl, sebacoyl, isophthaloyl, and terephthaloyl dichlorides utilizing the interfacial polycondensation technique. The polyester samples have been characterized by elemental and spectral analyses. The polyesters have inherent viscosities of 0.55,0.97 dL/g. All the polyesters are semicrystalline and most of them are partially soluble in most common organic solvents but freely soluble in concentrated sulfuric acid. Their glass transition temperatures (Tg) range from 103.34 to 208.81°C, and the temperatures of 10% weight loss as high as 190 to 260°C in air, indicating that these aromatic polyesters have high Tg and excellent thermal stability. Doping with iodine dramatically raised the conductivity and produced dark brown colored semiconductive polymers with a maximum conductivity in the order of 3.1 × 10,7 ,,1 cm,1. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]


    Can glycans unveil the origin of glycoprotein hormones?,human chorionic gonadotrophin as an example,

    JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 7 2008
    R. Ramírez-Llanelis
    Abstract Doping with (glyco)protein hormones represent an extremely challenging, analytical problem as nearly all are constitutively present at low concentrations that fluctuate according to circadian or alternative periodical, or external stimuli. Thus the mere concentration in a biological sample is only resolutive when this surpasses extreme values. As the vast majority of these molecules are produced by recombinant DNA technology it is believed that the exogenous molecules could bear the signature of the host cell. In particular, these could comprise structural differences originated from co or post-translational differences. In this study we have employed both proteomics and glycomics strategies to compare recombinant and urinary human chorionic gonadotrophin in order to evaluate this hypothesis. As anticipated the recombinant hormone could be shown to contain N -glycolyl neuraminic acid, a sialic acid that cannot be produced by humans. Furthermore, differences were observed in the overall glycosylation, in particular the presence of abundant hybrid-type glycans that were much less pronounced in the recombinant species. These differences were determined to occur predominantly in the ,-subunit for which antidoping strategies focussed on these elements could be used for both chorionic gonadotrophin and lutrophin as they share the same ,-subunit. Copyright © 2008 John Wiley & Sons, Ltd. [source]


    The Influence of ZnF2 Doping on the Electrical Properties and Microstructure in Bi2O3,ZnO-Based Varistors

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2010
    Lihong Cheng
    ZnO varistors with different amounts of ZnF2 from 0.00 to 0.80 mol% were prepared using a solid-state reaction technique, to explore the potential application of ZnO. The F-doping effects on the microstructure and electrical properties of ZnO-based varistors were investigated. The average grain size of ZnO increased from 4.93 to 6.48 ,m as the ZnF2 content increased. Experimental results showed that as the ZnF2 content increased, the breakdown voltage decreased from 617 to 367 V/mm, and the nonlinear coefficient did not change much. However, a slight increase was observed in the leakage current. Besides, when the ZnF2 content increased, the donor concentration increased from 0.669 × 1018 to 8.720 × 1018 cm,3. The study indicated that ZnF2 played a similar role as sintering aids to promote grain growth and the substitutional F atoms in the bulk served as a donor to increase the donor concentration. [source]


    Effect of La Doping on the Phase Conversion, Microstructure Change, and Electrical Properties of Bi2Fe4O9 Ceramics

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2009
    Ju Hong Miao
    Undoped and La-doped Bi2Fe4O9 ceramics were synthesized using a soft chemical method. It is observed that in calcining La-doped Bi2Fe4O9, Bi(La)FeO3 phase rather than Bi2,xLaxFe4O9 gradually increases with increasing La doping content. The phase conversion from mullite-type structure of Bi2Fe4O9 to rhombohedrally distorted perovskite one of Bi(La)FeO3 with increasing La doping content indicates that La doping can stabilize the structure of BiFeO3. This is further evidenced that Bi2Fe4O9 can be directly converted to Bi(La)FeO3 by heating the mixtures of nominal composition of Bi2Fe4O9/xLa2O3. Furthermore, the microstructure changes and the room temperature hysteresis loops and leakage current for Bi2,xLaxFe4O9 with x=0 and 0.02 were characterized. [source]


    Effect of Aluminum Doping on Microwave Permittivity of Silicon Carbide Powders

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2008
    Fa Luo
    The permittivity and structure of commercial SiC powders before and after thermal diffusion of aluminum were explored in this study. The X-ray diffraction analysis and permittivity results show that heat treatment at 2000°C for 1 h has no influence not only on the structure of the SiC powders but also on the permittivity. Thermal diffusion of aluminum at 1800°, 1900°, and 2000°C was carried out for 1 h at 5 Pa in Ar atmospheres, respectively. A graphite die with two chambers was used during the experiment to separate the aluminum powders from the SiC powders. Aluminum vapor at high temperatures passes to the upper chamber through holes and diffuses into the SiC powders. The permittivities of the as-received SiC powders at 8.2,12.4 GHz were measured, and the results indicate that the real and imaginary parts of permittivity are improved much more than those of the original SiC powder. Both the real and the imaginary parts of the doped SiC increase with the diffusion temperatures, which could be attributed to defects from thermal diffusion of aluminum. [source]


    Effect of Cation Doping on the Superplastic Flow in Yttria-Stabilized Tetragonal Zirconia Polycrystals

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2001
    Junpei Mimurada
    The superplastic characteristics of various cation-doped yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) were examined. For 1 mol% cation doping the true stress of Y-TZP is very dependent on the ionic radii of the doped cations; for instance, smaller cation radii give rise to lower true stress when compared with the other compositions for the same grain size, strain rate, and testing temperature. The altered true stress level must be due to the change in diffusivity of the accommodation process for grain boundary sliding caused by the addition of cations in ZrO2. The strain to failure of the doped zirconia is affected by both ionic radius and valence of the dopant cations. [source]


    Reply to "Comment on ,Influence of Yttrium Doping on Grain Misorientation in Aluminum Oxide'"

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2000
    Helen M. Chan
    No abstract is available for this article. [source]


    Effect of MgO Doping on the Phase Transformations of BaTiO3

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2000
    Toru Nagai
    The successive phase transformations in MgO-doped BaTiO3 were studied. Upon MgO doping, dielectric anomalies corresponding to lower phase transformations were broadened and depressed, while an anomaly for a cubic,tetragonal transformation remained and shifted to a lower temperature. XRD peak splitting upon tetragonality of BaTiO3 was decreased, and the peaks exhibited abnormally broadened profiles which are different from the one for cubic BaTiO3 above Tc. Raman spectroscopy revealed the existence of orthorhombic phase at room temperature for the solid solution with 0.5 mol% or more MgO. The temperature dependence of the Raman spectrum showed that orthorhombic and rhombohedral phases in MgO-doped BaTiO3 were stabilized at higher temperatures than pure BaTiO3. [source]


    Dissolution and Doping of Polyaniline Emeraldine Base in Imidazolium Ionic Liquids Investigated by Spectroscopic Techniques

    MACROMOLECULAR RAPID COMMUNICATIONS, Issue 5 2007
    Fabio Rodrigues
    Abstract Polyaniline is a model molecular system in the study of conductive polymers. Ionic liquids, on the other hand, are becoming more and more a very convenient alternative for conventional organic solvents. The dissolution of polyaniline-emeraldine base (PANI-EB) in imidazolium ILs leads to its doping, as indicated by optical and resonance Raman spectroscopies. In this study, it is proposed that the interaction of PANI-EB and imidazolium ILs involves the specific interaction of the quinoid moiety of the former with the imidazolium ring of the latter, an interpretation that is also based on N K -edge XANES measurements of neat PANI-EB, neat ILs, and of their solutions. [source]


    Multi-impurity complexes for n-type diamond: a computational study

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 9 2007
    R. J. Eyre
    Abstract Doping of diamond using multi-component, multi-species structures has been modelled using density functional methods. We find that few combinations of impurities yield donor levels shallower than phosphorus. Complexes involving impurities from the second or lower rows of the periodic table are unbound, and those involving the soluble element nitrogen can often be arranged in passive or even compensating geometries. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]