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Abstract: In this work, we studied the local environment of a series of LiNi y Mn y Co1−2y O2 materials synthesized by wet chemistry via oxalate route. Measurements included the temperature dependence of the magnetic susceptibility χ m (T), the magnetization M(H), and the electron spin resonance. The influence of the synthesis conditions on the magnetic and electronic properties is presented and discussed. Magnetic properties and electron spin resonance spectroscopy provides further information on Ni2+, Mn4+ ion distribution in LiNi y Mn y Co1−2y O2. The magnetic data allows the determination of the cationic disorder, i.e. the concentration of Ni2+ ions in the 3a lithium sites, as a function of the composition, in quantitative agreement with the results of XRD experiments. We find that the lithium extraction proceeds by different steps. In a first step, Ni2+ in converted first in Ni3+, then in Ni4+ as x decreases from x =1, while Co remains in the Co3+ valence state. The ESR spectra show a resonance due to Mn4+, which is analyzed self-consistently with magnetic experiments. [Copyright &y& Elsevier]

Abstract: Raman scattering spectra have been investigated to evaluate the local structure of lithiated oxides used as electrode materials for lithium-ion batteries. We report the analysis of the vibrational spectra of ordered spinel phases including the partially delithiated λ-Li0.5Mn2O4 ( SG), the partial charge-ordered LiMn2O4 orthorhombic form (Fddd SG) and the LiNi0.5Mn1.5O4 substituted oxide (P4132 SG). Analysis of spectroscopic data is performed using the classical factor group theory and the vibration features are compared with those of the ordered lithium ferrite α-LiFe5O8 and the normal spinels LiMn2O4 and LiNi0.5Mn1.5O4 (Fd3m SG), and the inverse spinel LiNiVO4. [Copyright &y& Elsevier]

Abstract: We present the synthesis, characterization and electrode behaviour of LiMn2−y Co y O4 (0≤ y ≤1) spinel oxides prepared by the wet-chemical route assisted by carboxylic acid. The phase evolution was studied as a function of the cobalt substitution and the modification on the intercalation and deintercalation of Li ions. Characterization methods include TG-DTA, XRD, SEM, Raman, FTIR, and SQUID. LiMn2−y Co y O4 samples crystallize with the cubic spinel-like structure (Fd3m S.G.). Raman scattering and FT-infrared spectroscopy indicate that the vibrational mode frequencies and relative intensities of the bands are sensitive to the covalency of the (Co, Mn)–O bonds. MEB micrographs show that the particle dimension of the LiMn2−y Co y O4 powders ranges in the sub-micron-sized domain with a narrow grain-size distribution. The overall electrochemical capacity of LiMn2−y Co y O4 oxides have been reduced due to the 3d6 metal substitution. However, a more stable charge–discharge cycling performances has been observed when the electrodes are charged up to 4.3V as compared to the performance of the native oxide. For such a cut-off voltage, the charge capacity of the Li//LiMn1.8Co0.2O4 cell is ca. 101mAh/g. Differences and similarities between LiMn2O4 and Co-substituted oxides are discussed there from. [Copyright &y& Elsevier]

We measured susceptibility, electron-spin resonance, magnetization and electrical conductivity of LiCo1−yNiyO2 powders synthesized by wet-chemistry method using succinic acid as chelating agent. We found unusual properties in the nickel-rich LiCo0.2Ni0.8O2, which shows several resonance lines as a function of the temperature in the range 3.5–300 K. The signal at low magnetic field is attributed to the magnetic domains in the nanostructured sample. The two other lines correspond to the typical ferromagnetic signal observed in powdered compounds. In the temperature range 120–300 K, the unique ESR line centered at 315 mT is the paramagnetic signal with a gyromagnetic factor g=2.12, which is in good agreement with the presence of a high concentration of Ni3+ (3d7) ions. In the nickel-rich oxide, LiNi0.8Co0.2O2, the magnetic data are qualitatively well-described by the model proposed by Drillon and Panissod for a 3D ferromagnetic order. [Copyright &y& Elsevier]

Studies the hydrogen passivation of nitrogen in 6H-SiC. Definition on the complexation of nitrogen with hydrogen.

Examines the effect of hydrogen passivation on donors and acceptors in silicon carbide crystals. Conduction of electron spin resonance and transport measurement; Extraction of hydrogen passivation by annealing in hydrogen ion atmosphere; Determination of free-electron concentration and mobility of SiC before and after hydrogenation.

Presents a study that investigated the vibrational absorption of semi-insulating oxygen-containing gallium arsenide using high-resolution spectroscopy. Detection of the presence of interstitial oxygen in the samples; Effect of near-infrared illumination on the observation of the (gallium, oxygen)-related modes; Evaluation of the localized vibrational modes of the samples.

A theoretical determination of the Jahn–Teller coupling constants of d5 ions in tetrahedral clusters is performed in the framework of the angular overlap model and the quasimolecular approximation. It is shown that the angular model correctly predicts the trend of the preponderant coupling of the 4T1(G) and 4T2(G) levels of Mn2+ in MnS4 and MnSe4 to the E-vibrational effective mode. Finally, the limitations of this model are discussed. In particular, it is shown that more elaborated covalent models are needed to interpret the Jahn–Teller coupling coefficients of the 4E and 4A1 levels of d5 configurations and to determine the influence of the crystal on the clusters. [ABSTRACT FROM AUTHOR]

A very detailed analysis of the fine structure of the 4E(G) state of Mn2+ in cubic and nearly cubic clusters is presented to account for the unusual fine structure observed in ZnSe:Mn. First, experimental results are reported which show that the spin-orbit interaction in the 4E(G) state of Mn2+ in ZnSe is about one half of that previously observed in cubic or nearly cubic clusters as MnS4, MnBr4, and MnCl4 and that the state Γ8 is neatly shifted with respect to the Kramers doublets Γ6 and Γ7. Second, a model is elaborated which shows that second-order spin-orbit interactions reduced by a Jahn–Teller coupling to E vibrational modes accounts well for the observed overall splitting of the 4E(G) state in the studied clusters and that fourth-order spin-orbit interactions correctly describe the shifts of the Γ8 state. The validity of the perturbation schemes is discussed and the results are compared to those obtained from a complete diagonalization in the d5 configuration. [ABSTRACT FROM AUTHOR]

Abstract: The structural properties of LiFePO4 prepared by the hydrothermal route and chemically delithiated have been studied using analytical electron microscopy and Raman spectroscopy. High-resolution transmission electron microscopy and selected area electron diffraction measurements indicate that the partially delithiated particles include LiFePO4 regions with cross-sections of finite size along the ac-plane, as a result of tilt grain boundary in the bc-plane, and dislocations in other directions. Only the boundary along the bc-plane is accompanied by a disorder over about 2nm on each side of the boundary. The Raman spectrum shows the existence of both LiFePO4 and FePO4 phases in the shell of the particles at a delithiation degree of 50%, which invalidates the core–shell model. This result also invalidates the recent model according to which each particle would be single-domain, i.e. either a LiFePO4 particle or a FePO4 particle. On the other hand, our results, like prior ones, can be understood within the framework of a model similar to the spinodal decomposition of a two-phase system, which is discussed within the framework of morphogenesis of patterns in systems at equilibrium. Both end-members, however, are well crystallized, suggesting a recovery similar to that observed in superplastic alloys, with dynamics that are due to the motion of nucleation fronts and dislocations, and not due to a diffusion phenomenon associated with a concentration gradient. [Copyright &y& Elsevier]

Abstract: Li x FePO4 glasses have been prepared by fast-quenching method in the whole range of composition 0 ⩽ x ⩽ 1. The amorphous state of glassy materials is confirmed by X-ray diffraction. Information concerning the local environment of Li and Fe cations and the configuration of (PO4)3− oxo-anions is obtained by Fourier transform infrared (FTIR) spectroscopy. While the LiFePO4 crystalline materials undergo a transition from the paramagnetic to the antiferromagnetic ordering at 52K, no magnetic ordering is observed in the vitreous samples that realize random field systems, so that a spin glass-like freezing is observed at low temperature. The paramagnetic Curie temperature of Li x FePO4 is independent of x and shifted to θ =−60K in the glassy state, due to a significant distortion of the FeO6 octahedra that alters the superexchange path inside the atomic FeO4 layers of the crystallized structure. On another hand, the PO4 tetrahedra are not significantly distorted in the glassy phase. The results are compared with highly disordered, but nanocrystallized LiFePO4 recently obtained at the early stage of synthesis by solid state reaction at 300°C. In this latter case, the lack of long-range antiferromagnetic ordering is due to substitutional disorder among the cationic sublattice. [Copyright &y& Elsevier]

Abstract: Currently, LiFePO4 is considered a good candidate as a positive electrode in rechargeable lithium-ion batteries for hybrid-electric vehicle (HEV) applications. A major difficulty with the preparation of the olivine structure (LiFePO4) comes from the existence of two oxidation states of iron, namely Fe(II) and Fe (III). Careful control of the synthesis procedure is needed to avoid any impurity which can poison the electrochemistry of LiFePO4 electrodes in Li-ion batteries. Analysis of the structure and morphology of the phospho-olivine LiFePO4 is presented as a function of the synthetic conditions. The combination of analytical methods, i.e. magnetization, M(H), susceptibility, χ m (T), and Raman scattering spectroscopy, appears to be a powerful tool for the detection of small amount of impurities. The electrochemical performance of optimized LiFePO4 is evaluated in Li4Ti5O12/LiPF6-EC-DEC/C-LiFePO4 cells operating at high temperature (60 °C). [Copyright &y& Elsevier]

Abstract: The layered LiNi0.5Mn0.5O2 was synthesized by wet-chemical method and characterized by X-ray diffraction and SQUID magnetometry. The powders adopted the α-NaFeO2 structure. The ferromagnetism observed below Tc=140K is attributed to the linear Ni2+(3a)–O–Mn4+(3b)–O–Ni2+(3a) magnetic paths, from which we derive that 7% of the nickel occupies the (3a) Wyckoff position in place of Li, constituting a Ni2+(3a) defect. The analysis of the magnetic properties in the paramagnetic phase in the framework of the Curie–Weiss law agrees well with the combination of Ni2+ (S =1) and Mn4+ (S =3/2) spin-only values. Results of structural and magnetic properties of chemically delithiated sample are consistent with the electronic state Mn4+/Ni4+ and the high-spin configuration for Ni4+ ions. The LiNi0.5Mn0.5O2 electrode sintered at 900°C delivers a capacity 166mAh/g at 0.1C rate which is capacity retention of 95%. [Copyright &y& Elsevier]

Abstract: We present the magnetic properties of LiNi0.5Mn1.5O4 spinels prepared by the sol–gel and pyrolysis techniques. Structural properties show that the material synthesized by pyrolysis method exhibit an ordered spinel structure. Characterization methods include SQUID magnetometry and ESR spectroscopy. Magnetic measurements have evidenced the ferromagnetic ordering below in LiNi0.5Mn1.5O4. Results show that actually no impurity phase is detected in LiNi0.5Mn1.5O4, thus the ferrimagnetic behavior is attributed to an intrinsic property of this material. The magnetic order in this case is trivially a collinear ferrimagnetic ordering in which both the Ni sublattice and the Mn sublattice are ferromagnetic. ESR measurements show a two-component signal with a complex shape. The dominant band is assigned to Mn4+ ions that are the only paramagnetic entities in this compound. [Copyright &y& Elsevier]

This paper reports the microstructure of LiXPO4 (X=Ni, Co, Mn) materials prepared by solid state chemical reaction. The variation in microstructure of these phospho-olivines is mainly due to a difference in the XO6 cationic octahedral environment, which is discussed using a molecular vibration model to elucidate the bonding between various structural units. A direct relationship is established between the vibrational frequencies and the second ionisation potential of the metal (X) in LiXPO4. [Copyright &y& Elsevier]

The temperature dependence of the interlayer exchange coupling has been investigated in epitaxial tunnel junctions Fe1/MgO/Fe2/Co/V with thin MgO layers using X-band ferromagnetic resonance (FMR) in the range 2–300 K. Variations of FMR parameters allow concluding that the coupling strength increases with temperature. This is in agreement with predictions of the theories considering pure tunneling mechanisms and contradicts the model of a resonant assisted tunneling related to defects in the insulator. The temperature dependence of the FMR linewidth shows the line narrowing under the sample heating. This may be due to the additional mechanism associated with the coupling. [ABSTRACT FROM AUTHOR]

The structure and magnetic properties of lithium iron pyrophosphate, i.e., Li2Fe3(P2O7)2 or LiFe1.5P2O7, synthesized using a facile metal acetate approach for application in lithium-ion batteries, are investigated in detail. The high-resolution transmission electron microscopy, selected area electron diffraction, and x-ray diffraction measurements indicate that Li2Fe3(P2O7)2 is crystallized in the monoclinic structure, without any indication of crystallographic defects such as dislocations or misfits, and exhibit smooth surface morphology. The evaluated lattice parameters are a=0.698 76 nm, b=0.812 36 nm, c=0.964 22 nm, and β=111.83° (P21/c space group). Infrared spectroscopic measurements indicate the presence of P2O7 groups, which are formed by the two PO4 tetrahedral groups connected together. The magnetic measurements indicate that Li2Fe3(P2O7)2 is a weak antiferromagnetic material with TN=20 K exhibiting a Curie constant Cp=3.38 emu K/mol per Fe ion and a negative value of the Weiss temperature (Θp=-15 K). The absence of higher valence state Fe impurities and antiferromagnetic interactions due to the greater distance between two equivalent magnetic ions, which vanishes the Fe–O–Fe superexchange interactions, is confirmed. [ABSTRACT FROM AUTHOR]

While nanosized ferromagnetic particles could poison the performance of the Li batteries containing phospho-olivine, the carbon-film coating the LiFePO4 particles has a beneficial effect on cycling life of the cells. In this paper, we present the properties of the carbon layer deposited at the surface of the LiFePO4 grains. Characteristics of the carbon layer are analyzed using scanning electron microscopy, high-resolution transmission scanning electron microscopy, Fourier transform infrared, and Raman scattering (RS) spectroscopy. The carbon deposit characterized by RS spectroscopy is hydrogenated with very small hydrogen/carbon ratio, so that it belongs to the family of the amorphous graphitic carbon. The carbon deposit is similar to that obtained by pyrolysis technique at high temperature. It is expected to have the same properties (small hardness, high electronic conductivity) that favor both the Li diffusion from the LiFePO4 bulk and the charge-discharge rate of the cell. A model for the Li-ion transport throughout the coating is given. [ABSTRACT FROM AUTHOR]

We report on a study of thin (500–4000 Å) and ultrathin (100–500 Å) yttrium–iron–garnet (YIG) films deposited onto amorphous quartz substrates by the pulsed laser deposition technique. The growth conditions of well-formed polycrystalline films have been determined. The crystalline structure and the magnetic behavior of the films are strongly influenced by the processes occurring on the film–substrate interface. Primarily, a strain due to the difference in thermal expansion coefficients of the film and substrate induces a uniaxial anisotropy. Another source of strain are lattice distortions due to oxygen vacancies. The results obtained from x-ray diffraction analysis, magneto-optical, superconducting quantum interference device, vibrating sample magnetometer, and ferromagnetic resonance (FMR) measurements indicate that films thicker than 200 Å can be approximated by a two-layer model. One of the layers with a highly distorted structure and low magnetization is located near the surface. The other one, the upper layer, can be estimated as an almost perfectly formed YIG. Their relative thickness determines the magnetic and FMR behavior of the samples. An equilibrium direction of the magnetization along the film normal has been found to occur in the ultrathin films with the lowest magnetization where the perpendicular anisotropy energy exceeds the dipolar energy. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Hepatocyte nuclear 4 alpha (HNF4α), involved in glucose and lipid metabolism, has been linked to intestinal inflammation and abnormal mucosal permeability. Moreover, in a genome-wide association study, the HNF4A locus has been associated with ulcerative colitis. The objective of our study was to evaluate the association between HNF4α genetic variants and Crohn's disease (CD) in two distinct Canadian pediatric cohorts. The sequencing of the HNF4A gene in 40 French Canadian patients led to the identification of 27 single nucleotide polymorphism (SNP)s with a minor allele frequency >5%. To assess the impact of these SNPs on disease susceptibility, we first conducted a case-control discovery study on 358 subjects with CD and 542 controls. We then carried out a replication study in a separate cohort of 416 cases and 1208 controls. In the discovery cohort, the genotyping of the identified SNPs revealed that six were significantly associated with CD. Among them, rs1884613 was replicated in the second CD cohort (odds ratio (OR): 1.33; P<0.012) and this association remained significant when both cohorts were combined and after correction for multiple testing (OR: 1.39; P<0.004). An 8-marker P2 promoter haplotype containing rs1884613 was also found associated with CD (P<2.09 × 10−4 for combined cohorts). This is the first report showing that the HNF4A locus may be a common genetic determinant of childhood-onset CD. These findings highlight the importance of the intestinal epithelium and oxidative protection in the pathogenesis of CD. [ABSTRACT FROM AUTHOR]

We have studied the magnetic properties at room temperature of Fe1-xGax (FeGa) epitaxial thin films grown on ZnSe/GaAs(100) for 0.14≤x≤0.29 range concentration, and film thicknesses, d = 36 and 72 nm. The study was performed by means of magnetometric measurements and magnetic force microscopy scans. Increasing x promotes the loss of the four-fold magnetic-crystalline anisotropy associated to an Fe-like behavior, which is lost completely above x = 0.20. Stripe domains with rotatable anisotropy are observed even in samples in which the theoretical conditions for stripe appearance are not completely fulfilled. An unexpected 'saw-tooth' stripe structure has been found under certain conditions. [ABSTRACT FROM AUTHOR]

Abstract: We show that the investigation of magnetic properties is the best tool to identify and quantify the impurities and defects that limit the ability of the lamellar intercalation compounds for use as cathode for Li-ion batteries. The results are illustrated for LiNiO2, LiNi1-yCoyO2, LiCoO2, LiNi0.5Mn0.5O2, and LiNi1/3Mn1/3Co1/3O2 (LNMCO). Despite the extensive studies of these ionic compounds in the past, not only for practical use, but also for themselves, the present work reveals that the magnetic properties of these lamellar compounds have been largely misunderstood, and that, at contrast with the common belief, they do not belong to the family of two dimensional frustrated antiferromagnets. The misunderstanding comes from confusion between extrinsic and intrinsic effects. This distinction allows for an overall understanding of the intrinsic properties of these materials, and opens the route to their optimization, in particular for LNMCO that is the most promising element of this family. [Copyright &y& Elsevier]

Abstract: A series of LiNi1/3Mn1/3Co1/3O2 samples with α-NaFeO2 structure belonging to the D3d 5 space group were synthesized using tartaric acid as a chelating agent by wet-chemical method. Different acid to metal-ion ratios R have been used to investigate the effect of this parameter on the physical and electrochemical properties. We have characterized the reaction mechanism, the structure, and morphology of the powders by TGA, XRD, SEM and TEM imaging, completed by magnetic measurements, Raman scattering spectroscopy, and complex impedance experiments. We find that the LiNi1/3Mn1/3Co1/3O2 sintered at 900°C for 15h with an acid to metal-ion ratio R =2 was the optimum condition for this synthesis. For this optimized sample, only 1.3% of nickel-ions occupied the 3b Wyckoff site of the lithium-ions sublattice. The electrochemical performance has been investigated using a coin-type cell containing Li metal as the anode. The electronic performance is correlated to the concentration of the Ni(3b) defects that increase the charge transfer resistance and reduce the lithium diffusion coefficient. The optimized cell delivered an initial discharge capacity of 172mAhg−1 in the cut-off voltage of 2.8–4.4V, with a coulombic efficiency of 93.4%. [ABSTRACT FROM AUTHOR]

Abstract: Li1+x (Ni1/3Mn1/3Co1/3)1−x O2 layered materials were synthesized by the co-precipitation method with different Li/M molar ratios (M =Ni+Mn+Co). Elemental titration evaluated by inductively coupled plasma spectrometry (ICP), structural properties studied by X-ray diffraction (XRD), Rietveld analysis of XRD data, scanning electron microscopy (SEM) and magnetic measurements carried out by superconducting quantum interference devices (SQUID) showed the well-defined α-NaFeO2 structure with cationic distribution close to the nominal formula. The Li/Ni cation mixing on the 3b Wyckoff site of the interlayer space was consistent with the structural model [Li1−y Ni y ]3b [Li x+y Ni(1−x)/3−y Mn(1−x)/3Co(1−x)/3]3a O2 (x =0.02, 0.04) and was very small. Both Rietveld refinements and magnetic measurements revealed a concentration of Ni2+-3b ions lower than 2%; moreover, for the optimized sample synthesized at Li/M =1.10, only 1.43% of nickel ions were located into the Li sublattice. Electrochemical properties were investigated by galvanostatic charge–discharge cycling. Data obtained with Li1+x (Ni1/3Mn1/3Co1/3)1−x O2 reflected the high degree of sample optimization. An initial discharge capacity of 150mAhg−1 was delivered at 1C-rate in the cut-off voltage of 3.0–4.3V. More than 95% of its initial capacity was retained after 30 cycles at 1C-rate. Finally, it is demonstrated that a cation mixing below 2% is considered as the threshold for which the electrochemical performance does not change for Li1+x (Ni1/3Mn1/3Co1/3)1−x O2. [Copyright &y& Elsevier]

Abstract: A novel lithium iron phosphate has been synthesized by a solution route at moderate temperature. The structure was determined from powder by XRD, HRTEM and SAED experiments. LiFe2P3O10 tripolyphosphate crystallizes in the monoclinic system, space group P21 /m, with lattice constants a =4.597(7)Å, b =8.566(4)Å, c =9.051(4)Å, β =97.47° and Z =2. Internal and external vibrational modes (Raman and FTIR) show that the dominant spectral features come from the (P3O10)5− oxo-anions displaying internal and external modes along with the P–O–P bridging modes. Magnetic measurements are consistent with the high-spin configuration of Fe2+ cation with an effective magnetic moment 5.51μB. A weak antiferromagnetic ordering is observed below the Néel temperature at T N =19K. Electron paramagnetic resonance spectroscopy confirms this electronic configuration and provides evidence of the presence of a carbonaceous layer onto the particle surface. Electrochemical measurements were carried out in lithium cells with LiPF6–EC–DEC electrolyte at 25°C. The material delivered a capacity 70mAh/g in the voltage range 2.7–3.9V, close to the theoretical value (72mAh/g). The resulting cyclic voltammogram indicates a stable structure with a good reversibility with the redox peaks at 3.26 and 3.13V vs. Li0/Li+. [Copyright &y& Elsevier]

Background and Objectives Large-scale genotyping of blood donors for red blood cell and platelet antigens has been predicted to replace phenotyping assays in the screening of compatible blood components for alloimmunized patients. Although several genotyping platforms have been described, novel procedures and processes are needed to perform genotyping efficiently and to maximize its benefits for blood banks. Materials and Methods Here we describe the processes and procedures developed to introduce large-scale genotyping in our routine operations. Results Preliminary cost–benefit analysis indicated that genotyping must target frequent blood donors (> 3 donations/year) to be efficiently used. A custom-designed computer application was developed to manage the whole project. It selects frequent donors among recent donations, prints coded labels to identify blood samples sent to the external genotyping laboratory, and stores genotyping results. It can search for donors compatible for any combination of the 22 genotyped antigens as well as consult the current inventory for the presence of the corresponding blood components. The phenotype of recovered components is confirmed by standard serology techniques prior to shipment to hospitals. Conclusion Since October 2007, 10 555 blood donors have been genotyped. The database is used on a regular basis to find compatible blood components with a genotype–phenotype concordance of 99·6%. [ABSTRACT FROM AUTHOR]

Amorphous analogues of lithium-iron phosphates (LFP), which are promising cathode materials for Li ion batteries, were prepared by the standard press-quenching method and their thermal stability, as well as structural and electrical properties, were studied for the first time. The glass transition temperature, Tg, determined by the differential thermal analysis (DTA) is composition-dependent and lies in the 492-523 °C range. The local structure, studied by the FTIR absorption spectroscopy, and the thermal stability are found to be almost insensitive to the lithium content. Studies on the electrical properties, carried out by impedance spectroscopy, have shown that the total electrical (predominantly polaronic) conductivity at 450 °C approaches 10 S ⋅ cm-1. The room temperature conductivity of samples after their nanocrystallization (induced by annealing at the temperature of the beginning of crystallization) was higher by a factor of 4-10 (depending on composition) than that of the as-received glass. Therefore, nanocrystallization seems to be a promising way to enhance the electrical conductivity of amorphous lithium-iron phosphates. [ABSTRACT FROM AUTHOR]

Abstract: A series of LiMn y Fe1−y PO4 samples have been prepared in the whole range 0≤ y ≤1. Chemical delithiation could be achieved to obtain Mn y Fe1−y PO4 in the range 0≤ y ≤0.8, keeping the same crystal phase (olivine structure, space group Pnma). The composition y =0.8 is the limit where the delithiated phase is still crystallized, but abruptly suffers strains at the molecular scale evidenced by both optical spectroscopy and X-ray diffraction. The analysis of the magnetic properties shows that in all the samples the concentration of impurities is negligible. The concentration of polarons, either holes associated to Li vacancies in LiMn y Fe1−y PO4 or electrons associated to the existence of Li left in the matrix of Mn y Fe1−y PO4, is found to be small (≤1%) in all the samples. For y ≤0.6, all the Mn3+ ions Mn y Fe1−y PO4 are in the high-spin state (S =2). At larger manganese concentration, however, the Mn3+ ions in excess of the critical concentration y c =0.6 undergo a transition to the low-spin state (S =1). As a consequence, and in contrast with prior works, we find that Mn0.8Fe0.2PO4 has magnetic interactions that are much smaller, and no antiferromagnetic ordering in this compound is detected, at least above 20K. Antiferromagnetic ordering that had been reported so far for Mn y Fe1−y PO4 at large y-composition might come from incomplete delithiation. The spin-transition of Mn3+ in concentration (y–y c) to the low-spin state is at the origin of the strain fields at the molecular scale that increase with y for y >0.6, and ultimately prevents the full delithiation for y >0.8. This result sheds light on the reason for the degradation of cathode properties in Mn-rich compounds of the heterosite–purpurite series, while the electrochemical properties are good in the range y ≤0.6 but only at slow rates, due to the very small hopping mobility of the small polaron. [Copyright &y& Elsevier]

Amorphous analogues of lithium-iron phosphates (LFP), which are promising cathode materials for Li ion batteries, were prepared by the standard press-quenching method and their thermal stability, as well as structural and electrical properties, were studied for the first time. The glass transition temperature, Tg, determined by the differential thermal analysis (DTA) is composition-dependent and lies in the 492-523 °C range. The local structure, studied by the FTIR absorption spectroscopy, and the thermal stability are found to be almost insensitive to the lithium content. Studies on the electrical properties, carried out by impedance spectroscopy, have shown that the total electrical (predominantly polaronic) conductivity at 450 °C approaches 10-2 S.cm-1. The room temperature conductivity of samples after their nanocrystallization (induced by annealing at the temperature of the beginning of crystallization) was higher by a factor of 4-10 (depending on composition) than that of the as-received glass. Therefore, nanocrystallization seems to be a promising way to enhance the electrical conductivity of amorphous lithium-iron phosphates. [ABSTRACT FROM AUTHOR]

Abstract: The effect of H2O on carbon-coated LiFePO4 particles was investigated by chemical analysis, structural analysis (X-ray diffraction, SEM, TEM), optical spectroscopy (FTIR, Raman) and magnetic measurements. Upon immersion in water, part of the product floats while the main part sinks. Both the floating and the sinking part have been analyzed. We find that the floating and sinking part only differ by the amount of carbon that partly detaches from the particles upon immersion in water. Exposure to H2O results in rapid attack, within minutes, of the surface layer of the particles, because the particles are no longer protected by carbon. The deterioration of the carbon coat is dependent on the synthesis process, either hydrothermal or solid-state reaction. In both cases, however, the carbon coat is permeable to water and fails to protect the surface of the LiFePO4 particles. The consequence is that this immersion results in the chemical attack of LiFePO4, but is restricted to the surface layer of the particles (few nanometers-thick). In case the particles are simply exposed to humid air, the carbon coat protects the particles more efficiently. In this case, the exposure to H2O mainly results in the delithiation of the surface layer, due to the hydrophilic nature of Li, and only the surface layer is affected, at least for a reasonable time of exposure to humid air (weeks). In addition, within this timescale, the surface layer can be chemically lithiated again, and the samples can be dried to remove the moisture, restoring the reversible electrochemical properties. [Copyright &y& Elsevier]

Abstract: spinels have been prepared by wet route technique in the whole concentration range . Structural analysis has been performed by X-ray diffraction and scanning electron microscopy and Raman spectroscopy. The investigation of impurity phases by magnetic experiments complete the sample characterization, allowing for a comparison with samples obtained by other chemical routes. The analysis of the intrinsic magnetic properties show that the magnetic interactions are interactions in a geometrically frustrated lattice, while the – interactions are negligible, with the consequence that the paramagnetic Curie temperature vanishes in the limit where only ions remain. A consistent description of both the extrinsic and the intrinsic properties including former investigations of electron paramagnetic resonance has been achieved in relation to the electrochemical properties. [Copyright &y& Elsevier]

Abstract: Amorphous analogs of lithium–iron–phosphates (LFP) with olivine-like local order were prepared by standard press-quenching method and their thermal stabilities as well as structural and electric properties were studied for the first time. Glass transition temperature T g determined by DTA method is equal to 492–523 °C depending on the glass composition. Fourier transform infrared (FTIR) absorption spectroscopy was used to study local order. Local structure and thermal properties are almost independent on the lithium content. Electrical properties were studied by impedance spectroscopy. Impedance measurements indicated that the studied lithium–iron–phosphate glasses with olivine-like local order exhibit predominantly electronic (polaronic) conductivity. Total electrical conductivity at 450 °C for a glass of nominal composition LiFePO4 approaches 10−2 S/cm. Electrical conductivity at 25 °C of Li0.4FePO4 glass after nanocrystallization (caused by heating up from room temperature to the beginning of crystallization temperature) increased by a factor close to 4. Nanocrystallization seems to be the way for electrical conductivity improvement of olivine-like cathode materials. [Copyright &y& Elsevier]

Abstract: The essential structural features of lithium-metal phosphates (LMP) have been studied using FTIR spectroscopy which is a sensitive tool to probe the local environment in the solid materials. Various LMP materials where M is iron have been investigated including phospho-olivine LiFePO4, diphosphate LiFeP2O7, Nasicon-type phosphate Li3Fe2(PO4)3 and dihydrate FePO4·2H2O. Vitreous and amorphous materials are also considered. Analysis of internal and external modes of vibration allows to distinguish between the different phases and the type of cationic environment in the framework. Results corroborate the contribution of the main factors which are responsible for the complexity of the spectra, i.e. departure from ideal symmetry, interactions between polyhedra, bridging atoms and lattice distortion. [Copyright &y& Elsevier]

Abstract: We report the structural and electronic characterization of Li2FeSiO4 synthesized by solid-state reaction. X-ray diffraction, Raman scattering, Fourier transform infrared (FTIR) spectroscopy, electron paramagnetic resonance (EPR) spectroscopy and magnetization measurements are analyzed. Magnetic susceptibility experiments give evidence that Li2FeSiO4 powders possess an antiferromagnetic ordering below T N =25K due to long range Fe–O–Li–O–Fe interactions. Analysis of the paramagnetic region giving the Curie–Weiss parameters θ p =−93.5K and C p =4.13emuKmol−1 shows the divalent state of Fe cations. Electron paramagnetic resonance experiments confirm this electronic configuration. Electrochemical measurements were carried out in lithium cells with LiTFSI in a poly(ethylene oxide) (PEO) polymer electrolyte at 80°C. The resulting cyclic voltammogram indicates a stable structure for the first cycle with redox peaks at 2.80 and 2.74V versus Li0/Li+. [Copyright &y& Elsevier]

Abstract: Microcrystalline LiFePO4 samples have been grown using four different techniques. The structural properties are analyzed using X-ray diffraction (XRD) spectroscopy and Fourier transform infrared spectroscopy (FTIR). Depending on which technique of preparation is used, the material is obtained either free of any detectable impurity, or include impurity phases under the form of nano-sized clusters. The magnetic properties are found to be a powerful tool to characterize them. They give evidence of nano-sized ferromagnetic particles, which can be either strongly magnetic (-Fe2 O3 clusters) or weakly ferromagnetic (Fe2 P clusters), depending on the preparation process. The concentration of magnetic clusters also depends on the preparation process and varies from small concentration ( of -Fe2 O3 per formula) in which case no collective behavior is observed, to large concentrations ( of Fe2 P clusters per formula) where the dipolar interaction generates superferromagnetism. Ferromagnetic resonance experiments are also reported, and are a probe of the -Fe2 O3 nanoparticles. An overall understanding of the different properties is achieved within a model of superferromagnetism induced by interacting Fe2 P nanoparticles, which is also reported. [Copyright &y& Elsevier]

Abstract: Two paintings by Murillo from the Louvre Museum entitled Agony in the garden and Penitent St. Peter kneeling before Christ and the column were analysed by PIXE to identify the nature of their unusual dark mineral backing. Considered until now as black marble, this support turns out to be obsidian, with an almost identical elemental composition for the two works. This composition was compared to that of six Mesoamerican unpainted obsidians labelled “smoking mirrors” with comparable size and shape from the Paris Museum National d’Histoire Naturelle and Musée de l’Homme and to that of geological samples from five Mexican sources. The trace element contents of Murillo’s obsidians, in particular those of Mn, Zr, Sr, Y, Rb, Zr, Nb and Zn appeared to be very similar to that of four smoking mirrors and to that of obsidians from the Ucareo-Zinapécuaro source in central Mexico, an important complex of obsidian quarries exploited since pre-Hispanic times. A literature survey showed no such similarity with obsidians from other Mesoamerican sources or even from Mediterranean and surroundings source-areas. This study points out that Murillo, although living in Sevilla, had occasionally employed for his paintings materials shipped from the New World to Spain. [Copyright &y& Elsevier]

Abstract: An experimental relationship between local structure and electrochemical properties is established for lithium metal phosphates LiMePO4 (Me = Fe, Co, Mn), LiFeP2O7 and Li3Fe2(PO4)3 which crystallise with either the olivine-like or the Nasicon-like structure. Structural features of several lithium metal phosphates are investigated by a local probe such as the FTIR spectroscopy in order to explain the influence of either or covalent bonds on redox energies. The local cationic arrangement is also discussed with the aid of a molecular vibration model to figure out the strong covalent bonds within a complex for glassy Nasicon compounds. [Copyright &y& Elsevier]

Deals with a study which examined the presence and function of ectoneucleoside triphosphate diphosphohydrolase enzyme in the mesenteric vein and artery. Materials and methods; Results; Discussion.

The results of optical absorption experiments on proton- and deuteron-implanted indium phosphide are reported. It is shown that these implantations produce two types of hydrogen- (or deuterium-) related defects. These defects also exist in as-grown material not intentionally doped with hydrogen. The nature of these two defects is discussed. [ABSTRACT FROM AUTHOR]