Valence State Of Mn Research Articles

Study on Conductive and Magnetic Properties of Ag-Doped La 0.67 Sr 0.33 MnO 3

Rare-earth doped manganese oxide La 0.67 Sr 0.33 MnO 3 (LSMO) has broad application prospects in the field of spin electronics, which has the paramagnetic-ferromagnetic transition temperature (T c ) above room temperature. Recent research shows that Ag-doping has effective improvements of grain size and conductivity of LSMO for improving the colossal magnetoresistance effect (CMR). In this paper, sol-gel method was used to prepare La 0.67 Sr 0.33 MnO 3 : Agx（x=0, 0.5 mol%） polycrystalline powder. By using X-ray diffraction (XRD), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM) and X-ray photoelectron spectroscopy (XPS) technologies, the microstructure, crystalline phase structure, resistivity, magnetic properties, Ag and Mn valence states of LSMO were tested before and after Ag doping, respectively. The analysis shows that some Ag atoms exist at the grain boundary of LSMO in the form of element to enhance the conductivity; other Ag atoms go into the crystal lattice replacing A site La 3+ in the perovskite structure ABO3, which obtains a small amount of La 2 O 3 hybrid phase in LSMO and decreases the ratio of Mn 3+ /Mn 4+ . Ag doping weakens the double exchange effect and the magnetic property of LSMO. The substitution of La with Ag also makes minority spinon band of LSMO slightly reduced, which can weakly decrease the conductivity of LSMO.

Effect of Mn-doping on the structure and electrical properties of (Pb0.325Sr0.675)TiO3 ceramics

Pb0.325Sr0.675Ti1-xMnxO3 ceramics (x = 0, 0.001, 0.005, 0.01, and 0.05) were successfully prepared by traditional solid-state reaction method. It was found that the lattice constant calculated through Rietveld refinement initially increased and then decreased with increasing Mn content, which was attributed to the variation in valence state of Mn and Ti ions. The microstructure gradually varied from the coexistence of large grains and fine grains for x = 0 to the uniform grain for x = 0.05 by increasing the doping Mn ions. With increasing Mn content from x = 0 to x = 0.05, the Curie temperature (Tc) dramatically decreased from 25 °C to − 40 °C and dielectric maximum decreased from 27,100 to 13,200. Pb0.325Sr0.675Ti1-xMnxO3 ceramics with x = 0.001 showed the lowest dielectric loss of 0.006 with a relatively high dielectric peak value of ~ 21,000. The grain boundaries resistance obtained from the complex impedance decreased with the increase of Mn content. The decrease in resistance was ascribed to oxygen vacancies and electronics produced by the change of ionic valence state. X-ray photoemission spectroscopy revealed that Ti ions were Ti4+ and the valences of Mn ions were deduced to be mainly in the form of Mn2+ and/or Mn3+ for ceramics with low content of Mn, while the Ti ions were in the form of Ti3+ and Ti4+ and Mn ions were diverse valence states with the coexistence of Mn2+, Mn3+, and Mn4+ for ceramics with x = 0.01 and 0.05.

Chemical disorder reinforces magnetic order in ludwigite (Ni,Mn)3BO5 with Mn4+ inclusion

Crystals of ludwigite Ni2.14Mn0.86BO5 were synthesized by flux growth technique. We show in the paper that it contains Mn3+ and Mn4+. A possible mechanism of the manganese valence states stabilization has been proposed. The structural and magnetic characterization of the synthesized samples has been carried out in detail. The cations composition and Mn valence states of the crystal were determined using X-ray diffraction and EXAFS technique. The comparative analysis was carried out between the studied crystal and Ni2MnBO5 synthesized previously. Magnetic susceptibility measurements were carried out. The magnetic transition in the studied composition occurs at the 100 K that is higher than in Ni2MnBO5 although the studied composition is more disordered. The calculations of the exchange integrals in the frameworks of indirect coupling model revealed strong antiferromagnetic interactions. The several magnetic subsystems existence hypothesis was supposed. The possible magnetic structure was suggested from the energies estimation for different ordering variants.

Cation distribution and valence in synthetic Al–Mn–O and Fe–Mn–O spinels under varying conditions

ABSTRACTThe spinel-group minerals, found in a range of igneous rocks, are resistant to weathering and can incorporate several multivalent elements, meaning they have the potential to provide insight into the redox conditions of parental magmas. Naturally occurring spinel can contain varying quantities of Mn, an element which occurs terrestrially and extra-terrestrially as Mn2+, Mn3+, Mn4+ and Mn5+. However, a lack of information on the effects of oxygen fugacity ($f_{{\rm O}_{\rm 2}}$) on: (1) Mn valence state and cation distribution; and (2) on spinel-melt partitioning means that the potential for a Mn-in-spinel oxy-barometer remains largely untested. Here, we use electron probe microanalysis, micro-focus X-ray Absorption Near Edge Structure (XANES) spectroscopy and single-crystal X-ray diffraction (SC-XRD) to investigate cation distribution and valence state in spinels in the Al–Mn–O and Fe–Mn–O systems synthesized at ambient pressure under varying $\hskip 2pt f_{{\rm O}_{\rm 2}}$ conditions. In contrast to previous studies, we find that the spectral resolution of the Mn K-edge XANES spectra is insufficient to provide quantitative data on Mn valence state and site occupancy, although it does verify that Mn is incorporated as both Mn2+ and Mn3+, distributed over tetrahedral and octahedral sites. Combination of data from XANES and SC-XRD refinements can, however, be used to model Mn, Al and Fe valence and site occupancy. It would be expected that Mn–Fe spinels have the potential to record $f_{{\rm O}_{\rm 2}}$ conditions in parental melts due to changes to the octahedral site under conditions that were more reducing. However, decoupling the effects of temperature and oxygen fugacity on the TFe3+–TMn2+ exchange in the Mn–Fe spinels remains challenging. In contrast, little variation is noted in Mn–Al spinels as a function of $\hskip 2pt f_{{\rm O}_{\rm 2}}$, implying that crystal chemistry and cation site geometry may significantly influence cation distribution, and by inference, crystal-melt partitioning, in spinel-group minerals.

Red Mn4+-Doped Fluoride Phosphors: Why Purity Matters.

Traditional light sources, e.g., incandescent and fluorescent lamps, are currently being replaced by white light-emitting diodes (wLEDs) because of their improved efficiency, prolonged lifetime, and environmental friendliness. Much effort has recently been spent to the development of Mn4+-doped fluoride phosphors that can enhance the color gamut in displays and improve the color rendering index, luminous efficacy of the radiation, and correlated color temperature of wLEDs used for lighting. Purity, stability, and degradation of fluoride phosphors are, however, rarely discussed. Nevertheless, the typical wet chemical synthesis routes (involving hydrogen fluoride (HF)) and the large variety of possible Mn valence states often lead to impurities that drastically influence the performance and stability of these phosphors. In this article, the origins and consequences of impurities formed during synthesis and aging of K2SiF6:Mn4+ are revealed. Both crystalline impurities such as KHF2 and ionic impurities such as Mn3+ are found to affect the phosphor performance. While Mn3+ mainly influences the optical absorption behavior, KHF2 can affect both the optical performance and chemical stability of the phosphor. Moisture leads to decomposition of KHF2, forming HF and amorphous hydrated potassium fluoride. As a consequence of hydrate formation, significant amounts of water can be absorbed in impure phosphor powders containing KHF2, facilitating the hydrolysis of [MnF6]2- complexes and affecting the optical absorption of the phosphors. Strategies are discussed to identify impurities and to achieve pure and stable phosphors with internal quantum efficiencies of more than 90%.

An Effective Way to Improve Bifunctional Electrocatalyst Activity of Manganese Oxide via Control of Bond Competition

A critical role of bond competition in tailoring Mn valence state and bifunctional electrocatalyst activity of manganese oxide is evidenced by the remarkable improvement of the electrocatalyst activity of α-MnO2 upon the partial substitution of electronegative Ru4+ ion. The replacement of Mn4+ ion with more electronegative Ru4+ one is quite effective in weakening adjacent (Mn−O) bonds in terms of bond competition, leading to the stabilization of Jahn-Teller active Mn3+ species, as well as in providing electrocatalytically active Ru sites. The resulting Ru-substituted α-Mn1−xRuxO2 nanowires show much higher electrocatalyst activities for both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) than does the physical mixture of α-MnO2 and RuO2, indicating the main role of (Mn−O) bond covalency in the optimization of the bifunctional electrocatalyst activity of manganese oxide. The present study underscores that, like the previous strategy of structural disorder enhancement, the substitution of highly electronegative cation can provide a novel efficient way of improving the electrocatalyst performance of manganese oxide via the bond competition between adjacent (Ru−O) and (Mn−O) bonds.

Electronic and Magnetic States of Pr and Mn in the Pr1–xSrxMnO3 Films Studied by XANES and XMCD Spectroscopy

The spectral dependences of X-ray absorption near-edge spectroscopy (XANES) and X-ray magnetic circular dichroism (XMCD) and the field dependences of XMCD near the K edge of Mn and the L2,3 edges of Pr in the Pr0.8Sr0.2MnO3 and Pr0.6Sr0.4MnO3 films at T = 90 K are studied. The spectral dependences point to a mixed valence state of Mn and Pr in the films. It is found that, as compared to XANES, XMCD is more sensitive to the valence state of Pr4+. The field dependences of XMCD point to ferromagnetic behavior of Mn ions and the Van Vleck paramagnetism of Pr ions, which makes a significant contribution to the total magnetization of the films. It is shown that as the Sr concentration increases, the XMCD intensity at the K edge of Mn increases, which indicates a growth of the total magnetic moment of the film due to an increase in the 4p–3d hybridization.

Characterization of Interaction between Fe‐Infiltrates and LSM Backbone in Solid Oxide Fuel Cells

In this paper, detailed materials characterization analyses on the interaction between FeOx nanoparticles infiltrated onto a La0.8Sr0.2MnO3 (LSM) backbone cathode in a solid oxide fuel cell (SOFC) are reported. The infiltration process leads to an increase of 3.4% in cell performance. X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) as well as energy dispersive X‐ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS) are utilized to perform a comprehensive examination of the microstructure and chemical properties at the interface of the infiltrate and backbone materials. Mn from the LSM backbone diffuses into the FeOx infiltrate and forms a Fe‐Mn‐O spinel. A small amount of Fe also diffuses into the LSM backbone, which could partially be responsible for the enhanced performance of the cell. The valence state of Mn increases from the surface of the Fe‐Mn‐O particle into bulk LSM, with the highest value being at the interface of the Fe‐Mn‐O/LSM backbone. Possible mechanisms are discussed for the change in Mn valence state within the LSM phase. Trace amounts of Mn and La are found in the YSZ phase, as a result of interdiffusion between LSM and YSZ.

Formation of diverse Mn oxides: a review of bio/geochemical processes of Mn oxidation

Mn (oxyhydr)oxides, widely distributed in most geological settings, are found in more than 30 different types with different atomic arrangements, a wide range of crystallinity, and mixed valences of structural Mn. Each type of Mn (oxyhydr)oxides is characterized by its crystal structure and the valence state of structural Mn, which are likely the primary factors controlling its distinct reactivity. It is well known that varying pathways of Mn(II) oxidation, including homogeneous, surface catalyzed, or microbial processes, are responsible for the diversity of Mn (oxyhydr)oxide formation. However, the investigation of Mn(II) oxidation products through various oxidation processes have not been fully understood yet partly because the chemical and mineralogical identification of nanosized and poorly crystalline Mn (oxyhydr)oxides has been difficult at times. In this work, the previous studies on the formation of diverse Mn (oxyhydr)oxides through varying geochemical or microbial oxidation processes are thoroughly reviewed. This work may provide general background information for understanding the complex bio/geochemical processes controlling the formation of Mn (oxyhydr)oxides under various conditions of the natural environment.

First principles density functional theory study of Pb doped α-MnO2 catalytic materials

The impact of Pb in the tunnels of manganese oxide octahedral molecular sieves on chemical state of Mn species and lattice oxygen were investigated utilizing density functional theory calculations. The results show that the Pb dopant in the tunnels of OMS-2 could reduce the average valence states of Mn. The lower energy required for bulk oxygen defects formation in Pb-OMS-2 validates the activation of lattice oxygen by inclusion of tunnel dopant. The inclusion of Pb promotes the catalytic oxidation activity of OMS-2 by reducing the energy required for the surface lattice oxygen migration during the Mars – van Krevelen oxidation process.

Operando Investigation of Mn3O4+δ Co-catalyst on Fe2O3 Photoanode: Manganese-Valency-Determined Enhancement at Varied Potentials

The development of efficient catalysts containing earth-abundant elements for the oxygen evolution reaction (OER) in photoelectrochemical (PEC) systems is highly desired for low-cost energy storage and conversion. In this work, mesoporous α-Fe2O3 thin film photoanodes coated with manganese oxide (Mn3O4+δ) co-catalysts are prepared by a dip-coating method. The co-catalyst coating significantly enhances PEC water oxidation performance as compared with the uncoated α-Fe2O3. To understand the origin of this enhancement, in situ X-ray absorption spectroscopy is employed to monitor the valence state of Mn in the Mn3O4+δ co-catalyst as a function of applied potential. It is found that the enhancement of the photocurrent is governed by the Mn valency, and the most prominent enhancement takes place at the valency of ∼3.4+, which is due to the optimal eg electron filling in Mn cations as the electrocatalyst for OER. Our investigation indicates that the contribution of Mn3O4+δ co-catalyst to OER kinetics is variable at different applied potentials.

Structural and magnetic properties of La2Ni1−xCoxMnO6 compounds

Single phase monoclinic La2Ni1−xCoxMnO6 (x = 0.2, 0.4, 0.8) compounds, henceforth, referred as LNCxMO (x = 0.2, 0.4, 0.8) have been prepared by Sol–gel technique. The structural study and redox titration suggest that the samples are both La and O deficient. The generated atomic models using Rietveld refined structural parameters show octahedral distortion in the double perovskite structure. X-ray photoelectron spectroscopy (XPS) study has been used to determine the predominant valence states of Ni, Mn and Co ions. LNCxMO (x = 0.2, 0.4) are found to be Heisenberg ferromagnets whereas LNC0.8MO is a phase segregated system. In LNC0.4MO and LNC0.8MO, at temperatures above TC, χ−1(T) curve shows the characteristics of Griffiths phase. The study of ac susceptibility and isothermal remanent magnetization (IRM) discard the possibility of any glassy state at low temperatures. The antiphase boundaries (APBs), antisite disorders (ASDs) and oxygen vacancies play important roles in this system.

Facile production of 2,5-diformylfuran from base-free oxidation of 5-hydroxymethyl furfural over manganese–cobalt spinels supported ruthenium nanoparticles

This work reports manganese–cobalt spinels (MnCo2O4) supported ruthenium (Ru) nanoparticles, Ru/MnCo2O4, efficiently catalyzed 5-hydroxymethyl furfural (HMF) oxidation to 2,5-diformylfuran (DFF) with high yield 98.3% at 130°C and 1.0MPa of O2 pressure in toluene used as solvent under base-free conditions. A new class of spinels MnCo2O4 having multiple valence states of Mn and Co was synthesized by using simple co-precipitation method and used as support with ruthenium nanoparticles as heterogeneous catalyst. The reusability tests of catalyst Ru/MnCo2O4 were also carried out and was found to be recyclable up to several consecutive cycles without significance loss of original activity.

Effect of sputtering power on structural, cationic distribution and optical properties of Mn2Zn0.25Ni0.75O4 thin films

•We investigate the synthesis of Mn2Zn0.25Ni0.75O4 (MZN) thin films by radio frequency (RF) sputtering method at different sputtering powers. The variation of the film morphology, the crystalline structure, the cationic distributions and the optical properties are reported and explained by the variation of the film growth rate. Scanning electron microscopy results indicate that a too fast growth rate of the film results in dense surface defects or the degradation of the film crystallinity. X-ray photoelectron spectroscopy analysis suggests that oxygen defects are almost inevitable in such thin films deposited by RF sputtering. At a moderate (120 W) sputtering power the Mn2+ content increases 10–20% and the Mn4+ content is accordingly reduced. The detailed cationic configuration is proposed, where Zn2+ ions occupy both the tetrahedral site and the octahedral site. Raman and spectroscopic results allows asserting the relation between Mn valence states and the sputtering power.

Electrochemically induced spinel-layered phase transition of Mn3O4 in high performance neutral aqueous rechargeable zinc battery

Mn3O4 is an electrochemically inactive in alkaline Zn–MnO2 battery. Here, we show that Mn3O4 shows superior electrochemical performance in mild aqueous zinc sulfate electrolytes. Mn3O4 can be a new cathode material for neutral aqueous rechargeable zinc battery. Results reveal that spinel Mn3O4 transforms to intermediate Mn5O8 and finally to Zn-birnessite. The initial charge cycle proceeds without participation of zinc ions, while zinc ions participate in the subsequent reaction. The intercalation of zinc ions into the interlamination of birnessite leads to the generation of Zn-birnessite in discharge process, accompanied by the reduction of Mn4+ to Mn3+. Our results demonstrate a new manganese oxide cathode with average Mn valence state lower than four for rechargeable zinc batteries.

First-Principles Calculation for the Half Metallic Properties of La2NbMnO6**Supported by the Scientific Research Plan Projects of Heilongjiang Education Department under Grant No 135109311, the National Natural Science Foundation of China under Grant Nos 11404180 and 11405092, and the Natural Science Foundation of Heilongjiang Province under Grant Nos A2015010 and B201420.

La2VMnO6 is measured to be insulating and ferrimagnetic experimentally. In this study, by substituting V with Nb, La2NbMnO6 is investigated using the density functional theory. The calculated results indicate that La2NbMnO6 is also ferrimagnetic and exhibits the half metallic properties due to the strong electron correlation of Mn. The valence states of Nb and Mn are assigned to be +4 and +2 in La2NbMnO6, respectively, which are different from V3+/Mn3+ in La2VMnO6.

Structural Distortion in MnO₂ Nanosheets and Its Suppression by Cobalt Substitution.

Co–Mn oxide nanosheets with the chemical composition H0.23Co0.23Mn0.77O2 (C23M77NS) and MnO2 nanosheets (M100NS) were prepared by exfoliation of layer-structured oxides via chemical processing in an aqueous medium. The optical properties of C23M77NS and M100NS were compared using UV-Vis spectroscopy, and the valence states of Mn and Co and local structures around them were examined using X-ray absorption spectroscopy. M100NS with an average Mn valence of 3.6 exhibits large structural distortion, whereas C23M77NS with an average Mn valence of 4.0 does not exhibit structural distortion. Spontaneous oxidization of Mn occurs during ion-exchange and/or exfoliation into nanosheets. These results have originated the hypothesis that structural distortion determines the valence state of Mn in compounds with CdI2-type-structured MnO2 layers.

Crystal Structure Analysis and Mg Battery Cathode Properties of Delithiated Li1-XNi0.5Mn0.5O2 with Layered Rock-Salt Structure

Introduction Recent interest in the magnesium rechargeable batteries may be attributed both to their technological potential and to the fact that they represented an intercalation mechanism of magnesium into the oxide materials. The chevrel compound, Mo6S8, has been attracted much attention because of its high reversibility and excellent cycle life. The low stability and capacity, however, have led to the investigation of alternative materials. So far, the delithiated Li compounds, LiFePO4 and Li3V2(PO4)3, have been studied to show high specific capacities of about 300 mAh g-1 and 200 mAh g-1, respectively. Although the theoretical capacity of delithiated Li1-xNi0.5Mn0.5O2 exceed 500 mAh g-1, the examination of the use as the cathode of magnesium rechargeable battery has not been performed. The synthesis of delihitated Li1-xNi0.5Mn0.5O2 has opened route for the electrochemically or chemically delihiated methods [1]. The advantage of such an electrochemically method is to control the deilthiation amount whereas a chemically method is to obtain the delithiated sample without the additives such as conductive carbon and PTFE binders. In this study, the delithiated Li1-xNi0.5Mn0.5O2 was synthesized and analyzed about the crystal structures and valence states of Ni and Mn before and after magnesiation. Experimental The LiNi0.5Mn0.5O2 was synthesized via a traditional solid-state reaction route. The LiOH·H2O, NiO and MnO2 were thoroughly mixed by planetary ball milling. The obtained powders were heated at 600 °C in air for 5 hours and then pressed into a pellet to calcine at 1000 °C in air for 10 hours. The delithiated Li1-xNi0.5Mn0.5O2 was prepared by electrochemical method and chemical one using NO2BF4 oxidizer. The LiNi0.5Mn0.5O2 powders were stirred in NO2BF4 solution in acetonitrile for 12 hours. When the reaction was completed, the solution was filtered and washed with acetonitrile. Chemical analyses for Li, Ni and Mn were carried out by inductively coupled plasma atomic emission spectroscopy (ICP-AES) to evaluate the delithiation amounts. Powder X-ray diffraction data were collected on a Panalytical X’pert-pro diffractometer. The morphology was observed by scanning electron microscopy (SEM, Hitachi, S-2600N). The crystal structure analysis was performed by using the synchrotron X-ray diffraction at BL19B2 (SPring-8, JAPAN). The valence states of Ni and Mn before and after magnesiation were examined by the XAFS at BL14B2 (SPring-8, JAPAN). Discharge and charge tests were performed at 60 °C using a positive electrode, which consisted of the delithiated Li1-xNi0.5Mn0.5O2, conductive carbon, and poly-tetrafluoroethylene powder between 0.5 and 3.0 V using an Mg-alloy negative electrode at a fixed current density of 5 mA g-1. A solution of 0.5 M Mg(TFSI)2 in a acetonitrile (Kishida Chemical Co., Ltd.) was used as the electrolyte. The cells were constructed in an argon-filled globe box. Results and Discussion The XRD pattern for the pristine LiNi0.5Mn0.5O2 was attributed to the ordered rock-salt structure with R-3m space group. The electrochemically delithiated Li0.1Ni0.5Mn0.5O2 was transformed to different layered structure. On the other hand, the chemically delithiation of LiNi0.5Mn0.5O2 resulted in the only peak shift of the XRD while retaining the original structure. The cathode performance of electrochemically delithiated Li0.1Ni0.5Mn0.5O2 showed about 35 mAh g−1 at first and second discharges (Fig.). Although the first charge capacity was too large for first discharge, the agreement of the discharge capacities at first and second cycles indicated to demagnesiate from the magnesiated MgxLi0.1Ni0.5Mn0.5O2 at first charge. The synchrotron X-ray diffraction patterns of pristine and delithiated and magnesiated samples were analyzed by Rietveld method and were not fully fitted to the layered rock-salt structure for delithiated and magnesiated those. The refined lattice parameters showed to intercalate the magnesium in the Li0.1Ni0.5Mn0.5O2. In addition the XANES spectra of the pristine and delithiated and magnesiated samples were measured to show the valence change corresponding to the delithiation and magnesiation. Reference [1] N. Ishida, N. Tamura, N. Kitamura, and Y. Idemoto, J. Power Sources, 319, 255 (2016) Figure 1

Crystal Structure Analysis of Electrochemically Magnesiated MgxLi0.1Mn0.54Ni0.13Co0.13O2

INTRODUCTION Recently, the Mg secondary battery has been studied for the purpose of the development of the rechargeable battery with larger energy density than the Li-ion battery. In this study, we focused attention on the Li1.2Mn0.54Ni0.13Co0.13O2, which is a positive electrode material of the high capacity lithium ion battery, to examine the use for the cathode material capable of inserting Mg ions. We have reported the crystal and electronic structures and thermodynamic stability of the chemically delithiated Li1.2-xMn0.54Ni0.13Co0.13O2 (x = 0.3, 0.6, 0.9)1). Although there is no knowledge about the insertion and desorption of Mg for the delithiated material, the high capacity such as shown in the Li ion battery is expected for Mg secondary battery. The purpose of the present study was to evaluate the electrode property of delithiated Li1.2-xMn0.54Ni0.13Co0.13O2 in the Mg secondary battery, to analyze the crystal and electronic structure changes before and after Mg insertion, to reveal the valence change of transition metals, and furthermore to examine the charge/discharge mechanism. EXPERIMENTAL Li1.2Mn0.54Ni0.13Co0.13O2 was synthesized by using a solid-state reaction via co-precipitated precursors. Precipitation was obtained by dissolving each metal nitrate in distilled water and adding it dropwise to an aqueous solution of lithium hydroxide. Based on the predetermined metal ratio of the precipitate, we added lithium hydroxide to the precipitate again, and dried and heated at 650 ºC for 15h in air. After that, the powder was calcined at 900 ºC for 8h in air to obtain a sample. The obtained samples were identified by powder XRD. The metal composition was determined by the ICP-AES. The chemically delithiation treatment was pursued as the previously reported using NO2BF4 in an argon filled glovebox1). The electrochemical measurements were subjected to a charge-discharge cycle test (at 3.0 – 0.5 V vs. Mg/Mg2 +, the negative electrode: AZ31, electrolyte: 0.5 mol/L Mg(N(SO2CF3)2)2 in acetonitrile, separator: polypropylene) at 60 ºC by using the HS cell (Hosen Ltd.). The XAFS (BL14B2, SPring-8) and synchrotron XRD measurements (BL19B2, SPring-8) were performed on the Li1.2-xMn0.54Ni0.13Co0.13O2, i.e. before Mg insertion, and the MgxLi1.2-xMn0.54Ni0.13Co0.13O2 electrode after Mg insertion to evaluate the valence change of transition metals and to analyze the crystal structures by Rietveld analysis (Rietan-FP). RESULTS AND DISCUSSION Chemically delithiated Li0.13Mn0.54Ni0.13Co0.13O2 was synthesized using NO2BF4 for Li1.2Mn0.54Ni0.13Co0.13O2. In order to refine the crystal structure of this sample, synchrotron X-ray diffraction measurement was performed and Rietveld analysis was performed. As a result of the analysis, it was revealed that the 97 % of the pristine monoclinic (C2/m) structure converted to the trigonal (R m) structure after delithiation. As a result of discharging test of this sample with the counter electrode of Mg alloy (AZ31), the discharge capacity was 287 mAh g-1 (Fig.1) which corresponded to 0.52 apfu as the insertion amount of Mg and corresponded to approximately half of chemically eliminated Li. In order to refine the crystal structure of the electrode after electrochemical Mg insertion, synchrotron XRD measurement was performed and Rietveld analysis was performed. As a result of the analysis, it was revealed that the 91% of the delithiated phase remained as trigonal R m structure. In addition, it was revealed that unit cell volume expanded by 2.8% at C2/m and by 2.7% at R m after Mg insertion. From the results of XANES, it was also revealed that the valence states of Mn and Co decreased by about 1 valence after Mg insertion, respectively. Therefore, it is concluded that the discharge mechanism was explained by the reduction of transition metals and the intercalation of Mg, which is supported that the lattice volume expanded due to the reduction of the transition metal by increasing the ionic radius. References 1) N. Ishida, N. Tamura, N. Kitamura, and Y. Idemoto., J. Power Sources, 319, 255-261 (2016) . Figure 1

Ab-Initio Investigations of Magnetic Properties and Induced Half-Metallicity in Ga1-xMnxP (x = 0.03, 0.25, 0.5, and 0.75) Alloys.

Ab-initio calculations are performed to examine the electronic structures and magnetic properties of spin-polarized Ga1−xMnxP (x = 0.03, 0.25, 0.5, and 0.75) ternary alloys. In order to perceive viable half-metallic (HM) states and unprecedented diluted magnetic semiconductors (DMSs) such as spintronic materials, the full potential linearized augmented plane wave method is utilized within the generalized gradient approximation (GGA). In order to tackle the correlation effects on 3d states of Mn atoms, we also employ the Hubbard U (GGA + U) technique to compute the magnetic properties of an Mn-doped GaP compound. We discuss the emerged global magnetic moments and the robustness of half-metallicity by varying the Mn composition in the GaP compound. Using GGA + U, the results of the density of states demonstrate that the incorporation of Mn develops a half-metallic state in the GaP compound with an engendered band gap at the Fermi level (EF) in the spin–down state. Accordingly, the half-metallic feature is produced through the hybridization of Mn-d and P-p orbitals. However, the half-metallic character is present at a low x composition with the GGA procedure. The produced magnetic state occurs in these materials, which is a consequence of the exchange interactions between the Mn-element and the host GaP system. For the considered alloys, we estimated the X-ray absorption spectra at the K edge of Mn. A thorough clarification of the pre-edge peaks is provided via the results of the theoretical absorption spectra. It is inferred that the valence state of Mn in Ga1−xMnxP alloys is +3. The predicted theoretical determinations surmise that the Mn-incorporated GaP semiconductor could inevitably be employed in spintronic devices.