Synthesis and crystal structure CoNi<Subscript>2</Subscript>(BO<Subscript>3</Subscript>)<Subscript>2</Subscript>

A new metal orthoborate compound, cobalt dinickel orthoborate, CoNi₂(BO₃)₂ has been successfully synthesized for the first time. The title compound was synthesized by thermally-induced solid-state chemical reaction at 900°C between the initial reagents of Co(NO₃)₂ · 6H₂O, Ni(NO₃)₂ · 6H₂O and H₃BO₃ which were mixed with the mol ratio of 1: 2: 2 respectively. The obtained product was structurally characterized by X-ray powder diffraction technique. It has been found that the CoNi₂(BO₃)₂ crystallizes in the kotoite type and isostructural with the compounds having the chemical formula M₃(BO₃)₂ where M—Mg, Co and Ni. The synthesized compound belongs to the orthorhombic crystal system with the refined unit cell parameters of a = 5.419(9) Å, b = 8.352(0) Å, c = 4.478(8) Å and Z = 2. The space group was determined as Pnmn. Further characterizations by FTIR, elemental analysis and thermal analysis were also performed.     

Enhanced electrochemical reduction of hydrogen peroxide by Co<Subscript>3</Subscript>O<Subscript>4</Subscript> nanowire electrode

Crystalline Co₃O₄ nanowire arrays with different morphologies grown on Ni foam were investigated by varying the reaction temperature, the concentration of precursors, and reaction time. The Co₃O₄ nanowires synthesized under typical reaction condition had a diameter range of approximately 500–900 nm with a length of 17 µm. Electrochemical reduction of hydrogen peroxide (H₂O₂) of the optimized Co₃O₄ nanowire electrode was studied by cyclic voltammetry. A high current density of 101.8 mA cm^?2 was obtained at ?0.4 V in a solution of 0.4 M H₂O₂ and 3.0 M NaOH at room temperature compared to 85.8 mA cm^?2 at ?0.35 V of the Co₃O₄ nanoparticle electrode. Results clearly indicated that the Ni foam supported Co₃O₄ nanowire electrode exhibited superior catalytic activity and mass transport kinetics for H₂O₂ electrochemical reduction.     

Enhanced electrochemical performance of Na<Subscript>3</Subscript>V<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>2</Subscript>F<Subscript>3</Subscript> for Na-ion batteries with nanostructure and carbon coating

Carbon-coating Na₃V₂(PO₄)₂F₃ nanoparticles (NVPF@C NP) were prepared by a hydrothermal assisted sol–gel method and applied as cathode materials for Na-ion batteries. The as-prepared nanocomposites were composed of Na₃V₂(PO₄)₂F₃ nanoparticles with a typical size of ~?100 nm and an amorphous carbon layer with the thickness of ~?5 nm. Cyclic voltammetry, rate and cycling, and electrochemical impedance spectroscopy tests were used to discuss the effect of carbon coating and nanostructure. Results display that the as-prepared NVPF@C NP demonstrates a higher rate capability and better long cycling performance compared with bare Na₃V₂(PO₄)₂F₃ bulk (72 mA h g^?1 at 10 C vs 39 mA h g^?1 at 10 and 1 C capacity retention of 95% vs 88% after 50 cycles). The remarking electrode performance was attributed to the combination of nanostructure and carbon coating, which can provide short Na-ion diffusion distance and rapid electron migration.     

Magnetic,magnetocaloric properties,and critical behavior in a layered perovskite La<Subscript>1.4</Subscript>(Sr<Subscript>0.95</Subscript>Ca<Subscript>0.05</Subscript>)<Subscript>1.6</Subscript>Mn<Subscript>2</Subscript>O<Subscript>7</Subscript>

We report the results of magnetic, magnetocaloric properties, and critical behavior investigation of the double-layered perovskite manganite La_1.4(Sr_0.95Ca_0.05)_1.6Mn₂O₇. The compounds exhibits a paramagnetic (PM) to ferromagnetic (FM) transition at the Curie temperature T _C = 248 K, a Neel transition at T _N = 180 K, and a spin glass behavior below 150 K. To probe the magnetic interactions responsible for the magnetic transitions, we performed a critical exponent analysis in the vicinity of the FM–PM transition range. Magnetic entropy change (??S _M) was estimated from isothermal magnetization data. The critical exponents β and γ, determined by analyzing the Arrott plots, are found to be T _C = 248 K, β = 0.594, γ = 1.048, and δ = 2.764. These values for the critical exponents are close to the mean-field values. In order to estimate the spontaneous magnetization M _S(T) at a given temperature, we use a process based on the analysis, in the mean-field theory, of the magnetic entropy change (??S _M) versus the magnetization data. An excellent agreement is found between the spontaneous magnetization determined from the entropy change [(??S _M) vs. M ²] and the classical extrapolation from the Arrott curves (µ₀H/M vs. M ²), thus confirming that the magnetic entropy is a valid approach to estimate the spontaneous magnetization in this system and in other compounds as well.     

Sorption of CH<Subscript>3</Subscript><Superscript>131</Superscript>I from water vapor-air medium on porous inorganic sorbents containing triethylenediamine and <Emphasis Type="Italic">d</Emphasis> element nitrates

Sorption of CH₃ ¹³¹I from a water vapor-air medium on porous inorganic sorbents based on silica gel of KSKG grade and containing triethylenediamine (CH₂-CH₂)₃N₂ and d element nitrates was studied. The sorbents prepared by impregnation with (CH₂-CH₂)₃N₂ and Zn, Ni, and Cu nitrates from aqueous solution recover CH₃ ¹³¹I from a water vapor-air flow poorly (degree of recovery <10%). Calcination of the sorbents at temperatures exceeding 250°C does not noticeably affect their sorption power. Heating of the complex Ag(NO₃)(OH)·(CH₂-CH₂)₃N₂H to 160°C causes its exothermic decomposition with a large heat release and formation of metallic silver. Thermal decomposition of the complex of Cu²⁺ with (CH₂-CH₂)₃N₂, synthesized from an aqueous solution at the molar ratio Cu(NO₃)₂: (CH₂-CH₂)₃N₂ = 1: 2, occurs similarly.     

Tunable luminescence properties and energy transfer of single-phase Ca<Subscript>4</Subscript>(PO<Subscript>4</Subscript>)<Subscript>2</Subscript>O: Dy<Superscript>3+</Superscript>, Eu<Superscript>2+</Superscript> multi-color phosphors for warm white light

The novel Ca_4?x(PO₄)₂O: xDy³⁺ and Ca_4?x?y(PO₄)₂O: xDy³⁺, yEu²⁺ multi-color phosphors were synthesized by traditional solid-state reaction. The crystal structure, particle morphology, photoluminescence properties and energy transfer process were investigated in detail. The X-ray diffraction (XRD) results demonstrate that the products showed pure monoclinic phase of Ca₄(PO₄)₂O when x < 0.1. The scanning electron microscopy (SEM) indicated that the phosphors were grain-like morphologies with diameters of ~ 3.7–7.0 μm. Under excitation of 345 nm, Dy³⁺-doped Ca₄(PO₄)₂O phosphors showed multi-color emission bands at 410, 481 and 580 nm originated from oxygen vacancies and Dy³⁺. Interestingly, Ca₄(PO₄)₂O: Dy³⁺, Eu²⁺ phosphors exhibited blue emission band at 481 nm and broad emission band from 530 to 670 nm covering green to red regions. The energy transfer process from Dy³⁺ to Eu²⁺ was observed for the co-doped samples, and the energy transfer efficiency reached to 60% when Eu²⁺ molar concentration was 8%. In particular, warm/cool/day white light with adjustable CCT (2800–6700 K) and high CRI (R_a > 85) can be obtained by changing the Eu²⁺ co-doping contents in Ca₄(PO₄)₂O: Dy³⁺, Eu²⁺ phosphors. The optimized Ca_3.952(PO₄)₂O: 0.04Dy³⁺, 0.008Eu²⁺ phosphor can achieve the typical white light with CCT of 4735 K and CRI of 87.     

Fe<Subscript>78</Subscript>Si<Subscript>9</Subscript>B<Subscript>13</Subscript> amorphous powder core with improved magnetic properties

The effects of pre-annealing treatments on the soft magnetic properties of the corresponding Fe₇₈Si₉B₁₃ amorphous powder cores were investigated. The amorphous powder cores prepared from pre-annealed powder have better soft magnetic properties compared with unpretreated powder core in the as-cast state. The result shows that the powder after pre-annealing in a magnetic field presents a regular domain structure and the soft magnetic properties of the corresponding powder cores are greatly improved. As the result, the magnetic-field annealed powder core has the highest effective permeability (μ _e) of 37, which is 23 % higher than the as-cast one and 7 % than only vacuum-annealed one. The total core loss (P _cv) for the core annealed in magnetic field is only 141 W/kg (100 kHz, 50 mT) and as low as 36 % of the P _cv for the powder core in the as-cast state. The one annealed in magnetic field also exhibits the best DC bias properties of 92 %. This work provides a novel approach to realizing low P _cv and high μ _e for Fe₇₈Si₉B₁₃ powder cores and also validates the application prospect of powder cores in the work condition of different ripple currents, different loads and a wide frequency (f) range (10 kHz–10 MHz).     

Low-temperature synthesis of Sr<Subscript>0.3</Subscript>Ba<Subscript>0.7</Subscript>Nb<Subscript>2</Subscript>O<Subscript>6</Subscript> ultrafine powder and its characteristics

Ultrafine strontium barium niobate (Sr_0.3Ba_0.7Nb₂O₆, SBN30) powders were prepared by urea method starting from a precursor solution constituting of Sr (NO₃)₂, Ba (NO₃)₂, NbF₅, urea and polyvinyl alcohol (PVA) as surfactant. Their structural behavior and morphology were examined by means of X-ray diffractometry (XRD) and Scanning electron microscopy (SEM). The results showed that the SBN30 powders crystallized to a pure tetragonal phase at annealing temperatures as low as 750 °C. The average particle size of SBN powders subjected to 750 °C was of the order of 150–300 nm. With increasing calcination temperature,however, the average particle size of the calcined powders increased. The SBN30 ceramic prepared from urea method can be sintered at temperature as low as 1,225 °C. The transition temperature from the ferroelectric phase to the paraelectric phase and the relative dielectric permittivity of the SBN30 powder were less than the corresponding values of the bulk ceramic. The permittivity and loss tangent (tan δ) at room temperature (1 kHz) was found to be 930 and below 0.025.     

Structural studies of a new electroceramic composite: Pb(Fe<Subscript>0.5</Subscript>Nb<Subscript>0.5</Subscript>)O<Subscript>3</Subscript> (PFN)-Cr<Subscript>0.75</Subscript>Fe<Subscript>1.25</Subscript>O<Subscript>3</Subscript>(CRFO)

A study of the structural characteristics of the composites [Pb(Fe_0.5Nb_0.5)O₃(PFN)] _x -[Cr_0.75Fe_1.25O₃(CRFO)]_100?x (x = 0 (CRFO100), 10, 50, 90, 100) was performed in this work. The compounds PFN100 and CRFO100 were prepared by conventional solid-state method and investigated by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and ⁵⁷Fe Mössbauer Spectroscopy techniques. The X-ray analysis shows that PFN100 is tetragonal and the CRFO100 phase has a trigonal symmetry. The refinement of all the composites was also performed and discussed in this paper. The Mössbauer spectrum for the composite samples shows a paramagnetic doublet and a sextet probably assigned to a magnetic phase associated to Fe⁺³. For the sample PFN100, only a magnetic field of 49.5 T (isomer shift (δ) = 0.21 mm/s) was detected. For the composite sample, the δ and Δ are typical of Fe ions at sites of octahedral coordination.     

Synthesis and conductivity studies of Li<Subscript>1.5</Subscript>Al<Subscript>0.5</Subscript>Ge<Subscript>1.5</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript> solid electrolyte

This paper describes the preparation of a lithium ion conducting solid electrolyte with the composition Li_1.5Al_0.5Ge_1.5(PO₄)₃ by a new liquid-phase method with the use of the water-soluble salts Al(NO₃)₃ · 9H₂O, LiNO₃ · 3H₂O, and (NH₄)₂HPO₄ and the germano-oxalic acid H₂[Ge(C₂O₄)₃]. The synthesized materials have been characterized by X-ray diffraction, differential scanning calorimetry, thermogravimetry, and impedance spectroscopy. The results demonstrate that sintering of the synthesized amorphous powders at a temperature of 650°C leads to the formation of phase-pure Li_1.5Al_0.5Ge_1.5(PO₄)₃. The ionic conductivity of the electrolyte measured at frequencies from 10 Hz to 2 MHz using pellets with an 86% relative density was 4.2 × 10^–4 S/cm.     

Mn-doped Li<Subscript>3</Subscript>V<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript> nanocrystal with enhanced electrochemical properties based on aerosol synthesis method

Mn-doped Li₃V_2?x Mn _x (PO₄)₃ nanocrystals with enhanced electrochemical properties for lithium-ion batteries were synthesized by aerosol process successfully. The nanocrystals synthesized from aerosol-assisted spray process have an average particle size smaller than 500 nm, with some initial particle size of about 100 nm. The Mn-doped Li₃V₂(PO₄)₃ cathode materials show higher capacity and coulombic efficiency than pure Li₃V₂(PO₄)₃ materials. Especially, the Mn-doped Li₃V_1.94Mn_0.06(PO₄)₃ shows a capacity of 130 mAh/g in the voltage range of 3.0–4.4 V and a coulombic efficiency of 99.5 % at 1C. The results from XRD, SEM, HRTEM, and EIS suggested that lattice changes of Li₃V₂(PO₄)₃ due to Mn doping and the fine particles enabled by aerosol-assisted spray process can significantly reduce the charge-transfer resistance and improve the apparent Li⁺ diffusion coefficient of insertion/desertion in the electrodes, which were the critical reason of better electrochemical performance of Mn-doped Li₃V₂(PO₄)₃ cathode materials.     

Crystal structure of a complex of Pu(VI) nitrate with triphenylphosphine oxide, [PuO<Subscript>2</Subscript>(NO<Subscript>3</Subscript>)<Subscript>2</Subscript>(OP(C<Subscript>6</Subscript>H<Subscript>5</Subscript>)<Subscript>3</Subscript>)<Subscript>2</Subscript>]

Single crystals of [PuO₂(NO₃)₂(TPPO)₂] (TPPO = OPPh₃) isostructural to the related compounds of uranyl and neptunyl were isolated, and the structure of this complex was determined. Contrary to the complexes [AnO₂(TPPO)₄](ClO₄)₂ studied previously, the interatomic distances and volumes of coordination polyhedra of An in these compounds somewhat decrease in the series U-Np-Pu. This difference was attributed to a change in the number of TPPO ligands in the compounds and weakening of their interaction with oxygen atoms of the AnO ₂ ²⁺ groups in passing from [AnO₂(TPPO)₂](ClO₄)₂ to [AnO₂(No₃)₂(TPPO)₂].     

Low temperature sintering and dielectric properties of Ba<Subscript>3</Subscript>(VO<Subscript>4</Subscript>)<Subscript>2</Subscript> microwave ceramics using Co<Subscript>2</Subscript>O<Subscript>3</Subscript> additives

The Ba₃(VO₄)₂–x wt% Co₂O₃ (x?=?0.5–5) ceramics were prepared by the solid state reaction method in order to reduce the sintering temperature. The effects of the Co₂O₃ additions on the phase composition, microstructures, sintering characteristics and microwave dielectric properties of Ba₃(VO₄)₂ ceramics are investigated by an X-ray diffractometer, a scanning electron microscope and a network analyzer. As a result, the Q?×?f value of 54,000 GH, the ε _r of 14.6 and the τ_f value of +58.5 ppm/°C were obtained in the sample of the Ba₃(VO₄)₂–3 wt% Co₂O₃ ceramic sintered at the temperature of 925 °C, which is capable to co-fire with electrode metal of high conductivity such as Ag (961 °C). Moreover, the Q?×?f values of the sample with Co₂O₃ higher than that of 3 wt% additions decreased because of the formation of Ba₂V₂O₇ phase.     

Chemical vapor deposition-based growth of aligned ZnO nanowires on polycrystalline Zn<Subscript>2</Subscript>GeO<Subscript>4</Subscript>:Mn substrates

ZnO nanowires have been grown on polycrystalline Zn₂GeO₄:Mn substrates for the first time using a chemical vapor deposition method. Both Zn and ZnO sources were used to supply Zn vapor in the growth process of ZnO nanowires. The Zn₂GeO₄:Mn substrates were prepared using solid-state ceramic synthesis methods, and average grain sizes of ~1 μm were achieved. The nanowires of diameters in the range of 100–200 nm and length of ~30 μm were observed. In addition to nanowires, other morphologies of ZnO nanostructures, such as ZnO tetrapods, were observed when Zn powder was used as the source for the CVD growth. The results reveal that polycrystalline substrates are also promising as novel alternative substrates for growth of ZnO nanostructures. The as-synthesized ZnO nanowire/Zn₂GeO₄:Mn composites are being developed for future electroluminescent devices.     

Crystallization from high-temperature solutions in the K<Subscript>2</Subscript>O-P<Subscript>2</Subscript>O<Subscript>5</Subscript>-V<Subscript>2</Subscript>O<Subscript>5</Subscript>-Bi<Subscript>2</Subscript>O<Subscript>3</Subscript> system

We have studied general trends of crystallization from high-temperature solutions in the K₂O-P₂O₅-V₂O₅-Bi₂O₃ system at P/V = 0.5?2.0, K/(P + V) = 0.7?1.4, and Bi₂O₃ contents from 25 to 50 wt % and identified the stability regions of BiPO₄, K₃Bi₅(PO₄)₆, K₂Bi₃O(PO₄)₃, and K₃Bi₂(PO₄)_{3 ? x} (VO₄) _x (x = 0?3) solid solutions. The synthesized compounds have been characterized by X-ray powder diffraction and IR spectroscopy, and the structure of two solid solutions has been determined by single-crystal X-ray diffraction (sp. gr. C ₂/c): K₃Bi₂(PO₄)₂(VO₄), a = 13.8857(8), b = 13.5432(5), c = 6.8679(4) Å, β = 114.031(7)°; K₃Bi₂(PO₄)_1.25(VO₄)_1.75, a = 13.907(4), b = 13.615(2), c = 6.956(2) Å, β = 113.52(4)°.     

Synthesis and crystal structure of [UO<Subscript>2</Subscript>(OH)(CO(NH<Subscript>2</Subscript>)<Subscript>2</Subscript>)<Subscript>3</Subscript>]<Subscript>2</Subscript>(ClO<Subscript>4</Subscript>)<Subscript>2</Subscript>

The complex [UO₂(OH)(CO(NH₂)₂)₃]₂(ClO₄)₂ (I) was synthesized. A single crystal X-ray diffraction study showed that compound I crystallizes in the triclinic system with the unit cell parameters a = 7.1410(2), b = 10.1097(2), c = 11.0240(4) Å, α = 104.648(1)°, β = 103.088(1)°, γ = 108.549(1)°, space group \(P\bar 1\), Z = 1, R = 0.0193. The uranium-containing structural units of the crystals are binuclear groups [UO₂(OH)· (CO(NH₂)₂)₃] ₂ ²⁺ belonging to crystal-chemical group AM²M ₃ ¹ [A = UO ₂ ²⁺ , M² = OH^?, M¹ = CO(NH₂)₂] of uranyl complexes. The crystal-chemical analysis of nonvalent interactions using the method of molecular Voronoi-Dirichlet polyhedra was performed, and the IR spectra of crystals of I were analyzed.     

Comparative study of dielectric properties of MgNb<Subscript>2</Subscript>O<Subscript>6</Subscript> prepared by molten salt and ceramic method

Magnesium niobate (MgNb₂O₆) powder was synthesized by the conventional ceramic route as well as by the molten salt route using a eutectic mixture of NaCl-KCl as the salt and Mg(NO₃)₂-6H₂O and TiO₂ as the starting materials. Pure phase of MgNb₂O₆ could be obtained by the molten salt method at 1100°C. However, in ceramic method the pure phase of MgNb₂O₆ was obtained by heating at 1025°C for 20 h. On sintering at 1100°C the dielectric constant and dielectric loss of MgNb₂O₆ obtained by the molten salt method was found to be 19.5 and 0.004 at 100 kHz at room temperature. Lower values were obtained for these oxides prepared by the ceramic route, 16.6 and 0.000518, respectively. In both cases the dielectric constant was quite stable with frequency.     

Synthesis,structure, and properties of the non-centrosymmetric borate Rb<Subscript>2</Subscript>CaB<Subscript>8</Subscript>O<Subscript>26</Subscript>H<Subscript>24</Subscript>

Single crystals of Rb₂CaB₈O₂₆H₂₄, a new non-centrosymmetric borate material, have been grown with sizes up to 8 × 5 × 3 mm³ by the slow evaporation of water solution at room temperature. The structure of the compound was determined by single-crystal X-ray diffraction. It crystallizes in the orthorhombic system, space group P2₁2₁2₁ with a = 11.5288(3) Å, b = 12.6334(4) Å, c = 16.6966(4) Å, Z = 4 and R ₁ = 0.0405, wR ₂ = 0.1043. Ultraviolet (UV)–vis spectrum transmission is performed on the Rb₂CaB₈O₂₆H₂₄, which shows an absorption edge about 195 nm in the UV region. Thermal properties were investigated by TG–DSC analysis. The powder second-harmonic generation (SHG) intensity measured by the Kurtz-Perry method indicates that Rb₂CaB₈O₂₆H₂₄ has about one-third of KDP (KH₂PO₄).The influence of different molar ratios and evaporation speed of water solution on crystal quality and size was also performed on the reported material.     

Characterization of atmospheric corrosion products of zinc exposed to SO<Subscript>2</Subscript> and NO<Subscript>2</Subscript> using XPS and GIXD

A complete characterization of corrosion products formed on zinc plates after exposure in a climatic chamber was conducted in this study. The dry deposition of NO₂, SO₂, and SO₂ + NO₂, at 25 °C and 35 °C, and relative humidity (RH) of 90% was simulated. Pollutant concentrations evaluated were selected to represent highly polluted industrial atmospheric levels. Analysis techniques included X-ray Photoelectron Spectroscopy (XPS) and Grazing Incidence X-ray Diffraction (GIXD). For tests conducted at 25 °C, the relative amount of sulfate was determined to be higher in the SO₂ + NO₂ atmosphere than in the SO₂ atmosphere, and was associated with greater corrosivity in the former atmosphere. NO₂ had an indirect role as a catalyst for SO₂ reduction to sulfate, as evidenced by the greater proportion of sulfate ions detected and the lack of nitrogen compounds in corrosion products. At 35 °C, effect of NO₂ was reduced, and was complicated by a greater tendency for drying so that it was more difficult to maintain the humidity layer. Therefore, no accelerating effect of exposure temperature was observed.     

Partially ordered organic-inorganic nanocomposites in the system UO<Subscript>2</Subscript>SeO<Subscript>4</Subscript>-H<Subscript>2</Subscript>O-NH<Subscript>3</Subscript>(CH<Subscript>2</Subscript>)<Subscript>9</Subscript>NH<Subscript>3</Subscript>

The compound [NH₃(CH₂)₉NH₃]₂[(UO₂)₃(SeO₄)₅(H₂O)₂](H₂O)_x (1) was prepared by isothermal evaporation from aqueous uranyl selenate solutions containing 1,9-diaminononane. A structural study showed that the compound is a partially ordered organic-inorganic nanocomposite. The structural model of the inorganic complex was determined by single crystal X-ray diffraction a = 19.5572(5), c = 47.878(2) Å, V= 15859.1(9) ų, Z= 12; R₁ = 0.1318, wR₂ = 0.3186 for 2808 reflections with |F_o| ≥ 4σ_F). The structure consists of double hydrogen-bonded [(UO₂)₃(SeO₄)₅(H₂O)₂]^2- layers parallel to the (001) plane. The disordered protonated 1,9-diaminononane molecules and water molecules are arranged between the layers. The inorganic layered complex [(UO₂)₃(SeO₄)₅(H₂O)₂]^2- belongs to a new type that was not observed previously in the structures of inorganic and organometallic compounds.