Crystal structure of a double Np(V) ammonium propionate, NH4[(NpO2)3(C2H5COO)4(H2O)]·3H2O

The structure of NH₄[(NpO₂)₃(C₂H₅COO)₄(H₂O)]·3H₂O was studied by single crystal X-ray diffraction. The single crystals were prepared by hydrothermal synthesis. In the structure, there are three crystallographically independent Np atoms with different equatorial surrounding. All of them have CN 7; the coordination polyhedron is a distorted pentagonal bipyramid. Each NpO ₂ ⁺ cation is bonded to four other cations, acting simultaneously as a bidentate ligand and a coordination center for two other dioxocations. The cation-cation interactions result in formation of trigonal-hexagonal cationic networks.     

Non-linearI–V characteristics of doped Sn1−x Ti x O2 (0.0 <x < 0.25) system

The solid solutions of Sn_1−x Ti _x O₂ (0.0 <x < 0.25) were prepared by the usual high temperature ceramic processing techniques with small amounts of dopants such as Nb, Co, Al. The electrical measurements (logI-logV) on the ohmically metal electroded sintered pellets showed the non-linear behaviour. The non-linear coefficient was found to decrease from 12 to 3 with increase inx. On the other hand, the breakdown voltage (E _b) showed the increase with the increase inx. This complex electrical behaviour is explained on the effects of the three dopants (as varistor former, performance enhancer and highlighter) on the microstructural features of the dense pellet.     

Electrical conductivity of α-H x V2O5 (X=0.00-0.27): Dependence of hydrogen concentration and orientation

The dependence of the electrical conductivity, , on the hydrogen concentration and crystallographic orientation has been investigated using single crystals of H_xV₂O₅, which were grown by the Bridgeman method and doped with hydrogen within the solid solubility in the phase by the spillover technique. The temperature dependence of showed the feature of diffusive hopping of thermally activated electrons above 180 K and variable range hopping below 180 K. The dependence of on the crystallographic orientation was little different from that of V₂O₅. The change in with the hydrogen concentration was not monotonic; increases withx up tox }-0.06, but decreases abovex }-0.06. This behaviour can be explained based on the competition between the increase in the carrier density and the depression of the mobility of carriers with increasingx.     

Phase Relations in the Li–V2O5–Cu System at 600°C and Cathodic Properties of Cu x V2O5

The phase relations in the Li–V₂O₅–Cu system at 600°C are studied by x-ray diffraction. The existence of the known vanadium bronzes M _x V₂O₅ (M = Li, Cu) is confirmed, and the composition ranges of the related solid solutions are determined. -Li _x V₂O₅ (0.22 x 0.49) and -Li _x V₂O₅ (0.88 x 1.0) are shown to dissolve Cu, forming Li _x Cu _y V₂O₅ solid solutions with y = 0.72 – 1.48x and y = 0.58 – 0.18x, respectively. Cu _x Li _y V₂O₅ solid solutions (y= 0.51 – 0.76 x) are only obtained from -Cu _x V₂O₅ (0.24 x 0.67). -Li _x V₂O₅ and -Cu _x V₂O₅ form a continuous series of solid solutions. The cathodic properties of Li–V₂O₅–Cu materials in high-temperature pulsed lithium batteries are investigated.     

Defect structure of xY2O3 · (1 − x)TiO2 (x = 0.5–0.58) solid solutions

X-ray diffraction characterization with monochromatic synchrotron X-rays has demonstrated that xY₂O₃ · (1 ? x)TiO₂ (x = 0.5–0.58) solid solutions consist of a fluorite-like (Fm3m) disordered phase and a nanoscale (?40–1000 nm) pyrochlore-like (Fd3m) ordered phase of the same composition, coherent with the disordered phase. In the composition range of the solid solutions (0.5 ≤ x ≤ 0.58), the lattice parameter of the fluorite-like phase follows Vegard’s law. The formation of nanodomains with different degrees of order is shown to be caused by the internal strain due to the high density of structural defects in their unit cells. The materials obtained in this study possess enhanced sorption capacity and can be used as catalysts, catalyst supports, gas sensors, etc.     

The Role of Ca in Superconducting and Magnetic Properties of Y1?x Ca x Ba2Cu3O7?δ (x=0.0–0.30)

We report the structural, superconducting, magnetic and granular properties of Y_1−x Ca _x Ba₂Cu₃O_7−δ ; x=0.0, 0.1, 0.2 and 0.3. Rietveld fitted X-ray diffraction data confirm the single-phase formation for all the samples. The orthorhombicity of the parent compound (x=0.0) decreases and becomes closer to the tetragonal structure for higher Ca concentration. The superconducting transition temperature (T _c) decreases with increasing Ca content due to both over-doping and ensuing disorder in the superconducting CuO₂ planes with Ca doping. DC susceptibility measurements reveal a reduction of the Meissner fraction with Ca doping, suggesting the flux pining effect. The ac susceptibility measurements reveal the enhancement of grain coupling with increasing Ca content in the system. The average grain size is found to increase with Ca doping. Scanning Electron Microscopy (SEM) observations indicate better grain connectivity in terms of narrow grain boundaries for Ca doped samples. It is concluded that limited Ca doping enhances the superconducting performance of the YBa₂Cu₃O_7−δ system.     

Magnetically Recyclable Spinel Mn x Ni1−x Fe2 O 4 (x= 0.0–0.5) Nano-photocatalysts: Structural,Morphological and Opto-magnetic Properties

Manganese doped nickel ferrite (Mn _x Ni_1?x Fe₂ O ₄: x = 0.0–0.5) spinel nanoparticles (NPs) were successfully prepared by a facile microwave combustion method (MCM) using urea as the fuel. The prepared samples were characterized by different techniques. Powder X-ray diffraction (XRD) analysis was confirmed the formation of a single-phase NiFe₂ O ₄ spinel structure. The average crystallite sizes of the samples were in the range of 11.49 to 17.24 nm, which was confirmed by Sherrer’s formula. The morphology of the samples showed a nanoparticle-like structure with smaller agglomeration, which was confirmed by high-resolution scanning electron microscopy (HR-SEM). The particle size diameter ranges from 15 to 20 nm, which was confirmed by high-resolution transmission electron microscopy (HR-TEM). Energy dispersive X-ray (EDX) analysis confirmed the elemental composition, which was also evidence for the formation of single pure phase. Selected area electron diffraction (SAED) analysis showed well crystalline nature. UV-visible diffuse reflectance spectra (DRS) and photoluminescence (PL) spectrum analysis was used to calculate the optical band gap, and the values are slightly increased (2.02 to 2.42 eV) with increasing the Mn-dopant, due to the decreasing of particle size, which may be due to the quantum confinement effect. Magnetic properties of the samples were analyzed by vibrating sample magnetometer (VSM) technique, which showed the magnetization (M _s ) value of the samples are increased with increasing Mn content and reach a maximum value of 67.82 emu/g for Mn_0.5Ni_0.5Fe₂ O ₄ sample. Photo-catalytic activity of the samples was measured and showed the photocatalytic degradation (PCD) of methylene blue dye with good results. The catalyst was magnetically recycled and reused five consecutive cycles and showed good reproducibility without change of catalytic activity.     

Magneto-transport and Magnetic Susceptibility of SmFeAsO1−x F x (x=0.0 and 0.20)

We report superconductivity in the SmFeAsO_1?x F _x for the x=0.2 system being synthesized using the single step solid state reaction route. Rietveld analysis of room temperature X-ray diffraction (XRD) data shows the studied samples, SmFeAsO_1?x F _x with x=0.0 and x=0.2, are crystallized in a single phase tetragonal structure with space group P4/nmm. The resistivity measurement shows superconductivity for the x=0.20 sample with T _c (onset) ～51.7 K. The upper critical field, [H _c2(0)] is estimated ～3770 kOe by Ginzburg–Landau (GL) theory. Broadening of superconducting transition in magnetotransport is studied through thermally activated flux flow in an applied field up to 130 kOe. The flux flow activation energy (U/k _B ) is estimated ～1215 K for 1 kOe field. Magnetic measurements exhibited bulk superconductivity with lower critical field (H _c1) of ～1.2 kOe at 2 K. In the normal state, the paramagnetic nature of compound confirms no trace of magnetic impurity, which orders ferromagnetically. AC susceptibility measurements have been carried out for SmFeAsO_0.80F_0.20 sample at various amplitude and frequencies of applied AC drive field. The intergranular critical current density (J _c ) is estimated. Specific heat [C _p (T)] measurement showed an anomaly at around 140 K due to the SDW ordering of Fe, followed by another peak at 5 K corresponding to the antiferromagnetic (AFM) ordering of Sm⁺³ ions in the SmFeAsO compound. Interestingly, the change in entropy (marked by the C _p transition height) at 5 K for Sm⁺³ AFM ordering is heavily reduced in the case of the superconducting SmFeAsO_0.80F_0.20 sample.     

Phase structure and microwave dielectric properties of Mn-doped (1−x)ZrTi2O6–xZnNb2O6(x = 0.13–0.53) ceramics

(1?x)ZrTi₂O₆–xZnNb₂O₆(x = 0.13–0.53) ceramics doped with 0.7 wt% MnCO₃ were prepared by solid-state reaction and they were all sintered well in air at 1,270 °C. XRD analysis suggested there were a two-phase region for ZrTi₂O₆–TiO₂(x = 0.20–0.33) and a single-phase region for ZrTi₂O₆(x = 0.40–0.53) because (Zn_1/3Nb_2/3)⁴⁺ preferentially substituted Ti⁴⁺ sites, and thereafter Zr⁴⁺ sites. The addition of Mn, working as acceptors to receive the electrons left by the lost oxygen, raised the Q × f value dramatically. For 0.7 wt% MnCO₃ doped (1?x)ZrTi₂O₆–xZnNb₂O₆ ceramics, with the increase of x, the ε_r and the τ_f dropped from 53.4 to 41.0 and from +95 ppm/°C to ?35 ppm/°C respectively, and the Q × f value increased from 26,300 GHz to 48,100 GHz. At last, 0.69ZrTi₂O₆–0.31ZnNb₂O₆+0.7 wt % MnCO₃ ceramics showed excellent dielectric properties: ε_r = 45.3, Q × f = 43,300 GHz and τ_f = ?0.5 ppm/°C. Another advantage is that the sintering atmosphere was in air, which is benefit to the commercial application.     

Synthesis and crystal structure of americium(V) dichromate, Cs3AmO2(Cr2O7)2·H2O

A new Am(V) chromate complex with outer-sphere cesium cation, Cs₃AmO₂(Cr₂O₇)₂·H₂O, was prepared from aqueous solution. Its composition and structure were determined by single crystal X-ray diffraction. The Am(V) atom has coordination surrounding in the form of a distorted pentagonal bipyramid with the O atoms of the AmO ₂ ⁺ group in apical positions. The equator of the bipyramid is formed by the O atoms of four dichromate groups and of the water molecule. The mean bond lengths (Å) are as follows: Am=O 1.802(5), Am-O(Cr₂O₇) 2.443(6), and Am-O_w 2.519(6). The Am(V) pentagonal bipyramids are combined via bidentate bridging Cr₂O ₇ ^2? anions into infinite chains [AmO₂(Cr₂O₇)₂H₂O] _n ^3? arranged in layers parallel to the series of diagonal planes (111). A system of hydrogen bonds links the chains in a layer and the layers with each other. The Cs cations are arranged between the layers, forming cationic interlayers.     

Crystal structure of mixed-valent Np(IV)/Np(V) chloride, [Np(NpO2)6(H2O)8(OH)Cl9]·H2O

A new mixed-valent Np(IV)/Np(V) chloride, [Np(NpO₂)₆(H₂O)₈(OH)Cl₉]·H₂O, was synthesized, and its crystal structure was determined. The crystals consist of NpO ₂ ⁺ and Np⁴⁺ cations, of Cl^? and OH^? anions, of coordination-bonded water molecules, and of water molecules of crystallization. The Np(V) atom, Np(1), has pentagonal bipyramidal coordination surrounding with O atoms in the apical position and with the equatorial plane formed by three Cl^? anions, O atom of the adjacent NpO ₂ ⁺ cation, and O atom of water molecule. The mutual coordination of the neptunyl(V) ions, cation-cation (CC) interaction, links the Np(1) coordination polyhedra via common vertices into rings around sixfold axes, with the Np(V)?Np(V) distance in these fragments of 4.276 Å. The ring fragments are linked with each other via common equatorial edges of the bipyramids into layers perpendicular to c-axis. The Np(IV) atom, Np(2), has coordination surrounding in the form of tricapped trigonal prism (CN 9) with the tetragonal lateral faces formed by the O atoms of the NpO ₂ ⁺ cations and the capping positions occupied by the O atoms of two water molecules and one hydroxy group. The Np(2) atoms act in CC interactions as coordination center for six NpO ₂ ⁺ ions, with the Np(IV)?Np(V) distance of 4.183 Å. The Np(2) polyhedra are arranged in the crystal between layers of the Np(1) coordination polyhedra, linking them with each other.     

Crystal Structure of Neptunium(V) Phthalate (NpO2)2(OOC)2C6H4·4H2O

The crystal structure of (NpO₂)₂(OOC)₂C₆H₄·4H₂O [rhombic cell: a = 15.937(3), b = 26.922(5), c = 8.020(2) Å, space group Pbcn, Z = 8, V = 3441.0(12) ų, d _calc = 2.988 g cm^{- 3}, CAD4, MoK , graphite monochromator, 2934 independent reflections; R ₁ = 0.0352, wR ₂ = 0.0951] was studied. The structure consists of NpO₂ ⁺ cations, H₄C₆(COO)₂ ^{2 -} anions, and molecules of coordinated and crystallization water. The crystal lattice involves neutral layers [(NpO₂)₂(OOC)₂C₆H₄(H₂O)₃] _n parallel to the {101} plane. The dioxocations in these layers are bonded to each other to form cationic networks [the Np···Np distance is 3.911(1)-4.202(1) Å]. The coordination polyhedra of Np(1) and Np(2) are pentagonal bipyramids (CN 7). The point group of the neptunyl(V) groups is close to D _h. These groups are bidentate ligands in the cation-cation interaction. The Np = O bond lengths are 1.852(6) [Np(1)-O(1)], 1.849(7) [Np(1)-O(2)], 1.845(7) [Np(2)-O(3)], and 1.841(7) Å [Np(2)-O(4)]; the O = Np = O bond angles are 178.6(3)° [O(2)-Np(1)-O(1)] and 177.4(3)° [O(3)-Np(2)-O(4)]. The equatorial plane of the Np(1) bipyramid consists of two oxygen atoms of adjacent Np(2)O₂ ⁺ dioxocations, two water molecules, and a single oxygen atom of the phthalate anion. The equatorial plane of the Np(2) bipyramid consists of two oxygen atoms of adjacent Np(1)O₂ ⁺ dioxocations, two oxygen atom of the phthalate anion, and a single water molecule. The bond lengths in the equatorial plane of the bipyramid lie in the following ranges: Np-Oyl 2.373(7)-2.437(7) Å (average 2.397 Å) , Np-Ophth 2.360(7)-2.474(7) Å (average 2.431 Å), and Np-Owater 2.534(8)-2.558(9) Å (average 2.544 Å). The phthalate anions are tridentate bridging ligands binding neptunium atoms only within a single cationic network.     

Framework materials containing polyoxovanadates as building units: synthesis and characterization of (N2H5)2[M3(H2O)12V18O42(EO4)]·24H2O (M = Mg,Ca) and Li6[Mn3(H2O)12V18O42(EO4)]·24H2O (E = V,S)

The reaction of an aqueous solution of lithium vanadate with hydrazinium sulfate results in a dark-colored solution that reacts with magnesium sulfate heptahydrate, calcium sulfate dihydrate, and manganese(II) chloride tetrahydrate to yield single crystals of (N₂H₅)₂[M₃(H₂O)₁₂V₁₈O₄₂(EO₄)]·24H₂O (M = Mg, Ca) and Li₆[Mn₃(H₂O)₁₂V₁₈O₄₂(EO₄)]·24H₂O (E = V, S), respectively. The crystal structures of the new solids consist of interpenetrating three-dimensional networks of {V₁₈O₄₂(EO₄)} clusters interlinked via bridging {M(H₂O)₄} (M = Mg, Ca, Mn) groups. The voids in these structures are occupied by lattice water and ion exchangeable cations.     

Proton Conductivity in H2 – x (NH4) x V9Mo3O32.5 – δ · nH2O Xerogel Films

The electrical conductivity of _{2 – x} (NH₄) _x V₉Mo₃O_{32.5 –} · nH₂O xerogel films containing different amounts of ammonium ions and water was measured as a function of temperature. The results demonstrate that, in a wide temperature range, the proton conductivity of the films reaches a maximum atx= 1.5. The activation energy of conductivity in the films, equal to 0.1–0.2 eV at low temperatures, rises upon partial dehydration above 100°C. The possible mechanisms of proton formation and transport are discussed.     

Electrical Conductivity of H2V12 – y W y O31 + δ · nH2O and H x V x W1 – x O3 · nH2O

The electrical conductivity of H₂V_{12 – y} W _y O_{31 +} · nH₂O (0 y 3) and H _x V _x W_{1 – x} O₃ · nH₂O (x = 0, 0.08, 0.17, 0.25, 0.33) prepared by the sol–gel method was measured between 293 and 473 K at a relative humidity of 12%. Partial substitution of tungsten for vanadium or V⁵⁺ and H⁺ for tungsten was found to reduce the conductivity of the phases studied. The only exception is the x = 0.33 phase. Below 373 K, the activation energy of conduction is 0.22–0.29 eV in the amorphous phases (0 y 3; x= 0.25, 0.33) and 0.06–0.11 eV in the crystalline phases (x = 0, 0.08, 0.17). The possible mechanisms of electrical transport are discussed.     

Relationship between pinning mechanism and excess conductivity analysis of x wt% C4H6O5 (x = 0.0, 4.0, and 6.0)-added bulk MgB2

Journal of Materials Science: Materials in Electronics - The influence of x wt% C4H6O5 (malic acid) (x?=?0.0, 4.0, and 6.0) addition on excess conductivity in bulk MgB2 superconductors...     

Fast ion transport in the new mixed system (CuI)x·[(Ag2O)2·(V2O5)]100−x (40≤x≤80)

The new mixed system (Cul) _x ·[(Ag₂O)₂·V₂O₅)]_100–x where x=40, 45, 50, 55, 60, 65, 70, 75 and 80 mol% was investigated as a possible glassy fast ion conductor by preparing molten mixtures and quenching them to low temperatures. The analysis of their composition was carried out using differential scanning calorimetry (DSC) and powder X-ray diffraction (XRD) techniques. These studies have confirmed the formation of new substances. Formation of AgI in some samples was also revealed by XRD analysis and by the occurrence of a characteristic phase transition temperature around 420 K identified through DSC experiments as well. Detailed temperature-dependent a.c. electrical conductivity studies were carried out on the new materials by a.c. impedance analysis in the frequency range 65.5 kHz-1 Hz and over the temperature range 293 to 398 K. It has been found that the highest electrical conductivity of 3.64×10^–3 S cm^–1 at 305 K due to the migration of Ag⁺ ions and the lowest activation energy of 0.1 eV in the above temperature range of investigation could be realized for the composition 40CuI-40Ag₂O-20V₂O₅ in the mixed system.     

Crystal structure and optimized microwave dielectric properties of (1 − x) LiZn0.5Ti1.5O4–xTiO2 ceramics for application in dielectric resonator

Microwave dielectric ceramics with the composition of (1?x) LiZn_0.5Ti_1.5O₄ (LZT)–xTiO₂ (0.05 ≤ x ≤ 0.4) were prepared by a solid-state reaction route. XRD patterns revealed that the samples consist of LiZn_0.5Ti_1.5O₄ and rutile TiO₂, and the amount of rutile TiO₂ phase increased with increasing the x values. The microwave measurements show that the dielectric properties of ceramics can be improved with increasing x values. When x = 0.1, the temperature coefficient of resonant frequency (τ _f ) of 0.9LZT–0.1TiO₂ ceramic can be adjusted to a near-zero value of ?1 ppm/°C, and permittivity (ε_r) and Q × f value are 26 and 45,000 GHz, respectively. These results indicate that 0.9LZT–0.1TiO₂ ceramic can be a candidate in microwave dielectric resonators.     

Sintering and properties of SrBi2(Ta1−x V x )2O9 ceramics

The effects of vanadium doping on the sintering, microstructure, dielectric properties, and ferroelectric properties of SrBi₂(Ta_1–x V _x )₂O₉ ceramics were investigated. The densification and grain-growth processes of the vanadium doped ceramics were shifted to a lower temperature range. For the ceramics with relative density 90%, the dielectric constant is 120–125 and 100–130 for the undoped and doped ceramics, respectively, and the dielectric loss tangent is below 1%. As compared with the undoped ceramics, the ferroelectric properties can be significantly improved by doping with an appropriate amount of vanadium and sintering at 1000°C. The variations of dielectric and ferroelectric properties are influenced by the incorporation of vanadium into crystal lattice and several microstructural factors.