Substitution Of V5 Research Articles

A novel Li3Mg4(Nb1-xVx)O8 ceramic with high Q×f value and good temperature stability with low sintering temperature

A series of low-loss Li3Mg4(Nb1-xVx)O8 (0.02 ≤ x ≤ 0.08) ceramics has been synthesized in this work, with the optimal sintering temperature lowered to 950°C due to the incorporation of V5+ ions. Moreover, the effects of substituting V5+ for Nb5+ on the sintering, composition, structure and properties of the ceramics have been systematically analyzed. It has been discovered that the permittivity (εr) and quality factor (Q×f) of Li3Mg4(Nb1-xVx)O8 ceramics exhibit a correlation with the relative density, which is influenced by the variation in grain size distribution resulting from the substitution of V5+ ions. Additionally, the total lattice energy of Li3Mg4(Nb1-xVx)O8 ceramics is also affected by the bond characteristics within the Nb-O octahedra, thus influencing the Q×f value. The resonant frequency temperature coefficient (τf) fluctuates within a small range. The Li3Mg4(Nb0.98V0.02)O8 ceramics exhibit excellent microwave dielectric properties at 950°C: εr∼14.03, Q×f∼93,425 GHz, τf∼-6.12 ppm/°C, with a relative density reaching 98.3 %. Compared to unsubstituted Li3Mg4NbO8 ceramics, the sintering temperature is reduced by 200°C without forming impurity phases. While adjusting the τf value to nearly zero, it maintains a high Q×f value, indicating promising applications in Low-Temperature Co-fired Ceramics (LTCC).

Facile Al2O3 coating suppress dissolution of Mn2+ in Mn-substituted Na3V2(PO4)3 with outstanding electrochemical performance for full sodium ion batteries

Na3V2(PO4)3 (NVP) encounters significant obstacles, including limited intrinsic electronic and ionic conductivities, which hinder its potential for commercial feasibility. Currently, the substitution of V3+ with Mn2+ is proposed to introduce favorable carriers, enhancing the electronic conductivity of the NVP system while providing structural support and stabilizing the NASICON framework. This substitution also widens the Na+ migration pathways, accelerating ion transport. Furthermore, to bolster stability, Al2O3 coating is applied to suppress the dissolution of transition metal Mn in the electrolyte. Notably, the Al2O3 coating serves a triple role in reducing HClO4 concentration in the electrolyte, inhibiting Mn dissolution, and functioning as the ion-conducting phase. Likewise, carbon nanotubes (CNTs) effectively hinder the agglomeration of active particles during high-temperature sintering, thereby optimizing the conductivity of NVP system. In addition, the excellent structural stability is investigated by in situ XRD measurement, effectively improving the volume collapse during Na+ de-embedding. Moreover, the Na3V5.92/3Mn0.04(PO4)3/C@CNTs@1wt.%Al2O3 (NVMP@CNTs@1wt.%Al2O3) possesses unique porous structure, promoting rapid Na+ transport and increasing the interface area between the electrolyte and the cathode material. Comprehensively, the NVMP@CNTs@1wt.%Al2O3 sample demonstrates a remarkable reversible specific capacity of 122.6 mAh/g at 0.1 C. Moreover, it maintains a capacity of 115.9 mAh/g at 1 C with a capacity retention of 90.2 mAh/g after 1000 cycles. Even at 30 C, it achieves a capacity of 87.9 mAh/g, with a capacity retention rate of 84.87 % after 6000 cycles. Moreover, the NVMP@CNTs@1wt.%Al2O3//CHC full cell can deliver a high reversible capacity of 205.5 mAh/g at 0.1 C, further indicating the superior application potential in commercial utilization.

Low-temperature sintering vanadium-substituted ZnNb2O6 microwave dielectric ceramics for LTCC applications

The ZnNb2-xVx/2O6-1.25x (0.1 ≤ x ≤ 0.6) dielectric ceramics were synthesized through conventional solid-state technique and sintered at 925 °C–975 °C for 6 h. The specimens with the substitution of V5+ for Nb5+ could be sintered at a lower temperature than pure ZnNb2O6 ceramic, densifying the microstructure more densely and improving the quality factor. Density analysis proves that the dielectric constant is related to the relative density. In addition, the [NbO6] octahedral distortion, the bond valence and the average bond energy of the Nb–O bond also change, leading to a nonlinear variation for the temperature coefficient of the resonance frequency from x = 0.1 to 0.6. The ZnNb2-xVx/2O6-1.25x (x = 0.2) ceramics sintered at 950 °C exhibited the superior characteristic while taking into account the applications of low temperature co-fired ceramics technology. Not only did it possesses outstanding dielectric performances of εr = 22.25, Q×f = 51,701 GHz, and τf = −67.02 ppm/°C, but also has excellent chemical compatibility with the widely used Ag electrode.

Low temperature sintered Li6MgTiNb1-xVxO8F microwave dielectric ceramics with high-quality factor

Li6MgTiNb1−xVxO8F (0 ≤ x ≤ 0.08) ceramics were prepared using a solid-state reaction. The correlations between their sintering characteristics and the microwave dielectric performance as functions of V5+ substitution and sintering temperature were investigated systematically. Rietveld refinements of the X-ray diffraction data showed that all the samples had a cubic rock-salt structure. The Li6MgTiNbO8F ceramic sintered at 1175 °C exhibited an attractive Q × f value of 105,700 ± 1600 GHz. The substitution of V5+ for Nb5+ decreased the sintering temperature while improving the relative density and relative permittivity. The V-beared Li6MgTiNb0.98V0.02O8F ceramic sintered at 850 °C showed outstanding dielectric properties of εr = 18.14 ± 0.05, Q × f = 58,300 ± 1300 GHz, and τf = −42.66 ± 0.33 ppm/°C. Good chemical compatibility with Ag electrodes highlighted the potential of the ceramic in low-temperature co-fired ceramic applications.

Modulating Na vacancies of Na4FeV(PO4)3 via Zr-substitution: Toward a superior rate and ultrastable cathode for sodium-ion batteries

The Na Super Ionic Conductor (NASICON)-type Na3V2(PO4)3 has aroused enormous attentions as the cathode material for sodium-ion batteries. However, the scarcity of vanadium resources and toxicity of vanadium complexes limit its large-scale application. Herein, we use a reductive acid assisted sol-gel method to replace half of V3+ in Na3V2(PO4)3 with Fe2+ for synthesizing a NASICON-structure Na4FeV(PO4)3/C, and substitute V3+ in Na4FeV(PO4)3 by small amount of Zr4+ for fabricating a series of Na4-xFeV1-xZrx (PO4)3/C (x = 0.1 and 0.2) materials. The substitution of V3+ by Fe2+ shows reduced cost, low toxicity, and increased Na+ concentration in per formula unit; while the substitution of V3+ by Zr4+ indicates expanded unit cell volume and abundant Na vacancies, which facilitate Na+ mobility and inherent electronic conductivity. Consequently, Na3.9FeV0.9Zr0.1(PO4)3/C electrode exhibits high discharge capacity (114 mAh g−1 at 0.1C), superior rate capability (66.7 mAh g−1 at 40C), and remarkable cyclic stability (capacity retention of 82.4% after 4000 cycles at 20C). The kinetic analyses and ex-situ characterizations confirm that small volume change (5.21%) and highly reversible redox reaction (Fe2+/3+ and V3+/4+) occur during the electrochemical process.

Substitution of V5+ in BiVO4 with Ni2+ and the Improved Photocatalytic Degradation of Crystal Violet Under White LED Light Irradiation

Substitution of V5+ in BiVO4 with Ni2+ and the Improved Photocatalytic Degradation of Crystal Violet Under White LED Light Irradiation

Double Donors Tuning Conductivity of LiVPO4F for Advanced Lithium-Ion Batteries.

To fulfill the increasing demand of lithium-ion batteries for realizing high energy density and great cycling stability under high rate, the cathode material capable of efficient electron and Li+-ion transportation is necessarily demanded. Herein, we propose a double-donor doping strategy by taking the carbon-coated LiVPO4F as a model system. The Hall effect confirms that either or both Mg2+ substitution of Li+ and Nb5+ substitution of V3+ cause the carrier-type transformation from p-type to n-type. The great enhancements of electronic conductivity and ionic conductivity are realized in Li0.995Mg0.005V0.98Nb0.02PO4F, which also exhibits a markedly improved Li+ diffusion coefficient and reduced electrochemical polarization. The carbon-coating layer can effectively prevent the decomposition reaction of electrolyte, allowing for good structural stability of Li0.995Mg0.005V0.98Nb0.02PO4F when suffering fast Li+ insertion/extraction. As expected, the Li0.995Mg0.005V0.98Nb0.02PO4F cathode exhibited superior electrochemical properties with an initial discharge capacity of 124.5 mA h g-1 and capacity retention of 97.3% after 600 cycles at 1.6C. Even under a high rate of 8C, the discharge energy density was 392 Wh kg-1 at the beginning and showed a retention rate of 84.4% after 2000 cycles.

Low loss and low temperature sintering of Li3Mg2NbO6 ceramics for LTCC applications

We fabricated the low loss Li3Mg2NbO6-xV2O5 (x = 0.25–1.25 wt%)ceramics by the solid-state reaction procedure and discussed the impacts of V2O5 addition on the phase structure, sintering characteristics, microstructure, grain growth, grain size and microwave dielectric characterizations of Li3Mg2NbO6-xV2O5 ceramics. Single-phase Li3Mg2NbO6 orthorhombic structure was obtained for all compositions and substitution of V5+ ions for Nb5+ ions occurred. Homogeneous and dense microstructures with grain size of ∼11.2 μm could be observed when sintered at 925 °C, indicating that suitable V2O5 addition content promoted the grain growth. The relative permittivity was associated with the relative density and the Q × f value was correlated to the grain size and relative density. The τf value was relevant to the porosity corrected relative permittivity. Remarkable microwave dielectric properties: εr = 15.1, Q × f = 91,000 GHz (9.76 GHz) and τf = −24 ppm °C−1 were acquired for the samples with x = 1 wt%, indicating a potential for LTCC applications.

Transport properties of rocksalt-type cluster sulfides V4GeS8 and Mn substitution effect

We experimentally and theoretically investigated the electronic and thermoelectric properties of rocksalt-type cluster sulfides V4-xMnxGeS8 (x = 0, 0.02, 0.05). For a polycrystalline sample of V4GeS8, the lnρ-T−1 curve shows good linearity over 250 K. On the other hand, the lnρ-T−1/4 curve shows linearity at less than 250 K. This result indicates that the Arrhenius type is dominant over 250 K and the 3D variable range hopping is dominant in the low-temperature region. For the Mn substitution V4-xMnxGeS8 (x = 0.02, 0.05), the absolute value of ρ and S decreases with increasing x. This result indicates that the hole doping occurred by the substitution of V3+ to Mn2+. The calculated HOMO of V4GeS8 using density functional theory calculation shows that the V-3d orbital in the V4S4 cluster is dominant. This result indicates that the conduction holes pass through V4S4 to other V4S4.

A thermodynamic investigation on the substitution mechanism of Mg-doped lithium vanadium phosphate

Monoclininc lithium vanadium phosphate, Li3V2(PO4)3, is regarded as a potential cathode material for the next generation of high-performance lithium ion batteries, since it exhibits a high discharge voltage (up to ∼4.1 V) and a large theoretical specific capacity (197 mAhg−1). However, the low intrinsic electronic conductivity of Li3V2(PO4)3, which is a prevailing challenge for olivine type compounds, inhibits its use in commercial applications. Although the substitution of V3+ by other cation species is a common procedure to increase the conductivity and electrochemical performance of Li3V2(PO4)3, the underlying mechanisms for the improved properties are not yet well understood. Therefore, a thermodynamic approach is used in this work to investigate the influence of dopant, i.e. Mg2+ as well as vacancies on the V3+ site on the stability of the resulting materials. On the basis of the measured partial molar Gibbs energies, entropies and enthalpies of the electrochemical reaction, a detailed discussion of the substitution mechanisms and their influence on the electrochemical performance is presented.

Structure and properties of vanadium-doped α-MnO2 and enhanced Pb2+ adsorption phenol/photocatalytic degradation

Vanadium (V)-doped cryptomelane was synthesized and characterized by powder X-ray diffraction, electron microscopy, N2 adsorption, diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy and X-ray absorption spectroscopy. Vanadium doping does not change the basic crystal structure but slightly decreases the lattice parameters (a, b, c, β and cell volume) and increases the coherent scattering domain (CSD) sizes (16–19 nm). These V-doped cryptomelane materials are granular particles with increased specific surface areas (149–183 m2 g−1) and increased concentrations of hydroxyl groups on the surfaces with increasing V doping. Both V 2p3/2 spectra and V K-edge X-ray absorption near edge spectroscopy indicates that V exists in +5. Substitution of V5+ for Mn4+ in cryptomelane framework results in reduction in Mn average oxidation state and increase in bond lengths of Mn-O in [MnO6] unit, edge- and corner-sharing Mn-Mn(V) pairs. These V-doped materials have greatly increased adsorption capacities for Pb2+ (937–1146 mmol kg−1). Doping ∼1.4 wt.% V can significantly enhance cryptomelane optical absorption properties and thus photocatalytic degradation of phenol, i.e., with a TOC removal rate of ∼77%. These results can facilitate the modification and application of environmental friendly Mn oxide materials in pollution control and remediation.

Effects of Transiotion Metal Co-Doping on the Electrochemical Properties of Li3V2-2xFexMnx(PO4)3/Graphene Cathode Material for Lithium Secondary Battery

A series of Fe and Mn co-doped Li3V2–2xFexMnx(PO4)3/graphene (x = 0, 0.005, 0.010, 0.015, 0.020, and 0.025) samples have been fabricated via a sol-gel assisted microwave synthesis method. The crystal structure and morphology of the synthesized Li3V2–2xFexMnx(PO4)3/graphene was investigated using an X-ray diffraction (XRD) and a scanning electron microscopy (SEM) systematically. Electrochemical measurement results prove that the Li3V1.98Fe0.01Mn0.01(PO4)3/graphene sample presents the best electrochemical performance as the cathode material for lithium ion batteries among the as-prepared samples in the potential ranges of 3.0–4.8 V. The resulting Li3V1.98Fe0.01Mn0.01(PO4)3/graphene cathode has an excellent specific capacity of 184.4 mAh g−1 at 0.1C rate, and even at 10C rate, it still delivers the specific capacity of 110.5 mAh g−1. The substitution of V3+ with an appropriate amount of Fe2+ and Mn4+ increases the Li+ diffusion coefficient assuming from the electrochemical impedance spectroscopy results, which is mainly responsible for the excellent electrochemical performance. Figure 1

Synthesis, Characterization, and Electrochemical Performance of Ce-Doped Ordered Macroporous Li3V2(PO4)3/C Cathode Materials for Lithium Ion Batteries

A series of Ce3+-doped ordered macroporous Li3V2–xCex(PO4)3/C (x = 0, 0.01, 0.03, 0.05) samples have been fabricated via a colloidal crystal template method. The X-ray powder diffraction and scanning electron microscopy analysis demonstrate that the Ce element doping does not affect the original monoclinic structure and macroporous morphology of the pristine Li3V2(PO4)3/C sample. Electrochemical measurement results prove that the Li3V1.97Ce0.03(PO4)3/C sample presents the best electrochemical performance as the cathode material for lithium ion batteries among the as-prepared samples in the potential ranges of both 3–4.3 V and 3–4.8 V. The substitution of V3+ with an appropriate amount of Ce3+ increases the Li+ diffusion coefficient based on the electrochemical impedance spectroscopy results, which is mainly responsible for the excellent electrochemical performance.

Compressibility of mimetite and pyromorphite at high pressure

High pressure X-ray diffraction experiments on mimetite [Pb5(AsO4)3Cl] and pyromorphite [Pb5(PO4)3Cl] were performed up to 14.1 and 14.9 GPa, respectively, at 300 K, using in situ angle-dispersive X-ray diffraction and a diamond anvil cell. No phase transition of mimetite and pyromorphite was observed within the experimental pressure range. Fitting the P–V data under hydrostatic stress conditions with a third-order Birch–Murnaghan Equations of State (BM-EoS) we obtained: K 0=46(7) GPa, V 0=680(2) Å3, and K 0′=15(4) for mimetite; K 0=44(5) GPa, V 0=636(1) Å3, and K 0′=15(3) for pyromorphite. The axial compressibility was also calculated with a third-order ‘linearized’ BM-EoS. We obtained K 0a :K 0c =1:1.00 for mimetite, and K 0a :K 0c =1:1.28 for pyromorphite, indicating that mimetite and pyromorphite are elastically isotropic and slightly anisotropic, respectively. Comparing the previous equation of state data of vanadinite [Pb5(VO4)3Cl] with the current results of mimetite [Pb5(AsO4)3Cl] and pyromorphite [Pb5(PO4)3Cl], we found that the substitution of V5+ by As5+ and P5+ has an insignificant effect on the bulk modulus, but has a greater effect on the axial parameters, compression ratio, and elastic anisotropy.

Investigation of phase stability and oxide ion performance in new perovskite-type bismuth vanadate

Samples of the BICDVOX system, formulated as Bi4CdxV2−xO11−(3x/2)−δ in the Cd substitution range 0 ≤ x ≤ 0.25 were synthesized using the standard solid state reaction.The correlation between phase stability and oxide ion performance were investigated by variable temperature XRPD, DSC and AC impedance spectroscopy. The substitution of V5+ by Cd2+ exhibited different phase transitions upon varying composition. For compositions with x ≤ 0.05, two successive transitions; α↔β↔γ are evident, while the β↔γ transition exists in the composition range 0.05 < x < 0.175. However, some temperature dependent phenomena confirmed the exixtence of the γ′↔γ transition, coupled with the tetragonal symmetry stabilization for x ≥ 0.175. The maximum oxide ion conductivity at lower temperatures was observed for x = 0.20. It has also been found that the slow V4+ → V5+ re–oxidation results in increased defect trapping effects in the system at higher temperatures.

Preparation and Photocatalytic Mechanism of Vanadium Doped NaTaO3 Nanoparticles

Pure and vanadium doped NaTaO3 nanoparticles were synthesized by hydrothermal conditions. From XRD studies, both pure as well as vanadium doped NaTaO3 are found to show pure orthorhombic phase of tatanlate. STEM studies show the formation of cube shape particles in all the samples with a particle size about 70 nm. UV-vis diffuse reflectance spectra clearly indicates the red-shift in the series of vanadium doped NaTaO3 catalysts, resulting in a decrease in the band gap of NaTaO3 caused by substitution of V5+ ions at Ta5+ site with an increase of vanadium doping concentration in NaTaO3. The results reveal that Vanadium doped NaTaO3 show good photocatalytic performance under visible light and RhodamineB (RB) degradation is improved with Vanadium doping. The photocatalytic mechanism was discussed by density functional theory. V5+ ions substitution of Ta5+ ions results in an intermediate band (IB) below the bottom of the conduction band (CB), which is mainly attributed to the state of V 3d. Meanwhile the broadening of valence band is formed due to the hybridization between the V 3d and O 2p states. Both these factors increase the transient behavior of the photogenerated charge carriers and inhibit the recombination of e–h+ pairs, showing enhanced activities over the entire visible region.

Influence of vanadium doping on the behavior of YBa2Cu3O7-y

YBa3Cu3-xVxO7-y(x=0, 0.1, 0.2, 0.3, 0.4, 0.S and 0.6) superconductors have been prepared. X-ray diffraction shows that the system remains orthorhombic for all compositions studied, but for x > 0.4 V2O5 was detected at an impurity phase. Substitution of V5+ for Cu2+ occurs in the Cu(2) sites on the Cu(2)—O planes. The introduction of the high valence element, vanadium, produces the extra free-electrons. These electrons recombine with the positive carrier of the system. It makes depression of the mobility and the Hall number of =YBa2 Cu3-xVO7-y and also results in a depression of TC.

145 The V1/V2 Loop Region of Simian-Human Immunodeficiency Virus Envelope gp120 is the Major Determinant of the Strain Specificity of the Neutralizing Antibody Response

Plasma samples from individuals infected with human immunodeficiency virus type 1 (HIV-1) are known to be highly strain-specific in their ability to neutralize HIV-1 infectivity. Such plasma samples exhibit significant neutralizing activity against autologous HIV-1 isolates but typically exhibit little or no activity against heterologous strains. Monkeys infected with the simian-human immunodeficiency virus (SHIV) clone DH12 generated antibodies that neutralized SHIV DH12 but not SHIV KB9. Conversely, antibodies from monkeys infected with the SHIV clone KB9 neutralized SHIV KB9 but not SHIV DH12. To investigate the role of the variable loops of the HIV-1 envelope glycoprotein gp120 in determining this strain specificity, variable loops 1 and 2 (V1/V2), 3 (V3) or 4 (V4) were exchanged individually or in combination between SHIV DH12 and SHIV KB9. Despite the fact that both parental viruses exhibited significant infectivity and good replication in the cell lines examined, three of the ten variable loop chimeras exhibited such poor infectivity that they could not be used further for neutralization assays. These results indicate that a variable loop that is functional in the context of one particular envelope background will not necessarily function within another. The remaining seven replication-competent chimeras allowed for unambiguous assignment of the sequences principally responsible for the strain specificity of the neutralizing activity present in SHIV-positive plasma. Exchange of the V1/V2 loop sequences conferred a dominant loss of sensitivity to neutralization by autologous plasma and gain of sensitivity to neutralization by heterologous plasma. Substitution of V3 or V4 had little or no effect on the sensitivity to neutralization. These data demonstrate that the V1/V2 region of HIV-1 gp120 is principally responsible for the strain specificity of the neutralizing antibody response in monkeys infected with these prototypic SHIVs.

Potassium-conductive solid electrolytes in systems K2 − 2x M2 − x V x O4(M = Al, Fe)

New high-conductivity solid electrolytes based on potassium monoaluminate and monoferrite are synthesized by partial substitution of V5+ for three-charged cations. In both systems, the introduction of vanadium cations leads to a substantial increase in the conductivity, with the maximum values corresponding to upper boundaries of the monophase solid solution regions. The principal factors responsible for the high conductivity are the formation of potassium vacancies at the substitutions M3+ → V5+ + 2V’K and the extension of the temperature range of existence of high-temperature modifications of KAl(Fe)O2.

Importance of the V1/V2 Loop Region of Simian-Human Immunodeficiency Virus Envelope Glycoprotein gp120 in Determining the Strain Specificity of the Neutralizing Antibody Response

Plasma samples from individuals infected with human immunodeficiency virus type 1 (HIV-1) are known to be highly strain specific in their ability to neutralize HIV-1 infectivity. Such plasma samples exhibit significant neutralizing activity against autologous HIV-1 isolates but typically exhibit little or no activity against heterologous strains, although some cross-neutralizing activity can develop late in infection. Monkeys infected with the simian-human immunodeficiency virus (SHIV) clone DH12 generated antibodies that neutralized SHIV DH12, but not SHIV KB9. Conversely, antibodies from monkeys infected with the SHIV clone KB9 neutralized SHIV KB9, but not SHIV DH12. To investigate the role of the variable loops of the HIV-1 envelope glycoprotein gp120 in determining this strain specificity, variable loops 1 and 2 (V1/V2), V3, or V4 were exchanged individually or in combination between SHIV DH12 and SHIV KB9. Despite the fact that both parental viruses exhibited significant infectivity and good replication in the cell lines examined, 3 of the 10 variable-loop chimeras exhibited such poor infectivity that they could not be used further for neutralization assays. These results indicate that a variable loop that is functional in the context of one particular envelope background will not necessarily function within another. The remaining seven replication-competent chimeras allowed unambiguous assignment of the sequences principally responsible for the strain specificity of the neutralizing activity present in SHIV-positive plasma. Exchange of the V1/V2 loop sequences conferred a dominant loss of sensitivity to neutralization by autologous plasma and a gain of sensitivity to neutralization by heterologous plasma. Substitution of V3 or V4 had little or no effect on the sensitivity to neutralization. These data demonstrate that the V1/V2 region of HIV-1 gp120 is principally responsible for the strain specificity of the neutralizing antibody response in monkeys infected with these prototypic SHIVs.