Effect Of Nb5 Research Articles

Analysis of ion conduction behavior of Nb- and Zr-doped Li3InCl6-based materials via material simulation

The Li-ion conductivities of Li3InCl6 (LIC), which is a promising chloride solid electrolyte, and its compositional derivatives, Nb5+- and Zr4+-doped LIC, i.e., Li3−2xIn1−xNbxCl6 and Li3−yIn1−yZryCl6, respectively, were experimentally and computationally investigated. An increase in the ionic conductivity caused by Nb5+ or Zr4+ doping, which was due to the increase in Li vacancies, was observed in both the experimental and computational results. Nb5+ doping yielded a larger increase in conductivity at 60 °C. First-principles molecular dynamics studies indicated two factors affecting the Li-ion conductivity under doping with higher-valent ions: (1) the vacancy trapping effect and (2) the reduction in the phase-transition temperature from a Li/vacancy ordered structure to a disordered structure. In particular, in factor (2), the effect of Nb5+ doping is larger than that of Zr4+ doping, which supports the improvement in ionic conductivity at 333 K in the experiment.

Effect of Nb5+ doping on microwave dielectric properties of MgTa2O6 ceramic

As the main carrier for microwave circuits, microwave dielectric ceramics are receiving a lot of attention as the main carrier for the current 5G and pre-developed 6G communication technologies. A series of Nb5+ doped MgTa2O6 ceramics were synthesized by the solid-state reaction method X-ray diffraction confirmed that a single tetragonal structure can be formed when the doping amount is lower than 0.03, a heterogeneous structure of tetragonal and orthorhombic crystal structure is formed when the doping amount is lower than 0.15, and the tetragonal structure is completely transformed into orthorhombic structure when the doping exceeds 0.15. SEM results also show the transformation process of the grains of tetragonal structure to orthorhombic structure. The optimum microwave dielectric properties were obtained for 9% Nb5+ doped samples: εr = 24, Q×f = 71,000 GHz (at 8.9 GHz), TCF = 15 ppm/oC.

Phase Composition, Crystal Structure and Microwave Dielectric Properties of Nb-Doped Yttrium Aluminum Garnet Ceramics

The Y3Al5-xNbxO12 (0 ≤ x ≤ 0.06) garnet ceramics were prepared by solid-state reaction method. The effects of Nb5+ substitution on the phase composition, microstructure and microwave dielectric properties were investigated. All samples retained the yttrium-aluminum garnet solid solution form until x up to 0.06 at which YNbO4 secondary phase precipitated. The doping of Nb2O5 improved the grain development and enhanced the physical properties of the ceramics under the sintering condition of 8 h at 1700 °C. Specifically, with the substitution of Nb5+, the degree of micromorphology improvement and quality factor first increased and then decreased, with a maximum value at x = 0.015. Finally, the best combination of microwave dielectric properties was obtained, i.e., εr = 10.79, Q×f = 165,478 GHz, τf = -31.7 ppm/°C. This study provides a theoretical basis for the further expansion and application of yttrium aluminum garnet in the microwave field. Keywords: Yttrium Aluminum Garnet ceramics, Nb2O5, microwave dielectric properties.

Enhanced piezoelectric performance in Na0.5Bi4.5Ti4O15‐based bismuth‐layered ceramics by Nb/Mn doping modification

AbstractIn this work, Na0.5Bi4.5Ti3.94–xMn0.06NbxO15+y bismuth‐layered ferroelectric ceramics were prepared by a solid‐state reaction method. The effect of Nb5+ content on crystal morphology, electrical properties, and piezoelectric performance were systematically investigated. The results show that the introduction of Nb5+ into Na0.5Bi4.5Ti3.94–xMn0.06NbxO15+y ceramics to replace Ti4+ increases the ratio of b/a lattice parameter, leading to the TiO6 octahedral distortion and the structural transformation tendency from the orthorhombic to tetragonal phase, which facilitates dipole movements of Na0.5Bi4.5Ti3.94–xMn0.06NbxO15+y ceramics. Therefore, the ferroelectric properties of Na0.5Bi4.5Ti3.94–xMn0.06NbxO15+y ceramics are improved, and an enhanced piezoelectric coefficient of 30 pC/N combining great temperature stability with d33 value higher than 25 pC/N in the temperature range of 25°C–450°C has been realized in Na0.5Bi4.5Ti3.94–xMn0.06NbxO15+y ceramics with x = 0.08 mol. Our work provides a good model for designing lead‐free ultrahigh Curie temperature piezoelectric devices that can be practically applied in extremely harsh environments.

Insight into the effect of Nb5+ on the crystal structure and electrochemical performance of the Li-rich cathode materials

The density functional theory (DFT) and electronic structure around the Fermi level results show that the binding energy change of Nb-doped samples is much higher than that of the pristine sample. • Nb-doped Li-rich materials are synthesized via a modified one-step sol–gel and high-temperature calcination method. • Nb-doped Li-rich materials show outstanding electrochemical performance. • The electrochemical performance of Nb-doped Li-rich materials was interpreted by the density of states. The Nb-doped Li-rich materials Li 1.2 (Mn 0.54 Ni 0.13 Co 0.13 ) 1-x Nb x O 2 are synthesized via a modified one-step sol–gel and high-temperature calcination method. The crystal structure and surface morphology of synthesized materials are analyzed through X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. After optimization, the Nb-0.02 sample exhibits exceptional electrochemical performance, that is, the initial discharge-specific capacity of 305.9 mAh g −1 at 0.08 C and 202.6 mAh g −1 at 1 C, respectively. Combined with the result of the density of states (DOS), we found that the doping of Nb 5+ into the crystal structure significantly reduces the value of the band gap of the Li 2 MnO 3 (1.07 eV). At the same time, the strengthened Nb–O bond and Nb 5+ with big ionic radius, regulate the degree of oxygen ion participation in the redox reaction and enhance the electrochemical performance of the Li-rich materials.

Effect of Nb5+ doping on the microstructure and conductivity of Li1.125Ta0.875Zr0.125SiO5 electrolyte

The microstructure and electrochemical properties of Li1.125Ta0.875-xNbxZr0.125SiO5 (x = 0, 0.0625, 0.1875, 0.25, 0.5) ceramics prepared via the solid-phase reaction method were studied. The results reveal that the conductivity of the ceramic specimens at 25 °C increases and then decreases as the Nb increases from 0 to 0.5 mol. 0.1875 mol of Nb doping facilitates the fusion and connection between grains, reduces the number of grain boundaries, leads to densification of the ceramics, decreases the total resistance, and thus increases the conductivity. Moreover, the small structural distortion caused of the discrepancy in ionic radii of Ta5+ and Nb5+ creates more space to accommodate Li ions and promotes the diffusion of Li+, reducing the energy potential barrier for ion transport. The best performing Li1.125Ta0.6875Nb0.1875Zr0.125SiO5 has a conductivity of 3.521 × 10-5 S/cm at 25 °C, with an order of magnitude greater than that of the original sample Li1.125Ta0.875Zr0.125SiO5, reaching 2.288 × 10-4 S/cm at 150 °C and has a minimum activation energy: 0.225 eV. The prepared Li1.125Ta0.6875Nb0.1875Zr0.125SiO5 ceramic is a new type of fast Li-ion conductor with potential for application in all-solid-state batteries.

Effect of Nb5+ Doping and LiNbO3 Coating on the Structure and Surface of a LiNi0.8Mn0.2O2 Cathode Material for Lithium-Ion Batteries

Layered LiNixMn1−xO2 structures with high discharge specific capacity and low cost are anticipated as the next-generation of high-energy density cathode active materials. However, the mixed arrangement of Li+ and Ni2+ in the cathode materials affects structural stability. Here, Nb5+ was doped into the structure of LiNi0.8Mn0.2O2 (NM82) to broaden the lithium-ion migration channels and alleviate the degree of ion mixing. LiNbO3 particle was coated on the surface of LiNi0.8Mn0.2O2 to form a spherical compound and reduce the erosion of HF and the dissolution of transition metals, which helped ameliorate the cyclic and structural stabilities of cathode materials. NM82 modified 1% Nb2O5 (LN/NM82-1.0) exhibited maximum discharge specific capacitance (177.7 mAh g−1 at 1.0C following 200 cycles) and excellent thermal stability (189.0 mAh g−1 at 1.0C following 200 cycles at 60 °C). The corresponding capacity retentions of this material were 87.54% and 85.37%, as LiNbO3 particle coating on the surface of NM82 decreased polarization and charge transfer resistor. Nb5+ in the host structure suppressed structural degradation and enhanced discharge capacity. This study determined the influence of Nb5+ substitution and LiNbO3 cladding on the structure and surface of LiNi0.8Mn0.2O2 and provides insights into commercial application of high-energy density layered structures of LiNixMn1−xO2 cathode materials.

Effect of Nb5+ and In3+ Ions on Moisture Sensitivity of Electrospun Titanium/Tungsten Oxide Nanostructures: Microstructural Characterization and Electrical Response

In this work, Nb5+ and In3+ ions were used as dopants in titanium/tungsten oxide nanostructures that are produced by the electrospinning and sintering process, for relative humidity (RH) detection. The microstructural properties were investigated by SEM, EDS, XRD, Raman and FTIR techniques. The electrical response characterization of the samples was performed by electrical impedance spectroscopy in the range of 400 Hz to 40 MHz, at 20 °C. The sensors sensitivity to moisture was evaluated in terms of the impedance variations to RH (10–100%). The combined analysis of the microstructural characterization results confirmed the surface interaction between the oxides and the ions incorporation in Ti crystal lattice. All the studied sensors showed a conduction transition from p- to n-type at around 30–40% RH: besides, they also displayed better sensitivity to moisture than those obtained in a previous work using titanium/tungsten combination using a different fabricationn route. The impedance modulus variation up to 1.1 and 1.3 orders of magnitude for the 4 wt % niobium and indium doped samples, respectively. The results are directly associated with the microstructure and alternative preparation process.

Niobium doping of Li1.2Mn0.54Ni0.13Co0.13O2 cathode materials with enhanced structural stability and electrochemical performance

Lithium-rich layered oxides with high energy density have been intensively investigated as advanced lithium-ion batteries cathode materials. However, capacity degradation and voltage decay caused by irreversible lattice oxygen loss and structural transformation during cycling restrict their application. Herein, we proposed a high valance cations Nb5+ doping strategy and synthesized a series of Li1.2Mn0.54-x/3Ni0.13-x/3Co0.13-x/3NbxO2 (x = 0, 0.01, 0.02 and 0.03) cathode materials. The effects of Nb5+ doping on crystallographic structure and electrochemical property were systematically studied. In virtue of the large ionic radii and strengthened Nb–O bonds, the doped samples present commendable structural stability and expanded interlayer spacing for Li-ions migration, which ensures the upgraded cyclic stability and rate performance. In particular, the electrode with x = 0.02 delivers a discharge specific capacity of 265.8 mAh g-1 at 0.2 C with decelerated voltage decay, while 86.9% capacity are remained after long-term cycles. Moreover, excellent discharge specific capacity of 153.4 mAh g−1 is still attained at 5 C accompanied with enhanced Li-ion diffusion kinetics.

Ultralow-loss and thermally stable Li4MgSn(2–1.25x)NbxO7 microwave dielectric ceramics

The Li4MgSn(2–1.25x)NbxO7 (L4MS-Nbx, 0 ≤ x ≤ 0.15) ceramics were prepared through a solid-state reaction method. The effects of Nb5+ substitution for Sn4+ on the phase composition, sintering behavior, and microwave dielectric properties were investigated systematically. The substitution of Nb5+ lowers the lattice thermal stability and declines the optimal sintering temperature of L4MS ceramics. The temperature at which the secondary phase occurs is lowered with increasing Nb5+ content owing to the promoted sintering behavior. The appearance of the secondary phase leads to the occurrence of cracks between grains. Moreover, the substitution of Nb5+ in L4MS causes Sn4+ vacancies, which increase the dielectric loss and therefore reduce Q × f values, and simultaneously leads to an increase in the dielectric polarizability, which makes τf move to near-zero values. As a result, excellent microwave dielectric properties of er = 14, Q × f = 123,000 GHz (9.34 GHz), τf = + 4.1 ppm/°C were obtained for the x = 0.11 ceramic sintered at 1125 °C for 6 h, showing large potentials in microwave devices.

Effect of Nb5+ and Cu2+ codoping on thermal properties of Gd2Zr2O7 ceramic

In this work, Nb5+ and Cu2+ were selected to partially substitute Zr4+ in Gd2Zr2O7 for studying the phase structure, microscopic morphology and thermal properties. Gd2(Zr1-3x/2NbxCux/2)2O7 (x = 0, 0.05, 0.1, 0.15, 0.2, 0.25) ceramic materials were synthesized by high-temperature solid-state reaction method. The results show that the Gd2(Zr1-3x/2NbxCux/2)2O7 ceramics present cubic pyrochlore structure with clear grain boundaries and dense cell structure. And the thermal expansion coefficient of Gd2(Zr1-3x/2NbxCux/2)2O7 ceramics gradually decreases because of the incorporation of Nb5+ and Cu2+ into Zr-site in Gd2Zr2O7. Meanwhile, its thermal conductivity decreases firstly and then increases with the doping of Nb5+ and Cu2+, which reaches the lowest value for the composition of Gd2(Zr0.85Nb0.1Cu0.05)2O7.

Correction to: Effect of Nb5+ doping on LiNi0.5Co0.25Mn0.25O2 cathode material

In the originally published article, the name of the first author “Lina Li” was inadvertently removed from the list during typesetting and the second author’s name was presented twice. The correct and complete list of authors is presented above.

Effects of B-site ion (Nb5+) substitution on the microstructure and ionic conductivity of Li0.5La0.5TiO3 solid electrolytes

Nb-doped lithium lanthanum titanate (LLTO) ceramic electrolytes were fabricated by the conventional solid-state reaction method. Effects of Nb5+ substitution on the microstructure and ionic conductivity of LLTO were investigated systematically. It is found that the 4 at.% Nb-doped Li0.5La0.5TiO3 sintered at 1350 °C for 12 h shows the minimum amount of pores in microstructure and the highest total conductivity, 1.04 × 10−4 S/cm, being 1.6 times of that without Nb addition. Therefore, it is proved experimentally that a proper amount of Nb doping could be an effective and facile approach to improve the LLTO’s microstructure and total conductivity, thus making Nb-doped LLTO a good solid electrolyte candidate for use in lithium-ion batteries.

Effect of Nb5+ doping on LiNi0.5Co0.25Mn0.25O2 cathode material

Li (Ni0.5Co0.25Mn0.25)1−xNbxO2 (x = 0, 0.005, 0.01, 0.02, 0.03) cathode material was synthesized by co-precipitation. X-ray diffraction spectroscopy (XRD) and scanning electron microscopy (SEM) were used to analyze the crystal structure characteristics and morphology of the powder. The charge and discharge test, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) were used to study the electrochemical properties of the battery in detail. XRD results show that Nb5+ substitution does not destroy the crystal structure, but it can enlarge the interplanar spacing, which is beneficial to the diffusion of lithium ions. The electrochemical properties of the material Li (Ni0.5Co0.25Mn0.25)0.99Nb0.01O2 are the best. The discharge specific capacity is 204.6, 186.0, 163.5, 141.6 mAh/g at 0.1C, 0.2C, 0.5C, and 1.0C, respectively. And the discharge specific capacity is as high as 174.1 mAh/g when returning to 0.1C again. After circulating 45 cycles at 0.1C, the capacity retention rate was 89.08%.

Diffuse phase transition in Nb-doped BaTi2O5 thin films

BaNbxTi2–xO5 (x = 0, 0.002, 0.004, 0.006, 0.008, 0.01) thin films were deposited on the Pt(111)/Ti/SiO2/Si substrates using the sol–gel method. The effect of Nb5+ substitution on the electric properties of BaNbxTi2–xO5 films was investigated. Diffuse phase transition was observed in all the thin films. The relationship between the dielectric constant and temperature of these films showed a wide platform and no frequency dependence. For the film with x = 0.006, an abnormally broadened dielectric platform was obtained in the temperature range of 200–400 °C, and its value fluctuated in the range of 350 ± 10. The research showed that Nb-doped and thermal stress contributed greatly to this abnormally broadened platform of e(T) curve. The substituting Nb5+ in BaTi2O5 thin films caused small microscopic composition fluctuation, which enhanced the degree of diffusion phase transition of the films. And the thermal stress on the films caused inhomogeneous polarization of the surface and center of the films, resulting in a change in phase transition behavior. In addition, the BaNbxTi2–xO5 thin films with high dielectric constant at high temperatures were successfully obtained, which were beneficial to the application of BaTi2O5 films under high temperature conditions.

Improving the electrochemical properties of Mn-rich Li1.20[Mn0.54Ni0.13Co0.13]O2 by Nb and F co-doping

The typical sol-gel method was adopted to synthesize the pristine Li1.20[Mn0.54Ni0.13Co0.13]O2 and Li1.20[Mn0.54-xNi0.13Co0.13Nbx]O1.95F0.05 (x = 0, 0.01, 0.02, 0.03). And the effects of Nb5+ and F− substitution on the lattice structures, particles morphologies and electrochemical properties were comprehensively studied by using the X-ray Diffractometer (XRD), Scanning Electron Microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and galvanostatic charge-discharge tests. The results demonstrated that the Nb5+ and F− doping modification could increase the lattice parameter of a and c, and would not obviously change the morphologies of cathode particles. Besides, the electrochemical properties of Li1.20[Mn0.54Ni0.13Co0.13]O2 were significantly improved after the Nb5+ and F− doping. Among all samples, the Li1.20[Mn0.52Ni0.13Co0.13Nb0.02]O1.95F0.05 delivered the highest discharge capacity of 117.1 mAh g−1 at 5C high rate and the most stable capacity retention of 92.5% at 0.5C rate after 200 cycles. The Electronic Impedance Spectroscopy (EIS) analysis reflected that the Nb5+ and F− doping could relieve the increase of charge transfer resistance and the ohmic resistance of interaction between electrolyte and cathode during cycling.

Effect of Nb5+ Doping on the Structure and Electrochemical Performances of LiFePO4

Nb-doped LixNb0.005FeyPO4/C cathode material for lithium-ion batteries were prepared by two-fluid spray-drying using FePO4·2H2O, LiOH·H2O, C6H12O6(glucose) as raw materials under N2 atmosphere. The effects of doping Nb5+ on the structure, morphology and electrochemical performances of LiFePO4 were investigated. The results show that LixNb0.005FeyPO4/C has Olivine Structure and pure phase. The LixNb0.005FeyPO4/C had an initial discharge specific capacity of 158.5mAh/g at 0.1C and its specific capacities were 109mAh/g at 5C. The initial charge/discharge efficiency reached 93.9%. The discharge specific capacity of the LixNb0.005FeyPO4/C at 253K is 82.2mAh/g. This investigation suggests that the Nb5+ doped material possess high rate capability and excellent low temperature electrochemical performance.

Effect of niobium doping on the dielectric and nonlinear current–voltage characteristics of [formula omitted] ceramics

The effect of Nb5+ on the crystallographic structure, electrical properties and the dielectric behaviour of Na0.5La0.5Cu3Ti(4−x)NbxO12 ceramics prepared via the solid-state reaction method were investigated. Rietveld refinement of the powder diffraction data confirmed a cubic, single phase structure with space group Im3. A low frequency Debye-type relaxation is observed for the Nb-doped samples in addition to the usually observed high frequency relaxation. The grain boundary resistance decreased significantly with increasing Nb5+ dopant. The reduced grain boundary resistivity was found to be responsible for the decrease in the potential barrier at the grain boundary as observed from the overall variation of current density-electric field (J–E) characteristics. The dielectric constant at low Frequency is increased with increasing Nb content. The dielectric behaviour of the compound is explained on the basis of the Internal Barrier Layer Capacitance (IBLC) model.

Effect of Nb5+ ion substitution on the dielectric property of BaTi2O5–Ba6Ti17O40 eutectic prepared by a floating zone method

Ti4+ ions of the materials solidified from the BaTi2O5–Ba6Ti17O40 (BT2–B6T17) eutectic melt were substituted with 0–1.0 at% Nb5+ ions (CNb = 0–1.0 at%) by a floating zone method, and the effects of CNb on the microstructure, permittivity and Curie temperature of the BT2–B6T17 eutectics were studied. The BT2–B6T17 eutectics at CNb = 0–1.0 at% consisted of BaTi2O5 and Ba6Ti17O40. b- and a-axes of BaTi2O5 and Ba6Ti17O40, respectively, were parallel to the growth directions of the BT2–B6T17 eutectic. Ba6Ti17O40 in the BT2–B6T17 eutectic had the rod-like structure parallel to the growth direction in the matrix of BaTi2O5. As CNb increased from 0 to 1.0 at%, the permittivity at room temperature increased from 70 to 214 and the Curie temperature decreased from 748 to 679 K.

Effect of Nb5+ charge neutralization substitution on the electrochemical performance of lithium-rich layered oxides

The effect of the Nb5+ substitution with a charge-compensated strategy in lithium-rich layered oxides (LLOs) Li1.2Ni0.13+xCo0.13-xMn0.54-xNbxO2 (x = 0, 0.01, 0.02, and 0.03) has been investigated systematically. A hydroxide co-precipitation method followed by a high-temperature solid-state reaction is adopted in the synthesis process. Structural characterization confirms that the low dose substituting of Nb5+ in the layered structures forms a solid solution, and the samples show low cation mixing and enlarged Li+-diffusing channels, which imply favorable high-rate capability. The initial charge/discharge measurements suggest that the oxygen loss from the network during the delithiation process has been suppressed by the substitution of Nb5+ due to the formation of robust Nb–O bonds and a decrease in TM-O (TMs are transition metals) covalence. Moreover, these Nb–O bonds contribute to the stabilization of the crystalline framework, resulting in an excellent cycle stability with a mitigated voltage decay.