Two-step Solid-state Method Research Articles

Effect of preparation methodologies on the electrical properties of lead-free 0.985(K0.485Na0.485Li0.03)(Nb0.96Sb0.04)O3-0.015(Bi0.5Na0.5)ZrO3 piezoceramics

Two methods of preparation namely, one-step solid state method and two-step solid state method, were used to synthesize composite 0.985(K0.485Na0.485Li0.03)(Nb0.96Sb0.04)O3-0.015(Bi0.5Na0.5)ZrO3 (0.985KNNLS-0.015BNZ) piezoceramics. In one-step method, all the raw materials were mixed in their stoichiometric ratios and then calcined to yield the desired composite. In two-step method, calcined samples of (K0.485Na0.485Li0.03)(Nb0.96Sb0.04)O3 (KNNLS) and (Bi0.5Na0.5)ZrO3 (BNZ) were initially prepared following the above procedure, these calcined powders were mixed according to the required compositional ratios and then again calcined to get the final composite. The calcined powders were again high-energy ball-milled in isopropanol medium at the speed of 250 rpm for 10 h. The powders were pressed into pellets and sintered at 1060 °C for 2 h. According to XRD analysis and Raman spectra, both the resulting ceramic samples show pure perovskite structure. The study reveals the great influence of the preparation technique on the microstructural, electrical and pieozoelectric properties of the resulting ceramics. Significantly higher value of Curie temperature Tc = 331 °C was observed for ceramics prepared via two-step method as compared to Tc = 197 °C for ceramics synthesized via one-step method. Modified Curie Weiss law and Vogel-fulcher relation suggest that two-step approach induces more relaxor character in the sample. The values of piezoelectric coefficient (d33 = 367 pC/N), remnant polarization (Pr = 13µC/cm2) and dielectric permittivity (εrt = 2166) corresponding to the two-step method far exceed those (d33 = 253 pC/N, Pr = 6.65 µC/cm2, εrt =1428) of the one-step method. These observed results are discussed in this paper.

Cation Disorder in Ferroelectric Ba4M2Nb10O30 (M = Na, K, and Rb) Tetragonal Tungsten Bronzes.

The crystal structure of tetragonal tungsten bronzes, with the general formula A12A24C4B12B28O30, is flexible both from a chemical and structural viewpoint, resulting in a multitude of compositions. The A1 and A2 lattice sites, with different coordination environments, are usually regarded to be occupied by two different cations such as in Ba4Na2Nb10O30 with Na+ and Ba2+ occupying the A1 and A2 sites, respectively. Here, we report on a systematic study of the lattice site occupancy on the A1 and A2 sites in the series Ba4M2Nb10O30 (M = Na, K, and Rb). The three compounds were synthesized by a two-step solid-state method. The site occupancy on the A1 and A2 sites were investigated by a combination of Rietveld refinement of X-ray diffraction patterns and scanning transmission electron microscopy with simultaneous energy-dispersive spectroscopy. The two methods demonstrated consistent site occupancy of the cations on the A1 and A2 sites, rationalized by the variation in the size of the alkali cations. The cation order–disorder phenomenology in the tungsten bronzes reported is discussed using a thermodynamic model of O’Neill and Navrotsky, originally developed for cation interchange in spinels.

Modification of NASICON Electrolyte and Its Application in Real Na-Ion Cells

The low ionic conductivity of solid-state electrolytes (SSEs) and the inferior interfacial reliability between SSEs and solid-state electrodes are two urgent challenges hindering the application of solid-state sodium batteries (SSSBs). Herein, sodium (Na) super ionic conductor (NASICON)-type SSEs with a nominal composition of Na3+2xZr2–xMgxSi2PO12 were synthesized using a facile two-step solid-state method, among which Na3.3Zr1.85Mg0.15Si2PO12 (x = 0.15, NZSP-Mg0.15) showed the highest ionic conductivity of 3.54 mS∙cm−1 at 25 °C. By means of a thorough investigation, it was verified that the composition of the grain boundary plays a crucial role in determining the total ionic conductivity of NASICON. Furthermore, due to a lack of examination in the literature regarding whether NASICON can provide enough anodic electrochemical stability to enable high-voltage SSSBs, we first adopted a high-voltage Na3(VOPO4)2F (NVOPF) cathode to verify its compatibility with the optimized NZSP-Mg0.15 SSE. By comparing the electrochemical performance of cells with different configurations (low-voltage cathode vs high-voltage cathode, liquid electrolytes vs SSEs), along with an X-ray photoelectron spectroscopy evaluation of the after-cycled NZSP-Mg0.15, it was demonstrated that the NASICON SSEs are not stable enough under high voltage, suggesting the importance of investigating the interface between the NASICON SSEs and high-voltage cathodes. Furthermore, by coating NZSP-Mg0.15 NASICON powder onto a polyethylene (PE) separator ([email protected]), a 2.42 A∙h non-aqueous Na-ion cell of carbon|[email protected]|NaNi2/9Cu1/9Fe1/3Mn1/3O2 was found to deliver an excellent cycling performance with an 88% capacity retention after 2000 cycles, thereby demonstrating the high reliability of SSEs with NASICON-coated separator.

Synthesis Method and Thermodynamic Characteristics of Anode Material Li3FeN2 for Application in Lithium-Ion Batteries.

Li3FeN2 material was synthesized by the two-step solid-state method from Li3N (adiabatic camera) and FeN2 (tube furnace) powders. Phase investigation of Li3N, FeN2, and Li3FeN2 was carried out. The discharge capacity of Li3FeN2 is 343 mAh g−1, which is about 44.7% of the theoretic capacity. The ternary nitride Li3FeN2 molar heat capacity is calculated using the formula Cp,m = 77.831 + 0.130 × T − 6289 × T−2, (T is absolute temperature, temperature range is 298–900 K, pressure is constant). The thermodynamic characteristics of Li3FeN2 have the following values: entropy S0298 = 116.2 J mol−1 K−1, molar enthalpy of dissolution ΔdHLFN = −206.537 ± 2.8 kJ mol−1, the standard enthalpy of formation ΔfH0 = −291.331 ± 5.7 kJ mol−1, entropy S0298 = 113.2 J mol−1 K−1 (Neumann–Kopp rule) and 116.2 J mol−1 K−1 (W. Herz rule), the standard Gibbs free energy of formation ΔfG0298 = −276.7 kJ mol−1.

Improved electrochemical behavior of Li rich cathode Li1.4Mn0.61Ni0.18Co0.18Al0.03O2.4 via Y2O3 surface coating

Better electrochemical properties of lithium batteries are achieved by a two-step solid state method with Y2O3 protective layer coated on Li1.4Mn0.61Ni0.18Co0.18Al0.03O2.4 (LNCMA) layered cathode material to meet the new requirements. XRD, TEM and various electrochemical investigations are used to reveal the fine structure and electrochemical behavior of the prepared Y2O3/LNCMA materials. The result indicates that Y2O3 layer covers the surface of the LNCMA cathode in our approach. Although Y2O3 coated LNCMA displays slight decrease in the initial capacity when compared with the original Li rich phase, the cathode with 3 wt% Y2O3 coating shows promoted cyclability with 92.9% capacity retention after 100 cycles at 0.2C and an improved rate behavior of 124.1 mAh g−1 even at 10C. Such an obvious increase in electrochemical behavior can be explained by the reduced interfacial resistance and increased ionic diffusion which caused by the suppressed transition metal dissolution in the electrolyte, as confirmed from the impedance spectra. The above results greatly suggest that Y2O3/LNCMA material can be applied as a potential cathode in LIBs with high energy.

CaS:Eu2+@CaZnOS:Mn2+: A dual-UV/green-excited and dual-red-emitting spectral conversion with all-weather resistance

To pursue green ecological agriculture, long-life functionalized green house is looking for solar spectrum conversions with well spectral match, outstanding thermal and chemical stabilities, excellent anti-photobleaching and UV-conversion performance. CaS:Eu2+-based phosphors are widely known as a candidate for agricultural films with remarkable green-to-red conversion performance while they are also notorious for poor stabilities. In this work, a core-shell structured CaS:Eu2+@CaZnOS:Mn2+ composite phosphor was synthesized by a two-step solid state method. The coating layer of thermally and chemically inert oxysulfide prevents the sulfide core phosphor from hydrophilic, air-sensitive and heat-induced decompositions. Moreover, the addition of Mn2+ in CaZnOS shell qualifies the composite phosphor with strong UV absorption, which contributes to the improvement of the anti-photodegradation of the inner CaS:Eu2+ and the anti-aging of practical polymer films. The additional UV-to-orange red conversion resulting from CaZnOS:Mn2+ further extends the red components for the indoor plants. As a result, this dual UV/green excited and dual red-emitting super stable chalcogenide phosphor can be used as a general spectral conversion for plant cultivation.

K3WOF7:Mn4+ ‒ A red oxyfluoride phosphor

Synthesis of K3WOF7:Mn4+ was accomplished via a facile two-step solid-state method. Characterization of the material was carried out by means of single-crystal and powder X-ray diffraction, energy dispersive X-ray spectrometry, as well as luminescence spectroscopy. The substance crystallizes in the monoclinic crystal system in space group P21/c (no. 14) with the lattice parameters a = 884.2(1), b = 1379.9(1), c = 679.7(1) pm, and β = 93.04(1)°. The crystal structure features a quasi-isolated [WOF5]− building block as its main motif. The material exhibits a red luminescence under excitation with blue light. The maximum-intensity emission line is located at λmax ≈ 627 nm and the CIE1931 coordinates of the phosphor are 0.689 and 0.310 for x and y, respectively.

Role of higher valent substituent on the dielectric and optical properties of Sr0.8Bi2.2Nb2O9 ceramics

Abstract The synthesis, structure, optical and dielectric properties of strontium deficient bismuth excess strontium bismuth niobate Sr0.8Bi2.2Nb2O9 (SBNex) ceramics were systematically studied with tungsten and molybdenum as a doping element. The ceramics were prepared with a two-step solid-state method with ∼ 98 % of relative density. The XRD spectrum established that the orthorhombic crystal structure of the Aurivillius oxides was formed and doped with 2.5 at. % of W and Mo resulted in a near phase transition to the tetragonal phase. The energy dispersive X-ray spectra confirmed the formation of the desired compound of strontium deficient bismuth excess SBNex ceramic. The W doped SBNex ceramics exhibited the maximum value of dielectric constant ∼ 270 at the lower frequencies. The dielectric study suggested that the relaxation mechanism be of Debye model with free from any space polarization. The complex modulus plots presented to establish the dielectric relaxation at higher frequency side of the spectra. The band-gap energy (Eg) decreased with Mo and W doping, being 3.00 and 2.85 eV respectively. The enhanced dielectric properties in W and Mo doped SBNex ceramics entitled them for the application to produce high density RAM.

TiO2/NiO/reduced graphene oxide nanocomposites as anode materials for high-performance lithium ion batteries

In this study, NiO was synthesized via a facile method and coated on the surface of a TiO2 anode material doped with rGO (reduced graphene oxide). TiO2/NiO/rGO nanocomposite structures were synthesized by a two-step solid-state method, and their lithium storage capacity was investigated and compared with that of both as-prepared TiO2/NiO and pure TiO2. The coating over the TiO2 surface helped to attain a higher capacity and cycle stability than that without it, even at high current rates. The TiO2/NiO/rGO nanocomposites show excellent performance with an initial discharge capacity of up to 324 mAh/g between 0 and 3 V vs Li at 20 mA/g. Furthermore, at a high current density of 100 mA/g, the TiO2/NiO/rGO nanocomposite still achieved a capacity of 245 mAh/g after 200 cycles. This excellent performance could be attributed to the stable framework and high electronic conductivity within the TiO2/NiO/rGO nanocomposite.

Synthesis of LiNiO2 by two-step solid-state method

Abstract LiNiO2 was prepared through two-step solid-state reaction by mechanochemical method and heat treatment, using LiOH (Li2CO3) and Ni(OH)2 as starting materials. The influence of grinding speed and time, heat treatment time, and starting materials on the structure of LiNiO2 was studied. The as-milled samples and products were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD). The results show that uniform as-milled samples can be obtained at grinding speed of 580 rpm for 0.5 h, using LiOH and Ni(OH)2 as raw materials. Perfect crystal LiNiO2 has been prepared by calcining the as-milled samples at 700 °C for 15 h. Composite material powders consisting of Li2Ni8O10 and LiNiO2 have been obtained using Li2CO3 as lithium source.

Solution, Solid-State Two Step Synthesis and Optical Properties of ZnO and SnO2 Nanoparticles and Their Nanocomposites with SiO2

Nanostructure luminescent ZnO and SnO2 materials are prepared by a two-step solid-state method based on the solution preparation of the macromolecular precursors ZnCl2·Chitosan and SnCl2·Chitosan having different ratios (1:1, 1:5 and 1:10), their pyrolysis under air at 800 °C. The pyrolytic ZnO and SnO2 nanomaterials show a dependence of the particle size, morphology and luminescent properties with the ratio [metal/polymer] in the MCl2·Chitosan precursors. Thus, ZnO semiconductor materials exhibit luminescence spectra with several emission at 440 nm corresponds to a radiative transition of an electron from the shallow donor level of oxygen vacancies, and the zinc interstitial, to the valence band. On the other hand, the photoluminescence spectrum of the nanostructured SnO2 shows an intense blue luminescence at a wavelength of 420 nm which may be attributed to oxygen-related defects that have been introduced during the growth process of the nanoparticles. Additionally, whereas SnO2 was successfully incorporated into SiO2 structure (SnO2//SiO2) by pyrolysis of solid-state mixtures of the precursors SnCl2·Chitosan in the presence of SiO2, the same reaction carried out with ZnCl2·Chitosan precursors led to a mixture of Zn2SiO4 and SiO2. Thus, this new methodology yields nanostructured semiconductor materials, ZnO and SnO2, suitable for optoelectronic and sensor solid-state devices.

Preparation and characterization of LiFePO4·xLi3V2(PO4)3 composites by two-step solid-state reaction method for lithium-ion batteries

LiFePO4·xLi3V2(PO4)3 (LFP·xLVP, x=0, 0.05, 0.1, 0.15, 0.2) composites were prepared by the two-step solid-state method. The structure, morphology and electrochemical properties were characterized by X-ray diffraction, scanning electron microscope, cyclic voltammetry, charge-discharge performance test and electrochemical impedance spectroscopy. It was indicated that composites were presented rough in surface of ball-like particles. Two phase of LFP and LVP combination improved electrochemical properties of LFP. The LFP·0.1LVP has the highest discharge capacity of 154mAh/g at 0.2C. Compared with LFP, the rate performance of the LFP·0.1LVP increased 13% and 8% at 1C and 10C after five cycles. It possessed excellent cycle life of 99.8% after 100 cycles at 1C especially. The all preparation process without any solvent addition was easy operation, energy saving and environmentally friendly.

Electrochemical Performances of Maricite NaFePO4/C as cathode material for Sodium-Ion and Lithium-Ion Batteries

Carbon-coated NaFePO4 (NaFePO4/C) with a maricite structure was synthesized by a two-step solidstate method with sucrose as carbon source. The electrochemical performances of NaFePO4/C were evaluated for sodium-ion batteries (SIBs) and lithium-ion batteries (LIBs), respectively. For SIBs, the initial reversible capacity of 48.8 mAh g(-1) at 0.05 C (1 C=154 mAh g(-1)) has obtained. For LIBs, the initial discharge capacity of NaFePO4 can reach up to 75.7 mAh g(-1) at 0.05 C. The reversible capacity of 50.6 and 38 mAh g(-1) can be obtained at 0.1 C, 0.2 C, respectively. With a simple synthetic process, cost-effective chemicals, and desirable electrochemical performance, the maricite NaFePO4/C is a possible application for large-scale energy devices and stationary storage.

Синтез нового сложного бората KBaSm(BO3)2

A novel compound containing three cation alkali, alkali earth, rare earth orthoborate KBaSm(BO3)2 was synthesized by using two-step solid-state method. Results of powder X-ray diffraction analysis (XRD) and FTIR spectroscopy showed that this compound is isostructural with known compounds KBaY(BO3)2 [1] and KBaTbB2O6 [2] and refers to trigonal crystal system (RǮm space group with unit cell parameters of crystalline lattice а=5,4845(10) A, с=18,135(13), Z=3). KBaSm(BO3)2 was obtained at a temperature of 825°C from initial reactants: samarium (III) oxide, barium and potassium carbonates and boric acid. Among KBaSm(BO3)2 – KBaTb(BO3)2 – KBaY (BO3)2 observed a regular linear variation of unit cell parameters, as well as regular shift of the bands in the IR spectra, depending on the size of the rare earth cation.

Improving the electrochemical kinetics of lithium manganese phosphate via co-substitution with iron and cobalt

High Mn content multicomponent olivine phosphate LiMn0.9Fe0.1−xCoxPO4/C (x=0, 0.05 and 0.1) are synthesized by two-step solid-state method and characterized by X-ray powder diffraction, FTIR spectra, XPS, electron microscopy and electrochemical measurements. Upon substitution, the cell volume decrease as a result of the smaller ionic radii of Fe2+ and Co2+ compared to Mn2+. Structural analysis demonstrates that Fe and/or Co substitution decrease the Mn–O and P–O bond length and increase the Li–O bond length, leading to enhanced physical stability and expanded Li diffusion channels. The Fe2+ and/or Co2+ substituted LiMnPO4 is found to have improved kinetics, lithium storage performance, and electronic conductivity during electrochemical reaction. In particular, LiMn0.9Fe0.05Co0.05PO4/C delivers a capacity of 145mAhg−1 at a current of 0.05 C and exhibits enhanced capacity retention compared to that of unmodified LiMnPO4/C. The enhanced electrochemical performance of co-substituted LiMnPO4 is attributed to the enhanced physical stability, the favorable delithiation/lithiation induced by previous redox reaction of Fe2+/Fe3+and Co2+/Co3+ and the improved electric/ionic transport properties.

High-performance carbon-coated LiMnPO4 nanocomposites by facile two-step solid-state synthesis for lithium-ion battery

LiMnPO4/C powders have been prepared by a solid-state method with sucrose as carbon source. The structure, morphology, and electrochemical performance of the LiMnPO4/C samples have been characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), transmission electronic microscopy (TEM), galvanostatic charge and discharge, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). The LiMnPO4/C sample prepared by the two-step solid-state method exhibits a specific capacity of 156 mA h g−1 after 40 cycles, and over 90 % of the initial capacity can be retained with a charge-discharge rate of 0.5 C and a voltage range of 2.5–4.4 V at 50 °C. The improvement of electrochemical performance attributes to the highly uniform distribution of the minimizing particle size as well as the superior electrical conductivity of the carbon-coated nano-LiMnPO4 materials by facile two-step solid-state synthesis.

Phase Characterization, Thermal Stability, High-Temperature Transport Properties, and Electronic Structure of Rare-Earth Zintl Phosphides Eu3M2P4 (M = Ga, In)

Two rare-earth-containing ternary phosphides, Eu3Ga2P4 and Eu3In2P4, were synthesized by a two-step solid-state method with stoichiometric amounts of the constitutional elements. Refinements of the powder X-ray diffraction are consistent with the reported single-crystal structure with space group C2/c for Eu3Ga2P4 and Pnnm for Eu3In2P4. Thermal gravimetry and differential scanning calorimetry (TG-DSC) measurements reveal high thermal stability up to 1273 K. Thermal diffusivity measurements from room temperature to 800 K demonstrate thermal conductivity as low as 0.6 W/m·K for both compounds. Seebeck coefficient measurements from room temperature to 800 K indicate that both compounds are small band gap semiconductors. Eu3Ga2P4 shows p-type conductivity and Eu3In2P4 p-type conductivity in the temperature range 300-700 K and n-type conductivity above 700 K. Electronic structure calculations result in band gaps of 0.60 and 0.29 eV for Eu3Ga2P4 and Eu3In2P4, respectively. As expected for a valence precise Zintl phase, electrical resistivity is large, approximately 2600 and 560 mΩ·cm for Eu3Ga2P4 and Eu3In2P4 at room temperature, respectively. Measurements of transport properties suggest that these Zintl phosphides have potential for being good high-temperature thermoelectric materials with optimization of the charge carrier concentration by appropriate extrinsic dopants.

Physicochemical Properties of Li4Ti4.95Zn0.05O12 Anode Material by a Two-Step Solid-State Method

Li4Ti5−x Zn x O12 (x = 0, 0.05) anode materials were prepared by a two-step solid-state method. The structure and over-discharge property of the as-prepared materials were analyzed by x-ray diffraction (XRD), scanning electron microscopy (SEM), differential capacitance, and galvanostatic charge-discharge measurements. XRD patterns demonstrate that both samples have the phase of Li4Ti5O12 with an ordered spinel structure indexed to the cubic Fd3m space group. The lattice parameter of the Li4Ti4.95Zn0.05O12 sample is slightly smaller than that for the pure Li4Ti5O12 samples. SEM exhibits that the size of the Zn-doped Li4Ti5O12 and pure Li4Ti5O12 is about 1-1.5 μm. Charge-discharge tests show that Li4Ti4.95Zn0.05O12 exhibits excellent cycling performance and higher discharge capacity than those of Li4Ti5O12 even at different charge-discharge rates. The differential capacitance curves confirm that the zinc doping is beneficial to the reversible intercalation and de-intercalation of Li+.

Electrochemical performance and lithium-ion intercalation kinetics of submicron-sized Li4Ti5O12 anode material

Submicron-sized Li4Ti5O12 anode was synthesized through a two-step solid-state reaction. The relationship between the structural properties, electrochemical performance discharged to 0V and lithium-ion intercalation kinetics was discussed using the experiments as well as the first-principles calculations. Structural analyses reveal that Li4Ti5O12 synthesized by the two-step solid-state method has high phase purity. Scanning electron microscopy (SEM) shows that Li4Ti5O12 has a homogeneous size distribution in the range of 0.4–0.6μm. The initial discharge capacity of Li4Ti5O12 is 234.6mAhg−1 at 0.5 C rate between 0 and 2.5V, and it is close to the theoretical capacity value. The high structure stability of Li4Ti5O12 is related to the strong covalent bonding characteristic between Ti and O according to the first-principles calculation. Electrochemical impedance spectroscopy (EIS) indicates that the charge transfer resistance of the Li4Ti5O12/Li cell evidently decreases with increasing of the temperature, and the apparent activation energies of Li4Ti5O12 electrode on the lithium diffusion process and the charge transfer are calculated to be 19.05 and 22.48kJmol−1, respectively.