O3 Powders Research Articles

Structural characteristics and crystalline nature of PZT powders topochemically synthesized from needle-like TiZrO4 precursors

Pb(Zr0.5Ti0.5)O3 (PZT) powders were synthesized from needle-like TiZrO4 (TZO) precursors by topochemical molten salt synthesis. The effects of the flux types, the raw powder sizes and the synthesis temperatures on the resultant particle morphologies and phase structures of both TZO and PZT were investigated. Via optimizing the synthesis conditions, needle-like TZO with a smooth surface and needle-like PZT with a rough surface were obtained. Transmission electron microscopy (TEM) analyses unveiled that TZO possesses a single-crystal structure with the axial direction along the [010] crystallographic orientation, while PZT exhibits a polycrystalline structure with a discernible degree of misorientation. Notably, the synthesized needle-like PZT from TZO were observed to be unstable and could not induce oriented grain growth of Pb(Mg1/3Nb2/3)O3-PbZrO3-PbTiO3 (PMN-PZT) ceramics. This study reveals that improving the thermal stability of needle-like PZT seeds is one of the key factors for the templated grain growth in textured piezoelectric ceramics.

Exploring the structural and magnetic properties of La-doped nickel ferrite for microwave absorbing application

The intrinsic properties of microwave absorbing materials are influenced by the permeability and permittivity of the material with indicators of changes in reflection loss characteristics. Nickel ferrite is a magnetic material with very high permeability, so the presence of La3+ ion substitution in nickel ferrite can increase the permittivity of this material and is denoted by increased reflection loss. The magnetic material NiLaxFe(2−x)O4 was synthesized effectively through co-precipitation techniques using NiCl2, FeCl3, and LaCl3 powders, with mole ratios varying from x = 0.01 to 0.04, then continued with the sintering process at a temperature of 1200 °C for 5 h.The X-ray diffraction (XRD) analysis indicates that all NiLaxFe(2−x)O4 samples consist of a single phase of NiFe2O4 with a cubic spinel structure. The scanning electron microscope (SEM) image of NiLaxFe(2−x)O4 powders reveals that all samples exhibit a consistent morphology, however, the powder doesn’t look uniform yet, with particle sizes ranging from 100-800 nm. The magnetic properties of the samples were examined using a vibrating sample magnetometer (VSM). The sample shows ferromagnetic behavior, but the Ms value decreases from 35.89 to 21.54 emu/g and the Hc value increases from 249 to 416 Oe as the La3+ ion content in the material increases. Meanwhile, the microwave absorption capacity measured using the vector network analyzer (VNA) shows that reflection loss increases from 11.16 dB to 15.41 dB as the La3+ ion content in the material increases. So, the substitution of La3+ ions in nickel ferrite structure up toa concentration of x = 0.04 can increase microwave absorption up to 97.11 %.

Highly Tuning of Sunlight-Photocatalytic Properties of SnO2 Nanocatalysts: Function of Gd/Fe Dopants

Gd/Fe-SnO2 nanopowders as novel photocatalysts for the active removal of Rose Bengal dye and methyl parathion pesticide were synthesized with a low-cost coprecipitation route. The X-ray diffraction analysis of SnO2, Sn0.96Gd0.02Fe0.02O2 and Sn0.94Gd0.02Fe0.04O2 nanopowders proved the formation of a tetragonal phase of tin oxide with average crystallite sizes in the range of 13–18 nm. The Fourier transform infrared (FTIR) spectra of all samples displayed the characteristic absorption bands of SnO2. The nanopowder of the pure SnO2 sample, as seen in its transmission electron microscope (TEM) image, contains spherical-like particles of variable sizes. The TEM images of the Sn0.96Gd0.02Fe0.02O2 and Sn0.94Gd0.02Fe0.04O2 powders revealed the synthesis of fine spherical nanoparticles. Based on the TEM images, the average particle size of the pure, (Gd, 2 wt% Fe) and (Gd, 4 wt% Fe) codoped SnO2 nanopowders was estimated to be 14, 10 and 12 nm, respectively. After the addition of (Gd, 2 wt% Fe) and (Gd, 4 wt% Fe) to the SnO2 structure, the band gap energy of SnO2 was reduced from 3.4 eV to 2.88 and 2.82 eV, respectively. Significantly, the Sn0.96Gd0.02Fe0.02O2 nanocatalyst exhibited a high removal efficiency of 98 and 96% for Rose Bengal dye and methyl parathion pesticide after activation by sunlight for 35 and 48 min, respectively. Furthermore, this catalyst has shown perfect mineralization as well as high stability properties for the treatment of Rose Bengal dye and methyl parathion pesticide. These results suggest the suitability of the Sn0.96Gd0.02Fe0.02O2 nanocatalyst for the treatment of agriculture and industrial effluent under sunlight light energy.

Inkjet Printing of Long-Range Ordering Two-Dimensional Magnetic Ti0.8Co0.2O2 Film.

The value of two-dimensional (2D) materials in printed electronics has been gradually explored, and the rheological properties of 2D material dispersions are very different for various printing technologies. Understanding the rheological properties of 2D material dispersions plays a vital role in selecting the optimal manufacturing technology. Inkjet printing is suitable for small nanosheet sizes and low solution viscosity, and it has a significant advantage in developing nanosheet inks because of its masklessness, high efficiency, and high precision. In this work, we selected 2D Ti0.8Co0.2O2 nanosheets, which can be synthesized in large quantities by the liquid phase exfoliation technique; investigated the effects of nanosheet particle size, solution concentration on the rheological properties of the dispersion; and obtained the optimal printing processing method of the dispersion as inkjet printing. The ultrathin Ti0.8Co0.2O2 nanosheet films were prepared by inkjet printing, and their magnetic characteristics were compared with those of Ti0.8Co0.2O2 powder. The films prepared by inkjet printing exhibited long-range ordering, maintaining the nanosheet powders' paramagnetic characteristics. Our work underscored the potential of inkjet printing as a promising method for fabricating precisely controlled thin films using 2D materials, with applications spanning electronics, sensors, and catalysis.

Impact of air and vacuum calcination on the properties of lead-free piezoelectric Ba0.85Ca0.15Zr0.1Ti0.9O3 ceramics for mechanical energy harvesting

Piezoelectric materials play a crucial role in energy harvesting applications, efficiently capturing renewable energy from sources like human activities and vibrations. Oxygen vacancies, common imperfections in these materials, significantly influence their overall effectiveness. In our study, Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) powder was calcined under different conditions (air and vacuum) to investigate their impact on crystal structure, microstructure, electrical properties, and energy harvesting performance. X-ray diffraction (XRD) and Rietveld analysis confirmed varied phases in vacuum calcined BCZT with a smaller particle size. X-ray photoelectron spectroscopy (XPS) revealed lower oxygen vacancy concentration for vacuum-calcined samples. The vacuum calcined BCZT ceramics demonstrated a remarkable 580% enhancement in the figure of merit (FOM) when contrasted with traditional ceramics, highlighting superior dielectric and piezoelectric characteristics. In mechanical energy harvesting, BCZT ceramics, protected by polyimide with Cu/Ag electrodes, outperformed conventional ceramics, generating a higher open-circuit voltage (10.61 V) and peak-to-peak power (1.510 mW/cm3). This energy harvester maintained stable output through 7000 cycles, suggesting its potential for powering miniature electronics.

Interphase design of LiNi0.6Mn0.2Co0.2O2 as positive active material for lithium ion batteries via Al2O3 coatings using magnetron sputtering for improved performance and stability

AbstractLiNixMnyCozO2 (x+y+z=1) is one of the most present and versatile positive active materials for lithium ion batteries due to comparatively high specific capacity and high operating potential. However, NMC materials are prone to various degradation effects including moisture uptake, formation of impurities at the particle surface and transition metal dissolution during charge/discharge cycling and/or at elevated temperatures. Beyond that, cation mixing can lead to phase transformation, oxygen evolution, particle cracking and particle disintegration. Therefore, an alumina coating was applied and optimized as protective interphase on LiNi0.6Mn0.2Co0.2O2 (NMC622) powders, using a specifically in‐house developed RF‐magnetron sputtering technique. The alumina coated NMC622 showed a 13 % improvement in capacity retention after 200 charge/discharge cycles in lab‐scale cells, compared to pristine uncoated NMC622. Using electrochemical impedance spectroscopy, the interfacial/interphasial resistance of pristine and alumina coated NCM622 based electrodes were explored to study the impact of the coating on lithium ion transport. Furthermore, the structural and thermal stability of cyclic aged NMC622 were analyzed via TEM, EELS and TGA. Therein, alumina coated samples demonstrated enhanced thermal stability, less structural degradation, and reduced particle cracking.

Thermochromism and thermal crystal structure evolution of YIn0.9Mn0.1O3

YIn1-x Mn x O3 is a newly discovered inorganic blue pigment whose vivid blue color results from MnO5 trigonal bipyramidal (TBP) polyhedra. Recently, it has been reported that commercial YIn1-x Mn x O3 powders exhibit a temperature-induced color change, i.e. thermochromism. In this study, we investigate the thermochromism and temperature-induced crystal structure evolution of synthetic YIn0.9Mn0.1O3 powders. We observe that a vivid blue color at RT gradually changed to a dark blue color with increasing temperature. This thermochromism is mainly attributed to a broadening of optical absorption bands in the visible and UV regions, and can also be contributed to by an enhancement of the UV absorption. Our crystal structure analysis using powder synchrotron X-ray diffraction data not only confirms the thermal expansion and enhanced thermal vibrations of oxygen, but also reveals a temperature-induced deformation of the TBP polyhedra. Based on these results, we discuss a possible mechanism for the thermochromism of the YIn0.9Mn0.1O3 system.

Novel lithium ion-sieve spinning fiber composite of PVDF-HMO for lithium recovery from geothermal water

With the increasing application of the industrialization of lithium and its derivatives, there has been a surge of interest in recovering this resource from liquid sources. However, synthesizing adsorbents with industrial significance is still a significant challenge. Herein, the precursor Li1.6Mn1.6O4 of H1.6Mn1.6O4 powder absorbent with the highest theoretical adsorption capacity and the lowest Mn dissolution loss rate was first synthesized by hydrothermal or high-temperature solid phase method. The commercialized wet spinning apparatus, which has convenient operation and a simple process, was used to prepare PVDF/HMO spinning fiber to recover lithium resources from geothermal water. It has a large specific surface area of 31.45 m2 g−1 and a pore size of 9.04 nm, and the adsorption capacity was 14.95 mg g−1, with the distribution coefficient of Li+ being 1404.96 mL g−1. Furthermore, the equilibrium was reached within just 2 h at pH 12, and the elution time was just 1 h. Even after the fifth cycle, the adsorption capacity remained high at 14.21 mg g−1. These characteristics indicate that the new material has excellent application potential for lithium recovery from geothermal water.

ZnCrXFe2-XO4 (X = 0–2) porous powder prepared through self-combustion glycine nitrate process and applied to methyl alcohol steam reforming for production of pure hydrogen

Climate change, global warming, and energy crisis have become an important problem due to the environmental impact of fossil fuels. Hence, alternate energy source is needed for environmental remediation. One such source could be hydrogen (H2). H2 is used as an alternate energy carrier due to it is non-toxic, clean, and efficient. Steam reforming of methyl alcohol (or) methanol (SRM) is a widely available and low-cost hydrogen production method. In this stream-reforming process, mostly commercial zinc-supported catalyst is used, these have some economic defect. Therefore, we need to find alternate suitable catalysts for the SRM process. In this study, ZnCrXFe2-XO4 (X = 0–2) porous catalyst powders of different ratios were synthesized by the glycine nitrate process (GNP) for hydrogen production by SRM. The specific surface areas of the ZnCrXFe2-XO4 powders ranged from 15.75 m2/g to 45.16 m2/g. The ZnCr0.4Fe1.6O4 powder had the highest H2 production without activation, reaching 6850.33 ml STP min−1 g-cat−1 at a reaction temperature of 450 °C. ZnCr0.4Fe1.6O4 porous powders prepared using the GNP method have simple, rapid process steps, low cost, high catalytic activity, and they can be applied to hydrogen fuel cells or other related catalysis applications in the future. The pure hydrogen production performance of these ZnCrXFe2-XO4 catalysts could be of great importance in industry and economic impact.

Correction: Influence of iron insertion in phase and Raman spectra of sol–gel-derived Ruddlesden Popper-type Sr2(Ce1-xFex)O4 (x = 0–1.0) powders

Correction: Influence of iron insertion in phase and Raman spectra of sol–gel-derived Ruddlesden Popper-type Sr2(Ce1-xFex)O4 (x = 0–1.0) powders

P2-type Na0.67Mn0.5-xVxFe0.43Ti0.07O2 powders for Na-ion cathodes: Ex-situ structural analysis and full-cell study

This study used a modified solid-state synthesis technique to synthesize Na0.67Mn0.5-xVxFe0.43Ti0.07O2 (x = 0.02 - 0.1) cathode materials. The XRD pattern shows that there are no impurity phases in the samples for x ≤ 0.06. The granular grain formation was observed in each sample and the largest surface area was obtained for x = 0.06 V-doped composition. According to XPS analysis of the x = 0.06 sample, the V and Ti ions have three different valence states in the structure and the ratio of V3+/V4+/V5+ ions in the powders was calculated as 13 %/36 %/51 % and the spin splitting binding energy gaps were found as 7.1 eV for each V-ions and they affected by cycling process. The redox mechanism of the half cells was investigated at 10 °C and room temperature. The diffusion coefficient values of Na+ were calculated by cycling voltammetry (CV) and GITT techniques for the x = 0.06. Although the highest capacity of the half cells for the V-substituted samples was found to be 188.3 mAh/g for x = 0.02 V-doping in the cells for C/3-rate, the best capacity fade among the cells was obtained for x = 0.06 as 36.9 %. The ex-situ analysis of the electrodes after 100 cycles at the environmental temperatures of 10 °C, 50 °C, and 60 °C was investigated and it was found that the valence state of the elements changed by the cycling process. The artificial solid electrolyte interface (SEI) formation on the anode surface was performed by pre-sodiation technique and the full cells were assembled using Na0.67Mn0.44V0.06Fe0.43Ti0.07O2/hard carbon architecture and the obtained first capacity values for C/3-rate were 90.1 mAh/g and 66.6 mAh/g, respectively, and the capacity value decreased with the cycling process up to 60 cycles and then gave a plateau with increasing cycle numbers up to 500 cycles.

New BaTi0.96Cu0.02X0.02O3 (X = V, Nb) Photocatalysts for Dyes Effluent Remediation: Broad Visible Light Response

The problem of industrial dyes depollution has pushed the scientific research community to identify novel photocatalysts with high performance. Herein, new photocatalysts composed of BaTiO3, BaTi0.96Cu0.04O3, BaTi0.96Cu0.02V0.02O3 and BaTi0.96Cu0.02Nb0.02O3 powders were prepared by solid-state reaction. The structural analysis of the samples confirmed the formation of the BaTiO3 structure. The splitting of (002) and (200) planes verified the formation of the tetragonal phase. The XRD peaks shifted, and the unit cell volume expansion verified the substitution of the Ti4+ site by Cu2+, V4+ and Nb5+ ions. The morphological measurements showed that the addition of (Cu, V) and (Cu, Nb) ions changes the particles’ morphology of BaTiO3, reducing its grains size. After the incorporation of (Cu, V) and (Cu, Nb) ions, the band gap of BaTiO3 was reduced from 3.2 to 2.84 and 2.72 eV, respectively. The modification of BaTiO3 by (Cu, Nb) ions induced superior photocatalytic properties for methyl green and methyl orange with degradation efficiencies of 97% and 94% during 60 and 90 min under sunlight irradiation, respectively. The total organic carbon results indicated that the BaTi0.96Cu0.02Nb0.02O3 catalyst has a high mineralization efficiency. In addition, it possesses a high stability during three cycles. The high photodegradation efficiency of Bi0.96La0.02Gd0.02FeO3 was related to the wide-ranging visible light absorption.

Influence of iron insertion in phase and Raman spectra of sol–gel-derived Ruddlesden Popper-type Sr2(Ce1-xFex)O4 (x = 0–1.0) powders

Influence of iron insertion in phase and Raman spectra of sol–gel-derived Ruddlesden Popper-type Sr2(Ce1-xFex)O4 (x = 0–1.0) powders

One-pot granulation of cross-linked PVA/LMO for efficient lithium recovery from gas field brine

Adsorption with granules is critical for lithium recovery from brines due to the simplicity, efficiency, and environmental-friendliness of its industrial process. However, obtaining hydrophilic and stable binders remains to be a challenging task. Herein, a one-pot green strategy for granulating Li1.33Mn1.67O4 (LMO-1) powder into PVA/LMO-1 composites was developed with hydrophilic poly(vinyl alcohol) (PVA) as a binder and glycidoxypropyltrimethoxysilane (GPTES) as a coupling agent. Hydrogen peroxide (H2O2) was added to the reaction process to create pores by its thermal decomposition. The powder in the coupling composites would be difficult to leach out when compared to the granulation method of physical blending. Furthermore, the resulting PVA/LMO-1 demonstrated high water absorbency, pH stability, and fast water/ion exchange without visible swelling, which are important in industrial scale-up experiments where energy consumption and time can be reduced. Additionally, the selectivity of different ions of granulated PVA/LMO-1 was evaluated and confirmed. The lithium adsorption efficiency in real brine (produced water from the Puguang gas field) was 93.5%, which is higher than that of other adsorbents with comparable adsorption capacity; Meanwhile the magnesium-lithium ratios (Mg2+/Li+ ratios) decreased from 8.92 to 0.15, Na+/Li+ ratios decreased from 997 to 1.35, K+/Li+ ratios decreased from 30.26 to 0.29, Ca2+/Li+ from 30.87 to 2.36, indicating that the high salt content and organic pollutants of real bine do not affect the performance of the adsorbent. Long-term cyclic results showed that the structure and adsorption capacity of PVA/LMO-1 were stable. All these properties demonstrate that the developed PVA/LMO-1 absorbent could provide an appealing and competitive method for the industrial process.

Optical and Photocatalytic Properties of Cobalt-Doped LuFeO3 Powders Prepared by Oxalic Acid Assistance.

B-site cobalt (Co)-doped rare-earth orthoferrites ReFeO3 have shown considerable enhancement in physical properties compared to their parent counterparts, and Co-doped LuFeO3 has rarely been reported. In this work, LuFe1-xCoxO3 (x = 0, 0.05, 0.1, 0.15) powders have been successfully prepared by a mechanochemical activation-assisted solid-state reaction (MAS) method at 1100 °C for 2 h. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy studies demonstrated that a shrinkage in lattice parameters emerges when B-site Fe ions are substituted by Co ions. The morphology and elemental distribution were investigated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The UV-visible absorbance spectra show that LuFe0.85Co0.15O3 powders have a narrower bandgap (1.75 eV) and higher absorbance than those of LuFeO3 (2.06 eV), obviously improving the light utilization efficiency. Additionally, LuFe0.85Co0.15O3 powders represent a higher photocatalytic capacity than LuFeO3 powders and can almost completely degrade MO in 5.5 h with the assistance of oxalic acid under visible irradiation. We believe that the present study will promote the application of orthorhombic LuFeO3 in photocatalysis.

Coating Ca2+–Fe3+ co-doped LaAlO3 on high-temperature electric furnace for energy-saving

The energy-saving effect of high-emissivity coatings on high-temperature electric furnaces has not been fully explored. In this study, high infrared emissivity coatings (ε1–2.5μm, 1200 °C = 0.81) are successfully prepared using La0.9Ca0.1Al0.9Fe0.1O3 powder as radiation agent and aluminium sol as binder. The experimental results on a high-temperature electric furnace reveal that the power consumption for heating air and heating refractory bricks before and after lining coating increase by 4.7% and 5.4%, respectively. This energy consumption increase is primarily concentrated in the heating stage because the high absorption of the coating causes an increase in the heat loss of the lining. Moreover, the scheme of the high-emissivity coating application on the outer surface of a crucible is proposed. Experimental results indicate that this technique can effectively improve thermal efficiency and, therefore, can be successfully implemented in future industrial applications.

Multifunctional BaTi0.98M0.02O3 (M = V, Co, Mo) compositions: High dye-photodegradation and relative permittivity characteristics

In this study, the relative permittivity and photocatalytic properties of BaTi0.98M0.02O3 (M = V, Co, Mo) compositions have been investigated. Polycrystalline BaTiO3, BaTi0.98V0.02O3 BaTi0.98Co0.02O3 and BaTi0.98Mo0.02O3 powders were synthesized by solid state reaction method. The X-ray diffraction analysis of all samples confirmed the formation of tetragonal BaTiO3 phase without any impurities. The scanning electron microscope images showed the formation of irregular grains for BaTiO3 and BaTi0.98V0.02O3 samples while BaTi0.98Co0.02O3 and BaTi0.98Mo0.02O3 powders revealed spongy and uniform crystalline grains shapes, respectively. Remarkably, the incorporation of V, Co and Mo ions was reduced the UV band gap energy of BaTiO3 from 3.25 eV to 2.96, 2.98 and 2.92 eV, respectively. These results verify that V, Co and Mo doped BaTiO3 samples have the ability to absorb the visible light spectrum compared to pure one. The study of the dielectric properties showed that the BaTi0.98V0.02O3 and BaTi0.98Mo0.02O3 samples have a colossal relative permittivity of 14263 and 1658, respectively. Besides, BaTi0.98Mo0.02O3 as a photocatalyst exhibits superior photodegradation efficiencies of 90 and 100% towards 10 ppm Congo red solution under sunlight irradiation during 20 and 60 min, respectively. For 50 ppm CR, the photocatalytic activity of this catalyst was reached to 53% and 70% in 20 and 60 min, respectively. The highest performance of BaTi0.98Mo0.02O3 catalyst can be ascribed to high crystallinity, formation of oxygen vacancies, well charge separation and visible light absorption.

MAGNETIC AND MICROWAVE ABSORBING PROPERTIES IN SEMI-HARD COXFE(3-X)O4 SYNTHESIZED BY SOL-GEL METHOD

Magnetic and microwave absorption properties of CoxFe(3-x)O4 semi-hard materials (x = 0.75, 1.0, and 1.5) synthesized have been carried out using the chemical method of sol-gel. The mixture of iron nitrate Fe2(NO3)3 and cobalt nitrate Co(NO3)2 dissolved in ethylene glycol, then the mixture was heated while stirring at 60 °C for 1 hour to form a gel. After that dried at a temperature of 120°C for 5 hours. A fine powder of CoxFe(3-x)O4 was obtained through the grinding process. The CoxFe(3-x)O4 powder crystallization was done by sintering at 1000 °C for 5 hours. The X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Vibrating-sample magnetometer (VSM), and Vector Network Analyzer (VNA) is used to investigate phase identification, particle morphology, magnetic properties, and microwave absorption ability, respectively. Based on the phase identification show that the samples with composition x = 0.75 have two phases, namely CoFe2O4 and Fe2O3. The sample composition for x ³ 1 is a single phase of CoFe2O4. The particle morphology is homogeneous with spherical and the particle size is about 100 – 500 nm. The samples act ferromagnetic behavior with a saturation magnetization (Ms) of 26.1-40.4 emu/g and coercivity field (Hc) of 223-299 Oe. The maximum reflection loss (RL) value of -14.03 dB at the frequency 10.98 GHz occurred in a single-phase sample with a composition of x = 1.0. This study provided a new composite material with great potential for the development of microwave-absorbing materials.

Controlling the Magnetic Properties of La0.9A0.1Mn0.9Cr0.1O3 (A: Li, K, Na) Powders and Ceramics by Alkali Ions Doping

Nanocrystalline La0.9A0.1Mn0.9Cr0.1O3 (A: Li, K, Na) powders have been synthesized by combustion method. The powders were used to prepare ceramics by high-pressure low-temperature sintering technique. For all samples the structure, elemental composition and morphology were studied using X-ray diffraction (XRD), Raman spectroscopy, Energy-Dispersive X-ray Spectroscopy (EDS) and Scanning electron microscopy (SEM). Magnetic properties were studied using magnetometry methods and the valency changes of the cations after alkali ions doping were studied using X-ray photoelectron spectroscopy (XPS). The influence of the sintering pressure on the structural and magnetic properties of the manganites doped with different alkali ions and chromium was also investigated. Magnetization properties were studied as a function of sintering pressure and type of the dopant. Chemical doping with alkali ions as well as external pressure significantly changed the magnetic properties of the compounds. It was found that the magnetic properties of the manganites could be predictably modified through the use of a suitable dopant element.

Calorimetric Studies on Chemically Delithiated LiNi0.4Mn0.4Co0.2O2: Investigation of Phase Transition, Gas Evolution and Enthalpy of Formation

Li1.11(Ni0.4Mn0.4Co0.2)O2 powders were chemically delithiated by (NH4)2S2O8 oxidizer to obtain Lix(Ni0.4Mn0.4Co0.2)O2 powders. The thermal behavior of two delithiated specimens, Li0.76Ni0.41Mn0.42Co0.17O2.10 and Li0.48Ni0.38Mn0.46Co0.16O2.07, was studied compared to the pristine specimen. Phase transitions at elevated temperatures were investigated by simultaneous thermal analysis (STA) and the gas evolution accompanying the phase transitions was analyzed by mass spectroscopy and an oxygen detector. The enthalpy of two delithiated samples and a pristine specimen were measured by a high temperature drop solution calorimeter. Based on these results, the enthalpies of formation were calculated.