Co substituted BaFe12O19 ceramics with enhanced magnetic resonance behavior and microwave absorption properties in 2.6 – 18 GHz

BaFe_12-xCo_xO₁₉ (BFCO, x ≤ 0.4) ceramics with superior magnetic and electromagnetic (EM) properties were prepared using Co³⁺ substituted BaFe₁₂O₁₉ (BFO) in 2.6–18 GHz. Compared with the ceramics without Co³⁺, the incorporation of 40 mol% Co³⁺ enhances magnetic properties; the saturation magnetization (M_S) is improved by about 55.6 emu·g⁻¹ due to the variety of magnetocrystalline anisotropy. The resonance behaviors of complex permeability are observed and resonance frequency shifts to lower frequency range from 6 to 3 GHz. The minimum reflection loss (RL) of −32.1 dB (<−10 dB) is obtained at 11.2 GHz in 8.5–13.5 GHz at 2.0 mm thickness in the sample with x = 0.4, which suggests that such ceramics is highly promising as effective microwave absorbers for EM applications.     

Facile synthesis of Mn3O4 hollow polyhedron wrapped by multiwalled carbon nanotubes as a high-efficiency microwave absorber

Investigating lightweight and high-efficiency electromagnetic wave (EM) absorbers is evolving as a desirable approach to solve the electromagnetic pollution. In this study, Mn₃O₄ hollow polyhedron wrapped by multiwalled carbon nanotubes (Mn₃O₄/MWCNTs) was successfully prepared by one-step hydrothermal treatment. Interestingly, the Mn₃O₄ polyhedron as a unique hollow structure can serve as a microwave receiver and the incident EM waves hardly escape in the intricate networks, which could be repetitiously attenuated and consumed. The Mn₃O₄/MWCNTs composite with a filler loading of 20 wt% exhibits most outstanding EM absorption performance over the whole frequency of 2–18 GHz. The optimal reflection loss (R_L) achieves −53.8 dB at 11 GHz, and the effective absorption bandwidth (R_L exceeding −10 dB) reaches 4.1 GHz (9.1–13.2 GHz) with a thickness of 2.5 mm. The effective absorption bandwidth (R_L < −10 dB) up to 13.7 GHz (85% absorption over 2–18 GHz) was achieved by adjusting the thickness from 1.5 to 4 mm. The remarkable EM absorption performances benefit from the synergistic effects of suitable impedance matching, dielectric loss, interfacial polarizations and relaxation polarizations. These results indicate that Mn₃O₄/MWCNTs composite with lightweight and high-efficiency microwave absorption properties could serve as a prospective microwave absorber in practical applications.     

Multiple magnetic phase transitions in NixMn1-xCo2O4

We prepared pure-phase Ni_xMn_1-xCo₂O₄ (x = 0, 0.25, 0.5, 0.75 and 1) nanoparticles using a low-temperature solid-state reaction method. Magnetization measurement results showed that with Ni doping, the Curie temperature and coercivity of Ni_xMn_1-xCo₂O₄ increased. Multiple magnetic phases that transition from paramagnetic to ferrimagnetic to ferrimagnetic and antiferromagnetic were observed to coexist in the Ni_0.5Mn_0.5Co₂O₄ sample. At low temperatures, the ferromagnetic and antiferromagnetic phases coexist in Ni_xMn_1-xCo₂O₄ (x = 0 and 0.25), and as the concentration of Ni increases, Ni_xMn_1-xCo₂O₄ (x = 0.75 and 1) show a spin glass state. The structure of Ni_xMn_1-xCo₂O₄ (x < 0.5) is mainly affected by cation defects, and by cation substitution when x is greater than 0.5. The results of first-principles calculations show that covalent bonds exist in Ni_xMn_1-xCo₂O₄ and that the strength of the Ni-O bond is greater than that of the Mn-O bond.     

Synthesis and microwave absorption properties of Ni–Zn–Mn spinel ferrites

A series of Ni_0·5?xZn_0·3?xMn_0·2+2xFe₂O₄ ferrites was successfully prepared by the sol–gel autocombustion method. The structure and electromagnetic properties of the powders were characterised by X-ray diffraction, SEM and vector network analysis. The pure powders were formed by heating at 1200°C for 3 h in air, and grain sizes increased as the amount of substitution ranged from x?=?0·0 to x?=?0·25. For samples with x?=?0·1, a minimum reflection loss of ?27·57 dB was observed at 11·0 GHz with the less than ?10 dB absorption bandwidth at 8·0 GHz with 3·8 mm thickness. The results indicate that substitution with Mn and Zn ions can greatly improve the microwave absorption properties of NiFe₂O₄ ferrites.     

Dielectric relaxation and magnetic resonance in microwave absorption performance of CoxFe3-xO4 (0≤x≤1) nanocrystals

Cobalt ferrites (Co_xFe_3-xO₄, 0 ≤ x ≤ 1) may possess large magnetocrystalline anisotropy and coercivity at certain cobalt/iron (Co/Fe) ratios, while further explorations on their microwave absorption mechanisms are not adequate so far. In this study, a series of Co_xFe_3–xO₄ nanocrystals were synthesized by a developed oxidation-precipitation method, and a combination of dielectric relaxation and magnetic resonance was revealed in electromagnetic studies. Dielectric relaxation peaks were originated from orientation polarization and affected by oxygen vacancy densities. Magnetic resonance peaks were shifted to higher frequency due to the increased magnetocrystalline anisotropy at higher Co/Fe ratios. The excellent microwave absorption performance of as-prepared Co_xFe_3–xO₄ were also obtained, which should be attributed to the electromagnetic matching of dielectric relaxation and magnetic resonance at higher frequency ranges.     

Design of magnetic triple-shell hollow structural Fe3O4/FeCo/C composite microspheres with broad bandwidth and excellent electromagnetic wave absorption performance

A three-step strategy combining solvothermal and liquid phase reduction method had been developed for preparation of magnetic triple-shell hollow structural Fe₃O₄/FeCo/C (TSH–Fe₃O₄/FeCo/C) composite microspheres. FeCo was used to enhance electromagnetic (EM) wave absorption in different frequency band and broaden effective absorbing bandwidth, while carbon was used to improve impedance matching. Triple-shell hollow structure was designed to enrich the multiple interfaces to favor the interfacial polarization, increase the multiple reflections and scattering, and provide physicochemical protection to Fe₃O₄ core from oxidation. The microstructure and morphology of TSH-Fe₃O₄/FeCo/C composite microspheres were characterized by TEM, XRD and Raman in detail. The results indicated that magnetic Fe₃O₄ was completely covered by FeCo and carbon via layer by layer. As an EM wave absorber, the maximum reflection loss of TSH-Fe₃O₄/FeCo/C composite microspheres was up to -37.4 dB due to better normalized characteristic impedance at a thickness of 2.2 mm and the bandwidth less than -10 dB even reached up to 5.9 GHz. The excellent EM wave absorption performance was attributed to the combination of shell materials (Fe₃O₄, FeCo and carbon) and unique triple-shell hollow structure, which lead to multiple relaxation processes and good impedance matching. Consequently, this work would contribute to the design and preparation of high performance EM wave absorbent with outstanding absorbing property and wider absorption range.     

Achieving ultra-high electromagnetic wave absorption by anchoring Co0.33Ni0.33Mn0.33Fe2O4 nanoparticles on graphene sheets using microwave-assisted polyol method

The Co_0.33Ni_0.33Mn_0.33Fe₂O₄/graphene nanocomposite for electromagnetic wave absorption was successfully synthesized from metal chlorides solutions and graphite powder by a simple and rapid microwave-assisted polyol method via anchoring the Co_0.33Ni_0.33Mn_0.33Fe₂O₄ nanoparticles on the layered graphene sheets. The Fe³⁺, Co²⁺, Ni²⁺ and Mn²⁺ ions in the solutions were attracted by graphene oxide obtained from graphite and converted to the precursors Fe(OH)₃, Co(OH)₂, Ni(OH)₂, and Mn(OH)₂ under slightly alkaline conditions. After the transformations of the precursors to Co-Ni-Mn ferrites and conversion of graphene oxide to graphene under microwave irradiation at 170?°C in just 25?min, the Co_0.33Ni_0.33Mn_0.33Fe₂O₄/graphene nanocomposite was prepared. The composition and structure of the nanocomposite were characterized by X-ray diffraction (XRD), inductive coupled plasma emission spectroscopy (ICP), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy (RS), transmission electron microscopy (TEM), etc. It was found that with the filling ratio of only 20?wt% and the thickness of 2.3?mm, the nanocomposite showed an ultra-wide effective absorption bandwidth (less than ?10?dB) of 8.48?GHz (from 9.52 to 18.00?GHz) with the minimum reflection loss of ??24.29?dB. Compared to pure graphene sheets, Co_0.33Ni_0.33Mn_0.33Fe₂O₄ nanoparticles and the counterparts reported in literature, the nanocomposite exhibited much better electromagnetic wave absorption, mainly attributed to strong wave attenuation, as a result of synergistic effects of dielectric loss, conductive loss and magnetic loss, and to good impedance matching. In view of its thin thickness, light weight and outstanding electromagnetic wave absorption property, the nanocomposite could be used as a very promising electromagnetic wave absorber.     

High temperature anti-oxidative and tunable wave absorbing SiC/Fe3Si/CNTs composite ceramic derived from a novel polysilyacetylene

With the rapid development of high power electromagnetic (EM) equipment and high-speed aircraft, the powerful and high oxidation-resistance absorbers are fundamentally desirable for the EM field. Herein, a novel high temperature anti-oxidative SiC/Fe₃Si/CNTs composite is synthesized by a facile polymer derived ceramic (PDC) route from a Fe-containing polysilyacetylene (PSA). The microstructure of as-prepared SiC/Fe₃Si/CNTs composite absorber is featured by micro-sized SiC ceramic grains with spherical Fe₃Si nanoparticles and carbon nanotubes (CNTs) attached to. The vector network analyzer tests show a tunable wave-absorbing performance by adjusting the thickness of layer, and the effective bandwidth (the reflection loss < −10 dB) is 3.3–16.8 GHz for the sample S-1400 (heat treatment at 1400 °C in nitrogen flow). The minimal RL value is −41.2 dB at 10.5 GHz at a thickness of 2 mm and an effective bandwidth is nearly 4 GHz (12.9–16.9 GHz) at the thickness of only 1.5 mm. Moreover, after the oxidation treatment at 800 °C in the air, this absorber maintains the main structure and shows a good high temperature oxidation resistance. This absorber still remains excellent wave absorption property, in view of a minimal RL value of −40 dB at the thickness of 3 mm and a bandwidth of 4.8 GHz (10.4–15.2 GHz) at the thickness of 2.5 mm. The mechanism of high EM wave absorption performance is studied and attributed to the impendence matching, polarization, and the magnetic properties. Thus, the SiC/Fe₃Si/CNTs composite is a promising EM absorber for high-temperature EM wave-absorbing applications.     

MOF-derived core-shell structured Cu9S5/NC@Co3S4/NC composite as a high-efficiency electromagnetic wave absorber

Constructing specific microstructures and designing multicomponent composites are regarded as effective approaches to obtaining high-efficiency electromagnetic (EM) wave absorbing materials. Herein, core-shell structured Cu₉S₅/N-doped carbon@Co₃S₄/N-doped carbon (Cu₉S₅/NC@Co₃S₄/NC) composites derived from Cu₃(BTC)₂@ZIF-67 were synthesized by facile carbonization and sulfidation processes. The Cu₉S₅ particles are embedded in the interior and surface of the carbon skeleton, and the Co₃S₄/NC particles are uniformly distributed on the surface of the carbon skeleton. Compared with Cu₉S₅/NC and Co₃S₄/NC, the Cu₉S₅/NC@Co₃S₄/NC composite displays improved impedance matching properties and much better EM wave absorbing properties. The minimum reflection loss (RL_min) reaches ?41.6 dB at 10.52 GHz with a thickness of 2 mm. In addition, the effective absorption bandwidth (EAB, RL < ?10 dB) is 4.08 GHz (12.73–16.81 GHz) with un ultrathin thickness of 1.5 mm. This work offers a facile strategy for synthesizing MOF-derived metal sulfides/carbon composites as EM wave absorption materials with strong absorption properties, a wide absorption bandwidth and ultrathin thickness.     

Improved magnetic performance of Co-doped La2NiMnO6 ceramics prepared at low temperature

Co-doped La₂NiMnO₆ (La₂Co_xNi_1-xMnO₆, LC_xNMO, x = 0.1-0.5) ceramics were fabricated at relatively low temperature of 700 °C, to obtain double-perovskite with remarkable magnetic performance. It was found that the LC_xNMO ceramics in P2₁/n and R-3 phases could be well densified, with high relative density (>99 %) and fine grain size (0.5−1 μm). An increasement in cell volume was observed with the doping of Co, and the valence state changed from (Mn³⁺ + Ni³⁺/Co³⁺) to (Mn⁴⁺ + Ni²⁺/Co²⁺), revealing the improvement of B-site cations ordering. Moreover, the smaller grains resulted from the lower sintering temperature also decreased the level of antisite disordering. Consequently, the value of M_S/M_theo was significantly improved from 75.49% to 88.36 % by optimizing Co-doping concentration while the Curie temperature was still rather high (>250 K). The LC_0.5NMO ceramic was found to have the maximum M_S (4.86 μ_B/f.u.), attributing to the large B-site ordering because of higher Mn⁴⁺ and Ni²⁺/Co²⁺ content.     

Multi-phase heterostructures of flower-like Ni(NiO) decorated on two-dimensional Ti3C2Tx/TiO2 for high-performance microwave absorption properties

Three-dimensional flower-like Ni(NiO) decorated on two-dimensional Ti₃C₂T_x/TiO₂ composites were successfully synthesized by an in situ solvothermal reaction, and the electromagnetic (EM) wave absorption performance of the hybrids were explored at 2.00–18.00 GHz. The as-prepared Ni(NiO)/Ti₃C₂T_x/TiO₂ composites include flower-like Ni(NiO) with uniform distribution on the surface of Ti₃C₂T_x MXenes and part of them get into the space between interlayers. The Ni(NiO)/Ti₃C₂T_x/TiO₂ composites exhibit a maximum reflection loss (RL) value of ?41.74 dB at 14.96 GHz with the absorber thickness of merely 1.3 mm and the effective absorption bandwidth (EAB) reaches 3.20 GHz. The outstanding electromagnetic wave absorbing performance can be attributed to the dielectric loss of Ti₃C₂T_x MXenes and multi-phase heterostructures, the magnetic loss of Ni(NiO) and their synergistic loss mechanism. Moreover, the zigzag path formed by flower-like Ni(NiO) also has a great consumption effect on electromagnetic waves by incurring the eddy current under the affect of alternating EM waves. The laminated structure of Ti₃C₂T_x MXenes also dissipates microwaves by offering the space for multiple reflections and scattering. This paper furnished a novel modus for synthesizing original EM wave absorption materials and making the balance among thickness, broad bandwidth, oxidation resistance and light weight, which makes Ni(NiO)/Ti₃C₂T_x/TiO₂ composites a hopeful material for microwave absorption (MA).     

Metal ions induced dielectric and magnetic loss in Co3O4 for electromagnetic wave absorption

Despite Co₃O₄ has been widely applied in electromagnetic wave (EMW) absorbers, single Co₃O₄ doesn't have excellent EMW absorbing performance. Modification of Co₃O₄ with other metal ions addition is an effective way to improve its impedance matching and EMW attenuation. Herein, CuO/Cu_0.3Co_2.7O₄/Co₃O₄ and NiCo₂O₄/Co₃O₄ composites have been obtained via a facile two-stage strategy, and the influence of Cu²⁺ and Ni²⁺ on the high-frequency and low-frequency EMW absorbing performance of the composites has been investigated as well. The electromagnetic parameters of samples are regulated by adding different metal ions to achieve optimum impedance matching. Dipole polarization and magnetic resonance are the main loss mechanisms. The composite with Cu²⁺ and Ni²⁺ additions exhibits the best EMW absorption with an effective absorption bandwidth (EAB) of 10.8–18.0 GHz for 2.1 mm thickness at high-frequency and 4.5–8.5 GHz for 4.9 mm thickness at low frequencies, respectively. This work offers an effective method for preparing composite materials with multicomponent broadband absorption of oxides.     

Dielectric behaviour of valence compensated system Ba1-x Lax Sn1-x NixO3

Abstract

Compositions in the system Ba_1-x La_x Sn_1-x Ni_xO₃ up to x ≤ 0·30 were prepared by solid state sintering, and the dielectric behaviour of single phase solid solutions studied. It has been found that solid solutions form for compositions with x ≤ 0·15, the structure remaining cubic, similar to BaSnO₃ . The grain size of all the sintered compositions was almost the same as that for BaSnO₃ , i.e. 2–3 μm. Dielectric relaxation in these materials is explained on the basis of the reorientation of dipoles due to hopping of electrons among Ni²⁺ and Ni³⁺ ions.     

Boosting the antimicrobial and Azo dye mineralization activities of ZnO ceramics by enhancing the light-harvesting and charge transport properties

Herein, we report the wet-chemical synthesis of a ferromagnetic nickel-doped ZnO (Zn_1-xNi_xO) nanocatalyst as a novel and visible-light-driven photocatalyst. Through X-ray diffraction, UV/Vis absorption, electronic studies, and current-voltage experiments, the effect of the ferromagnetic nickel dopant on the structural, optical, morphological, and electrical properties of the synthesized Zn_1-xNi_xO nanocatalyst was studied. The Ni-doping introduced the structural variation in the Zn_1-xNi_xO nanocatalyst, exhibiting a visible light-triggered optical band gap of 2.96 eV and an excellent current conductivity of 6.3 × 10⁻⁴ Sm⁻¹. Moreover, the synthesis of the Zn_1-xNi_xO catalyst at the nanoscale enhanced its surface energy, showing a robust affinity to stick with the dye and pathogenic microbes. The synergistic effects of all the mentioned features enable our Zn_1-xNi_xO nanocatalyst to efficiently generate and transport reactive oxygen species (ROS) under visible light illumination. Regarding antibacterial action, the as-synthesized Zn_1-xNi_xO nanocatalyst showed 1.7% higher activity against E. coli than that of the drug Ciprofloxacin. In addition, doped nanocatalysts mineralize almost 97% of the Allura red dye in just 80 min with a constant rate value of 0.036 min⁻¹. The impedance study and post-application XRD proposed that our Zn_1-xNi_xO nanocatalyst has good conductivity and structural stability. Applications studies show the unusual photocatalytic activity of as-synthesized Zn_1-xNi_xO nanocatalysts, which makes it a suitable candidate for industrial discharge treatment applications at the expense of solar light.     

Variable optical properties of La0.5Sr0.5Co1-xNixO3-δ for high-temperature resistant code application

La_0.5Sr_0.5Co_1-xNi_xO_3-δ (x = 0, 0.1, 0.3, 0.5) ceramics were prepared via tape casting and solid state reaction process. The influence of Ni concentration on the optical properties of La_0.5Sr_0.5Co_1-xNi_xO_3-δ has been investigated. Results showed that the reflectance in the range of 0.3–15 μm decreased with the increment of Ni concentration, thereby causing a change in the color phase parameters and emissivity. Based on the difference in L* values and emissivity, the letters (HOT) and QR codes (NJTECH) were fabricated. The developed letters and QR codes could be identified both at room and high temperatures. Furthermore, the QR codes were read out successfully even underwent heat treatment at 1000 °C. The results in this work demonstrate a new application of La_0.5Sr_0.5Co_1-xNi_xO_3-δ ceramics.     

One-step hydrothermal synthesis and enhanced microwave absorption properties of Ni0.5Co0.5Fe2O4/graphene composites in low frequency band

Ni_0.5Co_0.5Fe₂O₄/graphene composites were synthesized successfully via one-step hydrothermal method. The crystal structure, morphology and corresponding elemental distribution, electromagnetic parameters and microwave absorption performances of the as-prepared composites were measured by XRD, SEM, TEM and VNA, respectively. The results indicated that the microwave absorbing performance can be obviously enhanced through the addition of graphene in a suitable range, the magnetic loss plays a dominant contribution for the microwave absorption of composites. The maximum reflection loss of ?30.92?dB at 0.84?GHz with a ?10?dB bandwidth over the frequency range of 0.58–1.19?GHz is obtained when the composite contains 12?wt% graphene and the thickness of sample is 4?mm. This investigation presents a simple method to prepare Ni_0.5Co_0.5Fe₂O₄/graphene composites with excellent microwave absorption performance in the low frequency band of 0.1–3?GHz.     

One-pot-solid preparation of novel three-dimensional FexS1-x/g-C3N4 heterostructures for efficient photocatalytic mixed-pollutants removal

In order to overcome the problem of low photocatalytic rate of g-C₃N₄, the 3D Fe_xS_1-x/g-C₃N₄ heterojunction was prepared via a simple one-pot solid method. The X-Ray Diffraction (XRD) and scanning electron microscope (SEM) results demonstrated that the Fe_xS_1-x/g-C₃N₄ heterojunction was established and a g-C₃N₄ nanosheet was tightly bound to Fe_xS_1-x. Compared with g-C₃N₄ samples, Fe_xS_1-x coupling resulted in substantial enhancement of visible light absorption, moreover, the bandwidth of heterojunction was also expanded. In addition to effectively degrading RhB and reducing Cr(VI), the redox performance of Fe_xS_1-x/g-C₃N₄ was also increased in the Cr(VI)/RhB mixed system. Based on a variety of experimental results, the enhanced synergistic photocatalytic activity of the 3D Fe_xS_1-x/g-C₃N₄ heterojunction was attributed to enhancement of the separation of e^- and h⁺ in FeS_2, which resulted from the effective conversion of FeS into FeS₂ under UV-light irradiation. The type II heterojunction structure that was produced via one-pot solid fabrication also inhibited the recombination of electron/hole pairs. Fe_xS_1-x doping and heterojunction building improve the photocatalysis capacity of g-C₃N₄ and broaden the visible-light response of pure g-C₃N₄.     

Hydrothermal synthesis of 3D NixCo1−xS2 particles/graphene composite hydrogels for high performance supercapacitors

In this work, three dimensional (3D) Ni_xCo_1−xS₂/graphene composite hydrogels with different Ni contents (denoted as Ni_xCo_1−xS₂/GH (x = 0, 0.31, 0.56, 0.66, 1)) have been synthesized by a simple one-step hydrothermal method and utilized as the active materials of supercapacitors. The as-prepared samples present a 3D interconnected porous network with the pore sizes in the range of several to tens micrometers. Interestingly, the Ni_xCo_1−xS₂ particles are uniformly located on the graphene network and the particle size is evolved from ∼50 nm to ∼1.5 μm with the increase of Ni content. The electrochemical measurements revealed that the specific capacitance, rate capability and cyclability of different Ni_xCo_1−xS₂/GH electrodes are strongly affected by their different Ni content. Among these, the 3D Ni_0.31Co_0.69S₂/GH composite has the highest specific capacitance of 1166 F/g at a current density of 1 A/g. Furthermore, a specific capacitance of 559 F/g can be still maintained at high current density of 20 A/g. After 1000 charge–discharge cycles at 5 A/g, the specific capacitance remains a high value of 755 F/g.     

Enhanced photocatalytic activity of La1-xSrxCoO3/Ag3PO4 induced by the synergistic effect of doping and heterojunction

This study sought to design and synthesize a series of perovskite-based La_1-xSr_xCoO₃/Ag₃PO₄ (with x = 0–1) heterojunction photocatalysts with different Strontium (Sr) doping contents by a simple sol-gel method and properties of the material were comprehensively characterized. Moreover, tetracycline (TC) was chosen as the target pollutant to assess the effect of Sr doping on the catalytic performance of LaCoO₃/Ag₃PO₄. Our results demonstrated that the partial replacement of La³⁺ with Sr²⁺ coupled with shifting Co³⁺ to the mixed-valence state of Co³⁺-Co⁴⁺ led to the formation of substantially more oxygen vacancies in the crystal lattice of La_1-xSr_xCoO₃/Ag₃PO₄. Therefore, the doped catalyst La_1-xSr_xCoO₃/Ag₃PO₄ exhibited enhanced photocatalytic performance. When x = 0.9, the obtained La_0·1Sr_0·9CoO₃/Ag₃PO₄ exhibit an optimal performance for TC degradation. Kinetic analyses demonstrated that the degradation rate constant of TC in La_0·1Sr_0·9CoO₃/Ag₃PO₄ system was 0.0098 min^?1, which is 1.78 times that of LaCoO₃/Ag₃PO₄, and 2.45 times that of SrCoO₃/Ag₃PO₄. Additionally, free radical sequestration experiments indicated that OH^?, h⁺, and O₂^?? all participated in the degradation of TC in the following order: h⁺>O₂^??>OH^?. Finally, analyses of photocatalytic mechanisms suggested that the enhanced photocatalytic activity of La_0·1Sr_0·9CoO₃/Ag₃PO₄ was due to its strong electron transfer properties and the formation of substantially more surface oxygen vacancies in Sr-doped La_0·1Sr_0·9CoO₃.     

The first cycle characteristics of Li[Ni1/3Co1/3Mn1/3]O2 charged up to 4.7 V

In this research, we studied the first cycle characteristics of Li[Ni_1/3Co_1/3Mn_1/3]O₂ charged up to 4.7 V. Properties, such as valence state of the transition metals and crystallographic features, were analyzed by X-ray absorption spectroscopy and X-ray and neutron diffractions. Especially, two plateaus observed around 3.75 and 4.54 V were investigated by ex situ X-ray absorption spectroscopy. XANES studies showed that the oxidation states of transition metals in Li[Ni_1/3Co_1/3Mn_1/3]O₂ are mostly Ni²⁺, Co³⁺ and Mn⁴⁺. Based on neutron diffraction Rietveld analysis, there is about 6% of all nickel divalent (Ni²⁺) ions mixed with lithium ions (cation mixing). Meanwhile, it was found that the oxidation reaction of Ni²⁺/Ni⁴⁺ is related to the lower plateau around 3.75 V, but that of Co³⁺/Co⁴⁺ seems to occur entire range of x in Li_1−x[Ni_1/3Co_1/3Mn_1/3]O₂. Small volume change during cycling was attributed to the opposite variation of lattice parameter “c” and “a” with charging-discharging.