Al Substitution Research Articles

Magnetic phase transitions in Ba0.5Sr1.5Zn2Fe11.92Al0.08O22 hexaferrites

We report studies on the effect of substituting the magnetic Fe3+ cations with nonmagnetic Al3+ cations in Y-type hexaferrite Ba0.5Sr1.5Zn2Fe11.92Al0.08O22 powders on their magnetic properties and especially on the magnetic phase transitions responsible for observing the magnetoelectric effect. In this research, the Y-type hexaferrite powders were synthesized by citric acid sol-gel auto-combustion. After the auto-combustion process, the precursor powders were annealed at 1170 °C in air to obtain the Y-type hexaferrite materials. The effects of Al substitution on the structural, microstructural properties and phase content were investigated in detail using X-ray powder diffraction and scanning electron microscopy. Hysteresis measurements were performed by a physical-property-measurement-system (PPMS) (Quantum Design) at 4.2 K and at room temperature. Dc-magnetic measurements of the temperature dependence of the magnetization at magnetic fields of 50 Oe, 100 Oe and 500 Oe were used to determine the effect of applying a magnetic field on the temperature of magnetic-phase transitions. We demonstrated that the helical spin state can be modified further by varying the magnetic field.

Coercivity enhancement of hot-deformed NdFeB magnet by doping R80Al20 (R = La, Ce, Dy, Tb) alloy powders

Significant enhancement in coercivity for hot deformed (HD) NdFeB magnets is achieved by doping R80Al20 (R= La, Ce, Dy, Tb) alloy powders. All studied samples exhibit fine microstructure with good (00L) texture. By doping R80Al20 powders, the coercivity of HD NdFeB magnets is significantly increased from 16.0 kOe to 19.4 kOe, 20.0 kOe, 21.8 kOe, and 23.8 kOe for R = La, Ce, Dy, and Tb, respectively, while (BH)max is decreased from 41.5 MGOe to 39.3-40.8 MGOe slightly. Microstructure analysis shows that Ce or La prefers to distribute mostly at grain boundary, while Dy or Tb and Al locate at grain boundary and surface. The magnetic isolation due to R-rich phase containing Nd, Ce or La, Al at the grain boundary contributes to coercivity enhancement with the samples with R = La and Ce. In additional to magnetic isolation, the strengthened magnetic anisotropy field of 2:14:1 phase due to Tb or Dy, and slight Al substitutions gives rise to the significant enhancement of coercivity for those with R80Al20 (R = Dy and Tb).

Locating Structure Directing Agent and Al in CHA: Combined Study of Structure Determination of X‐Ray Powder Diffraction and Classical Lattice Energy Calculation

Locating the structure directing agent and Al in zeolite CHA has been performed using structure determination of X‐ray powder diffraction combined with General Utility Lattice Program (GULP) calculation. Trimethyladamantylammonium ion (TMAdaOH+) and benzyltrimethyl ammonium ion (BTMAOH+), respectively, have been found to fit in the pore, resulting in the formation of high silica zeolite CHA, which shows the superior catalytic performance in abatement of NOx using NH3 in the exhaust gas stream of mobile car. The intimate interaction between the corresponding structure directing agent (SDA) and the counter ion due to the Al substitution in the framework has been characterized using the lattice energy calculation. The difference in the lattice energy of the zeolite CHA prepared with TMAdaOH was large compared to that of the zeolite CHA prepared with BTMAOH, which can be attributed probably to the molecule's size. Thereby, the SDA in the zeolite pore has been located readily and the resulting information can be useful for increasing the understanding in the zeolite formation mechanism and designing novel zeolite.

A Queue-Ordered Layered Mn-Based Oxides with Al Substitution as High-Rate and High-Stabilized Cathode for Sodium-Ion Batteries.

Development of highly stabilized and reversible cathode materials has become a great challenge for sodium-ion batteries. O'3-type layered Mn-based oxides have deserved much attention as one of largely reversible-capacity cathodes featured by the resource-rich and low-toxic elements. However, the fragile slabs structure of typical layered oxides, low Mn-ion migration barriers, and Jahn-Teller distortion of Mn3+ have easily resulted in the severe degradation of cyclability and rate performances. Herein, a new queue-ordered superstructure is built up in the O'3-NaMn0.6 Al0.4 O2 cathode material. Through the light-metal Al substitution in O'3-NaMnO2 , the MnO6 and AlO6 octahedrons display the queue-ordered arrangements in the transition metal (TM) slabs. Interestingly, the presence of this superstructure can strengthen the layered structure, reduce the influence from Jahn-Teller effect, and suppress the TM-ions migrations during long-terms cycles. These characteristics results in O'3-NaMn0.6 Al0.4 O2 cathode deliver a high capacity of 160 mAh g-1 , an enhanced rate capability and the excellent cycling performance. This research strategy can provide the broaden insight for future electrode materials with high-performance sodium-ions storage.

Manufacture and Faraday magneto-optical effect of highly transparent novel holmium aluminum garnet ceramics

A novel transparent magneto-optical holmium aluminum garnet (HoAG) ceramic with a high in-line transmittance of ~80.3 % at 589 nm (~97.0 % of the theoretical transmittance of HoAG single crystal) and a maximal infrared cut-off at ~6.5 μm was successfully fabricated by vacuum sintering at 1650 °C. The facile co-precipitation strategy was employed to yield the precipitation precursor with hollow structures upon calcination into the sphere-like HoAG particle with a narrow particle distribution. Silica sintering aid creates point defect of Ho3+ vacancies to promote the HoAG densification rate during sintering by Si4+ substitution for Al3+ in tetrahedrally coordinated 24 (d) sites. The magneto-optical HoAG ceramic has Verdet constants of ~-154 rad/(T·m) at 635 nm and ~-36 rad/(T·m) at 1064 nm, which are higher than or similar to that of the commercial TGG single crystal. The thermal conductivity of the transparent HoAG ceramic was determined to be ~10.5 W/(m·K) at room temperature.

The influence of the Sc3+ dopant on the transmittance of (Y, Er)3Al5O12 ceramics.

High erbium content yttrium aluminum garnet (Er:YAG) and yttrium scandium aluminum garnet (Er:YSAG) ceramics have been fabricated from Er:YAG and Er:YSAG powders, respectively. The powders have been synthesized via a reverse precipitation technique, processed by uniaxial pressing followed by cold isostatic pressing, and sintered in a vacuum. TEOS (tetraethoxysilane) was used as a sintering additive. After vacuum sintering, all of the samples were processed by annealing in air to increase the transmittance and polished on both sides. The influence of the Sc3+ content and the synthesis conditions on the microstructure and optical transparency of the Er:YAG and Er:YSAG ceramics have been investigated in detail. It has been found that changing Al3+ for the bigger Sc3+ ion leads to the transmittance increasing to up to 60% at a wavelength of about 1500 nm.

A high throughput computational investigation of the solid solution mechanisms of actinides and lanthanides in zirconolite.

In this work, we perform a theoretical investigation of the actinide and lanthanide solid solution mechanisms of zirconolite-2M, prototypically CaZrTi2O7, as a candidate immobilisation matrix for plutonium. Solid solution energies were calculated using static atomistic simulations by means of the General Utility Lattice Program, for formulations of relevance to ceramic wasteform deployment, with substitution on the Ca2+ and Zr4+ sites by Ce4+, Pu4+, Th4+, and U4+, and appropriate charge balance by substitution of Al3+ or Fe3+ on Ti4+ sites. In simple solid solutions involving substitution on the Zr4+ site, we found that whereas substitution of Ce4+, U4+ and Pu4+ were energetically favoured, substitution of Th4+ was not energetically favoured. For more complex solid solutions involving Ce4+, Pu4+, Th4+, and U4+ substitution on the Ca2+ site, we found the most energetically favoured scheme involved co-substitution of Al3+ or Fe3+ on the five-fold co-ordinate Ti4+ site in the zirconolite-2M structure. Comparison of these computational data with experimental evidence, where available, demonstrated broad agreement. Consequently, this study provides useful insight into formulation design and the efficacy of Ce4+, U4+ and Th4+ as Pu4+ surrogates in zirconolite-2M ceramic wasteforms for plutonium disposition.

A dual vanadium substitution strategy for improving NASICON-type cathode materials for Na-ion batteries

Al substitution in Na3VAlxCr1−x(PO4)3 (0 ≤ x ≤ 1) induced a noticeable improvement of capacity at the highest rate, as evidenced by their high diffusion coefficients and low cell resistance.

In situ and tunable structuring of semiconductor-in-glass transparent composite.

SummarySemiconductor-in-glass composites are an exciting class of photonic materials for various fundamental applications. The significant challenge is the scalable elaboration of composite with the desirable combination of tunable structure, high semiconductor loading ratio, and excellent transparency. Here we report that the topological engineering strategy via hybridization of the glass network former enables to surmount the aforementioned challenge. It not only facilitates the in situ precipitation of (Ga2-xAlx)O3 domains with continuously tunable composition but also allows to simultaneously refine the grain size and enhance the crystallinity. In addition, the composites exhibit excellent transparency and can host various active dopants. We demonstrate the attractive broadband optical response of the composite and achieve the pulse laser operation in mid-infrared waveband. The findings are expected to provide a fundamental principle of in situ modification in hybrid system for generation of high-performance semiconductor-in-glass composites.

Mineralogy and spectroscopy (visible near infrared and Fourier Transform Infrared) of Mukundpura CM2: Implications for asteroidal aqueous alteration

We report the textures, mineralogy and mineral chemistry of the Mukundpura matrix component, a clast-bearing, brecciated, new CM2 carbonaceous chondrite. Like other CMs, Mukundpura is matrix-enriched and has experienced different degrees of aqueous alteration with evidences of fracturing and compaction of clasts due to the impact. A few relict chondrule clasts and CAIs (diopside and spinel) survived despite of the alteration amidst accessory phases of olivine, magnetite, sulphides and calcite. X-Ray Diffraction (XRD), Visible Near Infrared (VNIR) and Fourier Transform Infrared (FTIR) spectroscopic studies reveal higher phyllosilicate content (∼90 %) comprising of both Mg and Fe-serpentine and abundant serpentine-sulphide intergrowths. Even then, the presence of accessory olivine as relict clasts can be interpreted from the presence of certain typical olivine absorptions in the FTIR spectra. The non-stoichiometric, Tochilinite-Cronstedtite occurrences probably relate to broadening of XRD and FTIR spectra and can be explained by coupled Al–Si and Mg–Al substitutions in talc and serpentine. The FTIR spectra suggest widespread transformation of olivine to serpentine, unlike the largely unaltered chondrules. The correlations of mineralogical alteration index with FeO/SiO2 and S/SiO2 in different domains of matrix suggest different extent of alterations. Thus, the aqueous alteration is extensive but not pervasive. The majority of alteration seems to have occurred within the asteroidal parent body. The Mukundpura CM2 thus preserves a unique combination of relict chondrules and highly aqueous altered variegated matrix clasts, although the surface mineralogy resembles the C-type asteroids recently probed by OSIRIS-REx and Hayabusa-2 missions.

Application of Spinel MgMn2-X Al x O4 As Cathode for Mg Rechargeable Battery

【Introduction】Lithium-ion battery (LIB) has mainly used in our life, but its high price due to Li and Co metals are crucial problem. Magnesium rechargeable battery (MRB) has been recently studied as a post LIB due to elemental abundant supply and superior theoretical volumetric energy density of magnesium. For cathode materials, spinel oxides is one of a candidate of MRB due to its high redox potential and three-dimensional diffusion paths.[1] Especially, MgMn2O4 is expected to perform high theoretical capacity because utilization of both Mn3+/Mn4+ and Mn2+/ Mn3+ redox is possible in the potential window of the common electrolyte.[2] But structural change from tetragonal to cubic occurs due to Jahn-Teller effect of Mn3+ ion during charge/discharge, which decreases reversibility. In this study, we tried to enhance reversibility of MgMn2O4 spinel by substituting Al for Mn to release its Jahn-Teller distortion, and the optimal substitution ratio and their electrochemical property were evaluated.【Experimental】MgMn2-xAlxO4 (x = 0, 0.1, 0.2, 0.5) were synthesized by Pechini method[3] with an annealing process of 400 ºC, 10 hour. Cathodes were prepared by mixing the obtained samples with acetylene black and polytetrafuluoroethylene at a weight ratio of 60/30/10 . Mg alloy (AZ31) was used for an anode. Galvanostatic charge/discharge profiles were obtained by using a coin cell with a 0.3 M Mg[B(HFIP)4]2/triglyme electrolyte at 25 ºC, 10 mA/g.【Results and discussion】According to X-ray diffraction(XRD) patterns, MgMn2-xAlxO4 (x = 0, 0.1, 0.2, 0.5) spinel were obtained and their crystallinity become lower by Al substitution. In MgMn1.5Al0.5O4, the crystal structure changed from tetragonal to cubic phase, suggesting that the Jahn-Teller effect is suppressed by the formation of the solid solution of tetragonal MgMn2O4 and cubic MgAl2O4. The Al-substituted MgMn2O4 exhibited higher discharge capacities compared with MgMn2O4 (64.0 mAh/g), and especially MgMn1.9Al0.1O4 showed the highest discharge capacity of 92.3 mAh/g. In the poster session, X-ray absorption spectroscopy (XAS) and cycle characteristics will be reported.【Acknowledgment】This work was supported by JST ALCA-SPRING Grant Number JPMJAL1301, Japan.【References】[1] S. Okamoto, T. Ichitsubo, T. Kawaguchi, Y. Kumagai, F. Oba, S. Yagi, K. Shimokawa, N. Goto, T. Doi and E. Matsubara, Adv. Sci., 2015, 2, 1500072[2] H. Kobayashi, K. Yamaguchi and I. Honma, RSC Adv., 2019, 9, 36434-36439.[3] J. Yin, A. B. Brady, E. S. Takeuchi, A. C. Marschilok and K. J. Takeuchi, Chem. Commun., 2017, 53, 3665-3668.

Electrochemical Properties of High Nickel NMCA Materials

Lithium nickel manganese cobalt oxides (NMC) with high nickel composition are considered as the most promising candidates for the next-generation cathode because of their high reversible capacities (180−250 mAh g−1), high voltage window, and reasonable rate capability. However, the highly reactive Ni4+ ions tend to cause unfavorable side reactions with the electrolyte, which leads to an electrochemical inactive NiO-type rock-salt phase associated with oxygen loss on the surface at the highly delithiated state, degrading the structure of materials. Furthermore, the dramatic lattice contraction in a rather short period after charging to high voltage (>4V) causes cracks along the grain boundaries, which damages the particle integrity, delivering a gradual fading of the reversible capacity and thermal stability during cycling.Aluminum substitution is an effective strategy to stabilize the lattice structure and suppress oxygen release due to the Al-O bonds are stronger compared to other transition metal-oxygen bonds. To maximum the impact of the Al, a uniform substitution in the host structure is essential. Here we report an in-situ Al substitution strategy for NMC811, which leads to robust layered structures, reducing the phase transition and side reactions on the surface of high nickel NMC materials at the highly delithiated state. This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy, through the Advanced Battery Materials Research Program (Battery500 Consortium)

Effects of Al substitution with Si and Sn on tribological performance of Ti3AlC2

Since their discovery, the MAX phases have elicited engineering interest as potential choices for wear resistant parts. One such compound is Ti3AlC2 with nano-layered structure, low density (4.25 g/cm3), good oxidation resistant and self-lubrication properties. The purpose of this investigation was to evaluate the dominant effect of the A-site solid solution elements addition on dry sliding characteristics of Ti3AlC2 against 0.45% C steel (S45C) disk, a material which is widely used in wear-critical applications such as impeller, gear and axles. Dry sliding tribological behaviors of hot-pressed Ti3Al0.94C2, Ti3Al0.78Sn0.22C2 and Ti3Al0.67Si0.28C2 solid solutions were conducted using a block-on-disk type tester at surface sliding speed range from 10 to 30 m/s and in the normal load range from 20 to 80 N. The results show that friction coefficient of Ti3Al0.94C2 is higher than that of Ti3Al0.78Sn0.22C2, but lower than that of Ti3Al0.67Si0.28C2. However, the change in wear rate as a function of normal load for different sliding speed shows almost reversed trend. Difference in the phase composition of friction films were found to be responsible for observed change in tribological behaved after partial substitution of Al in Ti3AlC2 with Sn and Si. This study shows that friction coefficient of Ti3AlC2 can be adjusted from 0.2 to 0.38 by partially substituting Al with Si and/or Sn.

Influence of Al(III) and Sb(V) on the transformation of ferrihydrite nanoparticles: Interaction among ferrihydrite, coprecipitated Al(III) and Sb(V)

Ferrihydrite is ubiquitous in natural environments and is usually co-precipitated with impure ions and toxic contaminants like Al(III) and Sb(V) during the neutralization process of acid mine drainage. However, little is known about the dynamic interactions among ferrihydrite, Al(III) and Sb(V). In this study, the influence of coprecipitated Al(III) and Sb(V) on the transformation of ferrihydrite was investigated. The samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy before and after aging for 10 days at 70 °C. Results indicated that the Al(III) enhanced the immobilization of Sb(V) under neutral and alkaline conditions, and the presence of Sb(V) induced more production of extractable Al(III). XRD patterns revealed that the transformation rate of coprecipitated Al(III) and Sb(V) ferrihydrite was higher than Al-coprecipitated ferrihydrite. It is speculated that the presence of Sb(V) weakened the inhibition of Al(III) under experimental conditions. Competitive reaction of Al(III) and Sb(V) for substitution on the lattice Fe of ferrihydrite, likely decreased Al(III) substitution on ferrihydrite, and thus increased the observed transformation rate of ferrihydrite. These results have significant environmental implications for predicting the role of impurities and contaminants on ferrihydrite transformation processes.

Structural and optical properties of transparent, tunable bandgap semiconductor: α-(AlxCr1−x)2O3

Detailed structural and optical properties of α-(AlxCr1−x)2O3 (0 ≤ x ≤ 1) synthesized by the solid state reaction method have been investigated. Single phase α-(AlxCr1−x)2O3 with space group R3¯c is obtained for the full composition range of 0 ≤ x ≤ 1. Variations in the lattice parameters a and c have been determined. Lattice parameter c follows Vegard’s law, while the lattice parameter a shows a clear deviation with a bowing parameter of −0.035 Å. This behavior of the lattice parameters of α-(AlxCr1−x)2O3 with x is explained in detail by studying the local structure. Extended x-ray absorption fine structure spectroscopy shows a reduction in the values of Cr–O bond lengths with composition x. Optical absorption measurements of α-(Al1−xCrx)2O3 for 0 ≤ x ≤ 1 show a large bandgap tunability of 1.9 eV (from 3.4 eV to 5.3 eV). The photoemission spectroscopy data and the analysis of partial density of states obtained from first principles electronic structure calculations suggest that the valence band maxima is mainly composed of Cr 3d levels, which hybridize with the O 2p levels. Increased contribution of O 2p partial density of states is observed with Al substitution, which is expected to enhance p-type carrier conduction in the α-(AlxCr1−x)2O3 system as compared to the parent α-Cr2O3 system. Thus, the large bandgap, its tunability in the UV region, and the predicted enhancement of p-type conductivity in the α-(AlxCr1−x)2O3 system make it a potential candidate for application in UV based photo-detectors and transparent electronics.

Structural, infrared and magnetic properties of MgAlxFe2-xO4 compounds: Effect of the preparation methods and Al substitution

Aluminum substituted magnesium ferrite MgAlxFe2-xO4 (x = 0.0, 0.2, 0.3, 0.7 and 2.0) are prepared by two commonly-used methods: Sol-gel (SG) and Solid-phase reaction (SR). Structural studies are carried out using X-ray and neutron diffraction, and FTIR techniques, and heat generation ability in the AC magnetic field is explored by the specially designed device. Diffraction patterns revealed the formation of single cubic spinel MgAlxFe2-xO4 ferrites for SG and additional MgAl2O4 phases at higher concentration of aluminum (x > 0.3) in SR samples. Structural studies are carried out using X-ray and neutron diffraction, and FTIR techniques, scanning electron microscopy (SEM) and heat generation ability in the AC magnetic field is explored by the specially designed device. This study attempts to compare both chemical methods, and to correlate the properties with Al substitution concentration. Diffraction patterns revealed the formation of single cubic spinel MgAlxFe2-xO4 ferrites for SG and additional MgAl2O4 phases at higher concentration of aluminum (x > 0.3) in SR samples FTIR was used to confirm the spinel structure, the main vibrating modes were observed to shift to higher wave number with increasing Al3+ concentration. The tetrahedral force constant (KT) increases continuously with Al3+ concentration. The morphology investigations revealed the spherical morphology of particles with some agglomeration. The heat-generation ability was enhanced with decreasing Al concentration. Upon exposure to an external alternation magnetic field of 70 kHz and intensity of 54.3 mT, specific power absorption rate (SAR) of the Magnesium ferrite aluminates. The heat generation ability of the MgAlxFe2-xO4-SR ferrites are higher than those of MgAlxFe2-xO4-SG samples. Moreover, doping element is affected to cation distribution between tetrahedral and octahedral sites. For MgAlxFe2-xO4, heat generation ability will be influenced by additional magnetic properties and cation distribution. This will be distinguished by more detailed investigation for magnetic properties.

Quaternary Fe‐Cu‐Cr‐Al HT‐WGS Catalysts – Effect of Al Substitution on the Efficiency at Steam‐Lean Process Gas

In the present work, we report on Fe–Cu–Cr–Al systems with various Cr/Al substitution as catalysts for high‐temperature water‐gas shift (HT‐WGS) to evaluate the possibility of Cr elimination and usability for carrying out the HT‐WGS process at steam‐lean process gas. The set of Fe–Cu–Cr–Al catalysts with the same Fe/Cu molar ratio and different Cr/Al molar ratio (0/∞) were prepared by the precursors' co‐precipitation and thermal treatment. The catalysts were investigated by XRF, DTG/MS, XRD, N2 sorption, H2‐TPR methods and activity tests. A relationship between Cr/Al ratio and physicochemical parameters and HT‐WGS activity, selectivity and stability of the catalysts have been estimated. Experimental results demonstrated that complete elimination of Cr from the Fe–Cu–Cr–Al catalyst is unfavorable, and it would lead to negative consequences as Cr enhances the catalyst activity and improve its durability.

Spectroscopic analysis of allophane and imogolite samples with variable Fe abundance for characterizing the poorly crystalline components on Mars

AbstractNanophase materials including silicates, aluminosilicates, and iron oxides are widespread on Mars. These minerals are important because they likely represent a solid-phase record of ancient climatic conditions on the martian surface. Identification and characterization of nanophase compounds is technically challenging due to the small size and poorly ordered nature of these materials, particularly because their chemical compositions can vary widely.This study presents spectra of several synthetic allophane and imogolite samples with a range of chemical compositions that are typical of the natural variability of allophanic materials. These samples were formed under controlled conditions and have been thoroughly characterized in terms of chemical composition and short-range structure.Analyses confirmed that the synthetic materials were allophane and imogolite and were structurally similar to previously studied natural and synthetic examples of these phases. NMR and XAFS data indicated that high-Al proto-imogolite allophanes were similar in structure to imogolite but were less well ordered, and supported the proposed nanoball structures based on rolled octahedral Al sheets. Increasing Si content in allophane produced increasing tetrahedral Al substitution as well as polymerized Si chain structures at Al-Si mole ratios of 1:1, and sheets and possible framework structures at Al-Si mole ratios of 1:2. Fe in allophanes and imogolites substituted exclusively for octahedral Al.Reflectance spectra of the synthetic allophanes and imogolites were comparable to previously analyzed samples. Variations in Fe content of allophane and imogolite resulted in some observable changes in visible/near-infrared (VNIR) reflectance spectra, but these changes were not detectable in emission spectra. Emission spectra of the samples suggest that variations in Al-Si ratio of allophanes should be detectable using remotely sensed data. Because allophanes with different Al-Si ratios typically form in very different environments, this could be significant for interpretation of formation conditions on Mars, with high-Al compositions suggesting possible tephra weathering and high-Si compositions indicating possible formation from thermal waters.

Three-dimensional Al-substituted quasi-concentration gradient Ni-Co layered double hydroxide nanosheets for high-performance asymmetric supercapacitors

Based on an easy-to-operate stepwise electrochemical deposition method, Al-substituted layered bimetallic hydroxide (Ni-Co layered double hydroxide [LDH]) with quasi-concentration gradient (Al-QCG) was deposited on Ni foam. The three-dimensional porous heterostructured Al-QCG could significantly accelerate electron conduction and facilitate electrolyte penetration, effectively improving the specific capacitance and rate performance of the supercapacitor. In addition, Al substitution changed the crystal structure of LDH and prevented local agglomeration and splitting of the layered nanosheets effectively during reproducible charge/discharge cycling, further improving the electrode’s cyclic stability. Al-QCG demonstrated an excellent specific capacity of 2372.6 F g−1 at 1 A g−1 and 1180.0 F g−1 at 20 A g−1, and the cycling stability of the Al-QCG/NF electrode greatly improved from 30.0% of bulk Ni–Co LDH to 86.1% after 5000 cycles at 20 A g−1. The asymmetrical supercapacitors (ASCs) with the activated carbon anode also displayed a high specific capacitance of 48.1 F g−1 at 1 A g−1, and it remained at 56.3% of its capacity when the current density increased to 10 A g−1. The ASCs achieved a maximum energy density of 15.0 Wh/kg at 763.4 W/kg and an impressive capacitance retention of 90.9% after 10,000 cycles at 2 A g−1, showing promising application in high-performance supercapacitors. This work highlighted the complex interactions between the composition of different element ratios and multidimensional morphology on the dynamics and capacitive performance of LDH materials.

Influence of Al content on the optical band-gap enhancement and lattice structure of (Ga1-xAlx)2O3 single crystal

Abstract Single crystals of undoped, 4.8, 9.3 and 14.1 at.% Al substituted β-Ga2O3 have been grown by optical floating zone technique. It has been observed that it is not possible to grow good quality single crystal with higher Al content unlike the thin film grown by pulsed laser deposition [Appl. Phys. Lett. 105 (2014) 162107]. It has been found that the incorporation of Al in β-Ga2O3 has resulted a shrinkage in the lattice parameters and volume. This leads to a systematic increase in the band gap of the material and broadens the transmission window in the deep UV range up to 5.08 eV for 14.1 at.% of Al substitution in the lattice.