Effect Of Al-doping Research Articles

Effect of Al, Ti and Cr Doping on Vanadium Dioxide (VO2) Analyzed by Density Function Theory (DFT) Method.

Density function theory (DFT) method was developed and applied for fundamentally understanding the doping effect of various metals (Al, Ti and Cr) on vanadium dioxide (VO₂). The substitution doping of Al, Ti and Cr in VO₂ could lead to significant changes in electronic structure, band gap and optical property. Different from physical experiments, the DFT method could be utilized for fundamental understandings at an atomic scale. It was found via DFT calculations that: (i) Al doping caused a slightly distorted octahedron in monoclinic VO₂(M), and narrowed the band gap of VO₂(M) due to the upward shift of the valence band (VB), while Cr doping narrowed the band gap because of the downward shift of the conduction band (CB); (ii) Ti doping slightly widened the band gap of VO₂(M); and (iii) the optical reflectivity of VO₂(M) decreased after substitution doping low-valent metals (e.g., Al). This study will be beneficial for designing and controlling elemental doping to obtain metal oxide nanocomposites with unique band gap and electronic structure for thermochromic energy saving applications.

The Effect of Mg, Fe(II), and Al Doping on CH4: Adsorption and Diffusion on the Surface of Na-Kaolinite (001) by Molecular Simulations.

Because kaolinite includes a large range of defect elements, the effects of Mg, Fe(II), and Al doping on the CH4 adsorption and diffusion on the surface of Na-kaolinite (001) were investigated by molecular simulations. The simulation results illustrate that ion doping can significantly reduce the amount of CH4 adsorbed by kaolinite, but the type of doped ions has little effect on the amount of adsorption. The specific surface area of kaolinite and the interaction energy between CH4 and the kaolinite’s surface are two key factors that can determine CH4 adsorption capacity. The first peak value of the radial distribution functions (RDFs) between CH4 and the pure kaolinite is larger than that between Mg-, Fe(II)-, and Al-doped kaolinite, which indicates that ion doping can reduce the strength of the interactions between CH4 and the kaolinite’s surface. Besides hydrogen and oxygen atoms, interlayer sodium ions are also strong adsorption sites for CH4 and lead to a weakened interaction between CH4 and the kaolinite’s surface, as well as a decrease in CH4 adsorption. Contrary to the adsorption results, ion doping facilitates the diffusion of CH4, which is beneficial for actual shale gas extraction.

Effect of Al Doping on Hydrothermal Growth and Physical Properties of Doped ZnO Nanoarrays for Optoelectronic Applications

Abstract Renewable energy production via solar energy is a promising solution to advent the globally mounting energy needs. Therefore, our work has been planned to develop, high efficient optoelectronic devices, which are cost effective and easily fabricated. Successfully, we developed Al doped ZnO nanorods (NRs) by two step process. Initially by using sol-gel technique we grow the seed layers and further we succeed ZnO nanorods by a simple hydrothermal process without using any toxic solvents. The obtained nanorods show remarkable electrical and optical properties characterized by I-V characteristics, UV- vis, Photoluminescence (PL) spectroscopy techniques. In addition, we have also investigated the surface morphological properties from FESEM which indicates that NRs are hexagonal in shape and the diameter of the rod varies from 232 nm to 297 nm as the Al concentration changes from 1% to 10% in ZnO. Band gap of Al doped ZnO NR decreases on increasing the concentration of doping from 3.23 to 2.73 eV. The PL spectrum shows emission peaks in the UV and visible region. From this we conclude that, these materials are good candidate for the optoelectronic applications. Thus, our approach will probably fetch and derive a noble route for the fabrication of new materials.

P2-Na0.67 Alx Mn1-x O2 : Cost-Effective, Stable and High-Rate Sodium Electrodes by Suppressing Phase Transitions and Enhancing Sodium Cation Mobility.

Sodium layered P2-stacking Na0.67 MnO2 materials have shown great promise for sodium-ion batteries. However, the undesired Jahn-Teller effect of the Mn4+ /Mn3+ redox couple and multiple biphasic structural transitions during charge/discharge of the materials lead to anisotropic structure expansion and rapid capacity decay. Herein, by introducing abundant Al into the transition-metal layers to decrease the number of Mn3+ , we obtain the low cost pure P2-type Na0.67 Alx Mn1-x O2 (x=0.05, 0.1 and 0.2) materials with high structural stability and promising performance. The Al-doping effect on the long/short range structural evolutions and electrochemical performances is further investigated by combining in situ synchrotron XRD and solid-state NMR techniques. Our results reveal that Al-doping alleviates the phase transformations thus giving rise to better cycling life, and leads to a larger spacing of Na+ layer thus producing a remarkable rate capability of 96 mAh g-1 at 1200 mA g-1 .

Effects of aluminum doping upon properties of cadmium sulfide thin films and its effect on ITO/CdS:Al/NiOx/Ni/Au diodes

We analyze the Al doping effect in CdS films by chemical bath deposition and how it impacts this doping effect in a heterojunction, for the case of ITO/CdS:Al/NiOx/Ni/Au. The results show that the doping effect of aluminum on the CdS films by chemical bath deposition does slightly affect the structural and morphological properties. The impact of the doping is related to the electrical properties; first, with a decrement in the resistivity from 108 to 107 Ω cm, the work function decreases from 4.7 to 4.3 eV, the bandgap and the valence band suffers a small increment of 0.1 eV. The change in the electrical properties impacts the diode behavior, and the increment in the work function leads to an increment of the Fermi energy level difference between NiOx and CdS:Al; this difference was reflected in a wider depletion region and a reduction of the leakage current.

Effect of Al doping in zinc ferrite nanoparticles and their structural and magnetic properties

Aluminum doped zinc ferrite (ZnFe2−xAlxO4) nanoparticles with x ranging from 0 to 0.9 was prepared via thermal treatment method using PVP as a capping agent. The Al-dopant concentration was controlled by ratio of Al/Fe precursors. Structural, morphological, and magnetic properties were investigated for the effect of non-magnetic Al in ferrite samples. Single phase with normal spinel ferrite structure was revealed by XRD measurement. Furthermore, reduction in nanocrystalline particle size as the Al content increases has been confirmed by XRD analysis. It was discovered that particle size decreases as the Al concentration increases, which attributed to structural effect of Al on grain size. Complete formation of stable nanocrystalline ferrite at 500 °C was discovered by TGA measurement. Magnetic hysteresis loop measured at RT with a maximum magnetic field of 1.8 T revealed that Ms and Mr both decreased, which ascribed to the results of spin non-collinearity and weak interaction between sublattices.

Effects of co-doping on electronic structure and optical properties of 3C-SiC from first-principles method

Electronic structure and optical properties of Cr-, Al- and Cr-Al co-doped 3C-SiC systems are investigated by the first principles method. Al-, Cr- and Cr-Al co-doped systems present the characteristics of p-, n- and n-type semiconductor materials, respectively. Charge density difference results show that the covalency of bonding reduces after doping, which is verified by bond population values due to the fact that the values of single doped and Cr-Al co-doped systems are lower than that of un-doped 3C-SiC. The intrinsic 3C-SiC barely has microwave dielectric loss, however, it can be improved through Al or Cr doping, especially the effect of Al doping, indicating the enhanced ability of materials to absorb electromagnetic waves, which is helpful for SiC to be widely used in military and aerospace fields as absorbing materials. By analyzing the host peaks of the absorption coefficient and the loss function, it is found that there is a significant red shift after doping. SiC exhibits the “Transparent Type” characteristic based on the fact that it has a lower absorption coefficient and reflectance in the visible light region, which proves the foundation for optical property and opens a window for photoelectric devices.

The regulatory effect of Al atomic-scale doping in NiAlO for COS removal

Abstract In this paper, Al atomic-scale doping has been achieved by using NiAl hydrotalcite-like compounds (HTLCs) as precursors method. Regulatory effect of Al doping in NiO for carbonyl sulfide (COS) removal was studied. The samples were systematically characterized by XRD, SEM, N2 adsorption/desorption, FTIR, CO2-TPD, XPS, XAFS and In-situ DRIFTS. The results showed that the activity series for removal of COS decrease in the following sequence: Ni3Al-HTO > Ni5Al-HTO > Ni1Al-HTO. The enhanced activity after Al atomic-scale doping is attributed to the abundant surface basic sites as evidenced by results of CO2-TPD. XPS and XAFS provide evidence for the reduction of Ni2+ by Al doping in NiO, which suggest large amounts of O-vacancies present on Ni3Al-HTO. This work is useful to explore feasible routes to improve the performance of desulfurization material for the feed gas purification.

Tuning phase stability and short-range order through Al doping in (CoCrFeMn)100−xAlx high-entropy alloys

For (CoCrFeMn)$_{100-x}$Al$_{x}$ high-entropy alloys, we investigate the phase evolution with increasing Al-content (0 $\le$ x $\le$ 20 at.%). From first-principles theory, the Al-doping drives the alloy structurally from FCC to BCC separated by a narrow two-phase region (FCC+BCC), which is well supported by our experiments. We highlight the effect of Al-doping on the formation enthalpy and electronic structure of (CoCrFeMn)$_{100-x}$Al$_{x}$ alloys. As chemical short-range order (SRO) in multicomponent alloys indicates the nascent local order (and entropy changes), as well as expected low-temperature ordering behavior, we use thermodynamic linear-response within density-functional theory to predict SRO and ordering transformation and temperatures inherent in (CoCrFeMn)$_{100-x}$Al$_{x}$. The predictions agree with our present experimental findings, and other reported ones.

Effect of Al Doping on the Structural, Electrical, Gas Sensing Properties of ZnO Nanorods Synthesized by Hydrothermal Growth

The effect of Al doping on the morphology and sensing properties of ZnO nanorods have been shown. Undoped and Al-doped well-aligned ZnO nanorods have been grown on sputtered ZnO/SiO2/Si (100) pre-grown seed layer substrate by the hydrothermal method. The molar ratio of dopant (aluminum nitrate) in the solution, [Al/Zn], was varied from 0.1% to 3%. The prepared ZnO nanorods showed preferred orientation [Formula: see text]0001[Formula: see text] and were well aligned vertically. We observed that for 0.5% Al doping the diameter and resistivity of the nanorods became the least, carrier concentration became large. Sensing behavior of the doped samples tested for H2 gas shows the sensitivity of [Formula: see text] at [Formula: see text]C and [Formula: see text] at [Formula: see text]C, respectively.

Effects of thickness on photoelectric properties and perovskite solar cells application of transparent conductive F and Al co-doped ZnO films

ZnO films with excellent photoelectric properties have been realized in this study through low-concentration F-and-Al co-doping, conducted with radio-frequency magnetron sputtering. It has been demonstrated that the valence state of Al gradually changes from the incomplete oxidation state to the oxidation state, though the chemical valence states of F, O, and Zn are stable. The as-prepared films possess good performance with a mobility of ∼41.89 cm2/Vs, resistivity of ∼3.50 × 10−4 Ω cm, and an average transmittance over 90% in the range of 400–1200 nm. Moreover, the crystallinity of the films and effect of Al doping were further improved through post annealing. Consequently, the improved film mobility, carrier concentration, resistivity, and sheet resistance were, respectively, measured as 53.97 cm2/Vs, 5.18 × 1020 cm−3, 2.23 × 10−4 Ω cm, and 2.73 Ω/□. These films are, therefore, superior to the commercial F-doped SnO2 (FTO) and comparable to the Sn-doped In2O3 (ITO) films. High-performance perovskite with a conversion efficiency as high as 16.24% was achieved when the abovementioned optimized film was used as the front electrode. The reference perovskite solar cells that had commercial ITO and FTO as their front electrodes showed lower efficiency of 15.92% and 12.45%, respectively.

The Effect of Al Doping on the Sensitivity of SnO2 Films Prepared by Chemical Spray Pyrolysis

Pure and Al-doped SnO 2 as gas sensors with properties characteristics provoking gas sensitivity were used for measuring CO 2 atmospheres. In this paper we discussed the optical properties of undoped and Al (each 3, 5 and %) doped SnO 2 thin films were synthesized by spray pyrolysis on glass substrate. The samples were characterized using X-ray diffraction (XRD) and gas sensitivity. The XRD analysis reveals that the Al dopants were substituted into rutile SnO 2 nanoparticles without forming any secondary phase. The average particle size of the samples was increasing with increasing Al concentration. From XRD and AFM micrograph it was confirmed, the grain size in the range of 22.4-34.4 nm. The study reveals polycrystalline structure with prominent peaks. In particular, 7% Al-SnO 2 films have a higher sensitivity (30%). Keywords: Structural, gas sensitivity properties, Aluminum (Al) doped , Tin oxide (SnO2) nanocrystal. DOI : 10.7176/APTA/76-02 Publication date :March 31 st 2019

Effect of Al doping on the magnetic and elastic properties of Fe65Ni35Invar alloys

Invar alloys have great importance due to their low thermal expansion coefficient. The effect of Al doping on Fe65 Ni35 Invar alloy was investigated by temperature-dependent magnetization and elastic modulus measurements. First, 0.44 at% and 2.24 at% of Al were substituted for Ni. Then X-ray diffraction measurements, Rietveld refinements, and scanning electron microscopy studies were performed to understand the effect of Al-doping on the face-centered cubic structure. The elastic modulus of Fe65 Ni35 and the Al-doped samples were measured in the temperature range 300 ≤ T ≤ 870 K using impulse excitation. The temperature dependence of magnetization and elastic modulus results for the Al-doped Invar alloys were compared with those of nondoped Invar alloy. Al doping to Fe65 Ni35 Invar alloy led to volume shrinkage and decreasing Curie temperature as seen in the effect of hydrostatic pressure application.

Sol-gel derived aluminium doped zinc oxide thin films: A view of aluminium doping effect on physicochemical and NO2 sensing properties

Aluminium doped ZnO (AZO) thin films have been synthesized by using a sol-gel spin coating method. The effect of Al-doping on physicochemical and NO2 sensing properties of the AZO thin films were studied. The structural and compositional analysis confirms the phase formation of ZnO and substitution of aluminium atoms into zinc oxide lattice. The gas sensing performance of AZO thin films investigated at different operational temperatures towards NO2 gas. The NO2 sensing study reveals that the 2 at% AZO film sensor shows excellent gas sensing characteristics at 200 °C.

Facile synthesis of Al-doping 1D ZnO nanoneedles by co-precipitation method for efficient removal of methylene blue

High quality and uniform Aluminum-doped zinc oxide (AZO) nanoflowers were successfully fabricated by co-precipitation method and de-ionized water was used as solvent in the whole fabrication process, which was in agreement with the development of green chemistry. The obtained one dimensional (1D) ZnO nanoneedles and AZO nanoflowers were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectrometer (EDS), Photocurrent tests, which were conducive to know fully about crystal quality, the structure, surface composition and optical property of 1D ZnO nanoneedles and AZO nanoflowers. We not only synthesized 1D ZnO nanoneedles by adjusting the ratios of Zn 2+ and OH −, but also explored the effect of Al-doping and calcination temperature on the morphologies and performance of ZnO. The facile synthesis and environmentally-friendly method introduced by us is easy to control and industrialize. Moreover, there were no organic solvents, complexes and surfactants in the whole fabrication process, so it will exert a significant influence on the use of ZnO in the field of cosmetics and medical polymer materials. We investigated the photocurrent responses of ZnO and Al-doped ZnO and the photocatalytic activities of ZnO by degrading methylene blue (MB) solution. High quality 1D ZnO nanoneedles not only possess excellent photocatalytic activities, but also exhibit high photocatalytic stability and outstanding cycling stability.

The Effect of Al Doping on Structural, Electrical and Optical Properties of CdSe Films

The Effect of Al Doping on Structural, Electrical and Optical Properties of CdSe Films

Direct Observation of Surface Potential Distribution in Insulation Resistance Degraded Acceptor-Doped BaTiO3 Multilayered Ceramic Capacitors

Insulation resistance (IR) degradation in BaTiO3 is a key issue for developing miniaturized multilayer ceramic capacitors (MLCCs) with high capacity. Despite rapid progress in BaTiO3-based MLCCs, the mechanism of IR degradation is still controversial. In this study, we demonstrate the Al doping effect on IR degradation behavior of BaTiO3 MLCCs by electrical measurements and scanning Kelvin probe microscopy (SKPM). As the Al doping concentration in BaTiO3 increases, IR degradation of MLCCs seems to be suppressed from electrical characterization results. However, SKPM results reveal that the conductive regions near the cathode become lager with Al doping after IR degradation. The formation of conducting regions is attributed to the migration of oxygen vacancies, which is the origin of IR degradation in BaTiO3, in dielectric layers. These results imply that acceptor doping in BaTiO3 solely cannot suppress the IR degradation in MLCC even though less asymmetric IR characteristics and IR degradation in MLCCs with higher Al doping concentration are observed from electrical characterization. Our results strongly suggest that observing the surface potential distribution in IR degraded dielectric layers using SKPM is an effective method to unravel the mechanism of IR degradation in MLCCs.

Effect of Al Doping on Thickness, Optical, Morphological and Structural Properties of TiO2 Thin Film Prepared by Spin Coating Method

Pure TiO₂ thin films and Al doped TiO₂ thin films have been prepared by spin coating method. This work is carried out to determine the effect of Al on TiO₂ thin film. Because of Al doping thickness, optical properties, band gap, surface morphology, and structural properties of TiO₂ thin film changes. X-ray diffraction (XRD), Atomic Force Microscopy (AFM), Gravimetric Analysis, and UV-vis. Spectroscopy were carried out to find out the micro-structure, surface morphology, surface roughness, thickness and optical properties of the thin films. 0.5 M TiO₂ thin film shows 473 nm thicknesses where it changes with Al doping. Al also changes the crystal structure and the surface roughness of the film and both of them are carried out by using XRD analysis and AFM analysis. The surface roughness of the films was 12.239 nm for undoped TiO₂ thin film and for 6% Al doped the roughness increases to 85 nm which were calculated by using AFM analysis. The grain size of Al doped TiO₂ thin film was 19.51 nm and 26.95 nm were measured by XRD analysis.<div><br></div>

The electrochemical effect of Al-doping on Li4Ti5O12 as anode material for lithium-ion batteries

This work investigates the electrochemical performance of Al-doped Li4Ti5O12 (LTO) on the Li site (Li4-xAlxTi5O12) and Ti site (Li4Ti5-xAlxO12) (x = 0.15), evaluated by galvanostatic charge-discharge tests and the electrochemical impedance spectroscopy. The physical properties of the synthesized materials were determined by XRD, SEM, Raman and XPS analyses. The Al dopant observed on different sites of Li4Ti5O12 showed resultant effects on the morphology, particle size, structural arrangement and crystallinity of the materials. XRD and XPS results showed peak shifts to higher angles and lower binding energies, respectively. Moreover, XPS revealed the majority of Al doped into the Ti site for Li4Ti4.85Al0.15O12 and into the Li site for Li3.85Al0.15Ti5O12. Li4Ti4.85Al0.15O12 has shown much improvement of the reversible capacity and rate capability of LTO without Li deficiency compared with Li3.85Al0.15Ti5O12. Li4Ti4.85Al0.15O12 also demonstrated superior reversible capacity at 0.2 C (172.7 mAh/g), 0.5 C (143.7 mAh/g) and 1 C (132.1 mAh/g). These were comparatively higher than Li4Ti5O12 (154.8, 124.1 and 100.7 mAh/g, respectively) and Li3.85Al0.15Ti5O12 (154.4, 133.6 and 120.3 mAh/g, respectively).

Effect of Al Doping on the Structural and Optical Properties of SnO2 Thin Films Elaborated by Sol-Gel Technique

Effect of Al Doping on the Structural and Optical Properties of SnO2 Thin Films Elaborated by Sol-Gel Technique