Al Doping Contents Research Articles

First-principles study of the mechanical and thermodynamic properties of aluminium-doped magnesium alloys.

Magnesium-aluminum (Mg-Al) alloys are widely used in aerospace, automobile and medical equipment owing to their advantages of easy casting, high strength-to-mass ratio and good biocompatibility. The structural, mechanical, electronic and thermodynamic properties of MgxAly alloys (x + y = 16, x = 1, 2,…, 15) with varying Al-doping contents were studied using the first-principles method. In this work, the structures of MgxAly alloys were constructed by replacing Mg atoms in a supercell with Al atoms. The lattice parameters of the Al-doped MgxAly alloys decrease with an increasing Al content because of the smaller atomic size of Al than that of Mg. The calculated formation energies show that Mg11Al5, Mg5Al3 and Mg9Al7 have prominent structural stability. The analyses of the mechanical properties reveal that the doping of Al improves the ductility of MgxAly alloys. The elastic moduli increase with an increasing Al content, and Mg9Al7 has a notable ability to resist deformation, while Mg11Al5 and Mg5Al3 have better plasticity. The calculated results of their electronic properties reveal that Mg11Al5, Mg5Al3 and Mg9Al7 are good conductors without magnetism. Furthermore, CDD analyses show that the inner layer charges of Al atoms migrated to the outer layer, and the charges of Mg atoms accumulated significantly in the outer region of Al atoms. The Debye temperature of Mg9Al7 is higher than that of Mg11Al5 and Mg5Al3, indicating that it has better thermodynamic stability. Our findings would be helpful for the design of Mg-Al alloys with excellent mechanical and thermodynamic performances.

Dynamically modulating the mid-infrared localized surface plasmon resonance of Al-doped ZnO nanocrystals

The localized surface plasmon resonance (LSPR) regulation of semiconductor oxide nanocrystals (NCs) in the near-infrared region (0.8–2.5 μm) of the solar spectrum has attracted much attention for its potential in applications such as electrochromism and sensing. However, the LSPR modulation properties of doped semiconductor oxide NCs in the mid-infrared region (2.5–25 μm) have rarely been reported. Here, we synthesized aluminum-doped zinc oxide (AZO) NCs with various nominal Al doping contents (1–20at%). The LSPR absorption peaks of these films were regulated between ∼3.8 and 6.57 μm depending on the doping content. AZO NC films with 1at% nominal Al doping and a 1316 nm film thickness exhibited the highest electrochemical infrared absorption regulation, achieving 35.9% regulation at 3–5 μm and 32.5% at 7.5–13 μm. The infrared absorption regulation mechanism of the AZO NCs involved changes in the LSPR absorption intensity caused by electron injection/extraction into/from the surface depletion layer of the AZO NCs. After applying different voltages, the AZO NC film on the Al substrates exhibited different apparent temperatures, demonstrating its potential applications in infrared displays and camouflage.

Boosting high-rate capacity and long-cycle stability of spinel LiMn2O4 by the Cr[sbnd]Al co-doping strategy

Jahn-Teller distortion and Mn dissolution are easily generated at a high current density, whilst hindering the elevation of high-rate capacity and long-cycle performance of spinel LiMn2O4. Herein, a CrAl co-doping strategy is proposed for preparing a series of LiCr0.04AlxMn1.96-xO4 (0 ≤ x ≤ 0.08) cathode materials using facile solid-state combustion. Crystalline structure and particle morphology are regulated by changing the Al-doping contents. After optimizing the Al-doping, the LiCr0.04Al0.01Mn1.95O4 cathode shows a unique truncated octahedron with the preferred growth of {111} crystal surfaces, which is conducive to reducing the Mn dissolution. Meanwhile, the LiCr0.04Al0.01Mn1.95O4 also exhibits a relatively high Mn average valence (+3.53) and lattice shrinkage, which can stabilize the spinel structure of the LiMn2O4 by inhibiting the Jahn-Teller to improve the electrochemical performance. Therefore, the optimized LiCr0.04Al0.01Mn1.95O4 cathode delivers the high-rate discharge capacity of 103.0 mAh/g and maintains the capacity retention of 67.0 % after 2000 cycles at 10C. Even at an ultra-high current rate of 30C, a long cycle life with a capacity retention of 78.0 % is also obtained after 1000 cycles.

Aluminum Doping Contents Dependent Photoluminescence and Resistivity of ZnO Nanofilms

Using sol–gel spin-coating technique Al-doped ZnO nanofilms (AZONFs) were made on Si(100) substrates and characterized. The obtained nanofilms were annealed at 500 °C for 3 h in air. The effects of changing Al doping level (0 to 5 at%) on the structures, morphologies, electrical and photoluminescence characteristics of the nanofilms were evaluated. The XRD patterns of the AZONFs confirmed the formation of wurtzite hexagonal ZnO lattice with preferred growth along (101) lattice plane. In addition, the c-axis orientation of the AZONFs became weaker with the increase in Al doping contents. The surface morphologies, structures, electrical and optical properties of the AZONFs were found to be very sensitive to the Al contents changes. The nanofilm prepared with 1 at% of Al displayed lowest resistivity of 4.238 × 10−3 Ω.cm measured by the four-point probe method. The optical band gap energy (increased from 3.22 to 3.304 eV) and carrier mobility of the AZONFs were improved with the increase in Al contents. The proposed AZONFs may be advantageous for various high performance optoelectronic device applications.

Synthesis and Evaluation of Garnet Type Ga, Al-Doped Llzo Powder for All-Solid State Batteries

Lithium ion secondary batteries have been widely used with high capacity and energy density. Recently, many sorts of lithium batteries have been studied for EV and ESS applications. However, safety issues such as explosion of organic electrolytes have been raised, all-solid state batteries (ASSBs) which do not use organic electrolytes are promising next-generation batteries. Garnet-type solid electrolytes have good advantages with stable in the atmosphere and electrochemical potential window. In this study Ga, Al-doped LLZO materials (Li7-3(x+y)AlxGayLa3Zr2O12) which are cubic single phase were synthesized by Taylor reactor process. The ionic conductivity was investigated according to the contents of Al and Ga doping contents. Furthermore, composite solid electrolyte sheet composed of LLZO and PEO polymer was prepared and evaluated for its properties. ASSBs were fabricated by using composite electrolyte sheet and electrochemical properties were evaluated. Moreover, we describe about the electrochemical effects of the composition of Ga and Al on cell performance in more detail.

Fine-tuning the ductile-brittle transition temperature of Mg2Si intermetallic compound via Al doping

Brittleness is a dominant issue that restricts potential applications of Mg2Si intermetallic compounds (IMC). In this paper, guided by first-principles calculations, we found that Al doping will enhance the ductility of Mg2Si. The underlying mechanism is that Al doping could reduce the electronic exchange effect between Mg and Si atoms, and increase the volume module/shear modulus ratio, both of which are beneficial to the deformation capability of Mg2Si. Experimental investigations were then carried out to verify the calculation results with Al doping contents ranging from Al-free to 10wt%. Results showed that the obtained ductile-brittle transition temperature of the Mg2Si-Al alloy decreased and the corresponding ductility increased. Specifically, the ductile-brittle transition temperature could be reduced by about 100°C. When the content of Al reached 6wt%, α-Al phase started to precipitate, and the ductile-brittle transition temperature of the alloy no longer decreased.

Defect-induced room-temperature visible light luminescence in Mg2Si:Al films

The Al-doped Mg2Si thin films were fabricated on sapphire substrates by magnetron sputtering technique, and the influences of different Al doping contents on the Raman scattering and room-temperature (RT) photoluminescence (PL) of Mg2Si thin films were investigated. The crystal structure, morphology, composition, Raman scattering and PL property of the thin film were examined using X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM) equipped with energy dispersive X-ray spectroscopy (EDS) and Raman spectroscopy, respectively. XRD results indicate that the intensity of diffraction peaks of Al-doped Mg2Si thin films are higher than that of undoped Mg2Si thin film, and decrease with increasing Al doping content. The FESEM image shows a few cavities in the surface of the film. The EDS results show that the thin films have the Al content of 0, (1.17 ± 0.1) at.%, (1.53 ± 0.1) at.%, (1.86 ± 0.08) at.% and (2.76 ± 0.11) at.%, respectively. The results of Raman scattering measurement reveal that all samples have the characteristic peak of Mg2Si. And Al dopant-induced Raman peak centered at 441 cm−1 was detected. Room-temperature photoluminescence of the Mg2Si:Al film was observed for the first time. Two visible light luminescence peaks center about 580 nm (2.14 eV) and 630 nm (1.97 eV), respectively, which originate from the different energy levels transition at the interface between crystalline Mg2Si and MgO surface layer. With decreasing excitation power, the position of the maximum of PL has no obvious change and the intensity drops significantly.

Effect of aluminium doping concentration on microstructures, optical and electrical properties of ZnO thin films by spray pyrolysis technique

The effect of Al doping on a ZnO thin film, deposited on a glass substrate by spray pyrolysis under ambient atmosphere, is investigated. Zinc acetate and aluminum nitrate were used as precursors for Zn and Al ions, respectively. The Al-doped ZnO thin films, with Al doping contents of 0 at%(undoped), 1at.%, 2at.%, 3at.%, 4at.% and 5at.%, were deposited at 400 C. X-ray diffraction analysis showed that the undoped ZnO exhibited hexagonal wurtzite crystal structure with major diffraction peak along (002) plane and minor peaks of (101) and (103) planes. The relative intensities of the diffraction peaks and the crystallinity decreased with an increase in Al-doping concentration.Surface morphology of the films were investigated by Scanning Electron Microscope (SEM). The morphological analysis showed that the grain size decreased with higher doping concentration. The optical transmittance spectra of the films showed a high transmittance (higher than 80%) within the visible and near infrared wavelength region. The electrical properties were characterized by the four point probe technique. Undoped ZnO films exhibited the highest sheet resistance, while the 2 at% Al-doped ZnO exhibited minimum sheet resistance.

The significance of the stable Rhombohedral structure in Li-rich cathodes for lithium-ion batteries

The lithium-rich layered oxides offer higher capacity, but suffer from severe capacity fade and voltage decay. Aluminum doping can improve the stability of the structure, but the fundamental mechanism has not been fully revealed. In this work, cathode materials with different Al-doping contents are investigated. To characterize the structural evolutions upon cycling, ex situ XRD and ex situ TEM are performed. It is demonstrated that the voltage decay is attributed to the decrease of Rhombohedral phase, while capacity fade is possibly associated with the increase of surface impedance. Therefore, continuous voltage decay and capacity fade are observed for undoped Li-rich cathode. In comparison, the Al-doped cathodes have stable LiNi1/3Co1/3Mn1/3O2 and surface impedance, leading to superior capacity retention and a stable output voltage.

Insight about electrical properties of low-temperature solution-processed Al-doped ZnO nanoparticle based layers for TFT applications

Aluminium-doped zinc oxide nanoparticles (NPs) with controlled Al doping contents (AZOx with x=0–0.8at% of Al) were explored as new oxide semiconductor materials to study the impact of doping on both solution and solid states. Polycrystalline AZOx thin films were produced by spin-coating the dispersions following by a thermal post-treatment at low-temperature (80°C or 150°C). The coated AZOx films were employed as active layer in thin-film transistors. Morphology and microstructure were studied by scanning electron microscopy and X-ray diffraction. The impact on the device performances (mobility, conductivity, charge carrier density) of Al-doping content together with the solution state was examined. Spin-coated films delivered an electron mobility up to 3×10−2cm2/Vs for the highest Al-doping ratio AZO0.8. Despite highly different morphologies, extrinsic doping with aluminium significantly increases the conductivity of low temperature solution-processed AZOx NPs series based layers by several orders of magnitude from AZO0 to AZO0.8.

Thermoelectric properties of Al-doped Mg2Si thin films deposited by magnetron sputtering

The Al-doped Mg2Si thin films were fabricated by two-target alternative magnetron sputtering technique, and the influences of different Al doping contents on the thermoelectric properties of Al-doped Mg2Si thin films were investigated. The compositions, crystal structures, electronic transport properties and thermoelectric properties of the thin films were examined using energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Hall coefficient measurement and Seebeck coefficient measurement system, respectively. The EDS results show that the thin films doped with Al target sputtering power of 30W, 60W and 90W have the Al content of 0.68 at.%, 1.56 at.% and 2.85 at.%, respectively. XRD results indicate that the diffraction peaks of Mg2Si become stronger with increasing Al dopant. The results of Hall coefficient measurement and Seebeck coefficient measurement system reveal that all the samples are n-type. The conductivities of Al-doped Mg2Si thin films are significantly greater than that of undoped Mg2Si thin film, and increase with increasing Al doping content. With the increase of temperature, the absolute value of the Seebeck coefficients of Mg2Si base thin films increase firstly and then decrease. The maximum power factor obtained is 3.8mWm−1k−2 for 1.56 at.% Al-doped Mg2Si thin film at 573K.

Optical and electrical properties of Al–WS2 films via H2S sulfurization of Al–WOx

We have studied the composition, structure, optical and electrical properties of the Al–WS2 (un-doped and Al-doped WS2) films deposited by radio frequency (RF) magnetron sputtering and post-sulfuration processing. Results of Raman spectra show that Al–WS2 films have two predominant peaks at ∼350cm−1 and ∼420cm−1, assigned to E2g1 and A1g of pure WS2. Meanwhile, the intensity of the Raman peak (at ∼252cm−1) corresponding to Al2S3 increases with adding the Al doping contents. As for optical properties, absorption excitonic peaks at ~1.94 and ~2.35eV are comparable to those of WS2 single crystals. The optical band gaps of the Al–WS2 films can be tuned by different Al doping contents. Hall measurements were performed to study the electrical properties. Hall mobility of un-doped WS2 films is 1.40×101cm2V−1s−1, and that of the Al–WS2 films decreases to 1.16cm2V−1s−1 with Al content increasing to 3.66%. The comparable Hall mobility of Al–WS2 films can be obtained by controlling appropriate Al doping contents. Furthermore, WS2 films undergo transitions from n-type conductivity to p-type conductivity when the films are doped with Al.

Composition and optical properties of amorphous Al-MoSexOy thin films and electrical characteristics of Al-MoSexOy field effect transistors

Al-MoSexOy (un-doped and Al-doped MoSexOy) films are prepared by radio frequency (RF) magnetron sputtering, and influence of the Al doping contents on the structure, composition and optical properties of the Al-MoSexOy films has been studied. We find that the amount of the Al can modulate the Mo4+/Mo5+/Mo6+ composition ratios and tune the optical band gap of the Al-MoSexOy film. The concentrations of the higher molybdenum oxidation states (Mo5+, Mo6+) increase, and the value of the band gap increase from 1.86 to 2.90 eV with the increment of the Al doping contents. Back-gated field effect transistors (FETs) have been fabricated and investigated by utilizing the sputtered Al-MoSexOy film channel. The incorporation of the Al makes the ambipolar FET device based on un-doped MoSexOy channel into p-type FET. P-type conductive FET based on 5.2% Al-MoSexOy channel has the highest field-effect mobility (55.2 cm2 V−1 s−1) and preferable Ion/Ioff ratio (∼104).

Optical and Electrical Properties of Hierarchical Nanostructured Al‐Doped ZnO Powders Prepared through a Mild Solution Route

Hierarchical nanostructured Al-doped ZnO (AZO) powders were successfully prepared through a mild solution route. The crystal structure and morphology of AZO were determined by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The morphology of the samples changed from random flower-like nanostructures to uniform flower-like hierarchical nanostructures with different Al doping contents. The optical and electrical properties of AZO were studied by UV/Vis spectroscopy and four-point probe. The optical band gap of AZO increased initially but then decreased as the Al content was increased owing to the Burstein–Mass effect and the many-body effect. Conversely, the electrical resistivity of the AZO powders first decreased and then increased with the Al doping content increasing because of changes in the electron and dopant concentrations. AZO exhibited the smallest electrical resistivity with an Al doping content of 1.0 at-%, which is two orders of magnitude smaller than the electrical resistivity of ZnO.

Study on the optical absorption and green emission of ZnO phosphors by varying Al doping contents

The blue band optical absorption and green luminescence of ZnO phosphors doping with aluminum are systematic studied. The Al content is varied from 0.01at.% to 1at.%. SEM images illustrated that Al doping can effectively suppress the ZnO grain growth. XRD results clearly manifest that the Al solubility limit in ZnO is around 0.1at.%. It is also found that the E1 (LO) vibration mode in the Raman spectra exhibits a good correlation with the blue band optical absorption and green photoluminescence. The results revealed that both VO0 and VO+ can give rise to the E1 (LO) vibration mode. We conclude that the VO and Oi defects are the dominant reason of the green photoluminescence in ZnO phosphors, in oxygen-deficient and oxygen-rich conditions, respectively.

Synthesis, characterization and room temperature photoluminescence properties of Al doped ZnO nanorods

Zinc oxide nanorods with different Al doping contents were prepared by the hydrothermal method from zinc chloride solution and aluminum chloride solution assisted by cetyltrimethylammonium bromide (CTAB) in this paper. The effects of Al doping on the structural characteristics and optical properties of the nanorods were studied. The morphology and microstructure of as-synthesized samples were characterized by X-ray diffraction (XRD) spectra, Fourier transformed infrared (FTIR) spectra, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM) and UV–vis spectroscopy. The results reveal that all the products are one-dimensional rod-like nanostructures and have the high crystalline hexagonal wurtzite ZnO crystal structure. Two blue emissions located at 451 and 468nm, and two weak green emissions located at about 484 and 493nm are observed, and the room temperature photoluminescence (PL) mechanisms are discussed.

Studies on optical, structural and electrical properties of atomic layer deposited Al-doped ZnO thin films with various Al concentrations and deposition temperatures

We investigated transparent conducting aluminium-doped zinc oxide thin films fabricated by atomic layer deposition (ALD). For the thermal ALD, diethylzinc and trimethylaluminium were used as the Zn and Al precursors, respectively. The electrical, structural and optical properties were systematically investigated as functions of the Al doping contents and deposition temperature. The best resistivity and transmittance (4.2 mΩ cm and ∼85%) were observed at an Al doping concentration of about 2.5 at% at 250 °C. An increase in the carrier concentration was observed with increasing deposition temperature and doping concentration. This can be explained by the effective field model of layered structures. Also, the enhancement of the mobility with increasing doping concentration was studied by the grain-boundary scattering and percolative conduction mechanism. By correlating the electrical and structural properties, it was found that varying the carrier concentration was more effective in changing the mobility than the grain-boundary scattering, due to the hopping conduction.

The Al-doping contents dependence of the crystal growth and energy band structure in Al:ZnO thin films

We report the Al-doping contents dependence of crystal growth and energy band structure in Al:ZnO thin films on the quartz substrates by the sol–gel method. As the Al contents increase, the Al-doping in the lattice reveals a maximum while the dopant is 2 mol%. It is inferred that the doping deterioration attributes to the decrease of grain size, which might be induced by the pinning effect of amorphous Al 2O 3 on ZnO grains boundary. The blueshifts of optical bandgap imply the quantum size effect of crystallites and the Burstein–Moss shifts in photoluminescence spectra indicate the heavy doping level for all samples.

Preparation and properties for aluminum-doped zinc oxide powders with the coprecipitation method

Zinc oxide powders of different Al doping contents (AZO) were prepared with the coprecipitation method from zinc nitrate solution and aluminum nitrate solution in this study. The effects of process parameters such as the Al doping content, calcination temperature and calcination time etc. on electric conductivity were examined quantificationally. The AZO powders had good electric conductivity than that of zinc oxide powders. The resistivity of the AZO powders significantly depended on the Al doping content, calcination temperature and calcination time. The minimum resistivity 179.2 Ω·cm was obtained from the 2 mol% Al doped powders in this work, which were prepared at the calcination temperature 1300°C for 2 h. The AZO powders were also characterized with the X-ray diffraction (XRD) and scanning electron microscopy (SEM). The experimental results show that when the Al doping content is less than 2 mol%, the Al3+ enters into the ZnO lattice to form the solid solution, and causes the current carrier increase and the resistivity drop, but the excessive Al3+ doping brings the ZnAl2O4 spinel phase generate, resulting in the resistivity increase.