Al Co-doping Research Articles

Effect of Al and Zr co-doping on electrochemical performance of cathode Li[Li0.2Ni0.13Co0.13Mn0.54]O2 for Li-ion battery

The Li[Li0.2Ni0.13-x + y/3Co0.13-x + y/3Mn0.54-x + y/3]Al x Zr y O2 was synthesized via conventional solution combustion synthesis method. X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical experiment were used for material characterization and evaluation of powder morphology and electrochemical performance. According to XRD and SEM results, Zr-Al was successfully synthesized and it was inserted into crystal lattice. In addition, Zr-Al co-substitution distributed uniformly in Li[Li0.2Ni0.13Co0.13Mn0.54]O2. The results indicate that by addition of Zr, lattice parameters a and c are increased and lattice volume becomes larger. Addition of Al improves structural stability of cathode materials. The sample with Al (x = 0.02) and Zr (y = 0.015) exhibited high discharge capacity and best cycling performance. The Li[Li0.2Ni0.13Co0.13Mn0.54]0.965Al0.02Zr0.015O2 showed higher cycling stability and higher capacity in comparison with those of non-substituted material. The initial discharge capacity for Zr-Al co-doped electrode was 245.5 mAh g−1 at 25 mA g−1, and capacity retention was 98% after 50 cycle. While, the initial discharge capacity for bare electrode was 239.1 mAh g−1 at 25 mA g−1, and capacity retention was 93% after 50 cycle. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) revealed that by addition of Zr-Al ingredients, electrochemical performance of the Li[Li0.2Ni0.13Co0.13Mn0.54]O2 is improved.

Physical properties of solution processable n-type Fe and Al co-doped ZnO nanostructured thin films: Role of Al doping levels and annealing

The role of annealing temperature and Fe and Al co-doping on structural, optical, electrical and magnetic properties of solution processable ZnO thin films were investigated. ZnO:Fe thin films fixed with 2% of typical ferrous component were obtained to examine the role of 1–10% Al doping. X-ray diffraction analyses clearly indicates that the films to be polycrystalline and preferentially oriented along the c-axis of the hexagonal wurtzite structure. The film thickness, homogeneous distribution and decreasing/increasing of grain size dependence on Al content/annealing temperature (TA) were assessed by scanning electron microscopy. X-ray photoelectron spectroscopy revealed that Al3+ and Fe2+ ions to substitute for Zn2+ without changing the wurtzite structure. A slight decrease in the optical band gap of ZnO at fixed Fe dopant and a considerable increase of the optical band gap with increased Al doping concentrations and TA were observed. The refractive index increases with the fixed Fe dopant level and then decreases by Al doping levels, whereas the extinction coefficient clearly increases depended on both of Fe and Al concentrations. The refractive index and extinction coefficient both decrease with TA. Hall measurements show n-type conductivity and the increase of charge carrier concentration by Al doping levels and TA. Magnetic studies indicate room temperature ferromagnetism in Al and Fe co-doped ZnO thin films, whereas no room temperature ferromagnetism for the Fe-doped ZnO thin films was observed. An enhanced room temperature ferromagnetism in Al and Fe co-doped ZnO thin films was observed to depend on TA.

Synthesis and ionic conductivities of M (Mg, Ba, Zr) and Al co-doped apatite-type lanthanum germanate electrolytes for IT-SOFC

In this paper, the structure and ionic conductivities have been investigated for M (Mg, Ba, Zr) and Al co-doped apatite-type lanthanum germanates. La9.0.5Ge5.5Al0.5O26±δ (M = Mg, Ba and Zr) were prepared by solid state reaction. The results of XRD analysis showed that the space group is P63/m. M (Mg, Ba, Zr) substituting La site and Al substituting Ge site increased the cell volume and improved the lattice distortion of the apatite structure. In addition, M (Mg, Ba, Zr) and Al doping facilitated sintering and improved the relative density. Analysis of AC impedance spectroscopy showed that M (Mg, Ba, Zr) and Al co-doping in lanthanum germanates introduced local distortion and improved the ionic conductivities. Moreover, the thermal expansion coefficient (TEC) of La9.5M0.5Ge5.5Al0.5O26±δ (M = Mg, Ba and Zr) was improved after doping with M (Mg, Ba, Zr) and Al ions. La9.5Mg0.5Ge5.5Al0.5O26.5 sintered at 1400 °C exhibited the highest conductivity (1.26 × 10−2 S/cm, 800 °C) and improving TEC, which suggests that the (M (Mg, Ba, Zr), Al) doped apatite-type lanthanum germanate can be a potential material for the IT-SOFC electrolyte.

Anodic Performance of La0.5Sr0.5Mn0.9Al0.1O3 Perovskite Oxide for Solid Oxide Fuel Cells Using Dry C3H8 Fuel

Direct utilization of hydrocarbon for Solid Oxide Fuel Cells (SOFCs) using oxide ion conductor have the advantage of cost, high energy conversion efficiency and expanding the application area of SOFC. By eliminating the initial external reforming process of hydrocarbon fuels to syngas, significant advantages in cost and simplicity of gas handling process can be expected. Theoretically, direct utilisation of hydrocarbon for fuel is possible in SOFC using oxide ion conducting electrolyte, however, this is usually not easy when the conventional Ni base metal is used for anode because the formation of carbon is significantly occurred resulting in the deactivation of anode, or in the most serious case, permanent failure of the cell is occurred. Even methane as fuel, thermodynamic calculations predict that carbon will form at 1073 K unless steam is co-fed. In this study, Co and Al co-doping to La0.5Sr0.5MnO3 (LSM55) for anode were studied and it was found that doping Co is effective for decreasing anodic IR loss and the power density could be much increased by doping Co for Mn site of LSM doped with Al. XRD measurement suggests that Co was substituted Mn site over wide composition range and up to 40 mol%, partial substitution of Co to Mn in LaMnO3 structure was successfully performed. It was found that the maximum power density was increased by doping Co for LSM doped with 10 mol% Al for both H2 and C3H8 fuel. In particular, the smallest IR loss and anodic overpotential were achieved when 20 mol% Co was doped. The maximum power density of the cell using La0.5Sr0.5Mn0.7Al0.1Co0.2O3 was achieved 953 and 246 mW/cm2 for H2 and C3H8 fuel at 1273 and 1173 K, respectively. Increase in power density can be assigned to the increased surface activity to the electrochemical oxidation by doping Co. Although stability of LSM perovskite structure is still insufficient in dry C3H8 atmosphere, doping Al is effective for increasing stability and so co-doping Al and Co to Mn site of LaMnO3 is effective for decreasing anodic overpotential for direct C3H8 type SOFC. Mixing oxide ion conductor to Co and Al doped LaMnO3 anode was further studied for increasing power density. Among the examined mixed conductor, it was found that mixing Sm doped CeO2 is effective for increasing power density and the MPD of 850 mW/cm2 was achieved at 1173 K on 20 wt% SDC mixed with Co and Al doped LSM anode.

Electronic Structure and Magnetic Properties of V-Monodoped and (V, Al)-Codoped 4H-SiC

Electronic structure and magnetic properties of vanadium (V)-doped 4H-SiC are researched by using the first-principle plane wave pseudopotential method based on density functional theory. Ten kinds of doping position are calculated and the most stable configuration is found. The results indicate that V-monodoped 4H-SiC favors a spin-polarized state and the magnetic moment mainly comes from the unpaired 3d electronic of V atoms. Several doping configurations studied suggest the existence of ferromagnetic coupling between V dopant. Ferromagnetic order is activated by V doping via a V0:3d-C:2p-V7:3d coupling chain. Hybridization occurs between p − d orbitals. The doped V atom will induce additional holes carrier into the 4H-SiC. Al itself has no contribution to the magnetic moment, whereas V- and Al-codoped 4H-SiC can induce spin polarization, which reveals that the FM stability is reduced significantly by Al codoping. The calculated electronic structure implies that the presence of Si vacancies (V si ) weakens the FM state of V- and V si -codoped 4H-SiC.

Effect of doping concentration on Nd-related photoluminescence in TiO2 with Al co-doping

Nd doped, Nd-Al co-doped anatase phase TiO2 thin films were fabricated on silicon substrates by laser ablation and post annealing. The result of measuring PL spectra showed intense emissions from a luminescent centre of Nd3+ ions in these thin films. The luminescence of Nd-Al co-doped samples were stronger and broader than only Nd doped samples. Doping concentration of Nd determined suitable co-doping concentration of Al and post annealing temperature. Also there is the difference of shape of the PL spectra which indicates that the difference of local fine structure around Nd. Based on these facts, XAFS spectra was measured and suggested that the coordination around Nd was changed by this Al-co-doping.

Growth and ferroelectric properties of La and Al codoped BiFeO3 epitaxial films

Preparation of La and Al codoped BiFeO3 ((Bi1-xLax)(Fe1-xAlx)O3 (x = 0, 0.1, 0.2, 0.3, and 0.4): BFO-LA) thin films on Nb doped SrTiO3 (001) substrates was attempted by using a pulsed laser deposition (PLD) method. All obtained BFO-LA films grew epitaxially with a cube-on-cube relationship with the substrate. Upon La and Al codoping, the crystal system of the films changed from the rhombohedral-like monoclinic (MA) phase to the tetragonal phase, and the unit cell volume decreased monotonically. Although the ferroelectricity of the films was degraded by more than 20% La and Al codoping, 10% La and Al codoped BiFeO3 showed a larger remanent polarization than non-doped BiFeO3. The piezoelectric d constant (d33(AFM)) of the 10% La and Al codoped films was slightly reduced, in contrast to the drastic reduction observed for La doped BiFeO3.

Investigation of optical properties: Eu with Al codoping in aluminum silicate glasses and glass‐ceramics

AbstractEu‐doped transparent oxyfluoride aluminosilicate glass was prepared by controlling with Al codoping of melt‐quenched glass fabricated under air atmosphere. In the presence of Al input, the photoluminescence emission spectra under 393 nm excitation shows a blue shift by adjusting the ratio of Eu3+ and Eu2+. After heat treatment of glass, the ratio of Eu3+ and Eu2+ of luminescence emission were changed by controlling treatment temperature. The PL intensity of Eu3+ and Eu2+ ions in the glass‐ceramics (GC) was much stronger than in the precursor glass (PG). The possible mechanism responsible for color tuneability of the ratio of Eu3+ and Eu2+ doped was discussed.

Effects of Mg, Al Co-doping into Mn site on electrochemical performance of LiNi0.5Co0.2Mn0.3O2

In order to study the influence of multiple ions doping into single-site on the structure and electrochemical properties of Ni-rich layered-structure cathode material LiNi0.5Co0.2Mn0.3O2, the coprecipitation of hydroxides was applied to synthesize Mg, Al co-doped cathode material LiNi0.5Co0.2Mn0.3–x Mg1/2x Al1/2x O2 (x = 0.00, 0.01, 0.02, 0.04) in this paper. Morphology and structure, kinetic parameter, impedance and electrochemical performance of the material were respectively characterized by SEM, XRD, CV, EIS and galvanostatic charge/discharge test. The results of comprehensive analysis showed that the properties of material were improved obviously when the amount of doping was 0.02. At this amount of doping, the corresponding material has smaller cation mixing, higher hexagonal ordering of layered-structure, larger Li+ ion diffusion coefficients which are 2.444 × 10–10 and 4.186 × 10–10 cm2 s–1 for Li+ intercalation and deintercalation respectively, smaller impedance which is 33.93 Ω, higher specific capacity of first-discharge which is 168.01 mA h g–1 and higher capacity retention rate which is up to 95.06% after 20 cycles at 0.5 C (100 mA g–1).

Enhanced ferromagnetism in ZnGdO nanoparticles induced by Al co-doping

Abstract Dilute magnetic semiconductors with extended ferromagnetic properties are heavily sought for use in next-generation spintronic devices. In this work, we show that co-doping 3 at% Al into Zn 0.44 Gd 0.03 O 0.50 nanoparticles can change their magnetic nature from weak to well-defined ferromagnetism (FM) at room temperature. X-ray diffraction (XRD), selected area electron diffraction (SAED), and Raman spectroscopy show that the Gd and Al atoms replaced the Zn atoms in the ZnO crystal lattice without forming other impurity phases. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analyses of the suspensions revealed the high crystallinity and monodispersity of the 34–44 nm nanoparticles. The undoped and Gd-doped ZnO samples showed diamagnetism and weak FM, while the (Gd, Al) co-doped samples exhibited robust room temperature FM. The enhanced FM of the Zn 0.44 Gd 0.03 Al 0.03 O 0.50 sample can be achieved by increasing the carrier concentration via Al co-doping.

N and Al co-doping as a way to p-type ZnO without post-growth annealing

We demonstrate experimental results on p-type ZnO films grown by atomic layer deposition (ALD) and co-doped with aluminum and nitrogen (ANZO). The films were obtained at low temperature (100 °C) with different N to Al ratio and show conductivity type, which depends on the N and Al content. We applied the x-ray photoelectron spectroscopy in order to get insight into a chemical nature of dopants and we found three pronounced contributions of the N1s core level which appear at binding energies of 396.1, 397.4 and around 399 eV. Based on ANZO and undoped ZnO films, both grown by the ALD technique, the ZnO homojunction was obtained in one technological process without any post-growth high temperature processing. The rectification ratio as high as 4 × 104 at ± 2 V was achieved when an ultrathin Al2O3 layer was inserted between p- and n-type ZnO and a n-type ZnO buffer layer deposited on an insulating Si substrate was applied.

Effect of Al and Ca co-doping, in the presence of Te, in superconducting YBCO whiskers growth.

High-Tc superconducting cuprates (HTSC) such as YBa2Cu3O7 - x (YBCO) are promising candidates for solid-state THz applications based on stacks of intrinsic Josephson junctions (IJJs) with atomic thickness. In view of future exploitation of IJJs, high-quality superconducting YBCO tape-like single crystals (whiskers) have been synthesized from Ca-Al-doped precursors in the presence of Te. The main aim of this paper is to determine the importance of the simultaneous use of Al, Te and Ca in promoting YBCO whiskers growth with good superconducting properties (Tc = 79-84 K). Further, single-crystal X-ray diffraction (SC-XRD) refinements of tetragonal YBCO whiskers (P4/mmm) are reported to fill the literature lack of YBCO structure investigations. All the as-grown whiskers have also been investigated by means of X-ray powder diffraction (XRPD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Our results demonstrate that the interplay of Ca, Te and Al elements is clearly necessary in order to obtain superconducting YBCO whiskers. The data obtained from SC-XRD analyses confirm the highly crystalline nature of the whiskers grown. Ca and Al enter the structure by replacing the Y and the octahedral coordinated Cu1 site, respectively, as in other similar orthorhombic compounds, while Te does not enter the structure of whiskers but its presence in the precursor is essential to the growth of the crystals.

Mg and Al co-doping of ZnO thin films: Effect on ultraviolet photoconductivity

Thin films of Zinc Oxide were deposited by the sol-gel technique on glass substrates. The films were doped with Al, Mg or co-doped with both by introduction of appropriate compounds in the solution before dip-coating and annealing in air at 500°C. Energy Dispersive X-Ray Spectroscopy was employed to measure the dopant incorporation. X-ray diffraction studies indicate that Mg doping increases grain size, while Al doping reduces it. Photoluminescence (PL) measurements indicate that undoped and Al-doped films show, along with a broad near band-edge (NBE) peak, additional peaks at longer wavelengths related to various defect states. However Mg doped films show only a sharp NBE peak, which is blue shifted compared to undoped ZnO, and there are no prominent sub band gap luminescence peaks. This is also the case for Mg and Al co-doped ZnO samples, provided the Mg content is low. Photocurrent measurements were carried out using silver contacts using a De source under atmospheric conditions. Undoped and Mg doped ZnO films showed high resistances and low photocurrent levels. With low Al doping, both the dark current and the photocurrent increase significantly, but the films show very long photocurrent transients. With optimized concentration of Mg/Al co-doping in ZnO, the photocurrent increased by ~98 times compared to ZnO films doped only with Mg. Simultaneously, the photocurrent transients became ~44 times faster than ZnO films doped only with Al.

Characterization of F- and Al-codoped ZnO Transparent Conducting Thin Film prepared by Sol-Gel Spin Coating Method

ZnO thin film co-doped with F and Al was prepared on a glass substrate via simple non-alkoxide sol-gel spin coating. For a fixed F concentration, the addition of Al co-dopant was shown to reduce the resistivity mainly due to an increase in electrical carrier density compared with ZnO doped with F only, especially after the second post-heat-treatment in a reducing environment. There was no effective positive contribution to the reduction in resistivity due to the mobility enhancement by the addition of Al co-dopant. Optical transmittance of the ZnO thin film co-doped with F and Al in the visible light domain was shown to be higher than that of the ZnO thin film doped with F only.

Effect of WS2/Al co-doping on microstructural and magnetic properties of Nd−Fe−B sintered magnets

The effect of WS2 (0–1.2 wt.%) and Al (0.3 wt.%) doping on microstructural and magnetic properties of Nd2Fe14B sintered magnets was investigated. Grain growth in WS2-doped magnets was inhibited by the grain boundary (GB) pinning resulting in increased magnet coercivity. Al co-doping (0.3 wt.%) produced continuous Nd-rich grain boundary phases (GBPs), in which fine WFeB precipitates were distributed selectively at the grain boundaries due to the higher fluidity of the liquid phases. 0.6 wt.% WS2/Al co-doped magnets are characterized by the optimum magnetic properties because of the smaller grain sizes and formation of continuous Nd-rich GB phases. When the WS2 content exceeds 0.6 wt.%, magnetic properties of the resulting magnets deteriorate due to the reduction in magnet density and relatively large WFeB precipitates formed inside the main phase and at the GBs.

Increased Anodic Performance of La0.5Sr0.5Mn0.9Al0.1O3 by Doping with Co for Solid Oxide Fuel Cells Using Dry C3H8 Fuel

Effects of Co and Al co-doping to La0.5Sr0.5MnO3 (LSM55) for anode were studied and it was found that doping Co for Mn site is effective for decreasing anodic IR loss leading to increased power density. XRD measurement suggests that Co substituted Mn site over wide composition range and up to 40 mol% partial substitution of Co in LaMnO3 structure was successfully performed. The maximum power density was increased by doping Co for LSM doped with 10 mol% Al for both H2 and C3H8 fuel. In particular, the smallest IR loss and anodic overpotential were achieved when 20 mol% Co was co-doped. The maximum power density of the cell using La0.5Sr0.5Mn0.7Al0.1Co0.2O3 was achieved at 953 and 246 mW/cm2 for H2 and C3H8 fuel at 1273 and 1173 K, respectively. Increase in power density can be assigned to the increased surface activity to the electrochemical oxidation by doping Co. Although stability of LSM perovskite structure is still insufficient in dry C3H8 atmosphere, doping Al is effective for increasing stability and so co-doping Al and Co to Mn site of LaMnO3 is effective for decreasing anodic overpotential for direct C3H8 type SOFC.

Microstructure and property of diamond-like carbon films with Al and Cr co-doping deposited using a hybrid beams system

DLC films with weak carbide former Al and carbide former Cr co-doping (Al:Cr-DLC) were deposited by a hybrid beams system comprising an anode-layer linear ion beam source (LIS) and high power impulse magnetron sputtering using a gas mixture of C2H2 and Ar as the precursor. The doped Al and Cr contents were controlled via adjusting the C2H2 fraction in the gas mixture. The composition, microstructure, compressive stress, mechanical properties and tribological behaviors of the Al:Cr-DLC films were researched carefully using X-ray photoelectron spectroscopy, transmission electron microscopy, Raman spectroscopy, stress-tester, nanoindentation and ball-on-plate tribometer as function of the C2H2 fraction. The results show that the Al and Cr contents in the films increased continuously as the C2H2 fraction decreased. The doped Cr atoms preferred to bond with the carbon while the Al atoms mainly existed in metallic state. Structure modulation with alternate multilayer consisted of Al-poor DLC layer and Al-rich DLC layer was found in the films. Those periodic Al-rich DLC layers can effectively release the residual stress of the films. On the other hand, the formation of the carbide component due to Cr incorporation can help to increase the film hardness. Accordingly, the residual stress of the DLC films can be reduced without sacrificing the film hardness though co-doping Al and Cr atoms. Furthermore, it was found that the periodic Al-rich layer can greatly improve the elastic resilience of the DLC films and thus decreases the film friction coefficient and wear rate significantly. However, the existence of the carbide component would cause abrasive wear and thus deteriorate the wear performance of the films.

Colossal Dielectric Permittivity in (Nb+Al) Codoped Rutile TiO2 Ceramics: Compositional Gradient and Local Structure

(Nb+Al) codoped rutile TiO2 ceramics with nominal composition Ti4+0.995Nb5+0.005yAl3+0.005zO2, z = (4–5y)/3 and y = 0.4, 0.5, 0.6, 0.7, and Ti4+0.90Nb5+0.05Al3+0.05O2 have been synthesized. The resultant samples in ceramic pellet form exhibit a colossal dielectric permittivity (>∼104) with an acceptably low dielectric loss (∼10–1) after optimization of the processing conditions. It is found that a conventional surface barrier layer capacitor (SBLC) effect, while it contributes significantly to the observed colossal permittivity, is not the dominant effect. Rather, there exists a subtle chemical compositional gradient inward from the pellet surface, involving the concentration of Ti3+ cations gradually increasing from zero at the surface without the introduction of any charge compensating oxygen vacancies. Instead, well-defined Gr ± 1/3[011]* satellite reflections with the modulation wave-vector q = 1/3[011]r* and sharp diffuse streaking running along the Gr ± e[011]* direction from electron diffraction su...

Production and Photoelectric Activity of P and Al Co‐Doped ZnO Nanomaterials

Materials that have both conductivity and photocatalytic activity are widely applied in electrical devices and as environmental pollution handles. Based on such requirements, phosphorus and aluminium co-doped conductive zinc oxide nanocrystals (PAZO NCs) with novel visible-light catalytic activities have been mass produced by the combustion method. The PAZO NCs have diameters of 30–100 nm and BET specific surface areas of 15.27–18.99 m2 g–1. These PAZO NCs exhibited novel photocatalytic activity and good conductivity [the powder conductivity was (0.98–1.76) ×10–4 S cm–1], the reason being mainly attributed to the increase in carrier concentration and defects through P and Al co-doping. In addition, we found that the 3PAZO NCs, in which the molar ratio of Zn to P atoms is 100:3, had the best visible-light catalytic efficiency of the PAZO NCs, and the size of PAZO NCs decreased with increasing doping of phosphorus and aluminium. This study is useful as a reference for the mass production of modified ZnO NCs and its applications, such as in environmental management, photocatalysis, and anti-static electricity.

Structural and optical characterization of Zn0.95−xMg0.05AlxO nanoparticles

The structural and optical properties of ZnO nanoparticles doped simultaneously with Mg and Al were investigated. XRD results revealed the hexagonal wurtzite crystalline structure of ZnO. The FE-SEM study confirmed the formation of nano-sized homogeneous grains whose sizes decreased monotonously with increasing doping concentrations of Mg and Al. The absorption spectra showed that band gap increased from 3.20 to 3.31eV with Mg doping. As the Al concentration changed from x=0.01 to x=0.06mol% at constant Mg concentration the band gap observed to be decreased. Particle sizes estimated from effective mass approximation using absorption data and these values are in good agreement with the crystallite sizes calculated from XRD data. Raman spectra of ZnO showed a characteristic peak at 436cm−1 correspond to a non-polar optical phonon E2 (high). With increase of the Al doping concentrations, E2 (high) phonon frequency shifted to 439cm−1 from to 436cm−1. The origin of E2 (high) peak shift in ZnO nanoparticles is attributed to optical phonon confinement effects or the presence of intrinsic defects on the nanoparticles. PL spectra indicated that with increase of Al co-doping along with Mg into ZnO, intensity of the peak positioned at 395nm was initially increased at x=0 and then decreased with increase of the Al concentrations from x=0.01 to x=0.06mol%.