Al Substitution Research Articles

Enhanced Quantum Efficiency via Co‐Substitution in Red‐Emitting Phosphor Sr2[MgAl5N7] : Eu2+ for Advanced Spectroscopic Applications Including Laser Displays with Ultra‐High Luminescence Saturation Threshold

AbstractIn order to obtain novel and more efficient red light‐emitting materials, a series of Sr2[Mg1−xLixAl5−xSixN7] : 0.01Eu2+ (SMAN‐xLS, 0≤x≤0.5) red phosphors were devised and successfully synthesized via the high temperature solid state reaction and the effects of the co‐substitution of [Mg−Al]5+ by [Li−Si]5+ on structural and luminescence properties is investigated in detail. A series of powder XRD data and Rietveld refinement indicate that [Li−Si]5+ co‐substitution can successfully enter the Sr2[MgAl5N7] : 0.01Eu2+ (SMAN) lattice. With the entry of [Li−Si]5+ into the lattice, the substitution of Al3+ by Si4+ leads to the weakening of the nephelauxetic effect of the 5d level of Eu2+, which shifts the emission peak from 657 nm to 647 nm and reduces the excitation in the green region, i.e., lowers the absorption of green light. When the amount of [Li−Si]5+ co‐substitution is x=0.1, the luminescence intensity and thermal stability of the sample are enhanced, in which the external quantum efficiency (EQE), reflecting the luminescence intensity, is elevated by 49.6 %. The increase in lattice rigidity gives rise to higher luminescence intensity, and the introduced trap levels for the compensation of luminescence enhances the thermal stability. Under blue laser excitation, the SMAN‐0.1LS can achieve an ultra‐high luminescence saturation threshold of 52.22 W/mm2, which is remarkably superior to other existing red phosphors, a breakthrough performance that has enormous potential for application in high‐power laser display light sources. Cathodoluminescence (CL) characterization and measurements attest to the favorable CL properties of SMAN‐0.1LS. By measuring the pressure‐dependent luminescence of SMAN‐0.1LS, the emission peak can be shifted from 650 nm to 702 nm with the increase of pressure, and the sensitivity dλ/dP is 5.07 nm/GPa, which is indicative of the potential application of this system as an optical pressure sensor.

Superconductivity in Ternary Germanite TaAl x Ge2-x with a C40 chiral structure

Abstract We report a new family of chiral intermetallic superconductors TaAl x Ge2-x . The mother compound TaGe2 has a C40-type chiral hexagonal crystal structure with a pair of enantiomorphic space groups of P6222 and P6422. By substituting Ge with Al, TaAl x Ge2-x polycrystals with the C40 structure were synthesized with Al substitution x from 0 to 0.8. Magnetic susceptibility, magnetization curves and electrical resistivity revealed that TaAl x Ge2-x with x of 0.2 to 0.4 was a type-II superconductor with a superconducting transition temperature T c of 2.0 to 2.2 K. The superconductivity disappeared at with x less than 0.2 or was largely suppressed at with x of 0.5 or more, although all the measurements were performed at temperatures above 1.8 K. An emergence of superconductivity is discussed in terms of the lattice constants changes with the Al substitution.

A W/Al Co-doped Na0.44MnO2 Cathode Material for Enhanced Sodium-Ion Storage.

The Na0.44MnO2 cathode has attracted enormous interest owing to its low cost, low toxicity, and stable structure, but its practical application is still hindered by the limited sodium storage sites. Element doping is widely used to improve its capacity. However, cation and anion substitution could barely reach a satisfactory compromise between the structural stability and reversible capacity. Herein, we show that the above issue could be overcome via the synergetic effect of W and Al substitution. Combining the electrochemical and in situ X-ray powder diffraction (XRD) measurements, we reveal that the substitution of W effectively facilitates the tunnel-to-layered phase transformation, while the further substitution of Al eliminates the Na+/vacancy ordering during the extraction/insertion of Na+ ions, resulting in a layered Na0.44Mn0.94W0.01Al0.05O2 (NMO-1W5Al) with negligible Na+/vacancy ordering upon cycling. In addition, NMO-1W5Al represents a wider Na+ interlayer spacing to accelerate the diffusion of Na+, which improves the rate performance. The high specific capacity, remarkable rate performance, and high cycling stability of NMO-1W5Al are promising for large-scale energy storage systems.

Unravelling the incorporation mechanisms of water in aluminous orthoenstatite: I. First-principles calculations

We performed first-principles calculations on the energy, and NMR and polarized infrared (IR) spectra for anhydrous and hydrous aluminous orthoenstatite (OEn) models to help clarify the incorporation mechanisms of Al and OH defects in OEn. Our calculations revealed that proton pairs in M2 vacancies ((2H)M2) adjacent to a tetrahedral Al (AlIV) are energetically more favorable than those remote from Al, and may contribute to the observed correlated 1H NMR peaks near 3.7 and 8.0 ppm, and IR bands near 3550–3570 and 3066 cm−1 (A4 band) for aluminous OEn. Coupled substitutions of AlVI (octahedral Al) + H for 2Mg were found to adopt multiple configurations, and may contribute to the observed IR bands near 3520, 3475 and 3320 cm−1. Coupled substitution of AlIV + H for 1Si may contribute to the observed IR band near 3380–3400 cm−1. 4H in SiB vacancies ((4H)SiB) adjacent to an AlVI were found to be energetically more favorable than those remote from Al, and may be the origin for an IR band observed near 3600–3620 cm−1. These results allow the incorporation mechanisms of water in synthetic and natural aluminous orthopyroxenes to be deciphered from the available NMR and IR data, and suggest that both (2H)M2 defects associated with Al and simultaneous coupled substitutions of Al + H for 2Mg and 1Si contribute to the observed correlation between Al and water incorporation, and the nearly unity AlIV/AlVI ratio. (4H)SiB defects associated with Al may also be present in some synthetic OEn and mantle-derived orthopyroxene.

Investigating base-catalyzed aldol condensation reactions on alkali-free hydrotalcites and the role of thermal decomposition

Aldolization is a crucial carbon–carbon coupling reaction used in the conversion of biomass-derived platform molecules into valuable chemicals and fuels. In this work, we combine experiment and theory to explore the role thermal decomposition has in controlling the structure of alkali-free Mg-Al layered double hydroxides (LDHs) and their subsequent performance in the base-catalyzed aldol condensation of acetone, focusing on the constituent aldolization and dehydration steps. LDHs were synthesized via co-precipitation and subjected to calcination at temperatures up to 600 °C to produce mixed metal oxides of the form Mg3AlOz which were further examined by SEM, N2 physisorption, XRD, and CO2-TPD. Aldolization and dehydration behaviors were examined in a batch reactor and fit with kinetic models to capture the sensitivities of both reactions to calcination temperature. Additional experiments involving the selective blocking of base sites by CO2 poisoning and reversal at varying temperatures showed that both aldolization and dehydration are likely driven by the strongest base sites, yielding a site density (0.19 μmol m−2) in agreement with separate propionic acid titration studies. Density functional theory (DFT) simulations of Mg5Al2O8 surfaces were employed to gain microscopic insights into these materials, revealing the importance of Al substitution in creating cation vacancies which can drive aldol condensation through enolate intermediates stabilized in the oxyanion resonance form. High-coverage simulations of the surface show participation of the vacancy in both aldolization and dehydration, rationalizing the coupling of rate trends observed experimentally. Ultimately, this study provides new insights and approaches useful in the design of heterogeneous aldolization catalysts.

Enhanced Quantum Efficiency via Co-Substitution in Red-Emitting Phosphor Sr2[MgAl5N7] : Eu2+ for Advanced Spectroscopic Applications Including Laser Displays with Ultra-High Luminescence Saturation Threshold.

In order to obtain novel and more efficient red light-emitting materials, a series of Sr2[Mg1-xLixAl5-xSixN7] : 0.01Eu2+ (SMAN-xLS, 0≤x≤0.5) red phosphors were devised and successfully synthesized via the high temperature solid state reaction and the effects of the co-substitution of [Mg-Al]5+ by [Li-Si]5+ on structural and luminescence properties is investigated in detail. A series of powder XRD data and Rietveld refinement indicate that [Li-Si]5+ co-substitution can successfully enter the Sr2[MgAl5N7] : 0.01Eu2+ (SMAN) lattice. With the entry of [Li-Si]5+ into the lattice, the substitution of Al3+ by Si4+ leads to the weakening of the nephelauxetic effect of the 5d level of Eu2+, which shifts the emission peak from 657 nm to 647 nm and reduces the excitation in the green region, i.e., lowers the absorption of green light. When the amount of [Li-Si]5+ co-substitution is x=0.1, the luminescence intensity and thermal stability of the sample are enhanced, in which the external quantum efficiency (EQE), reflecting the luminescence intensity, is elevated by 49.6 %. The increase in lattice rigidity gives rise to higher luminescence intensity, and the introduced trap levels for the compensation of luminescence enhances the thermal stability. Under blue laser excitation, the SMAN-0.1LS can achieve an ultra-high luminescence saturation threshold of 52.22 W/mm2, which is remarkably superior to other existing red phosphors, a breakthrough performance that has enormous potential for application in high-power laser display light sources. Cathodoluminescence (CL) characterization and measurements attest to the favorable CL properties of SMAN-0.1LS. By measuring the pressure-dependent luminescence of SMAN-0.1LS, the emission peak can be shifted from 650 nm to 702 nm with the increase of pressure, and the sensitivity dλ/dP is 5.07 nm/GPa, which is indicative of the potential application of this system as an optical pressure sensor.

Atomistic Mechanism of Al Substitution Effects on the Ferroelastic Post-stishovite Transition by High-Pressure Single-Crystal X-Ray Diffraction

Atomistic Mechanism of Al Substitution Effects on the Ferroelastic Post-stishovite Transition by High-Pressure Single-Crystal X-Ray Diffraction

Specifics of Al substitution into boron carbide: A DFT study

Boron carbide (B4C), known for its hardness and low density, is prone to local amorphization under high non-hydrostatic loads, limiting its applications. Aluminum doping is promising due to aluminum's atomic size, fitting into the B4C crystal lattice, particularly the intericosahedra chain, potentially reducing amorphization. This work uses first-principles calculations to study aluminum placement in B4C. We examine the potential for Al substitution in the icosahedron and intericosahedra chain, identifying possible locations. Results show that aluminum can't replace atoms in the icosahedron, but substituting one central atom in the intericosahedra chain with aluminum is energetically favorable and likely changes the chain configuration to an angular one. Additionally, aluminum can substitute one carbon in the (C-B-C) chain of B12(C-B-C) boron carbide. Comparative analysis suggests these configurations may coexist. Our study offers a theoretical model that can guide future experimental efforts and provides valuable insights into the structural specifics of aluminum-doped boron carbide.

Tailoring electronic structure and thermodynamic stability of (Al, In)-substituted GaAs: Ab-initio insights into bulk and (001) surfaces

Ab-initio calculations are conducted to investigate the structural properties, electronic structure, and thermodynamic stabilities of bulk and (001) surface systems of the GaAs semiconductor in its zinc-blende crystal phase. For the bulk case, we focus on the impact of substituting gallium atoms with M atoms (M = Al, In) at various concentrations (5.55 %, 11 %, and 22 %). We present the resulting structural parameters, along with the formation and substitutional energies associated with these substitutions. For surface systems, we explore indium (In) or aluminum (Al) substitutions at coverages of 0.25, 0.50, and 1.0 monolayers. This includes investigating the effects of substituting M atoms within the first atomic layer of the slabs. Ab-initio thermodynamic calculations reveal that high Al substitutions, in both bulk and surface, result in more favorable formation and surface energies. In contrast, In substitutions exhibit the opposite behavior, with increasing In content leading to less favorable energetics. Moreover, density of states analysis reveals that bulk systems maintained a semiconducting character, while all studied surface configurations exhibited a metallic electronic behavior. This study provides valuable insights into the influence of Al and In substitutions on the structural, electronic, and thermodynamic properties of GaAs, both in bulk and on the (001) surface.

Electromagnetic wave absorption properties of La-Ca-Co-Al substituted M-type Sr-hexaferrite-rubber sheets in 50–75 GHz range

This study reports on the electromagnetic (EM) wave absorption characteristics of M-type hexaferrite-rubber sheets, where Al was additionally substituted into high-performance permanent magnet compositions, Sr0.2La0.4Ca0.4Co0.25Fe9.75-xAlxO19-d (LCCA-SrM, x = 0, 0.2, 0.4). While non-substituted SrFe12O19 powder-rubber sheet had a ferromagnetic resonance frequency (fFMR) of 48.5 GHz, the LCCA-SrM (x = 0, 0.2, 0.4) rubber sheets showed increased fFMR values of 63.3, 66.2, and 68.5 GHz, respectively, with the increasing x values. The frequency of minimum reflection loss (fRLmin) also increased correspondingly with the change in fFMR. This significant increase in fFMR and fRLmin is attributed to the greatly enhanced magnetocrystalline anisotropy from the La-Ca-Co substitution in SrM and the incremental increase in magnetic anisotropy field (Hani) due to Al substitution. The absorption band (Δf) satisfying RL < −10 dB, was 45.0–53.4 GHz for SrM, and 52.9–75, 50–75, and 59–74.2 GHz for the x = 0, 0.2, and 0.4 samples, respectively. The x = 0.2 sheets demonstrated the widest absorption, covering 50–75 GHz. This study is highly promising as it is the first to demonstrate the feasibility of developing an EM wave absorber sheet for frequencies above 50 GHz using hexaferrite powder synthesized via the solid-state method, which offers scalability and cost-efficiency for mass production.

Tailoring the Lattice Thermal Conductivity of Al‐Incorporated Ag2Se for Near Room Temperature Waste Heat Recovery

AbstractAg2Se is categorized as a typical ′phonon‐liquid‐electron‐crystal (PLEC)′material, exhibiting an extremely low . In this study, Al substituted Ag2Se samples were synthesized by mechanical alloying process followed by hot press densification technique. The Al substituted sample shows an exceptionally high mobility of 2360 cm2 V−1 S−1 at room temperature and a maximum power factor of 1442 μWm−1 K−2 at 383 K. The phonon scattering induced by various crystal imperfections due to Al substitution helped to obtain a very low lattice thermal conductivity value of 0.3 W/mK. A high figure of merit (zT) of 0.4 at 383 K was obtained as a result of the simultaneous effect of boosting the electrical transport properties and decreasing the thermal conductivity. This present work summarizes that the Al substitution is highly significant in improving the thermoelectric properties of Ag2Se.

Nanoporous CoFe2O4 with inherited cation doping from matrix realizing ultra-stable alkaline hydrogen evolution for over 1000 hours

Spinel-type oxides have been acknowledged for their eminent catalytic ability towards alkaline hydrogen evolution reaction (HER) due to the special metal occupying structures. To further improve conductivity, inherited cation doped spinel has been rapidly synthesized via scalable alloying-dealloying strategy. Specially, the resultant Al-doped CoFe2O4 possesses typical bi-continuous pore-ligament structure, showing a huge surface area for electrocatalysis. It only demands HER overpotentials of 22.9 and 275 mV to achieve 10 and 100 mA cm-2, respectively. Furthermore, it also exhibits ultra-stable hydrogen evolution for 1000 h Under the industrial conditions (6 M KOH, 60 °C), Al-CoFe2O4 || RuO2 couple just needs 1.75 V to reach high current density of 500 mA cm-2 and could steadily produce hydrogen for over 50 h with merely 8 % voltage loss. Theoretical calculation confirms that Al substitution could indeed increase valence electron concentration. Based on this optimized configuration, H2O molecule is preferred to adsorb on Co site and conducive to dissociate into *OH-*H co-adsorption. And thus, the energy barrier of alkaline HER can be reduced to 0.98 eV on Al-doping CoFe2O4 model. To further clarify the active species derived from HER, operando X-ray diffraction and Fourier transform infrared are used to prove that the superficial CoFe2O4 has been transformed into more active CoOOH/FeOOH. This work offers a guide to facilely fabricate cost-effective HER catalysts that are suitable for industrial hydrogen production.

Effects of Sm2O3 and TiO2 on the performance of MgAl2O4-Si3N4 ceramics for solar thermal absorber in concentrating solar power

Aiming to further improve the properties of novel MgAl2O4-Si3N4 ceramic used as solar thermal absorbing material in concentrating solar power, effects of Sm2O3 and TiO2 on performance of the composites were investigated especially the mechanisms of different additives on microstructure and high temperature stability. The results show that both additives can accelerate sintering, reduce sintering temperature, improve the density and high temperature stability via liquid phase sintering mechanism. Besides, TiO2 can form displacement solid solution with Al2O3 to promote the sintering process. Sm2O3 is more conducive to improving the bending strength due to its function of increasing the length diameter ratio of β-Si3N4. TiO2 is more favorable for improving solar absorption owing to the distinctive absorption spectrum and large number of cation vacancy caused by substitution of Al3+ by Ti4+. MgAl2O4-Si3N4 composites with Sm2O3 and TiO2 additives have better performance than MgAl2O4-Si3N4, Si3N4 and SiC ceramics prepared via the same procedure, which makes it a certain choice for solar thermal absorbing material.

Effect of Al substitution on the electron-phonon interaction for β-Ga2O3

The relevant parameters of electron–phonon (e-ph) interaction, like mean phonon temperature and e-ph interaction strength for Al-substituted β-Ga2O3, i.e., β-(AlxGa1–x)2O3 alloys, have been determined from the fitting of the temperature dependence of the band gap using Bose–Einstein empirical model. Both e-ph interaction strength and mean phonon temperature decrease sharply for initial Al compositions; then, they increase slightly and become more or less constant. This is explained by using the already existed concepts of propagon and diffuson for the phonon modes that interact with the electrons. Presence of two sublattices at the local level is found to be the origin of diffuson-like behaviour of phonon modes in β-(AlxGa1–x)2O3 alloyed system, which vibrate independently like a non-propagating oscillator and diffuse through the β-(AlxGa1–x)2O3 lattice. The diffuson-like behaviour of phonon modes in the β-(AlxGa1–x)2O3 alloy is found to be responsible for the reduction in e-ph interaction. The reduction of e-ph interaction strength of β-Ga2O3 with Al substitution may lead to the better performance of power devices working at higher temperatures.

Stability and transformation of jarosite and Al-substituted jarosite in an acid sulfate paddy soil under laboratory and field conditions

Jarosite, a prominent mineral in oxidised acid sulfate soil, is known to sorb and incorporate a variety of elements, including Al. However, to understand the role that jarosite plays in regulating element cycles, it is crucial to understand the stability and transformation pathways of jarosite in an acid sulfate soil under dynamic biogeochemical conditions. In this study, we observed the transformation of unsubstituted jarosite and Al-substituted jarosite, collectively referred to as ‘jarosite’, in an acid-sulfate rice paddy topsoil and subsoil from Thailand. Jarosite was incubated in flooded paddy topsoils and subsoils for up to sixteen weeks, both in laboratory mesocosms and in the field, using bags made of polyethylene terephthalate mesh. One set of mesh bags contained jarosite that was not mixed with any other minerals, and referred to as ‘pure mineral’ incubations. Mineral transformations occurred under the influence of the soil porewater only and were primarily followed by X-ray diffraction analysis. A parallel set of mesh bags contained soil with 57Fe-labelled jarosite enrichment (Fe enriched in soil by a factor of 1.3 but 57Fe enrichment factor of 12.5–13.6), which allowed jarosite transformation to occur in close association with the soil matrix. Mineral transformations in 57Fe-jarosite-enriched soil were followed using 57Fe Mössbauer spectroscopy. In laboratory mesocosms and in the field, jarosite transformed most quickly in topsoil, whereas jarosite underwent limited transformation in subsoils, especially in laboratory mesocosms where Fe reduction was slow. The chemical environment around the jarosite affected the outcome of the transformation processes. Crystalline Fe oxyhydroxides, such as goethite, dominated the products in mesh bags where jarosite was not mixed with soil, whereas short-range-ordered or non-mineral Fe phases, such as Fe(II) sorbed to mineral surfaces or complexed with organic ligands, were dominant transformation products of jarosite when mixed in soil. Furthermore, Al substitution in jarosite caused contrasting effects in mesh bags containing pure minerals or mineral-enriched soil. Aluminium substitution slowed the transformation of jarosite in pure mineral mesh bags, but Al-substituted and unsubstituted jarosite showed similar transformation rates and pathways when incubated as a mixture with soil. The contrasting rate of transformation in topsoil and subsoil, the contrasting products of transformation in pure mineral mesh bags and 57Fe-jarosite-enriched soil, and the contrasting effect of Al substitution in pure mesh bags or jarosite-enriched soil, all demonstrate that the rate and products of jarosite transformation are defined by a balance between competitive transformation pathways that affect the transforming minerals.

NiAlFe catalysts based on hydrotalcite-like precursors for low temperature CO2 methanation: Electronic effects among components and intrinsic activity of Ni site

NiAlFe catalysts based on the hydrotalcite-like precursor were prepared and the catalysts exhibit excellent low temperature catalytic activity for CO2 methanation. CO2 conversion over the NiAlFe0.3 catalyst is nearly 80 % under the condition of T = 225 °C, P = 1 atm, and WHSV = 24000 mL/(g∙h). With the increase in the substitution of Fe for Al, the hydrotalcite-like structure of the catalyst precursor is gradually destroyed; the reducibility of NiO component is promoted; the amount of surface basic site decreases. There is a strong electronic push–pull effect between NiO and Al2O3 in the calcined catalyst, and the electronic effect is weakened with the introduction of Fe because Fe3+ shares the responsibility of Ni2+ for donating electron to Al3+. In the reduced catalysts, the Ni3Fe alloy was formed and the electrons are pushed from Ni0 to Fe0. With the increase in the Fe amount, the number of surface Ni atom decreases, while the intrinsic activity of Ni active site enhances. The number and intrinsic activity of Ni site are the main two factors determining the CO2 methanation activity at low temperature. Moreover, the substitution of Al3+ by Fe3+ is beneficial for the stability of the catalysts by inhibiting the agglomeration of catalyst particle.

Effect of Al Substitution on Visible Short-Wave Infrared Reflectance Spectroscopy (VSWIR) of Goethite and Ferrihydrite

Goethite and ferrihydrite are the two major iron hydroxides, essential mineral constituents in the terrestrial surface system. Aluminum (Al) is the most common substituent in iron hydroxides, and it may significantly change the bulk and surficial physicochemical properties of iron hydroxides. Consequently, a practical and convenient approach is needed to efficiently identify the Al substitution degrees of iron hydroxides in natural occurrences. This study presents a comprehensive investigation of the VSWIR characteristics of laboratory-synthesized Al-substituted goethite and ferrihydrite, to establish diagnostic VSWIR parameters for the identification and quantification of Al substitution levels in iron hydroxides. The findings revealed that Al substitution can affect the band positions (P) of goethite and ferrihydrite at ~650 nm, ~900 nm, and ~1400 nm. The relationships between the Al substitution of ferrihydrite and VSWIR parameters can be expressed as P900 = −0.43 × Al(%) + 931 and P1400 = −0.07 × Al(%) + 1428, while that of goethite can be expressed as P650 = 0.42 × Al(%) + 657 and P900 = 2.29 × Al(%) + 936. The peak fitting results showed that the absorption intensity at 480–550 nm linearly decreases with increased Al substitution. The obtained VSWIR spectra of Al-substituted goethite and ferrihydrite provide a critical supplement to the spectral library for (Al) iron hydroxides, and these VSWIR parameters can be utilized for the semi-quantitative determination of Al substitution in natural iron hydroxides

Aluminum substitution stabilizes organic matter in ferrihydrite transforming into hematite: A molecular analysis

The association of soil organic matter (SOM) with iron (Fe) oxyhydroxides, particularly ferrihydrite, plays a pivotal role in the biogeochemical cycling of carbon (C) in both terrestrial and aquatic environment. The aging of ferrihydrite to more crystalline phases can impact the stability of associated organic C, a process potentially influenced by aluminum (Al) substitution due to its abundance. However, the molecular mechanisms governing the temporal and spatial distribution of SOM during the aging process of Al-substituted Fe oxyhydroxides remain unclear. This study aims to bridge this knowledge gap through a comprehensive approach, utilizing batch experiments, solid characterization techniques, and atomic force microscopy (AFM) based peak-force quantitative nanomechanical mapping (PF-QNM). Batch experiments revealed that humic acid (HA) was released into the aqueous phase during aging, with Al inhibiting this release. Various solid characterization methods collectively suggested that Al hindered the crystalline transformation of ferrihydrite and significantly preserved HA on the surface of newly formed hematite, rather than it being occluded within the interior of the new minerals. Results from 3-Dimensional fluorescence spectroscopy (3D-EEM) and Fourier-transform infrared spectroscopy (FTIR) indicated that the structure of HA remained constant, with the carboxyl-rich and hydroxyl-rich portions of HA fixed at the mineral interface during the aging period. Furthermore, we developed AFM-based PF-QNM to both quantify and visualize the interactions between Fe oxyhydroxides and HA, demonstrating variations in HA affinity among different Fe oxyhydroxides and highlighting the influence of the Al substitution rate.

Enhancement the electrical and linear/nonlinear optical properties of ZnCo2O4 through Al3+doping

In this work, ZnCo2O4 samples doped with Al3+ were prepared by the hydrothermal method. Synchrotron x-ray diffraction, FTIR, SEM and EDX techniques were used to investigate the structure, microstructure, morphology, and composition of ZnCo2-xAlxO4 samples. Rietveld analysis revealed a nearly inverse structure for the undoped ZnCo2O4. The degree of inversion is increased upon increasing the Al3+ doping content. Al ions preferentially occupy the octahedral B-site. The optical band gaps of ZnCo2−xAlxO4 samples are 1.9, 1.8 and 1.91 eV for x = 0, 0.1 and 0.2, respectively. Different empirical models were used to obtain the refractive index of the different samples using their corresponding optical band gaps. The increase in non-linear optical values in the sample with x = 0.1 suggested that this sample could be used in a variety of photonic applications. The effects of frequency and temperature on the dielectric permittivity, impedance and electrical modulus of different samples were explored. All samples exhibited the non-Debye relaxation phenomenon. The relaxation time of each sample is affected with the frequency and temperature. The Cole-Cole curve is employed to reduce uncertainty regarding the electrical characteristics of these ZnCo2−xAlxO4 samples induced by grain boundaries or bulk grain. The substitution of Al3+ ions can regulate the conductivity of the ZnCo2O4 sample.

Phase composition, crystal structures and enhanced microwave dielectric properties of Mg2+/Zr4+ co-doped Al2Mo3O12 ceramics

In this work, the substitution of Al3+ by Zr/Mg in Al2Mo3O12 was designed to enhance the quality factor while simultaneously adjusting the thermal stability of the resonant frequency. The Al2–2x(Zr0.5Mg0.5)2xMo3O12 (AMZM) (0.1 ≤ x ≤ 0.5) ceramics were synthesized using a simple solid-state method, resulting in all components exhibiting single-phase crystallinity and a dense structure. A phase transition temperature below room temperature was observed when x ≥ 0.4. Furthermore, the quality factor of the synthesized samples, compared to pure-phase Al2Mo3O12 (εr = 6.79, Q×f = 28471 GHz, τf = −48.77 ppm/℃), increased by nearly threefold. A detailed investigation of the crystal structure of the samples was conducted through Rietveld refinement. The composition with x = 0.3 (monoclinic phase) exhibited optimal dielectric performance after sintering at 800 ℃ for 6 h: εr = 7.84, Q×f = 86511 GHz, τf = −42.08 ppm/℃. By forming a composite ceramic with (Li1/2Sm1/2)MoO4, the negative τf value was further adjusted to near zero.