Cation Distribution Research Articles

Modulation of Ion Transport in Nanopores Using Polyethylene Glycol.

Ion transport in nanopores is crucial for various biological and technological processes, exhibiting unique behaviors compared to bulk solutions. In this study, we systematically explore how polyethylene glycol (PEG) modulates ion transport within a conical nanopore. Our experiments reveal that introducing PEG into the ionic solution induces a reversal in ion current rectification (ICR). We further investigate the impact of PEG concentration, molecular weight, nanopore size, and cation type on ion transport. Additionally, we assess three different configurations of PEG introduction, identifying diffusive flow driven by an asymmetric cation distribution within the nanopore as a dominant transport mechanism. Our results confirm that the interactions between PEG and cations significantly affect ion transport properties. These findings advance our understanding of macromolecular crowding effects on ion transport and suggest potential applications in iontronic devices and biomolecule sensing.

Insight into CO2/CH4 separation by ionic liquids confined in MXene membrane from molecular level

Composite membranes incorporating ionic liquids (ILs) within MXene demonstrate promising potential for CO2 separation. However, studies on the separation of CO2/CH4 using MXene-confined ILs membranes are limited, especially in terms of understanding the mechanisms at the molecular level. In this work, the system of CO2/CH4 in MXene-confined ILs membranes was studied by molecular dynamic simulations. The number density results reveal that MXene stratifies the ILs between the layers, with higher concentrations of ILs near MXene and lower concentrations in the middle layer. Notably, MXene has a greater impact on cations distribution compared to anions. As the layer spacing of MXene expands from 1.5 to 3 nm, the interaction between MXene and IL weakens, while that between the cations and anions strengthens. The confined ILs enhance gas solubility capability but impede gas diffusion. CO2 is distributed closer to anions, while CH4 tends to be closer to cations, with the distance between CH4 and cations decreasing as the layer spacing increases. Additionally, with the increase of layer distance, the proportion of confined ILs gradually decreases, and the gas diffusion coefficient gradually increases. Furthermore, compared to 1-Ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]) and 1-Ethyl-3-methylimidazolium hexafluorophosphate ([EMIM][PF6]), MXene-confined 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][TF2N]) is identified as the most effective for CO2/CH4 separation, owing to its superior CO2 solubility and highest diffusion selectivity.

Magneto-structural properties of Mg-substituted copper ferrite nanoparticles

Abstract This study explores the synthesis and characterization of magnesium-substituted copper ferrite (MgxCu1-xFe2O4, 0.0≤x≤1.0) nanoparticles using the polymer-assisted sol–gel self-combustion method. The effects of magnesium substitution on the structural, elastic, and magnetic properties of the ferrites were systematically investigated. X-ray diffraction (XRD) analysis confirmed the formation of single-phase cubic spinel structures with particle sizes ranging from 8–21 nm. A slight increases in the lattice parameter was observed with higher magnesium content, attributed to the substitution of smaller Cu2+ ions with slightly larger Mg2+ ions. Fourier Transform Infrared (FTIR) spectroscopy and Mössbauer spectroscopy revealed the spinel structure and complex magnetic interactions between ferromagnetic and superparamagnetic phases. The spin canting was observed and found to vary significantly across compositions, with a maximum canting angle of 58.47°. This notable result highlights the important magnetic behavior of these materials. The saturation magnetization (MS) varied across samples, with the x = 0.6 composition exhibiting optimal magnetic performance. Cation distribution analysis using XRD, Mössbauer spectroscopy, and magnetic measurements consistently showed the redistribution of cations between the tetrahedral (A) and octahedral (B) sites in the spinel structure. This research demonstrates the potential of magnesium-substituted copper ferrites for magnetic applications, with notable improvements in magnetic and structural properties due to cation substitution.

Elastic and magnetic characteristics of nano-spinel ferrite Co0.5 MgxCu0.5−xFe2O4

Wet-chemical co-precipitation was used to create Co0.5MgxCu0.5−xFe2O4 nano-ferrites (x = 0.0, 0.2, 0.3, and 0.4). XRD, FT-IR, HRTEM, and EDX analyses were used to confirm each sample’s single-phase spinel cubic crystal structure. The crystallite size was calculated from the XRD data and determined to be between (11.1570 and 16.1457 nm), with a lattice constant between (8.359 to 8.387Å). The two absorption bands found in the FTIR data were utilized to show metal cation and oxygen bond stretching at tetrahedral and octahedral positions, as well as to calculate the elastic moduli. The elemental composition and structural behavior of every sample were examined using FE-SEM and EDS. The magnetic parameters were also estimated based on the VSM data, the contribution of magnetic anisotropy (K), and the magnetic interaction by Neel’s and Y-K-type magnetism modify as the Mg2+ ion substitution increases, thus we must consider how this variation in cation distribution affects all of these factors. As per the ferromagnet theory, ions originating from the magnetic tetrahedral A and octahedral B sites engage in super-exchange interactions with one another. Anti-ferromagnetic alignment occurs as a result (MB-MA). Magnetization occurs as a result.

Annealing-induced changes in Sol-Gel synthesized nano-CoFe2O4: A study of structure, morphology and magnetism

Magnetic nano-sized CoFe₂O₄ spinel ferrites were synthesized using the sol-gel auto-combustion technique, and the impact of annealing temperature on their structural and magnetic properties was systematically studied. Samples were annealed at 500 °C, 700 °C, and 900 °C for 5 hours. XRD analysis confirmed crystallization in the Fd3m space group, with average crystallite sizes ranging from 30 to 34 nm. Structural parameters such as ionic radii, bond lengths, and cation distribution were also calculated, revealing partial inversion with an inversion factor of 0.68. FE-SEM analysis showed uniform morphology and increasing grain size with higher annealing temperatures. EDS confirmed stoichiometric Co and Fe ion content, while FTIR indicated strong metal-oxide bonds characteristic of CoFe₂O₄. Magnetic measurements demonstrated that higher annealing temperatures enhanced saturation magnetization and magnetocrystalline anisotropy while reducing coercivity, highlighting the significant influence of annealing temperature on CoFe₂O₄ nanoparticles' performance.

Interplay Between Calcination Temperature and Alkaline Oxygen Evolution of Electrospun High-Entropy (Cr1/5Mn1/5Fe1/5Co1/5Ni1/5)3O4 Nanofibers.

Spinel-structured transition metal (TM) oxides have shown great potential as a sustainable alternative to platinum group metal-based electrocatalysts. Among them, high-entropy oxides (HEOs) with multiple TM-cation sites are suitable for engineering octahedral redox-active centers to enhance the catalyst reactivity. This paper reports on the preparation of electrospun (Cr1/5Mn1/5Fe1/5Co1/5Ni1/5)3O4 nanofibers (NFs) and their evaluation as electrocatalysts. Its main aim is to unveil the nanostructural features that play a key role in the alkaline oxygen evolution reaction. Differing calcination temperature (300-800°C) and duration (2 or 4h) leads to different morphology of the NFs, crystallinity of the oxide, density of defects, and cation distribution in the lattice, which reflect in different electrocatalytic behaviors. The best performance (overpotential and Tafel slope at 10mAcm-2: 325mV and 40mVdec-1, respectively) pertains to the NFs calcined at 400°C for 2h. To gain a deeper understanding of their electrocatalytic properties, the pristine NFs are investigated by a combination of analytical techniques. In particular, broadband electric spectroscopy reveals that the mobility of oxygen vacancies in the best electrocatalyst is associated to very fast local dielectric relaxations of metal coordination octahedral geometries and experimentally demonstrates the key role of O-deficient octahedra.

Limiting Current Investigations for PEM Water Electrolysis in the Presence of Metal Cations

Pretreatment and purification of water is necessary to use it as a feed for the oxygen evolution reaction (OER) at the anode of PEM water electrolysis (PEMWE). Fresh water typically contains several multivalent cations such as Ca2+ and K+. In addition, iron cations may accumulate in PEMWE over a long period of time due to corrosion of system components and fittings of the PEMWE. The presence of these multivalent cations in the feed water causes higher ohmic resistance of the cell and higher iR-free voltages, resulting in a performance loss.[1] Furthermore, the cations can be transported by the water crossover stream from anode to cathode and by diffusion transport.[2] In other words, even traces of metal cations drastically influence the efficiency and durability of PEMWE stacks. Despite this knowledge, contamination with multivalent cations is one to the main reason for the breakdown of PEMWE stacks.[3]Very interestingly, simulations of cationic contamination for PEM fuel cells (PEMFCs)[4] have shown that the distribution of metal cations in the through-plane direction depends on the proton current through the membrane. The cation concentration profile indicates an accumulation of metal cations close to the cathode side and leads to an increase of the proton transport resistance. In addition, the simulations indicate that in case of a complete substitution of protons by metal cations, the proton transport resistance approaches infinity. Finally, the proton current cannot increase further and a limiting current is reached.[4] The transfer/adoption of these simulations from PEMFC to PEMWE allows to clarify the behavior of the limiting current in dependence of the nature of metal cations such as Ca2+ and K+ and their concentrations, which is still poorly understood to date.In this work, we investigated if the concept of limiting protonic current from simulations for the PEMFC can be (partially) transferred to PEMWE on a laboratory scale. For this purpose, we evaluated the effect of trace metal cations in the anode feed water on the performance of a PEMWE single cell and quantified the cation concentration in the membrane using spectroscopic techniques such as micro X-ray fluorescence (µ-XRF) and energy-dispersive X-ray (EDX). Electrochemical measurements were carried out in an in-house PEMWE test bench equipped with a single cell of 5 cm2 geometric electrode area and potentiostat with booster. Commercially available catalyst coated membranes with a loading of 0.3 mg cm-2 geo of Pt/C and 1 mg cm-2 geo of IrOx were used. The measurements were carried out at atmospheric pressure and a cell temperature of 80°C. First, a conditioning procedure was performed using highly purified feed water (>20 MΩ cm at room temperature) until a stable cell performance had been achieved. Cation contamination experiments were conducted by introducing various concentrations of metal sulfates (1-100 µmol L-1 cation concentration) into the anode feed water. Performance evaluation was carried out by measuring the polarization curves and electrochemical impedance spectroscopy (EIS) to determine the Tafel slope, overvoltage, and high frequency resistance (HFR). µ-XRF and EDX spectroscopy techniques were used to detect the cation concentration profile along the membrane.We observed a significant rise of the cell voltage by adding cations to the anode water feed within few hours. More precisely, a limiting current density of 1 A cm-2 geo after 16 hours of exposure to 100 µmol L-1 K+-ions in the anode feed water was determined using the Koutecký-Levich equation. This result is in line with our first simulations. The switch back to purified feed water allows us to monitor the dynamics of the performance recovery process obtained from EIS data. Additional measurements of the polarization curves and HFR were used to distinguish between reversible and irreversible degradation processes due to the cation contamination. Very interestingly, a partial reversibility was observed after the K+-contamination, as the limiting current increased from 1 to 2 A cm-2 geo after 16 hours recovery with purified water feed.Altogether, this study evaluated the transferability of limiting protonic current concept from simulations in PEMFC to PEMWE to uncover the impact of trace metal cations in the anode feed water on the performance of PEMWE.[1] C. Immerz, M. Singer, F. Hasché, B. Bensmann, M. Suermann, R. Hanke-Rauschenbach, M. Oezaslan, Meet. Abstr. 2020, MA2020-02, 2456.[2] M. Friedrichs-Schucht, F. Hasché, M. Oezaslan, ECS Trans. 2023, 111, 3.[3] N. Danilovic, K. E. Ayers, C. Capuano, J. N. Renner, L. Wiles, M. Pertoso, ECS Trans. 2016, 75, 395.[4] B. L. Kienitz, H. Baskaran, T. A. Zawodzinski, Electrochim. Acta 2009, 54, 1671.

La3+ doped ZnFe2O4 synthesized via green chemistry approach using Uncaria gambir Roxb: A study on structural, optical, magnetic, and photocatalytic properties

Lanthanum-doped zinc ferrite (ZFLa) nanoparticles were synthesized via a hydrothermal method, utilizing Uncaria gambir Roxb leaf extract as a capping and stabilizing agent. X-ray diffraction (XRD) and Le Bail refinement confirmed a cubic spinel structure formation with an Fd-3m space group. Fourier-transform infrared spectroscopy (FTIR) analysis indicated a shift of the vibration mode of the tetrahedral site to a higher frequency with increasing lanthanum concentration. Raman spectroscopy revealed an additional peak in the A1g mode at 605 cm−1 for ZnFe1.9La0.1O4 (ZFLa10), suggesting the formation of an inverse spinel structure due to a complex cation distribution at the tetrahedral sites. Scanning electron microscopy (SEM) showed that all samples exhibited spherical grains at the nanoscale, with particle size decreasing as lanthanum concentration increased. UV–Vis diffuse reflectance spectroscopy (DRS) indicated band gap energies within the visible light range (1.84 to 1.86 eV). Brunauer-Emmett-Teller (BET) analysis confirms the increased surface area and pore diameter due to the introduction of La3+ ions, the specific surface area and pore diameter were 96.76 m2/g and 8.78 nm for ZFLa0, and 106.21 m2/g and 10.49 nm for ZFLa10, respectively. The adsorption percentage increased from 17.59 % for ZFLa0 to 55.56 % for ZFLa10. Photocatalytic investigations demonstrated that all catalysts exhibited good activity in degrading Direct Red 81 dye, with ZFLa10 showing the highest photocatalytic activity under direct sunlight, achieving up to 99.68 % degradation of the dye. Stability tests demonstrated remarkable durability, with ZFLa10 maintaining 90.20 % degradation efficiency after five cycles, establishing it as an excellent photocatalyst candidate.

Study of structural, elastic, optical, dielectric, and magnetic properties of sol-gel synthesized Li0.2Co0.3Zn0.3Fe2.2O4 ferrite for optoelectronic and electrical applications

This work presents a detailed investigation of the structural, elastic, optical, dielectric, and magnetic properties of Li0.2Co0.3Zn0.3Fe2.2O4 ferrite synthesized through the sol-gel process. The experimental structural parameters closely match the theoretical values, confirming the proposed cation distribution of the prepared sample. The FTIR spectrum and ultrasonic pulse transmission method analysis showed that the sample has brittle mechanical properties. According to UV-Vis optical absorbance analyses and based on Tauc's law, the sample exhibits a direct optical transition, with the band gap energy (Eg) determined to be 2.51 eV. The study of electrical conductivity showed that the sample exhibited a reduced activation energy (Ea= 0.154 eV) and remarkable electrical resistivity at room temperature (ρdc ∼ 104 Ω.m), indicating the material's potential for microwave device applications. The conduction process of the sample aligns with the NSPT model. Additionally, the temperature coefficient of resistance (TCR) suggests that the sample is a promising candidate for infrared radiation detection. A low coercive field was also derived from the hysteresis loop, confirming the soft nature of the sample operating within a microwave frequency range of 8–9 GHz. Our results show that the Li0.2Co0.3Zn0.3Fe2.2O4 compound offers advantages over the undoped Li0.5Fe2.5O4 compound, including a lower band gap, reduced activation energy, and higher electrical resistivity. This suggests that substituting Co and Zn into Li0.5Fe2.5O4 ferrites improves their performance in electrical and optoelectronic applications.

Al³⁺-substituted magnesium ferrites (MgAlₓFe2-xO4) for advanced hydroelectric cells and pseudocapacitors: Insights into the structural, morphological, and electrical studies

Electrochemical energy conversion and storage systems are currently at the forefront of the global energy landscape. Here, we have exhibited the generation of current by fabricating the hydroelectric cells (HEC) of Al3+ substituted magnesium ferrites with the general chemical composition [MgAlxFe2-xO4, x = 0.00, 0.10, and 0.20]. The structural confirmation has achieved using X-ray diffraction (XRD) and Raman spectroscopy. The Rietveld refinement was done to verify the cubic shape structured unit cell along with the analysis of cationic distribution. The adsorption of water molecules on the surface of ferrite has been verified using Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron (XPS), and Photoluminescence spectroscopy (PL). The V-I response revealed the maximum value of current (Isc) is 16.03 mA generated in AMG10 and a voltage of 0.99 V. The maximum current density of 15.695 mA/cm2 is demonstrated by the HEC (x = 0.10) which suggested its utility for pseudo-capacitive device application.

Synergistic Catalytic Sites in High-Entropy Metal Hydroxide Organic Framework for Oxygen Evolution Reaction.

The integration of multiple elements in a high-entropy state is crucial in the design of high-performance, durable electrocatalysts. High-entropy metal hydroxide organic frameworks (HE-MHOFs) are synthesized under mild solvothermal conditions. This novel crystalline metal-organic framework (MOF) features a random, homogeneous distribution of cations within high-entropy hydroxide layers. HE-MHOF exhibits excellent electrocatalytic performance for the oxygen evolution reaction (OER), reaching a current density of 100mA cm-2 at ≈1.64 VRHE, and demonstrates remarkable durability, maintaining a current density of 10mA cm-2 for over 100 h. Notably, HE-MHOF outperforms precious metal-based electrocatalysts despite containing only ≈60% OER active metals. Ab initio calculations and operando X-ray absorption spectroscopy (XAS) demonstrate that the high-entropy catalyst contains active sites that facilitate a multifaceted OER mechanism. This study highlights the benefits of high-entropy MOFs in developing noble metal-free electrocatalysts, reducing reliance on precious metals, lowering metal loading (especially for Ni, Co, and Mn), and ultimately reducing costs for sustainable water electrolysis technologies.

High-Entropy Selenides with Tunable Lattice Distortion as Efficient Electrocatalysts for Oxygen Evolution Reaction.

Developing stable and active electrocatalysts is crucial for enhancing the oxygen evolution reaction (OER) efficiency, which sluggish kinetics hinder sustainable hydrogen production. High entropy selenides (HESes) feature with random distribution of multiple metals cations and unique electronic and size effect of Se anion, allowing for precious regulation of their catalytic properties towards high OER activity. In this work, we report a series of high-entropy selenides catalysts with tunable lattice strain for electrocatalytic oxygen evolution. Electrochemical measurements show that the quinary (NiCoMnMoFe)Sex requires only 291 mV to reach 10 mA cm-2 and exhibits a superior stability with negligible current decay during 100 h's continuous operation. By combining experimental measurements and theoretical calculation, the study reveals that the lattice distortion, reflected by the local microstrain near the active site, plays a vital role in boosting the OER activity of HESes.

Controlling Chelation and Esterification in Pechini Synthesis for Enhancing Chemical Looping Steam Methane Reforming using LaFeO3 Perovskite.

The properties of an oxygen carrier, such as crystalline structure, textural properties, and surface chemical species, significantly influence the redox performance in thermochemical redox applications. This study presents the synthesis of various lanthanum orthoferrite (LaFeO3) perovskites by adjusting Pechini synthesis parameters, including chelating agent ratio, calcination temperature, and solution pH. A larger surface area emerged as a dominant factor contributing to improved redox performance. The porosity of the polyester resin proves crucial in achieving a large surface area and a small particle size for the oxygen carrier. This goal could be attained by controlling the pH of the precursor solution. A low degree of chelation or precipitation may lead to uneven cation distribution, resulting in the enrichment of trace hydroxide impurities. These impurities can suppress the reducibility of particles during the looping experiment. Various investigations, using XRD, XPS, XAS, SEM, and N2 physisorption, revealed that porosity and crystallinity can be controlled by altering the synthesis parameters.

Controllability of optical, electrical, and magnetic properties of synthesized Cd-doped MgFe2O4 nanostructure

This study explores the synthesis of cadmium-magnesium co-doped magnesium ferrite (Mg1+xCdxFe2–2xO4, 0.00 ≤ x ≤ 0.30, Δx = 0.05) via a citric acid-assisted sol-gel auto-combustion method. X-ray diffraction (XRD) analysis revealed crystal structure changes due to Cd and Mg co-doping, with the 0.25 Cd sample showing the smallest crystallite size and highest lattice strain. High-resolution transmission electron microscopy (HRTEM) confirmed the nanostructure and largest surface area for this sample. Diffuse reflectance spectra, analyzed using the Kubelka-Munk relation, indicated that the 0.25 Cd sample had the lowest energy gap (2.08 eV), supported by band position calculations. Electrical conductivity and charge transport mechanisms were examined at various temperatures. Magnetization studies showed reduced saturation magnetization at x = 0.25, ascribed to cation distribution changes and spin canting, with coercivity and anisotropy decreasing with higher Cd content. Overall, the 0.25 Cd sample exhibited optimized optical, electrical, and magnetic properties due to its distinct microstructure.

Inhibiting Cation Segregation to Enable Highly Efficient Perovskite Light‐Emitting Diodes

AbstractPerovskite light‐emitting diodes (PeLEDs) present potential applications for next‐generation displays due to their excellent luminescent properties and solution processing. The formamidinium‐caesium lead bromide (FAxCs1−xPbBr3) mixed cation strategy is one of the primary methods to achieve high‐performance of Cs‐dominate PeLEDs system. However, the inhomogeneous distribution of cations is detrimental to the photoelectronic performance of Cs‐dominated PeLEDs. Here, in mixed FA/Cs perovskite films, it is observed that Cs, Br and trace Pb elements precipitated on the surface of the perovskite films. It is found that the segregation of cations is induced by the uncontrollable crystallization process of Cs/FA cations. By introducing biuret additive, the hydrogen bonding interaction of biuret and FA cation balances crystallization rate, which therefore significantly improves the crystal quality and cations distribution of perovskite films. As a result, green PeLEDs with a high external quantum efficiency of 28.8% are obtained, and represent five times enhancement in half‐life time (T50) of 2.48 h at an initial luminance of 100 cd m−2 relative to the control device. The results help to understand the relationship between cationic distribution and PeLEDs properties, offering significant insights for modulating the performance of PeLEDs.

Effects of Zn2+/Si4+ co-doping on the cation distribution, crystal structure, and microwave dielectric characteristics of spinel-structured MgAl2O4 ceramics

Investigating the relationship between the structure and dielectric properties of cation-mixed spinel ceramics is crucial for overcoming the limitations of conventional microwave materials. In this study, MgAl2-x(Zn0.5Si0.5)xO4 (x = 0, 0.02, 0.04, 0.06, and 0.08) ceramics were prepared by a solid-state reaction method. The co-substitution for Al with Zn2+/Si4+ induces Al3+ cations for preferential occupation of the 8a site in the oxygen tetrahedra, forming a solid-solution ceramic at x ≤ 0.06. Enhanced ionic diffusion and compressive stress contribute to a dense microstructure (ρ > 95 %) with uniform grain-size distribution after heating at 1650 °C for 4 h. Raman and 27Al NMR spectra reveal a relationship between cation distribution and covalency, consistent with the results of Rietveld refinement. The increases in cation disorder and degree of inversion are accompanied by an enhanced covalency of the Al–O bonds, which reduces intrinsic dielectric loss. In addition, the combination of Shannon ion polarizability and bond valence theory suggests that the increases in permittivity (εr) and the temperature coefficient of resonant frequency (τf) are related to the high polarizability of the dopant ions and the abnormal polarizability derived from the decreasing bond valence of the Al2–O site. The sample at x = 0.06 exhibits a low εr of 8.31, high Q × f of 194,159 GHz (at ∼11.35 GHz), and τf of −30.8 ppm/°C, indicating superior microwave application prospects as compared with traditional Mg-Al spinel ceramics.

Revealing crucial factors governing magnetic properties of high-energy ball-milled CoFe2O4 nanoparticles

Nanostructured spinel-type ferrites have attracted significant interest from both the aspects of fundamental research and industrial application owing to their outstanding electronic and magnetic properties. Understanding the factors governing their magnetic properties is important for designing advanced materials with tailored features. In this work, we have conducted a systematic investigation on the structural, electronic, and magnetic properties of high-energy ball-milled CoFe2O4 nanoparticles, which possess a cubic spinel structure and average crystallite sizes (D) ranging from 334 nm for the initial bulk material to 11.7 nm after 120 min of milling. Our observations indicated that the high-energy milling leads to the migration of Co2+ ions from the octahedral B site to the tetrahedral A site, and vice versa for Fe3+ ions. The concentration of Co2+ ions at the A site increases linearly versus the 1/D value. Unlike previous studies on CFO, we have found that the spin canting of Fe3+ ions occurred at both the A and B sites within the inner core, not only on the surface of nanoparticles. The spin canting angles φA and φB increase with grain-size reduction. Although the milling-induced changes in the cation distribution and spin canting are expected to significantly increase the saturation magnetization, this effect is overshadowed by the decrease caused by surface spin disorder. In other words, the surface effects play the primary role affecting the magnetic properties of the milled CFO nanoparticles.

Improvement in magnetic behaviour on Erbium addition to Co-Mn ferrite nanoparticles for magnetic device applications

Magnetic nanoparticles exhibit remarkable and notably unique magnetic characteristics, owing to their high ratio of surface-to-volume and various configurations of crystals. The properties of these nanoparticles are also significantly influenced by their preparation method. In the present work, Er3+ substituted ferrite nanoparticles of Co0.5Mn0.5ErxFe2-xO4 (x = 0, 0.005, 0.01, 0.05, and 0.1) have been synthesized by using an aqueous sol-gel method. The prepared samples have been characterized using XRD, FESEM, RAMAN, FTIR, VSM, and UV-Visible spectroscopy to investigate various physical properties. XRD, RAMAN and FTIR spectroscopy confirm the formation of face centred cubic inverse spinel structure. There is variation in the structural parameters with the substitution of Er3+. The intrinsic vibrations of metal ions at tetrahedral and octahedral sites are observed in the FTIR spectra. Ferrimagnetic behaviour has been obtained for these ferrite nanoparticles. An increase in remanence ratio has been observed with erbium substitution. There is strengthening of A-B super-exchange interaction altering the magnetic characteristics on Er3+ substitution in the Co-Mn ferrites. The same has been corroborated by the suggested cation distribution and the computed values of Yafet-Kittel angles. There is an increase in the value of optical band gap from 3.63 eV (x=0) to 3.85 eV (x=0.1) with Er3+ content. An improvement in saturation magnetization (Ms), coercivity (), and magnetic moment ( have been obtained on addition of Er3+ to Co-Mn ferrites, suggesting their potential application for data storage devices.

Cerium doped superparamagnetic Mn-Zn ferrite as a promising material for self-regulated magnetic hyperthermia

Recently, cubic ferrites (CF) have been widely explored in biomedical applications, especially those that display superparamagnetism behavior due to the desirable absence of remanent field. In this study, we report the self-stabilization of the magnetic fluid hyperthermia (MFH) temperature in the cancer therapy range (42 - 48 ºC) by Ce3+ substitution in superparamagnetic Mn0.8Zn0.2Fe2-xCexO4 ferrite with x = 0.0; 0.015; 0.030; 0.050 and 0.100. A comprehensive characterization was performed in order to investigate the influence of this replacement on the magnetic and structural properties of the ferrite. The samples were synthesized by the sol-gel auto-combustion method and the properties were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), Raman spectroscopy (RS), Mössbauer spectroscopy (MS), vibrational sample magnetometry (VSM), and ferromagnetic resonance (FMR). Magnetic hyperthermia essays were used to obtain the heat induction curves and calculate energy dissipation. We refined the XRD data by the Rietveld method to determine the cation distribution and calculate interionic parameters. Magnetic characterization confirms the superparamagnetic behavior at 300 K, which is expected from the TEM results that show a narrow distribution of particle sizes, with a mean size of about 6.5 nm for all samples. The VSM results show a consistent decrease in magnetization saturation with cerium content that result in a weaker self-heating induction capacity for the cerium-doped samples. FMR results also show a smaller relaxation time T2 for these samples, suggesting a slower energy dissipation rate. These conclusions are confirmed by the heat induction curves and the values of the specific absorption rate (SAR), which are smaller for cerium-doped samples. For the a field with an amplitude of 35.33 kA/m and a frequency of 222 kHz, the temperature of the cerium-doped samples saturates in the optimum interval for cancer treatment, between 42 and 48 ºC. These results suggest that Ce3+ is a promising doping ion to optimize the heating rate behavior of Mn-Zn ferrite for cancer treatment by hyperthermia.

Impact of atomic layer deposition supercycle design on the reliability of heterogenous IGZO channel TFTs

Oxide semiconductor thin-film transistors (TFTs) are promising candidates for application in display backplanes and memory devices. To ensure both high performance and stable electrical properties of oxide TFTs over long-term use, superior mobility and device stability need to be obtained. In this regard, atomic layer deposition (ALD) has gained attention as a facile method for obtaining conformal oxide films under defect-free conditions and adjusting the composition or distribution for targeted TFT performance. Here, we propose that, even with the same bulk composition, variations in the local composition using an ALD supercycle design can significantly affect the TFT performance, particularly the bias-temperature stability. To ascertain the influence of the local cation distribution on the performance, we compared two supercycle designs by reversing the sub-cycles of indium, gallium, and zinc with identical bulk In–Ga–Zn ratios. Despite minimal changes in the electrical characteristics, such as the mobility and threshold voltage, of the two TFTs designed with ALD supercycles, there was a significant difference in their reliability. Devices with an indium-rich IGZO active layer on the back channel exhibited a hump phenomenon and approximately five times greater Vth degradation (ΔVth: −0.67 V to −3.36 V). By conducting an additional case study of IGZO TFTs and film analysis, we confirmed that mobility is largely governed by the bulk composition, whereas the local surface composition, serving as the back channel, is the key to reliability. The device performance results could be confirmed through the surface and bulk analyses of heterogeneous films engineered through the ALD supercycle design. Furthermore, it has been proposed that optimizing the ALD supercycle design is the key to obtaining high-performance oxide semiconductor TFTs.