Effect Of Mn Doping Research Articles

Optimization of chemically sprayed ZnS films by Mn doping

In this study, undoped and Mn doped ZnS films were grown on microscope glass substrates at substrate temperature of 400 ± 5 °C by using a low cost Ultrasonic Spray Pyrolysis technique, and the effect of Mn doping on some physical properties of ZnS films was investigated. Structural, optical, electrical and morphological properties of all films were analyzed using X-ray diffractometer (XRD), UV–Vis spectrophotometer, two-probe technique and atomic force microscope (AFM), respectively. X-ray diffraction studies showed that all films were formed in ZnS hexagonal structure and the crystallization levels of the films were relatively improved due to the increase in the Mn doping ratio, especially for 4% doped films. It was determined that the average transmittance value of undoped ZnS film in the visible region is 38% and this value increases to 60% for the sample doped by Mn at the highest rate (12%). The band gap values of the films were calculated using the Tauc equation and determined to be between 3.82 and 3.94 eV. Electrical resistivity values of the films decreased significantly due to the Mn doping. Mn doping also caused ZnS films to have uniform surface morphologies consisting of noticeable particle formations. Figure of merit calculations showed that Mn doping has a favorable effect on ZnS films and ZnS:Mn (12%) films may be promising materials for applications such as photovoltaic solar cells and optoelectronic devices.

Prominent ferroelectric properties in Mn-doped BiFeO3 spin-coated thin films

BiFe1-xMnxO3 (BFMO, x = 0–0.05) thin films were successfully deposited onto fluorine-doped tin oxide (FTO)/glass substrates via sol–gel technique. According to results obtained from XRD, Raman spectroscopy, SEM, and energy-dispersive EDS, it was found that films have rhomboid perovskite structure and Mn ions were successfully and uniformly incorporated into BiFeO3 (BFO) films. Doping process was accompanied by the reduction in grain size. From XPS pattern, it was found that both Fe2+ concentration and oxygen vacancies are reduced as a result of Mn doping. Compared with pure BFO samples, ferroelectric, dielectric, and optical properties of BFMO films are noticeably enhanced. BiFe0.96Mn0.04O3 film exhibited excellent remnant polarization (2Pr of 312 μC/cm2) accompanied by a low leakage current. Underlying mechanism can be explained in terms of Mn doping-induced structural transition, reduction in grain size, and oxygen vacancies. Additionally, increased bandgap (Eg = 2.68 eV) was obtained in BiFe0.98Mn0.02O3 film compared with BFO film (Eg = 2.58 eV). This work demonstrates remarkable effect of Mn doping on BFO, indicating that BFMO is promising candidate for ferroelectric photovoltaic device applications.

Enhanced aging behaviors and electric thermal stabilities in 0.75BiFeO3–0.25BaTiO3 piezoceramics by Mn modifications

AbstractLead‐free 0.75BiFeO3–0.25BaTiO3 (0.75BF–0.25BT) ceramics have been extensively studied because of their high Curie temperature. The aging behavior and thermal stability of piezoceramics play decisive roles in their device applications. In this work, effects of Mn doping on the phase structure, aging behavior, and thermal stability of 0.75BF–0.25BT ceramics were characterized and related mechanisms were investigated. With the increase in Mn content, the typical rhombohedral phase of 0.75BF–0.25BT ceramics changed to the coexistence of pseudo‐cubic and rhombohedral phases. Mn modification enhanced the aging behavior and thermal stability of ceramics obviously. The aging rates of d33 and kp for 0.75BF‐0.25BT ceramics with 1.0 mol% Mn are 1.3% and 1.1%, respectively, which are only 1/4 those values for the undoped ceramics. The variation of εr of 0.75BF‐0.25BT ceramics with 1.0 mol% Mn is half of undoped ceramics under 500℃. The depoling temperature of 0.75BF‐0.25BT ceramics with 1.0 mol% Mn was 450℃, which is about 200℃ higher than that of undoped ceramics. The enhanced aging behavior results from the decreased defect concentrations, and the better thermal stability is owing to the significantly improved poling state due to the enhanced resistivity, large grain size, and decreased crystal distortion by Mn modification. These results reflect that a proper amount of Mn doping is an effective way to enhance the aging behavior and electric thermal stability.

The Role of Mn Doping on Ce-Based γ-Al2O3 Catalysts for Phenol Degradation

In this article, Mn doping on Ce-based γ-Al2O3 (i.e., Mn-Ce-γ-Al2O3) was synthesized and then employed as catalysts to study the removal of phenol from aqueous solutions through catalytic ozonation process. The results showed that the phenol removal was remarkably increased to 97.50% if Mn-Ce-γ-Al2O3 was adopted as the catalyst. In addition, the kinetic rate of the reaction was increased, approximately, about 1.49 times when using Ce-γ-Al2O3 catalyst with Mn doping. Moreover, X-ray diffraction, transmission electron microscopy, Brunner-Emmet-Teller measurements, and X-ray photoelectron spectroscopy techniques were used to comprehensively characterize the physicochemical properties of the synthesized Mn-Ce-γ-Al2O3 catalyst, including the phases, morphologies, textural properties, and dispersity of the surface active species. More uniform channel mesoporous structures were obtained after Mn doping on Ce-γ-Al2O3, which could enhance the gas-liquid mass transfer rate, surface hydroxyl groups, Ce3+/Ce4+ ratio, and the formation of Mn-Ce solid solution. In this study, the effects of Mn doping on Ce-based γ-Al2O3 on phenol degradation were investigated and the removal mechanisms were suggested for a better understanding of the improved removal efficiency.

Mn-promoted CaO-based adsorbents with enhanced CO2 uptake performance

The adsorption of CO2 over CaO-based adsorbents has been an effective way to capture CO2 at high temperature, but the adsorption capacity was hampered and the cycle durability was poor. To address the said problems, this paper reported the effect of Mn doping on the structure, morphology and CO2 adsorption performances of CaO-based adsorbents synthesized by a sol-gel method. The characterization results showed that the addition of Mn was helpful to form abundant micropores and mesopores in the doped CaO-based adsorbent, and Mn can effectively prevent the sintering and agglomeration of CaO particles. Moreover, electron transfer occurred on the modified CaO-based absorbents. These findings suggested that Mn species induced both structural and electronic promotion effect, resulting in smaller particle, higher dispersion and specific surface area of CaO-based adsorbents and formation of some electron-rich oxygen and Ca species, ultimately boosting CO2 adsorption performance. Especially, with the molar ratio of Ca/Mn being 20, the adsorbent Ca/Mn-20 presented the best CO2 uptake and excellent cycle stability (up to 10 cycles). In addition, it can be concluded that the adsorption process of CO2 was more obedient to the pseudo-second-order kinetic model, indicating the adsorption process was dominated by chemical adsorption.

Effects of Mn-doping on the structure and in vitro degradation of β-tricalcium phosphate

β-tricalcium phosphate (β-TCP) is an ideal biomaterial for the bone repair because of its biocompatibility and biodegradability. In this study, 0 mol%, 5 mol%, 15 mol% and 30%mol bivalent manganese ion (Mn2+) doped β-TCP (Mn-TCP) powders were synthesized by a sol-gel method. The amount of the dopants significantly influences the crystallinity and the parameters related with structure of β-TCP, such as the lattice parameters and crystallite dimensions. The particle size and the particle distribution of doped β-TCP powers were evaluated as well. Meanwhile, the as-synthesized powders were consolidated by sintering at 1000 °C in muffle furnace for 5 h to get Mn-TCP porous material and the degradation experiment was carried out in Simulated Body Fluid (SBF) solution for 28 days. Then, Mn-TCP porous material were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscope (SEM). Significantly, there were bone-like apatite materials deposited on the surface of bone-like porous materials. With the increasing doping amount of Mn2+, the newly formed apatite-like materials decreased, while the crystallinity increased significantly. Besides, pH results showed that alkaline environment was more favorable for the formation of sedimentary materials.

Steering of Magnetic Interactions in Ni0.5Zn0.5Fe2–x(Mn)xO4 Nanoferrites via Substitution-Induced Cationic Redistribution

Ni0.5Zn0.5Fe2O4 is one of the most versatile and technologically indispensable soft magnetic materials; however, a detailed investigation on the effect of substitution-induced cation redistributionon the magnetic and ferromagnetic resonance (FMR) properties of Ni–Zn-nanoferrites (NFs) remains elusive. Herein, we demonstrate that the modulation of the superexchange interactions via dopant-driven cationic redistribution is an efficient way to maneuver the static and dynamic magnetic properties of Mn-substituted Ni0.5Zn0.5Fe2–x(Mn)xO4 NFs. Employing a combination of Raman and X-ray photoelectron spectroscopies, the effect of Mn-doping on cation distribution is revealed. It was found that Mn2+ cations initially occupy tetrahedral A-sites; however, as substitution of Mn increases from Mn = 0.1 to 0.5, the higher percentage of Mn-cation exhibits the Mn3+ oxidation state and preferably occupies the octahedral B-sites. The Mössbauer study elucidates that the Fe3+–O–Mn2+ superexchanges are weaker than the Fe3+–O–Fe3+ superexchange. We demonstrate that the Mn-substitution-driven redistribution of cations is responsible for the remarkable decrease in magnetocrystalline anisotropy. Composition-dependent FMR studies reveal that the substitution of the Fe3+ cation by the Mn2+ cation weakens the magnetic coupling, causing shifts in the FMR relaxation frequency. The analysis of magnetic relaxation suggests that there are two kinds of interparticle interactions present in these NFs, namely, dipolar interaction and the surface spin interaction (broken superexchange). The superparamagnetic NFs with Mn = 0.1 substitution exhibit a magnetization value as high as 58 emu/g along with a very low coercivity of ∼20 Oe, making them an excellent candidate for a broad range of technological applications.

Effect of different Mn doping and point vacancy ratios on the magnetic properties of ZnO

The magnetic source of Mn doping and Zn vacancy coexisting in ZnO is controversial. To solve this problem, this work used the generalized gradient approximation first-principles plane-wave ultrasoft pseudo potential + U method based on density functional theory to calculate the effect of different Mn doping to point vacancy ratios on the magnetic properties of ZnO. The formation energy of ZnO with different Mn-substituted Zn (MnZn) to oxygen/zinc vacancy (VO/VZn) ratios can be smaller and more stable in zinc (Zn)-rich conditions than in oxygen (O)-rich conditions. The ZnO system exhibits p-type half-metallic ferromagnetism when the MnZn to VZn ratio is 2:1 or 2:2. When the Mn doping amount is constant, the Zn vacancies increase and the total magnetic moment of the doped system decreases. For the ZnO system in which Mn doping and oxygen vacancies coexist, when the amount of oxygen vacancies is constant, with Mn doping increase, the magnetic moment becomes larger. Both Zn22Mn2O22 and Zn20Mn2O24 can achieve ferromagnetic characteristics above room temperature.

Modifying the electronic and optical properties of nano-ZnS via doping with Mn and Fe

5% Fe- and Mn-doped nano-ZnS (Zn0.95A0.05S, A = Fe or Mn) was prepared using the thermolysis technique. The effect of Fe and Mn doping on the lattice parameter, crystallite size, and lattice microstrain was examined applying the Rietveld refinement. The analysis showed the incorporation of Fe and Mn substitutionally for Zn ions; a result confirmed by Fourier transforms infrared spectroscopy spectra from the shift in the vibration bands upon doping. The energy of ZnS band gap was reduced by doping, giving ZnS new applications in visible region. The different defects inside the different samples were investigated using photoluminescence spectroscopy. The reduction in PL intensity upon doping nominated doping material to be used in photocatalytic application. The effect of Fe/Mn doping and incorporation of atmospheric oxygen on the band-gap characteristics, the absorption, optical conductivity, refractive index, reflectance, and the dielectric constant were explored using density function theory calculation (DFT).

Effect of Mn doping on structure, the dielectric and electric properties of BCZT ceramics

The synthesis of (Ba0.99Ca0.01)(Zr0.2Ti0.8)O3 (BCZT) and doped (Ba0.99Ca0.01)(Zr0.2Ti0.8-xMnx)O3 (BCZT-xMn) ceramics was successfully carried out by the solid-state method. The doping effect is followed by X-ray powder diffraction, scanning electron microscopy (SEM), and dielectric and conductivity measurements. Indeed, X-ray diffraction measurements show the crystalline structure of ceramics. SEM images indicate the doping effect on the studied perovskite microstructure. The results indicate that during doping the maximum value of the temperature (Tm) of the dielectric constant varies slightly, and there will be a considerable decrease in permittivity, dielectric losses and conductivity. Manganese ions are well integrated in the perovskite while maintaining the solid solution.

Effect of low amount Mn doping on structural and magnetic properties of SrFe12O19: Effective magnetic anisotropy study by Stoner - Wohlfarth model

A series of strontium hexaferrites (Sr-HF) compounds, doped with a low amount of manganese SrFe12-xMnxO19 (where x = 0.00, 0.03 and 0.05), were prepared by a sol-gel method. Structural and microstructural characterizations were performed by X-ray diffraction (XRD) and scanning electronic microscopy (SEM) in order to determine some basic properties such as lattice parameters and particles size. Moreover, magnetic properties of the samples were measured in a temperature range from 2 to 900 K. The results show that the transition temperature (TC) decreases from 764 to 721 K with Mn doping at x = 0.05 content. Also, temperature and doping effects on the coercivity (Hc), the remanent magnetization (Mr) and the magnetization of saturation (MS) were discussed considering the Stoner - Wohlfarth model. A slight improvement of the magnetic properties (Hc =5.56 kOe, Mr =49.99 emu/g, MS =101.9 emu/g (i.e. 19.37 μB/u.f)) for low content (x = 0.03) is evidenced, yielding to promising material for permanent magnet devices. This improvement was explained by the relationship between the microstructure and to the effective magnetic anisotropy.

Manganese-doping enhanced local heterogeneity and piezoelectric properties in potassium tantalate niobate single crystals.

Ion doping, an effective way to modify the nature of materials, is beneficial for the improvement of material properties. Mn doping exhibits gain of piezoelectric properties in KTa1-x Nb x O3 (KTN). However, the impact mechanism of Mn ions on properties remains unclear. Here, the effects of Mn doping on local heterogeneity and piezoelectric properties in KTN are studied. The electric field-induced strain of Mn-doped KTN is ∼0.25% at 10 kV cm-1, 118% higher than that of pristine KTN. Meanwhile, as a result of Mn doping, the dielectric permittivity was tripled and the ferroelectricity was modified. The changes in A1(2TO), B1 + E(3TO) and E(4TO) vibrations characterized by Raman spectra indicate increased local polarization, weak correlation of dipoles and distorted lattices in Mn-doped KTN, respectively. First-principles calculations demonstrate stronger local heterogeneity introduced by Mn dopants, which weakens the dipole correlations and reduces domain sizes. As a result, the decreased domain sizes, combined with the larger ratio of lattice parameters c and a of the Mn-contained portion, are responsible for the higher piezoelectricity. This work reveals the impact on properties of KTN from Mn dopants and the prominent role of local heterogeneity in improving piezoelectricity, being valuable for the optimization and design of material properties.

Effects of Mn-doping on anti-fatigue and anti-leakage current characteristics in KNN single crystals

In this work, we illuminate the influences of Mn doping on the domain structure, ferroelectric properties, and piezoelectric properties of K0.4Na0.46NbO3 (KNN) lead-free single crystals. We simultaneously obtained a low leakage current and high anti-fatigue properties in Mn:KNN single crystals. The valence state of the Mn ion changes after annealing from trivalent to bivalent. The micro-domain structure images show that the domain structure of Mn-doped KNN single crystals is more complex with a smaller size. In addition, the occupying mechanism of Mn in KNN is discussed. Moreover, ion doping is of great significance to the further study of low leakage resistance and good anti-fatigue properties for KNN-based ferroelectric materials.

Morphological studies of p-type Mn-doped SnO2 nanostructure

SnO2 thin films doped with various manganese concentrations were prepared on glass substrates by sol–gel dip coating method. The decomposition procedure of com- pounds produced by alcoholysis reactions of tin and manganese chlorides was studied by thermogravimetric analysis (TGA). The effects of Mn doping on structural, morphological, electrical and optical properties of prepared films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), Hall effect measurement, Fourier Transform Infrared (FTIR) spectral analysis, UV–Vis spectrophotometry, and photo- luminescence (PL) spectroscopy. The results of the X-ray diffraction show that the samples are crystalline with a tetragonal rutile structure and the grain size decreases with increasing the doping concentration. The SEM and AFM images demonstrate that the surface morphology of the films was affected from the manganese incorporation. The Sn1−x Mnx O2 thin films exhibited electrically p-type behavior in doping level above x = 0.035 and electrical resistive increases with increase in Mn doping. The optical transmission spectra show a shift in the position of absorption edge towards higher wavelength (lower energy). The optical constants (refractive index and extinction coefficient) and the film thickness were determined by spectral transmittance and using a numerical approximation method. The oscillator and dispersion energies were calculated using the Wemple–DiDomenico dispersion model. The estimated optical band gap is found to decrease with higher manganese doping. The room-temperature PL measurements illustrate the decrease in intensity of the emission lines when content of Mn is increased in Mn-doped SnO2 thin films.

Effect of Mn-doping on the optical and electronics characteristics of cadmium sulfide photocatalyst prepared under different conditions

CdS and Cd0.95Mn0.05S were synthesized using a thermolysis procedure in the air and underflow of nitrogen. Rietveld analysis for X-ray diffraction data revealed that all samples have two phases (hexagonal wurtzite and cubic zinc blende). The effect of Mn doping and the preparation conditions on the phase percentages, the crystallite size, lattice parameters and vibrational bands were investigated in detail. The optical band gap of CdS reduced when formed in N2 compared with sample formed in air. Upon doping with Mn, the optical band gap of samples (in air or nitrogen) exhibited a redshift. Density function theory calculation (DFT) revealed a semiconductor feature with a direct band gap for all samples except Mn-doped CdS with cadmium deficiency; it has a half metallic nature. DFT calculations manifested that for the Mn-doped samples, the optical conductivity was enhanced in the visible range considering sulfur deficiency, while considering Cd deficiency the sample has an optical conductivity response only in the IR region. The calculations were performed to examine the influence of Mn doping on the structure, optical, magnetic and electronic characteristics of CdS (stoichiometric and non- stoichiometric).

Effect of Mn doping on hydrolysis of low-temperature synthesized metastable alpha-tricalcium phosphate

In the present work, effect of Mn doping on hydrolysis rate of low-temperature synthesized metastable α-tricalcium phosphate (α-TCP) was investigated. α-TCP powders containing different amount of Mn2+ ions (0, 0.5 and 1 mol%) were synthesized by wet co-precipitation process, followed by annealing and crystallization of as-precipitated amorphous calcium phosphate at 700 °C. It was demonstrated that the presence of Mn2+ ions significantly retards hydrolysis rate of α-TCP. While pristine α-TCP fully hydrolyzed with a conversion to calcium-deficient hydroxyapatite in 10 h, complete hydrolysis of α-TCP doped with 0.5 and 1 mol% of Mn occurred only after 20 and 35 h, respectively. Initial and final products were characterized by X-ray diffraction (XRD) analysis, infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). Chemical composition of starting and fully hydrolyzed α-TCP powders was determined by inductively coupled plasma optical emission spectrometry (ICP-OES).

Structural, morphological, optical and enhanced photodetection activities of CdO films: An effect of Mn doping

In this work, undoped and Mn of various concentration (1, 3 and 5 %) doped CdO films prepared by spray pyrolysis procedure using perfume atomizer is reported. XRD analysis of the samples approves polycrystalline nature with cubic system. Change in crystallite size, lattice constant, and cell volume are observed due to the imperfection of crystal lattice. Tightly packed uniformed spherical shape particles are visualised from the morphology anaysis. In PL studies, the emission peaks are observed at 360, 490, 520, and 590 nm. From the UV–vis, the absorbance is increased with doping concentration, which may be due to electronic transition from V to C-band. The bandgap values are decreased with increasing doping concentration (2.51, 2.47 and 2.21 eV) and furher increased for higher doping concentration (2.37 eV). The high resistivity obtained for 3% Mn doped film may be the vital to decrease the dark current and increase the photodetector properties. I–V characteristics of the devices showed increased photosensitivity, responsivity, and quantum efficiency for 3 % of Mn doped film due to high crystallinity, low bandgap, and maximum energy transfer of Mn ions.

Effect of Mn doping in CdS quantum dot sensitized solar cells grown by SILAR method

The manganese-doped cadmium sulfide (Mn-doped CdS) quantum dots on titanium dioxide nanoparticles was fabricated using the successive ionic layer absorption and reaction (SILAR) method. The quantum dots were applied to photovoltaic cells. The mixing percentage of manganese in cadmium sulfide precursors was in the range of 1–20 mol%. The study of transport mechanisms and photovoltaic properties of the Mn-doping into CdS QD were investigated using a solar simulator (AM 1.5 G) and current–voltage (J-V) measurements in the dark and under illumination conditions (100 mW/cm2) at room temperature. The photovoltaic performance results indicate that Mn-doped in CdS ratio of 15 mol% exhibits the photovoltaic performance maximum convention efficiency (PCE) is 0.33%. The X-ray diffraction (XRD) patterns of Mn/CdS photoanodes show the nanoparticle average grain size in the range of 4–5 nm, which the formation of the nanoparticles was confirmed by scanning electron microscopy (SEM). The energy dispersion spectroscopy (EDS) shows that Mn is doped into the lattice of CdS QDs. The optical property of the quantum dots was investigated by UV–VIS absorption spectroscopy. The optical band gap was obtained and found to be 2.19 eV from Tauc's plot technique..

Effect of Mn doping on the electron injection in CdSe/TiO2 quantum dot sensitized solar cells.

Promotion in power conversion efficiency is an appealing task for quantum dot-sensitized solar cells that have emerged as promising materials for the utilization of clean and sustainable energy. Doping of Mn atoms into quantum dots (QD) has been proven to be one of the effective approaches, although the origin of such a promotion remains controversial. While several procedures are involved in the power conversion process, electron injection from the QD to the semiconductor oxide substrate is focused on in this work using first-principles calculations. Based on the Marcus theory, the electron injection rates are evaluated for the quantum dot-sensitized solar cell models in which the pure and Mn-doped core-shell CdSe clusters are deposited on a semiconductor titanium dioxide substrate. Enhanced rates are obtained for the Mn-doped structure, which is in qualitative agreement with the experiments. A large number of dominant injection channels and strong QD-substrate coupling are responsible for the Mn-induced rate enhancement, which could be achieved by manipulating the band structure mapping between the QD and the semiconductor oxide. By addressing the role of an Mn dopant in the electron injection process, strategies for the promotion of electron injection rates are proposed for the design of quantum dot-sensitized solar cells.

Effect of Ag and Mn doping for methylene blue photodegradation performance

Currently, wastewater management is ineffective, operationally expensive, and difficult to be implemented in Indonesia. The photocatalyst is a technology that may answer this problem. Titania (TiO2) is a high-activity, inexpensive, stable, and non-toxic photocatalyst material. However, TiO2 has large band-gap energy and rapid recombination. In this research, TiO2 was doped by Ag (a noble metal) and Mn (a transition metal) to compare the performance of photocatalysts in organic pollutant degradation, using methylene blue. Ag/TiO2 catalyst was synthesized by Photo Assisted Deposition (PAD) method, while Mn/TiO2 was synthesized by impregnation method. The physicochemical properties of both catalysts were assessed by SEM-EDX and UV-Vis DRS. SEM-EDX indicated that both methods successfully doped Ag and Mn into TiO2. Besides, UV-Vis DRS confirmed the presence of metal dopants that caused the narrowing of the bandgap. Ag/TiO2 catalyst increased the degradation of methylene blue by up to 97% in 30 minutes. Meanwhile, the Mn/TiO2 catalyst inhibited the degradation of methylene blue. The increased activity by Ag dopants is due to the Localized Electromagnetic Field (LEMF) and Schottky barrier phenomena which increase charge separation. Meanwhile, decreased activity by Mn dopants is due to the shading effect and Mn electronic structure that can facilitate recombination at high loading. Ag/TiO2 catalyst also improved photodegradation performance of TiO2 when irradiated by visible light.