Increase In Lattice Parameter Research Articles

Investigation of crystal structure, electrical and dielectric response of Ga3+ substituted Sr–Ni Y-type hexaferrites as a suitable material for high frequency applications

Technology important ferrites ceramic Sr2Ni2GaxFe12-xO22 (x = 0.00, 0.2, 0.4, 0.6, and 0.8) samples were produced using sol-gel auto combustion route. Structural, electrical, dielectric, and magnetic parameters were identified by substituting Ga3+ at the Fe3+ site. It was recognized that an increase of Ga3+ content in (Sr2Ni2GaxFe12-xO22) ceramic samples first decreased, then increased lattice parameters, and the density of samples was observed. This is because of the ionic radii and atomic weight of Ga3+ and Fe3+ cations. FTIR spectra show two characteristic absorption bands at 444-513 cm−1 caused by metal-oxygen vibrations. Due to the contribution of smaller grains of samples, the higher values of resistivity were observed, which vary from 3.78 × 1010 (Ω cm) to 1.13 × 1011 (Ω cm) by the substitution of Ga3+ ions at the octahedral site. The activation energy was measured between 0.20 and 0.61 eV. The dielectric response of Ga3+ substituted ferrite ceramic samples were studied in the 1 MHz-6 GHz frequency region. The Maxwell-Wagner bilayer model studied the effect of polarization with applied frequency on dielectric parameters. With the substitution of Ga3+, minimal losses in the range 0.34–0.44, about 6 GHz, and a high Q-value of about 10,000 were observed for each sample. In impedance spectroscopy analysis Cole-Cole plots confirm that the dielectric response is because of the influence of grain boundaries. The substitution of Ga3+ enhances saturation magnetization (68.20–71.78 emu/g) while coercivity decreases (655.86–507.86 Oe). In the present finding, the low dielectric loss, moderate permittivity, high value of the Quality factor, and very high value of resistivity of about 1.13 × 1011 that reduces the eddy current losses suggested that these materials are appropriate candidates for many high-frequency applications such as multilayer chip inductor, dielectric resonators, power applications, and microwave devices.

Rare earth-doped mixed Ni–Cu–Zn ferrites as an effective photocatalytic agent for active degradation of Rhodamine B dye

In this study, a series of Gd3+-doped mixed Ni–Cu–Zn ferrites with composition of Zn0.5Ni0.3Cu0.2Fe2–xGdxO4 (x = 0, 0.025, 0.05, 0.075, 0.1) was prepared using self-ignition sol–gel method. The prepared nanoparticles with an average size ranging from 22 to 26 nm show a single-phase cubic structure belonging to the spinel matrix. A rise in the Gd3+ concentration leads to an increase in crystallite size and lattice parameter. In Fourier transform infrared spectra, two main absorption bands belonging to the spinel structure are observed. The high-frequency bands (υ1) represent the tetrahedral complex, while the low-frequency bands (υ2) signify the octahedral complex. The optical bandgap of the nanoferrites is found within the range of 2.91 to 2.41 eV, depending on their size. The magnetic characteristics of the material, such as saturation magnetization and coercivity are significantly altered with the concentration of Gd3+ in the solution. Using Rhodamine B (RhB) as a model organic pollutant, an in-depth investigation of the photocatalytic activity of the compounds was carried out. The present outcomes show that adding an adequate amount of Gd3+ significantly enhances the number of hydroxyl radicals produced by the ferrite, in turn, increasing the photocatalytic activity of the material. Mechanism elucidated by scavenger studies reveals that •OH and holes are the primary reactive radicals responsible for the degradation process. Prepared photocatalysts show an insignificant performance loss in five consecutive cycles. Thus, it is concluded that these photocatalysts are highly suitable for the remediation of dye-contaminated wastewater.

Structural, electrical and magnetic properties of evaporated FexNi1-x thin films

Polycrystalline FexNi1-x thin films were successfully synthesized via physical vapor deposition under vacuum. The iron atomic content is ranging from 20 to 45%. The thin films physical properties are studied and the impact of Fe percentage on their structural, electrical and magnetic properties is examined. To determine their structure, microstructure, surface morphology, chemical compositions, electrical and magnetic properties, the deposited films were analyzed by Rutherford Backscattering Spectrometry, X-ray diffraction, atomic force microscopy, Hall Effect measurement system (HMS-5300) and Vibrating Sample Magnetometer tools. The achieved X-ray diffraction spectra exhibited face centered cubic structure with<111> preferred orientation. The crystallite size and lattice parameter increase with increasing iron content. Both of electrical resistivity and magnetoresistance decrease with increasing film thickness, whereas mobility increases. Magnetization curves infer an in-plane easy axis without any preferential direction. It is also found that Ms increases and Hc decreases with iron content increase.

Structural, Mossbauer spectra and magnetic properties of Ni(1-x) Cdx Fe2O4 by solid state Reaction method

The preparation of Ni-Cd ferrite having the chemical formula Ni(1-x)CdxFe2O4 where x varies from 0, 0.1, 0.2, 0.3, 0.4, and 0.5 were synthesized by solid state reaction method. The X-ray analysis shows the existence of single phase spinel structure with increase of lattice parameter and density with increasing Cd contents were as the porosity decreases. The particle size was calculated by X-ray broadening studies. The Vickers hardness of Ni-Cd ferrite system variation between 532 to 568.6. The increase in hardness of composites results from increased Cd-content. The Atomic Force Microscopy (AFM) showed that the average grain size was increases with the increase in Cd content. The variation of dielectric constant, loss tangent and AC conductivity as a function of frequency in frequency range 100Hz-5MHz was studied. The dielectric constants decreases with increasing frequency for all the samples and follow the Maxwell-Wagner's interfacial polarization. The Hall coefficient was found to be positive. It demonstrates that the majority of charge carriers of p-type. The magnetic properties of Ni(1-x)CdxFe2O4 ferrites were strongly affected by the Cd content. The Mossbaure spectra show canted spin structure for all the samples.

Effect of Divalent / Trivalent Doping on Structural, Electrical and Magnetic Properties of Spinel Ferrite Nanoparticles

Five doped nanosized spinel ferrites were synthesized using the dicarboxylate and hydroxide coprecipitation method. XRD of doped samples confirmed the increase in lattice parameters as compared to undoped samples. Decrease in saturation magnetization and increase in coercive force are found in these doped samples as compared to undoped samples.

Type-II ternary Bi2WO6/rGO/SnFe2O4 heterojunction nanocomposites and their photocatalytic efficiency towards 4-nitrophenol reduction.

In this study, tin ferrite (SnFe2O4-spinel) and bismuth tungstate (Bi2WO6) encapsulated on reduced graphene oxide (rGO) were synthesised using the hydrothermal method. This heterostructure nanocomposite was characterised using Fourier transform infrared spectroscopy (FT-IR), Ultraviolet-visible spectroscopy (UV-Vis), powder X-ray diffraction (XRD), Scanning electron microscopy (SEM), FT-Raman Spectroscopy (FT-Raman) and X-ray photoelectron spectroscopy (XPS) methods. The powder XRD results showed an increase in lattice parameters and a decrease in size when SnFe2O4 and Bi2WO6 were encapsulated on rGO. The catalytic activity of the type-II ternary Bi2WO6/rGO/SnFe2O4 heterojunction nanocomposite was checked using a model reduction reaction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of NaBH4 as the reducing agent under light exposure. Bi2WO6/rGO/SnFe2O4 showed better catalytic efficiency than the individual components like SnFe2O4, rGO/SnFe2O4, Bi2WO6, rGO/Bi2WO6 and Bi2WO6/SnFe2O4 nanocomposites. Thus, the type-II ternary Bi2WO6/rGO/SnFe2O4 heterojunction nanocatalyst with better surface area and lower surface energy could be considered as a promising UV-light sensitive catalyst for the detoxification of various environmental pollutants and for other environmental remediations.

Thickness dependent physical properties of evaporated permalloy/GaAs(100) thin films

Thermally evaporated Permalloy Ni80Fe20(Py) thin films on GaAs (100) substrates, for thickness ranging from 132 to 277 nm, are studied. The effect of Py thickness on their physical properties is examined. In order to determine their structure, microstructure, surface morphology, chemical compositions and electrical properties, the deposited Py films were analyzed by X-ray diffraction (XRD), scanning electron microscopy equipped with an energy dispersive X-ray analyzer (SEM-EDS), atomic force microscopy (AFM) and the Hall Effect measurement system (HMS-5300) tools. The obtained X-ray diffraction spectra showed that all samples crystallize in FCC structure with &lt;111&gt; preferred orientation. The grain size and lattice parameter increase with increasing thickness. SEM micrographs revealed very dense structure without micro-cracks and very fine spherical grain distribution. AFM images showed a very smooth surface for all deposited Py films. Electrical measurements revealed that the electrical resistivity and the magnetoresistance decrease with increasing film thickness, while mobility increases.

Enhanced Electrocatalytic Activity and Surface Exsolution in PrOx-Substituted Cerium Gadolinium Oxide

The electrocatalytic activity of Pr-substituted cerium gadolinium oxide (CGO) was examined to assess its suitability as a composite air electrode in solid oxide cells. The solid-state reaction of CGO and Pr6O11 yielded fluorite-type solid solution, (Ce0.9Gd0.1)1–xPrxO2−δ (x = 0, 0.17 and 0.33), with an increased lattice parameter. Electrochemical tests of electrolyte-supported cells with CGO-PrOx and LSCF-CGO-PrOx electrodes exhibited that the PrOx addition significantly improves the electrical conductivity and electrocatalytic activity for oxygen reduction reaction (ORR). In-depth characterization showed that the improved ionic and electrical conductivities of CGO-PrOx are associated with high concentration of oxygen vacancies created by replacement of Ce4+ ions with Pr3+ ions. TEM analysis revealed that annealing of CGO-PrOx results in the exsolution of PrOx nanoparticles, indicating local lattice strain around Pr3+ and eventually their outward migration. TPD, TPR, and TPO measurements further demonstrated that CGO-PrOx has greater oxygen reduction reaction (ORR) activity at low temperatures (400–600 °C) when compared to CGO. These findings suggest the high potential of Pr-substituted CGO for low-temperature solid oxide cell applications.

Abstracts

In this article, the effect of Zr addition on the crystalline structure, ferroelectric and piezoelectric properties of Barium Strontium Titanate (BST) ceramic have been studied. Zr was doped in the range of 0 ≤ x ≤ 0.20 in Ba0.90Sr0.10Ti1-xZrxO3 (BSZT) and it was prepared via solid state reaction technique. From the characterization studies, it was realized that Zr addition in BSZT ceramics results in slight modification of BSZT lattice, but due to diffusion of Zr into the lattice, the crystallite size as well as the microstructure of combined BSZT system got modified drastically. Zr addition in BSZT ceramics results in increase of lattice parameter due to larger ionic radius of Zr ions compared to Ti ions. Reduction of grain and crystallite size was also observed, which affects the ferroelectric behaviour of BSZT ceramic by influencing the polarization contribution from individual domains. This causes a slow transformation of sharp paraelectric-ferroelectric transition to diffusive ferroelectric phase transition and it also introduces relaxation phenomenon in the system at higher Zr compostion, which convert it to a relaxor ferroelectric. At relaxor phase a decreased spontaneous polarization and slimmer P–E hysteresis loop was observed with increasing Zr content. The main reason behind this conversion and modification in microstructural properties is because of the presence of strain in BSZT lattice which is due to replacement of Zr4+ (0.72 Å) inplace of smaller Ti4+ (0.609 Å) in more than a tolerable limit. Substitution of Zr4+ for Ti4+ in BaSrTiO3 introduces structural disorder, causing perturbations like local electric and strain fields. These perturbations reduce the long-range polar order resulting in relaxor behavior.

Effect of Zr substitution on electrical properties of Ba0.90Sr0.10Ti1−xZrxO3 (0 ≤ x ≤ 0.20) ceramics

In this article, the effect of Zr addition on the crystalline structure, ferroelectric and piezoelectric properties of Barium Strontium Titanate (BST) ceramic have been studied. Zr was doped in the range of 0 ≤ x ≤ 0.20 in Ba0.90Sr0.10Ti1-xZrxO3 (BSZT) and it was prepared via solid state reaction technique. From the characterization studies, it was realized that Zr addition in BSZT ceramics results in slight modification of BSZT lattice, but due to diffusion of Zr into the lattice, the crystallite size as well as the microstructure of combined BSZT system got modified drastically. Zr addition in BSZT ceramics results in increase of lattice parameter due to larger ionic radius of Zr ions compared to Ti ions. Reduction of grain and crystallite size was also observed, which affects the ferroelectric behaviour of BSZT ceramic by influencing the polarization contribution from individual domains. This causes a slow transformation of sharp paraelectric-ferroelectric transition to diffusive ferroelectric phase transition and it also introduces relaxation phenomenon in the system at higher Zr compostion, which convert it to a relaxor ferroelectric. At relaxor phase a decreased spontaneous polarization and slimmer P–E hysteresis loop was observed with increasing Zr content. The main reason behind this conversion and modification in microstructural properties is because of the presence of strain in BSZT lattice which is due to replacement of Zr4+ (0.72 Å) inplace of smaller Ti4+ (0.609 Å) in more than a tolerable limit. Substitution of Zr4+ for Ti4+ in BaSrTiO3 introduces structural disorder, causing perturbations like local electric and strain fields. These perturbations reduce the long-range polar order resulting in relaxor behavior.

Spectroscopic and Magnetic Performance of Cobalt (Co) Incorporated NiMn0.05Fe1.95O4 Nanoferrites: A Potent Antifungal Activity Against Aspergillus niger (MT675916)

We investigated the impact of cobalt (Co) incorporation on the structural, optical, and magnetic properties of ferrite Ni[Formula: see text]CoxMn[Formula: see text]Fe[Formula: see text]O4, also known as NCMF for [Formula: see text], 0.02, and 0.04, which were successfully synthesized using a low-temperature sol-gel combustion process with nitrates as cations and citric acid (C6H8O7) as the combustion/chelating agent. In X-ray diffraction studies, cobalt incorporation resulted in a significant increase in lattice parameter from 8.31 to 8.36, as well as a significant increase in density from 5.42 to 5.52[Formula: see text]g/cm3; crystal size formation was observed in the range of 44.76[Formula: see text]nm to 48.54[Formula: see text]nm for all samples. Raman spectra analysis confirmed that single phase belongs to the Fd3m space group. Fourier transform infrared (FTIR) spectra were used to identify functional clusters and residual groups in all samples. UV–visible spectroscopy showed a redshift of 0.92[Formula: see text]eV for [Formula: see text]. The effect of dopants on nickel ferrites’ magnetization was observed in the range 52–59[Formula: see text]emu/g, indicating that all samples contain soft magnetic content. Antifungal activity of synthesized sample was analyzed against Aspergillus niger (MT675916) species of plant pathogenic fungi isolated from Capsicum during storage. Biological analysis designated that the sample for [Formula: see text] has shown a 100% potent antifungal activity against Aspergillus niger (MT675916) species. For [Formula: see text] treatment completely inhibits the growth of fungus after 7 days. Therefore, NCMF NPs can be used as applicant resources for industrial, medical, and biological applications.

The Role of Strain in Proton Conduction in Multi-Oriented BaZr0.9Y0.1O3-δ Thin Film.

Within the emerging field of proton-conducting fuel cells, BaZr0.9Y0.1O3-δ (BZY10) is an attractive material due to its high conductivity and stability. The fundamentals of conduction in sintered pellets and thin films heterostructures have been explored in several studies; however, the role of crystallographic orientation, grains, and grain boundaries is poorly understood for proton conduction. This article reports proton conduction in a self-assembled multi-oriented BZY10 thin film grown on top of a (110) NdGaO3 substrate. The multiple orientations are composed of different lattices, which provide a platform to study the lattice-dependent conductivity through different orientations in the vicinity of grain boundary between them and the substrate. The crystalline stacking of each orientation is confirmed by X-ray diffraction analysis and scanning transmission electron microscopy. The transport measurements are carried out under different gas atmospheres. The highest conductivity of 3.08 × 10-3 S cm-1 at 400 °C is found under a wet H2 environment together with an increased lattice parameter of 4.208 Å, while under O2 and Ar environments, the film shows lower conductivity and lattice parameter. Our findings not only demonstrate the role of crystal lattice for conduction properties but also illustrate the importance of self-assembled strategies to achieve high proton conduction in BZY10 thin films.

Hybrid density functional theory study of substitutional Gd in [formula omitted]-Ga2O3

Substitutional Gd alloying in β-Ga2O3 is studied using hybrid density functional theory. Calculations of structural properties reveal a monotonic increase in lattice parameters, volume and interplanar spacing with increasing Gd content. Cohesive energy and formation energy calculations show monotonically decreasing energy for increased Gd concentrations, implying stability even for large concentration Gd alloying. Partial density of states and electronic band structures reveal that Gd substitution does not result in any inter band gap states, a requirement for p-type conductivity. The electronic band gap does, however, decrease with increasing Gd content where the pronounced Gd levels are deep lying f-orbital electronic states. The frequency dependent dielectric response spectra reveal spatial anisotropy and a red shift for all optical properties for Gd content up to 37.5%, which, coupled with the electronic structure results show how Gd alloying may be used to tune Ga2O3 without significantly modifying the band edge contributions.

Effect of dopants and microstructure on the electrochemical cyclic stability of layered P2-type Na0.67MnO2 prepared by different chemical routes: An experimental and theoretical study

High specific capacity layered transition metal oxide, NaxMnO2 is considered a potential cathode for sodium-ion batteries (SIBs). However, its poor capacity retention due to irreversible phase transitions during sodium ion insertion/extraction remains a critical challenge for practical applications. Herein, we report Fe and Co co-doped P2-type Na0.67MnO2 cathode material prepared via different facile chemical routes to understand the effect of dopants and microstructure on its electrochemical cyclic stability. The Rietveld refinement analysis depicts an increase in lattice parameter c of Fe and Co doped materials as compared to parent material; thereby favouring sodium-ion storage (in turn enhancing and stabilizing specific capacity). XPS analysis confirms the presence of Mn in both 3+ and 4+ oxidation states; whereas Fe and Co in 3+ oxidation states occupy Mn3+ in Na0.67MnO2. Both experiment and ab initio magnetic calculations show a reduction in Mn3+ content after Fe and Co doping, reducing the tendency for Jahn-Teller distortion. This is concomitant with Fe and Co doping showing improved cyclic stability when cycled under similar conditions. At 0.1 C (where 1 C = 174 mAh g−1), Fe and Co-doped Na0.67MnO2 showed significant improvement with higher discharge specific capacities of 80 and 103 mAh g−1 even after 60th cycle when compared to 36 mAh g−1 after 25th cycle for the parent material Na0.67MnO2.

Understanding the structure-property correlation of tin oxide nanoparticles synthesized through the sol-gel technique

The present study aims at exploring the structural, morphological, optical, defects and phase related aspects of the sol-gel synthesized highly pure tin oxide (SnO2) nanocrystallites as a function of sample annealing temperature by carrying out experiments using various spectroscopic and analytical techniques. The X-ray diffraction (XRD) and high resolution transmission electron microscopic (HRTEM) studies confirmed the nanocrystallinity of the samples as the average sizes of the crystallites were found in between 10 and 20 nm. Williamson – Hall (W − H) analysis was employed for estimating the lattice strain and exact crystallite size of nanoparticles (NPs). The monotonous decrease of lattice strain with sample annealing temperature is consistent with increase of crystallite size by increase in temperature. The NPs exhibited some specific anomalous behaviour, among which a prominent one is the increased lattice parameters and unit cell volumes with the decrease of crystallite sizes. The optical band gap was observed to increase when the nanocrystallites became smaller in size. The latter aspect is attributable to the onset of quantum confinement effect, as observed in a few other metal oxide NPs. The atomic vibrations were characterized through distinct absorbance bands appeared in Fourier-transform infrared (FT-IR) spectroscopy. The photo-induced luminescence properties were studied by Fluorescence (FL) spectroscopy in terms of defects and/or oxygen vacancies related transitions. Positron annihilation lifetime spectroscopy (PALS) was employed to study the vacancy type defects, which were abundant in the samples and played crucial roles in modulating their properties. The results suggest the feasibility of tailoring the properties of SnO2 NPs synthesized through sol-gel route-for technological applications. It also provides the physical insight into the structural build-up process when crystallites were formed with a finite number of atoms, and their distributions were governed by the site stabilization energy. Since the samples of smaller crystallite sizes have remarkably larger defect concentrations.

Distribution Evaluation of Optical Properties in Silicon Germanium Films Grown on Silicon Substrates with Graded Silicon Germanium Buffer Layers

Background and Objectives Silicon germanium (SiGe) is expected to be applied for the optical devices such as infrared sensors, because of its narrower band gap than Si. Therefore, it is important to understand the optical properties of SiGe. In general, SiGe films epitaxially grown on Si or Ge substrates are the candidate materials for the optical devices. Inhomogeneous dislocation and strain in the SiGe films may reduce process yields. Although there are some literatures regarding to the distribution of dislocations and strain in the SiGe films [1, 2], the optical properties have not been evaluated sufficiently yet. In this study, we investigate the distribution of optical properties in the SiGe films by spectroscopic ellipsometry. Experiments Graded SiGe buffer layers (10% Ge / μm) and strain-relaxed SiGe layers (6 μm) with Ge fraction of 20% and 50% were grown on 200 mm diameter Si (001) substrates by molecular beam epitaxy. It is widely recognized that the dislocation density and strain are reduced in the SiGe layer epitaxially grown on a graded buffer layer on a Si (001) substrate. Since the optical properties are affected by strain [3], this structure, which can reduce strain, is useful for applying SiGe films in optical devices. In order to investigate the distribution of the optical properties, strain and Ge fraction in the SiGe films, we measured several points from the center to the edge of the wafer by spectroscopic ellipsometry and X-ray diffraction (XRD). The spectroscopic ellipsometry measurements were performed with an incident angle of 70°, a 70 W xenon lamp as the light source, and a wavelength range of 200 to 1600 nm. For XRD, we measured the (004) plane using a Cu Kα X-ray source with a wavelength of 1.5406 Å. The lattice parameters were calculated based on the 004 diffraction peak from the SiGe films. Results and Discussion Figure 1 (a) and (b) show the distribution of the extinction coefficient in the SiGe films with Ge fraction of 20% and 50%, respectively. The distributions of the extinction coefficient in the infrared region are enlarged in these figures. We found that the extinction coefficient of SiGe (50%) is higher than that of SiGe (20%) in the near-infrared region, indicating that the higher Ge fraction is able to absorb longer wavelength light. From Fig. 1, it is clear that the SiGe wafer (50%) has a larger variation than the SiGe wafer (20%), especially in the long wavelength region.Figures 2 and 3 show XRD peak of SiGe films and the distribution of the lattice parameter in the SiGe films with Ge fraction of 20% and 50%, respectively. The lattice parameters of Si1-x Ge x assuming strain-free were calculated using Vegard's law (dx [Å] = 0.027x 2 + 0.2x + 5.431).From Fig. 3, it is clear that the SiGe wafer (50%) shows a larger variation than the SiGe wafer (20%) with respect to the lattice parameter. Since the lattice parameter of SiGe varies with the Ge fraction and strain state, first the cause of this variation can be cited that of the Ge fraction. The lattice parameters at the edge of the wafers are much larger than those at the center of the wafers, suggesting that variations in Ge fraction at the edge of the wafers. The same behavior has been observed in previous studies regarding SiGe wafers [1, 2]. Also, it is considered that the variations of the lattice parameter vary not only due to Ge fraction, but also residual strain. Although sample structures are designed to induce strain relaxation in SiGe films, it is considered that the strain in the epitaxially grown SiGe film on the graded buffer layer cannot be fully relaxed based on the results of XRD. These variations of Ge fraction and strain may cause the variation of the extinction coefficient of SiGe films.The result that the SiGe wafer (50%) has a larger variation than the SiGe wafer (20%) indicates that the inhomogeneity of the optical properties and the lattice parameter increase and it may reduce process yields with increasing Ge fraction, for SiGe films on Si substrates.

RF Magnetron Sputtering of Substituted Hydroxyapatite for Deposition of Biocoatings.

Functionalization of titanium (Ti)-based alloy implant surfaces by deposition of calcium phosphates (CaP) has been widely recognized. Substituted hydroxyapatites (HA) allow the coating properties to be tailored based on the use of different Ca substitutes. The formation of antibacterial CaP coatings with the incorporation of Zn or Cu by an RF magnetron sputtering is proposed. The influence of RF magnetron targets elemental composition and structure in the case of Zn-HA and Cu-HA, and the influence of substrate’s grain size, the substrate’s temperature during the deposition, and post-deposition heat treatment (HT) on the resulting coatings are represented. Sintering the targets at 1150 °C resulted in a noticeable structural change with an increase in cell volume and lattice parameters for substituted HA. The deposition rate of Cu-HA and Zn-HA was notably higher compared to stochiometric HA (10.5 and 10) nm/min vs. 9 ± 0.5 nm/min, respectively. At the substrate temperature below 100 °C, all deposited coatings were found to be amorphous with an atomic short-range order corresponding to the {300} plane of crystalline HA. All deposited coatings were found to be hyper-stochiometric with Ca/P ratios varying from 1.9 to 2.5. An increase in the substrate temperature to 200 °C resulted in the formation of equiaxed grain structure on both coarse-grained (CG) and nanostructured (NS) Ti. The use of NS Ti notably increased the scratch resistance of the deposited coatings from18 ± 1 N to 22 ± 2 N. Influence of HT in air or Ar atmosphere is also discussed. Thus, the deposition of Zn- or Cu-containing CaP is a complex process that could be fine-tuned using the obtained research results.

Investigation of crystal structure, electrical and dielectric response of Zr4+ -Co2+ substituted Ba–Sr–Ni Y-type hexagonal ferrites synthesized by sol-gel route

A series of (Zr–Co) substituted Y-type polycrystalline hexaferrite with composition SrBaNi2(ZrCo)xFe12-2xO22 (x = 0.0, 0.25, 0.50, 0.75, 1.0) were fabricated by sol-gel auto combustion method. Pure Y-type single phase formation was achieved at a relatively lower temperature of 1150 °C for 5:30 h. The fabricated nano ferrites were examined by X-ray powder diffraction to confirm the pure single-phase formation of Y-type hexaferrites. An increase in lattice parameters (a& c) was observed by adding Zr4+-Co2+ metal cations. Crystallite size (D) measured in the 48-19 nm range. FTIR spectra clarified iron-oxygen vibrational bands at 417-487 cm−1, which approved the Y-type hexaferrites formation. DC electrical resistivity has an opposite trend at high and low temperatures with increasing Zr4+-Co2+ content (x). DC electrical resistivity values depend on grain size; they have an inverse relation. Activation energy, drift mobility, and Curie temperature were also determined. Conduction is due to the hopping of electrons below the Curie temperature, and polarons are responsible for hopping above the Curie temperature. Activation energy varies from 0.39 to 0.10 eV with the substitution of Zr4+-Co2+ ions. A wide frequency range of dielectric characteristics (1 MHz–6GHz) was observed, and these parameters revealed a considerable fluctuation with the substitution of Zr4+–Co2+ ions. Dielectric constant, dielectric loss and ac conductivity of nano ferrites materials increased with frequency and Zr4+-Co2+ content (x). Complex impedance spectroscopy formalism using the Cole-Cole plots indicated that most dielectric responses arise from grain boundary contributions.

Cation Valences and Multiferroic Properties of EuTiO3 Co-Doped with Ba and Transition Metals of Co/Ni.

Eu1−xBaxTi1−yMyO3 (M = Co or Ni) was sintered at 1400 °C under a reduction atmosphere. X-ray photoelectron spectroscopy revealed the mixed valences of Eu2+/Eu3+ and Ti4+/Ti3+ in EuTiO3 and Eu0.7Ba0.3TiO3, as well as some oxygen vacancies required to keep the charge neutrality. The co-doping of Co2+/Ni2+ in Eu0.7Ba0.3TiO3 resulted in the disappearance of oxygen vacancies, as a result of a reduction in Ti3+ numbers and an increase in Eu3+ numbers. On the other hand, Ba2+ doping led to an increased lattice parameter due to its larger ionic size than Eu2+, whereas the Co2+/Ni2+ co-doping resulted in smaller lattice parameters because of the combined effects of ionic size and variation in the oxygen-vacancy numbers. Eu0.7Ba0.3TiO3 exhibited a clear ferroelectricity, which persisted in the Co2+/Ni2+ co-doped samples until the doping levels of y = 0.05 and 0.10, respectively. Eu0.7Ba0.3TiO3 remained to be antiferromagnetic with a reduced transition temperature of 3.1 K, but co-doping of Co2+/Ni2+ turned the samples from antiferromagnetic to ferromagnetic with transition temperatures of 2.98 K and 2.72 K, respectively. The cause for such a transition could not be explained by the larger lattice volume, oxygen vacancies and mixed valences of Eu2+/Eu3+, which were proposed in previous works. Instead, it was more likely to arise from a large asymmetric distortion of the Eu–O polyhedron introduced by the aliovalent doping, which promotes the admixture of Eu 5d and 4f states.

Structural, magnetic, and dielectric properties of Ni/Zn co-substituted CuFe2O4 nanoparticles

Microstructural, magnetic and dielectric properties of NixCu1-3xZn2xFe2O4 nanoparticles were investigated by various techniques. Samples were structurally analyzed using X-ray diffraction and Rietveld refinement. A structural phase transition from a tetragonal spinel structure with space group I41/amd to a cubic spinel structure with space group Fd3‾m was observed by increasing the Ni/Zn co-substitution and also the lattice parameter increases. These structural results were confirmed by Raman and Fourier-transform infrared spectroscopy. The magnetic hysteresis loops of the samples indicated a magnetic phase transition from the hard to soft ferrimagnetic and the magnetization values increase for x up to 0.2, and then it decreased. The results of impedance analysis indicated that the increase in the mobility of charge carriers in the samples with x between 0 and 0.15 can be attributed to the reduced porosity and surface area, because a smaller number of defects commonly would block the movement of carriers.