Reduction In Lattice Parameter Research Articles

Structural, Electronic, and Magnetic Properties of Gd-Substituted Bi2Fe4O9 Multiferroic: A Combined Experimental and DFT Approach

Abstract We present the structural, electronic, and magnetic properties of Gd3+ substituted Bi2Fe4O9 (BFO) via experimental analysis as well as density functional theory (DFT). Rietveld refined X-ray diffraction data shows phase purity of the samples having orthorhombic phase with space group: ‘Pbam’. Gd3+ ions substitution at Bi3+-site is confirmed by the shift in peaks ((002) and (220)) at higher 2θ angles as well as the reduction in lattice parameters. The PBE+U calculations predict a band gap of 1.76 eV (BFO) and 1.6 eV (Gd substituted BFO) which is in close agreement with the experimental values. This reduction in band gap due to Gd3+ substitution enhances conduction in substituted samples. The calculated density of states illustrates considerable hybridization between Fe-3d and O-2p states with substantial overlap among the Bi-6p and O-2p states. Incorporating Gd3+ ions further introduces additional exchange interactions between Gd-Fet and Gd-Feo, thus leading to enhanced magnetization as well as an increase in antiferromagnetic transition temperature (TN). This characteristic feature is supported by temperature-dependent magnetic susceptibility (χ) and dχ/dT plots. Hence, our experimental and theoretical findings suggest that BFO and its substituted samples are potential multiferroic materials for various device applications.

Study on the structure, Mössbauer spectroscopy, and magnetic properties of Sr1-xYxFe12O19 hexaferrites

The Sr1-xYxFe12O19 (x =, 0.05, 0.1, 0.15) series hexagonal ferrite samples were successfully prepared by the sol-gel method. X-ray diffraction (XRD) showed that Y3+ successfully replaced Sr2+ sites, resulting in a reduction of lattice parameters and unit cell volume. Mössbauer spectral analysis showed that Y3+doping caused the conversion of some Fe3+ to Fe2+ at the 2a site, resulting in a decrease in the average hyperfine field of the doped samples. Vibrating sample magnetometer (VSM) measurements indicated that with increasing Y3⁺ content, the saturation magnetization of the samples decreased, while the coercivity significantly increased. Notably, at a doping level of x = 0.05, the sample exhibited a coercivity of 4798.09 Oe, representing a 99.11% increase compared to the undoped sample, while the saturation magnetization only decreased by 3.24%.

Investigating grain and grain boundary effects on charge transport and dielectrics in BaCoxAlxFe12-2xO19 nanoferrites

This investigation centres on the sol-gel preparation of M-type barium hexagonal ferrite (M-BaFe12O19) incorporating Co2+ and Al3+ as dopants. X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) were employed to assess the impact of dopants on the crystallographic structure and microstructure. The dielectric characteristics, electric modulus, impedance, and conductivity of the synthesized materials were evaluated at ambient temperature using an impedance analyzer. The structural analysis verified the presence of the hexagonal M-type crystal phase. Increasing dopant levels led to a reduction in lattice parameters, signifying unit cell shrinkage. FESEM imaging exposed the emergence of needle-shaped grains resulting from the doping process. Dielectric spectroscopy showed a decrease in both the dielectric constant (from 135.95 at x = 0.0 to 39.8) and the loss tangent (from 3.68 to 0.610) as dopant concentration increased. Conductivity exhibited relaxation at varying intervals, supported by the electric modulus spectra, which validated non-Debye relaxation behavior. Both relaxation time and AC conductivity diminished with higher dopant concentrations (from 0.000222 Ωm−1 to 0.000036 Ωm−1). The relaxation observed in conductivity and dielectric responses implies their contribution to the charge transport processes within BaCoxAlxFe12-2xO19. Electrochemical impedance spectroscopy (EIS) software was used to generate complex impedance plots, which aligned with the experimentally obtained impedance values for the synthesized compositions. Micrographs revealed a distribution of grains and grain boundaries that were consistent with calculated characteristics. This further substantiates the measured dielectric and electrical parameters.

Unveiling the impact of Cd and Zn substitutions on the structural, mechanical, electronic, and optical properties of SrS: A first principles analysis

This study employs ab-initio calculations based on density functional theory (DFT) to comprehensively investigate the multifaceted effects of Cd and Zn substitutions on the structural stability, mechanical behavior, electronic characteristics, and optical properties of SrS alloy. Structural analysis unveils a marginal reduction in lattice parameters for both doped compounds, signifying a subtle influence on the crystalline structure. Mechanical evaluation reveals that SrS and Sr0.75Cd0.25S keep their intrinsic brittleness, whereas the inclusion of 25 % Zn imparts a subtle ductile nature. The conservation of rigidity is observed post-doping, albeit with anisotropic features and differing degrees of stiffness among the compounds. Investigating electronic properties, the band gap of Sr0.75Cd0.25S persists as an indirect transition between M and Γ points, mirroring SrS's behavior. In contrast, a remarkable transformation is noted with 25 % Zn doping, shifting SrS to a direct band gap semiconductor. Interestingly, Cd and Zn incorporation leads to a band gap reduction, suggesting potential avenues for tuning the material's electronic behavior. Dielectric constant analyses unravel intriguing phenomena. The binary compound exhibits Mie resonance across the visible-infrared spectrum, a feature that contracts to the infrared range after doping. This nuanced shift has direct implications on the material's interaction with incident light and its resulting optical properties. Evaluation of the refractive index, absorption coefficient, reflectivity, and optical conductivity demonstrates a striking resemblance in the optical behavior of Sr0.75Zn0.25S and Sr0.75Cd0.25S to the pristine SrS alloy.

Cr content dependent lattice distortion and solid solution strengthening in additively manufactured CoFeNiCrx complex concentrated alloys – a first principles approach

In the previous study, the authors reported that multicomponent CoFeNiCrx (x = 0, 12, 18, 24 at%) complex concentrated alloys fabricated through laser directed energy deposition experienced a substantial reduction in the saturation magnetization (Ms) and the Curie transition temperature (Tc) with the increase in Cr content. The present investigation additionally explores the effect of Cr concentration on the structural and strengthening behavior in laser directed energy deposition processed CoFeNiCrx alloy system. The novel approach adopted in the present work included the integration of experimental and computational efforts involving laser direct energy deposition (L-DED) based synthesis/fabrication of a series of new CoFeNiCrx alloys through in-situ compositional tuning which is often difficult using conventional techniques and prediction of mechanical properties of these compositionally tuned alloys using a computational methodology based on the density functional theory (DFT). X-ray diffraction and nanoindentation studies revealed that while there was a slight reduction in lattice parameters, the elastic modulus increased by approximately 30 % and the yield strength increased by 25 % with increasing Cr content. The density functional theory framework was employed to interpret the influence of Cr atoms on local lattice distortions and observed yield strength. The calculated local lattice distortion, in terms of first nearest neighbors, significantly increased with Cr concentration, which is attributed to the enlargement of Cr atomic radius in the alloyed multielement environment in comparison to its radius in the elemental form. This distortion at the local level caused solid solution strengthening. The theoretically predicted solid solution strengthening values using the Varvenne model are consistent with experimental results.

Curie temperature and magnetic permeability regulation of Cr–Mg co-doped NiCuZn ferrite for tumor hyperthermia

The controllable Curie temperature and high magnetic permeability of NiCuZn ferrites make them promising candidates for magnetic thermal medium. However, the temperature control of existing NiCuZn ferrite materials is not accurate enough to achieve the low Curie temperature required for tumor hyperthermia. In order to further achieve the desired Curie temperature and facilitate the advancement of temperature control materials for tumor hyperthermia, Cr–Mg co-doped NiCuZn ferrite was studied. The study investigated the influence of varying concentrations of Cr3+ on the crystal structure and magnetic properties of Mg–NiCuZn ferrites. The results of structural characterization demonstrate that Cr–Mg co-doped NiCuZn ferrites exhibit high density and uniform distribution of elements. The introduction of Cr3+ leads to a reduction in lattice parameters and a preference for octahedral B-sites. The hysteresis loop results show that the saturation magnetization first increases and then decreases with the increase of Cr3+ concentration. Ni0.09Mg0.20Cu0.14Zn0.60Fe1.89Cr0.050O3.94 ferrite at 0.30 wt% of Bi2O3 exhibits optimal magnetic characteristics, including a saturation magnetization of ∼36.7 emu/g, low coercivity of ∼0.07 kA/m, high permeability of ∼982.43 @1 MHz, and an appropriate Curie temperature of 45.59 °C. Such permeability and Curie temperature can be used in the body cavity perfusion hyperthermia and deep thermal therapy.

Lead free A2NaInI6 (A = Cs, Rb, K) double perovskites for optoelectronic and thermoelectric applications

Alkali metal substitution in double perovskites is an appropriate approach to deliberate tuning of band edges which play a vital role in bandgap engineering of emerging semiconducting materials. Here we tuned the optoelectronic behavior by carefully engineering the band edges in A2NaInI6 (A = Cs, Rb, K) systems and by tuning the alkali atoms at A site using density functional theory based WIEN2K code. First of all, the unit cell is relaxed to find the optimized lattice parameters. The substitution of smaller-sized cation at the A site leads to the reduction in lattice parameter which shifts the absorption edge towards a shorter wavelength and reduces the bandgap energy. The value of bandgap energy is noticed at 1.60 eV for Cs2NaInI6 which increases to 1.65 and 1.70 eV for Rb2NaInI6 and K2NaInI6 respectively. The computation of the elastic constant’s dependent modulus of elasticity and the Pugh and Poisson ratio confirm their brittle nature. Their viability for solar-thermoelectric generators is carried out by computing the temperature-dependent transport parameters using the BoltzTrap code showing the potential of these systems for solar thermoelectric generators.

Signatures of nearly compensated magnetism and spin glass behavior in highly frustrated β-Mn-type Mn50Fe25+xAl25-x Heusler alloys.

The present study examines the effect of Fe/Al concentration on the structural and magnetic properties of Mn-rich Mn50Fe25+xAl25-x (x = 5, 10, 15) Heusler alloys through x-ray diffraction, temperature- and field-dependent DC magnetization, thermoremanent magnetization, magnetic memory effect, AC susceptibility measurements, and DFT calculations. The samples crystallize in a cubic β-Mn structure. The trend shows a reduction in lattice parameters (unit cell volume) with the increasing Fe proportion. These alloys exhibit strong antiferromagnetic interactions with large frustration parameters, indicating the presence of competing magnetic interactions. The DC magnetization data reveal spin glass-like features with a peak at spin glass freezing temperature (Tf). The observation of bifurcation in temperature-dependent zero-field-cooled and field-cooled magnetization curves, exponential dependence of the temperature variation of remanence and coercivity, magnetic relaxation, and magnetic memory effect below Tf support the spin-glass character of these alloys. The frequency dependence of Tf is also examined in the context of dynamic scaling laws, such as the Vogel-Fulcher law and critical slowing down model, which further supports the presence of spin glass behavior. In the theoretical DFT calculations, the electronic structure is found to be metallic and similar for both spin projections. Moreover, the antiferromagnetic arrangement of the magnetic moments, in line with the experimental observations, is stabilized by exchange interactions, resulting in an almost compensated total magnetic moment of 0.02-0.38µB/f.u. This is probably caused by the frustrated structure and non-stoichiometric compositions of Mn50Fe25+xAl25-x.

Effect of Co doping on the structure and magnetic properties of Bi0.8Ba0.2FeO3 nanoparticles

A series of Bi[Formula: see text]Ba[Formula: see text]Fe[Formula: see text]CoxO3 ([Formula: see text], 0.05, 0.10, and 0.15) samples were synthesized using the tartaric acid modified sol–gel method. The crystal structure of the prepared samples was analyzed by XRD, and the samples co-doped with Ba and Co were all rhombohedral distorted structures with the R3c space group. With an increase in the doping amount, a reduction in lattice parameters was observed along with crystallite sizes consistently being below 62[Formula: see text]nm. Mössbauer spectral analysis at room temperature reveals a good fit with two sextets and a doublet, all attributed to the Fe[Formula: see text] state. This suggests that the charge balance within the samples is maintained through the generation of oxygen vacancies in the system. The hysteresis loops of all samples revealed the weak ferromagnetic of the Co-doped Bi[Formula: see text]Ba[Formula: see text]FeO3 nanoparticles. With the increase in Co doping, the magnetic parameters such as saturation magnetization and coercive field significantly improved.

Studying of cadmium oxide/ Aluminium films for optoelectronics: structural, optical and electrical characteristics

In the results of this research, thin films of CdO-Al were produced using the spray pyrolysis (SP) technique. The primary aim was to explore how varying concentrations of aluminum (Al) influence the physical properties of the films. The X-ray diffraction (XRD) analysis confirmed the presence of a cubic crystal structure in the pure CdO films. Additionally, it revealed that the introduction of increased Al doping led to lattice shrinkage and a reduction in lattice parameters. Elevated levels of aluminum (Al) content were correlated with a decrease in crystallite size and an augmentation in lattice strain, as indicated by both scanning electron microscopy (SEM) and X-ray diffraction (XRD) data. Additionally, an X-ray photoelectron spectroscopy (XPS) examination revealed the presence of Al3+ ions within the films. The optical energy gap of CdO-Al films exhibited a slight increase, reaching up to 3% aluminum doping. The analysis of the refractive index dispersion and non-linear refractive index revealed a decreasing trend up to 3% aluminum content, with subsequent fluctuations at higher concentrations. The measurements of sheet resistance demonstrated a noticeable decrease with an increase in aluminum content, specifically up to 3%.

Effect of coercive aluminium on the structural and magnetic characteristics of calcium and magnesium based hexaferrites

Aluminum substituted Calcium-Magnesium (Ca-Mg) hexaferrites having general formula Ca0.5Mg0.5Fe12-xAlxO19 (where x is increased with increment of 0.5 from 0.0 to 2.0) are prepared by sol–gel auto combustion technique. X-ray diffraction patterns confirm the hexagonal structure with no evidence of secondary phases. The reduction in lattice parameters is observed as the Al+3 doping level increases. This can be attributed to the short ionic radii of Al+3 ions (0.535 Å) compared to Fe+3 ions (0.645 Å). The obtained c/a ratio falls within the acceptable range of 3.98. Consequently, the formation of magnetoplumbite structure is also confirmed. The SEM image reveals the uniform distribution of particles. The exchange of Fe+3 ions with coercive Al+3 ions led to a decline in saturation magnetization Ms and a significant increase in the coercivity Hc. The magnetic moment mB and Mr of hexaferrites exhibit a decline when Al ions are introduced. This reduction can be ascribed to several factors: the substitution of non-magnetic Al3+ ions in place of Fe3+ ions, the spin-canted ordering of Fe3+ ions, and the valency of Fe ions from 3+ to 2+.

Investigation of stress-induced effects on structural, optoelectronic, and elastic characteristics of cubic CaHfO3 perovskite oxide; A DFT study

Perovskite oxide being a fascinating class of perovskite materials, captured the significant attention of the scientific community in diverse fields due to its intriguing features. A cubic Calcium Hafnium Oxide (CaHfO3) perovskite supercell was designed using a DFT approach within the CASTEP framework with PBE-GGA approximation. The primary objective was to thoroughly investigate the effect of varying applied stress (0–160 GPa) on the structural, optoelectronic, and elastic characteristics in detail for appropriate device application. Findings reveal that with increasing stress levels, no phase transformation occurs, and cubic structure remains intact, as confirmed from the XRD profile, while a reduction in lattice parameters and volume of the unit cell is observed. Moreover, the optical analysis reveals the reduction in the band gap from 3.170 to 2.299, unveiling the narrow as the stress level rises. Additionally, optical characteristics showed that stress influences optical behaviour, resulting in low loss function, high absorption, high conductivity, and low reflectivity. The elastic constants and their derived parameters were investigated in this study. The results indicate that the material exhibits a ductile nature and anisotropy, as evidenced by Poisson's ratio, Cauchy pressure, and Frantsevich ratio. Notably, the mechanical stability of the material is maintained even as the stress level increases (0, 40, 80, and 120 GPa). These comprehensive findings contribute to a deeper understanding of stress-induced effects on perovskite oxides, offering valuable insights for their potential application and opening new avenues for experimental researchers by bridging the gap between theory and practical implementation for next-generation real practice in diverse fields.

Sunlight-assisted photocatalytic degradation of tartrazine in the presence of Mg doped ZnS nanocatalysts

In this work, Mg2+ doped ZnS nanoparticles were prepared by solvothermal method, using ethanol as solvent at 135 °C.The nanoparticles were characterized by XRD, SEM, UV–vis and PL. After doping, XRD revealed a reduction in lattice parameter, confirming Mg2+ substitution into the ZnS host lattice. The UV–vis study indicated that the incorporation of Mg2+ ions does not modify the band gap width of the nanoparticles. The PL spectra measured at 325 nm excitation wavelength, reveals that the photogenerated electrons of Zn0·9Mg0·1S have a slower recombination rate than ZnS nanoparticles. The XPS finding confirm that the chemical environment of the elements has been affected by the presence of the Mg2+. The Valence Band Maximum (VBM) was determined to be 0.2eV for ZnS and 1eV for Zn0·9Mg0·1S, respectively. These findings confirm the perturbation of electronic properties when Mg2+ is added to the ZnS. The photocatalytic ability was estimated through the degradation of tartrazine under natural-sunlight irradiation. Zn0.9Mg0.1S shows a high photocatalytic activity, compared to ZnS nanoparticles. The photocatalytic degradation was studied through different parameters, such as: the source of irradiation, the pH, the dye concentration, the catalyst concentration, and the recyclability. The degradation investigation shows that tartrazine is better oxidized at free pH = 6,7, with a dye concentration of 20 mg/L and a catalyst dosage of 1 g/L. Zn0.9Mg0.1S degraded 98% of tartrazine under natural-sunlight irradiation. In addition, the catalyst retained a good photo-degradation capacity, even after many treatment cycles. The scavengers study confirmed that the main active species responsible for the photocatalytic degradation of tartrazine were the oxidation groups (O2•-).

Cavitation erosion of the CoCrFeNi high entropy alloy having elemental segregation

The cavitation-erosion (CE) damage features and a microstructural peculiarity of the CoCrFeNi high entropy alloy (HEA) are presented in this paper. While this HEA is theoretically predicted and often experimentally demonstrated to be a single-phase solid solution, noticeable elemental segregation has been observed in both the interdendritic regions and dendrite interiors in this study. This segregation causes a subtle reduction of lattice parameter, and the interdendritic segregated regions are frequently CE damage initiation sites. In the dendrite interiors, oxygen-rich particles with elemental segregation as their wrappings and the small speckles of elemental segregated regions show different CE damage features. In the dendrite interiors, CE-induced martensite formation is negligibly, and slip lines and their intersections are CE damage initiation sites. While a few CoCrFeNi-based HEAs have been shown to be CE-resistant in the literature, the CE resistance of the CoCrFeNi base itself is not high.

Valence electron concentration- and N vacancy-induced elasticity in cubic early transition metal nitrides

Motivated by frequently reported deviations from stoichiometry in cubic transition metal nitride (TMNx) thin films, the effect of N-vacancy concentration on the elastic properties of cubic TiNx, ZrNx, VNx, NbNx, and MoNx (0.72≤x≤1.00) is systematically studied by density functional theory (DFT) calculations. The predictions are validated experimentally for VNx (0.77≤x≤0.97). The DFT results indicate that the elastic behavior of the TMNx depends on both the N-vacancy concentration and the valence electron concentration (VEC) of the transition metal: While TiNx and ZrNx exhibit vacancy-induced reductions in elastic modulus, VNx and NbNx show an increase. These trends can be rationalized by considering vacancy-induced changes in elastic anisotropy and bonding. While introduction of N-vacancies in TiNx results in a significant reduction of elastic modulus along all directions and a lower average bond strength of Ti–N, the vacancy-induced reduction in [001] direction of VNx is overcompensated by the higher stiffness along [011] and [111] directions, resulting in a higher average bond strength of V–N. To validate the predicted vacancy-induced changes in elasticity experimentally, close-to-single-crystal VNx (0.77≤x≤0.97) are grown on MgO(001) substrates. As the N-content is reduced, the relaxed lattice parameter a0, as probed by X-ray diffraction, decreases from 4.128 Å to 4.096 Å. This reduction in lattice parameter is accompanied by an anomalous 11% increase in elastic modulus, as determined by nanoindentation. As the experimental data agree with the predictions, the elasticity enhancement in VNx upon N-vacancy formation can be understood based on the concomitant changes in elastic anisotropy and bonding.

Growth of Cd1-xMnxTe crystals by vertical Bridgman method and analysis of composition dependence on the bandgap

This article reports the growth of cadmium manganese telluride (Cd1-xMnxTe, CMT) single crystal by vertical Bridgman method and the property measurements for three different Mn compositions (x = 0.05, 0.10 & 0.15). The single crystalline nature of the grown crystals was confirmed with Laue back reflection method. The lattice constants were calculated using single-crystal X-ray diffraction analysis. Phase formation and zinc blende crystal structure were confirmed with powder X-ray diffraction analysis. The shifting of the diffraction peak position indicates the reduction in lattice parameter of Cd1-xMnxTe crystals with Mn concentration. Raman spectra exhibited two mode behavior having CdTe and MnTe-like structures and their longitudinal optical phonon modes displaying peak shift with Mn concentration. The increase in the Mn concentration in CMT lattice made a blueshift in photoluminescence emission band leading to changes in the bandgap from 1.5776 to 1.7250 eV. The experimentally observed IR transmittance was found to be in line with theoretically observed transmittance. The observed Mn concentration dependent structural and optical properties confirm the formation of high quality CMT single crystals by vertical Bridgman technique.

Tailoring properties of nano-crystalline CdO thin films by incorporation of Al for enhanced photo-voltaic applications

Nano-crystalline thin films of Al doped and undoped CdO thin films were successfully deposited using home-built spray pyrolysis unit. The consequence of Al in CdO was explored and found that the doping of Al has influenced the characteristics of CdO. The CdO was doped with varying concentration of Al viz.0, 0.1, and 10 At.%. The physical, optical and morphological properties were analyzed. These films showed a preferential growth along [111] and [020] direction. The reduction in lattice parameter found to be, the undoped film had lattice parameter of 4.6833×10-10 m whereas, 10 At.% had 4.6819×10-10 m. All crystallites were below 50 nm and grain size was estimated using Scherrer and Williamson-hall plot. The 0.1 At.% of Al showed a larger absorbance whiled 10 At.% had the lowest absorbance. Which is also reflected in transmittance. All film showed transmittance from 70% to 86%. The 10 At.% had the largest transmittance. The reduction in bandgap was observed 10 At.% has the lowest bandgap of 2.04 eV against undoped which has a bandgap of 2.37 eV. The 10 At.% Al film showed an average reflectance of 0.061 at 700 nm whereas; undoped film has an average reflectance of 0.083. The refractive index found to decrease as the doping concentration increases. The electrical conductivity was estimated from optical analysis and found that the electrical conductivity found to increase from 4.7×104 S/cm to 5.2×104 S/cm as the concentration of Al is increased. Haacke’s figures of merit (φH) was calculated and found that doping has increased the φH. 10 At.% showed 8.23×10-3cm-1. Nonlinear optical parameters were also studied. The Scanning electron microgram suggests the incorporation of Al has increased in density of particles in the film. Hence, the developed nano-crystalline CdO thin films by incorporation Al for enhanced photo-voltaic applications.

Structural investigation of ZrN+Si3N4 thin films co-deposited by magnetron sputtering

ABSTRACT Zirconium silicon nitride thin films with 1.6% Si addition were deposited via reactive magnetron sputtering and characterized by RBS, SEM-FEG, GAXRD, XPS and high temperature oxidation tests, aiming to investigate how silicon is structurally inserted in Zirconium nitride (ZrN) matrix. GAXRD results show a reduction in lattice parameter and grain size due to Si incorporation and XPS analyses demonstrate Si is present only in nitride form. Such observations proved the non-formation of substitutional or interstitial solid solution in ZrN, but the presence of Si3N4, even in low Si concentrations.

Novel low modulus beta-type Ti–Nb alloys by gallium and copper minor additions for antibacterial implant applications

This study aims to develop novel low-modulus, corrosion-resistant Ti-based alloys with enhanced antimicrobial properties for bone-related implant applications. Novel β-type (Ti–45Nb)-based alloys with minor additions of the antibacterial elements Ga and/or Cu (up to 4 wt.%) were produced by a two-step casting process followed by homogenization treatment. Three nominal compositions (Ti–45Nb)96-4 Ga, (Ti–45Nb)96–4Cu and (Ti–45Nb)96-2 Ga–2Cu (wt.%) were prepared based on alloy design approach using [Mo]eq and electron per atom (e/a) ratio. The influence of Ga and/or Cu addition on the phase constitution, mechanical response and corrosion characteristics in simulated body fluids (PBS, 37.5 °C) has been investigated. X-ray diffraction studies displayed a single β phase structure for all alloys, with an observed lattice contraction evidenced by the reduction of lattice parameters during Rietveld analysis. Homogenous equiaxed microstructures with grain sizes ranging from 55 μm up to 323 μm were observed for (Ti–45Nb)96-4 Ga, (Ti–45Nb)96-2 Ga–2Cu and (Ti–45Nb)96–4Cu alloys. The alloys displayed excellent plasticity with no cracking, or fracturing during compression tests. Their tensile strength, Young's modulus, maximum tensile strain and elastic energy were measured in the ranges of 544–681 MPa, 73–78 GPa, 17–28% and 2.5–3.7 MJ/m3, in the order (Ti–45Nb)96-4 Ga > (Ti–45Nb)96-2 Ga–2Cu > (Ti–45Nb)96–4Cu. In addition, it has been observed that micro-alloying Ti–Nb alloy with Ga and/or Cu posed no deleterious effect on the corrosion resistance in simulated body fluid conditions. The improvement in strength of the developed alloys has been discussed based on grain boundary and solid-solution strengthening, whereas the improved plasticity is attributed to work hardening.

Ce-doped (Mn,Co)3O4 coatings for solid oxide fuel cell interconnect applications

In order to improve the electrical conductivity of solid oxide fuel cell (SOFC) interconnect coatings, a series of Ce-doped (Mn,Co)3O4 (Mn1.5-xCo1.5-xCe2xO4+δ, x = 0, 0.025, 0.05, and 0.1) coatings are prepared. The chemical composition, lattice structures, morphology, electrical properties, and weight gain of the coatings are characterized. Experimental results show that doping Ce lowers the area-specific resistance of (Mn,Co)3O4 coatings from 6.83 to 2.62 mΩ cm2 at 800 °C. The electrical conductivity improvement can be attributed to the ion substitution by Ce3+ that turns (Mn,Co)3O4 into (Mn,Co)2CeO4, an N-type semiconductor with a higher electrical carrier density. However, the coatings with heavier doping of Ce exhibit more structural defects due to the lattice parameter reduction and volume shrinkage, which weaken the oxidation resistance of the coatings. This study verifies that doping Ce can effectively improve the electrical conductivity of spinel coatings. The negative influence of doping Ce can be mitigated by modifying the coating preparation technique or by changing the SOFC operating temperature.