Lattice Parameter Of Phase Research Articles

Effect of B4C nanoparticles addition on the refinement of Fe-rich phase in ZL108 alloy

Refining effect of B4C nanoparticles in ZL108 alloy on Fe-rich phase was studied in this work. It was observed that B4C nanoparticles apparently refines the size of the Fe-rich phases and partially transforms Fe-rich phases morphology from hollow polyhedron to petal-like shape. The DSC results show that B4C nanoparticles does not affect the initial nucleation temperature of the Fe-rich phase. However, the addition of B4C nanoparticles to ZL108 alloy inhibits the growth of Fe-rich phase. The TEM results confirm that the addition of B4C nanoparticles alters the lattice parameter of Fe-rich phase due to incorporation of C atoms, thereby suppressing the growth of the Fe-rich phase and ultimately leading to its refinement. From the perspective of fracture behavior, the addition of B4C nanoparticles remarkably reduces the stress concentration of Fe-rich phase, and the elongation of the alloy increases by 25.3%. These findings provide a new perspective for further research and development to refine Fe-rich phase.

Structural and magnetic properties of α-Fe2O3 with lithium ferrite prepared using co-precipitation method and annealed at different temperatures

Using Co-precipitation method, an attempt was made to prepare lithium ferrite. However, during the synthesis, formation of an additional α-Fe2O3 phase along with Li0.5Fe2.5O4 was observed. To reduce the α-Fe2O3 phase, samples were annealed at 700°C, 800°C and 900°C temperatures for 2 hours. The investigated samples were then characterized using X-Ray diffraction for phase formation and Rietveld analysis was carried out to determine the different structural parameters such as phase percentage, lattice parameter and cell volume. The Chi square values were observed to be within the limit along with goodness of fit less than 3 for all the samples annealed at different temperatures. Surface morphology was carried out using scanning electron microscope and the average grain size was found to be 1.43 µm for the sample annealed at 900°C. Magnetic properties of samples were investigated, and it was observed that all the samples exhibit low values of saturation magnetization along with coercivity. The presence of two phases such as α-Fe2O3 phase and lithium ferrite phase dilutes the exchange interaction, tuning the magnetic parameters.

Small polaron hopping and tunneling mechanisms in Ba0.9La0.1Fe12O19 hexaferrite ceramic at low temperatures

The correlation between dielectric relaxation and conduction mechanisms in the Ba0.9La0.1Fe12O19 ceramic hexaferrite, at temperatures below 100 K was investigated. The sample was prepared using the conventional solid-state reaction method. X-ray diffraction analysis indicated that the sample is composed of a hexagonal BaFe12O19 phase (lattice parameters a = 5.8778(6) Å and c = 23.170(3) Å) and a small proportion of hematite (α-Fe2O3). The average grain size is 1.48 ± 0.4 μm, with irregular hexagonal and agglomerated grains. The magnetic hysteresis curve shows characteristics typical of ferro and ferrimagnetic materials, with an effective magnetic anisotropy coefficient of 0.960×106 emu/cm3 and an anisotropy field of 1.587×104 Oe. A dielectric relaxation process is observed between 50 and 100 K, with an activation energy of 60.4 ± 0.4 meV and a characteristic relaxation time of 2.09 ×10−10 s, mainly attributed to the electrical behavior of the grains. Two conduction mechanisms were identified: small polaron tunneling (high temperatures and low frequencies) and correlated barrier hopping of electrons (low temperatures and high frequencies). The activation energy for free polaron formation, according to the Komine-Iguchi hopping polarization model, was 7.12 ± 0.02 meV. In the dielectric modulus relaxation process between 30 and 54 K, the activation energy was 40.8 ± 0.9 meV, with a characteristic relaxation time of 2.41×10−10 s. The small polaron conductivity in the grain region was 67.52 meV and 54.0 meV in the grain boundary region. The results highlight that the polarization and conduction mechanisms in this ceramic at low temperatures are dominated by small polaron hopping and tunneling, and emphasize the influence of La3+ doping on the structural, magnetic, and electrical properties of barium hexaferrite.

SYNTHESIS STRUCTURAL AND MAGNETIC PROPERTIES OF TITANIUM DOPED MAGNESIUM ZINC FERRITE

Magnetic ceramics or ferrites are very well established group of magnetic materials which exhibits ferrimagnetism. It possess high electrical resistivity, low eddy current and dielectric loss which makes it superior than the other ordinary magnetic oxides that contain the ferric oxide (Fe₂O₃) as their basic magnetic compounds. The ceramic magnets are widely used in high frequency transformer application. [(Mg, Mn, F12o4)] spinels are used in square-loop application. Ceramic materials found application in nuclear physics. In nuclear reactors ceramics are used as core components. The studies include the preparation and analysis of Titanium doped Magnesium zinc ferrite. Here, Titanium doped magnesium zinc ferrite nanoparticles (NPS) were synthesized using solid state reaction method. Titanium doping can enhance the magnetic properties of magnesium zinc ferrite in several ways these can contribute to improved magnetic properties , such as increased magnetic moment, saturation magnetization, and magnetic ordering , making titanium – doped magnesium zinc ferrite a promising material for various applications including magnetic storage, sensors, and spintronics. According to the stoichiometric equation [Mg0.9Zn 0.1TixFe2-xO4] at different values of x, (x=0.1, 0.3) are synthesised. Calcination and sintering of the samples is made by high temperature PID controlled muffle furnace which can go up to 1000°C. The structural and magnetic properties are examined using XRD, FTIR and Curie temperature analysis. From the XRD analysis it revels the phase structure and lattice parameters of the samples. XRD analysis gives maximum intensity of (h k l) values as (3 1 1) in both cases. It also reveals that no secondary phases are produced during growth. That means the specimens FCC stacking. FTIR analysis of the samples done using Fourier transformer infrared spectroscopy. From this analysis it revels the detailed atomic structure and bonding of the samples. The bands obtained reveal spinal ferrite structure. Curie temperature of the specimens is determined by Curie temperature apparatus for the study of magnetic properties of the specimens.

Phase stability and elastic properties of NbMoTaWMx (M = Al, V, Zr, Tc, Re and Ir) RHEAs: A first-principles assessment

Using the exact muffin-tin orbital (EMTO) method in combination with the coherent potential approximation (CPA), we studied the influence of alloying elements Al, V, Zr, Tc, Re and Ir on the phase stability, lattice parameters, densities, and elastic properties of NbMoTaWMx (M = Al, V, Zr, Tc, Re, Ir; 0 ≤ x ≤ 1.0) refractory high entropy alloys. The predicted lattice parameter and elastic parameters agree with the available experimental and theoretical data. We calculated the atomic size difference (δ), the valence electron concentration (VEC) and the total energy of face-centered cubic (fcc), body-centered cubic (bcc) and hexagonal closed-pack (hcp) structures. We found that all studied NbMoTaWMx (M = Al, V, Zr, Tc, Re, Ir; 0 ≤ x ≤ 1.0) systems have the bcc structure. We showed that Al and Ir decrease the stability of the bcc structure and Zr significantly enlarges the lattice parameter of the host. Vanadium increases the ductility of NbMoTaW system. On the other hand, Al and Ir have strongly non-linear effect on the ductility, with clear minimum at x = 0.55. The present results provide consistent theoretical data and call for experimental investigation for these alloys.

Effect of Cold-Rolling Deformation on the Microstructural and Mechanical Properties of a Biocompatible Ti-Nb-Zr-Ta-Sn-Fe Alloy.

The primary focus of the current paper centers on the microstructures and mechanical properties exhibited by a Ti-30Nb-12Zr-5Ta-2Sn-1.25Fe (wt. %) (TNZTSF) alloy that has been produced through an intricate synthesis process comprising cold-crucible induction in levitation, carried out in an atmosphere controlled by argon, and cold-rolling deformation (CR), applying systematic adjustments in the total deformation degree (total applied thickness reduction), spanning from 10% to 60%. The microstructural characteristics of the processed specimens were investigated by SEM and XRD techniques, and the mechanical properties by tensile and microhardness testing. The collected data indicate that the TNZTSF alloy's microstructure, in the as-received condition, consists of a β-Ti phase, which shows polyhedral equiaxed grains with an average grain size close to 82.5 µm. During the cold-deformation processing, the microstructure accommodates the increased applied deformation degree by increasing crystal defects such as sub-grain boundaries, dislocation cells, dislocation lines, and other crystal defects, powerfully affecting the morphological characteristics. The as-received TNZTSF alloy showed both high strength (i.e., ultimate tensile strength close to σUTS = 705.6 MPa) and high ductility (i.e., elongation to fracture close to εf = 11.1%) properties, and the computed β-Ti phase had the lattice parameter a = 3.304(7) Å and the average lattice microstrain ε = 0.101(3)%, which are drastically influenced by the applied cold deformation, increasing the strength properties and decreasing the ductility properties due to the increased crystal defects density. Applying a deformation degree close to 60% leads to an ultimate tensile strength close to σUTS = 1192.1 MPa, an elongation to fracture close to εf = 7.9%, and an elastic modulus close to 54.9 GPa, while the computed β-Ti phase lattice parameter becomes a = 3.302(1) Å.

The study of La and Mg elements on the improved structure and hydrogen storage performance of Ca2MgNi9 alloy

In order to improve the comprehensive hydrogen storage performance of AB3-type (RE/Ca)-Mg-Ni alloys, a new series of Ca(Ca0.75La0.25)2-xMgxNi9 (x = 0.8, 0.9, 1.0, 1.1, 1.2) alloys is designed and prepared. Based on the as-cast Ca2MgNi9 alloy, La is introduced, and the ratio of rare earth (RE) to Mg is adjusted using the induction melting method. This alteration modifies the microstructure of the alloy and significantly enhances its hydrogen storage performance. The effects of microstructure on hydrogen storage performance and mechanism are analyzed. The phase composition and lattice parameters of the main phase are regularly regulated by appropriate element substitution. The lattice parameter of the main phase is increased, the capacity and kinetics of hydrogen storage are significantly improved. The initial hydrogen absorption capacity of the alloy increases from 1.744 wt% for Ca2MgNi9 to 1.975 wt% for Ca(Ca0.75La0.25)1.2Mg0.8Ni9 alloy. Furthermore, the synergistic regulation of La and Mg elements can increase the hydrogen desorption ratio and crystal structure stability of the alloy. This leads to the concurrent enhancement of effective hydrogen storage and cycle performance of the Ca2MgNi9 hydrogen storage alloy. The retention rate of hydrogen absorption capacity for the 50th cycle is increased from 77.13% for Ca2MgNi9 to 84.26% for Ca(Ca0.75La0.25)0.8Mg1.2Ni9. At the same time, owing to the adjustment of the cell volume and phase composition, the platform pressures of hydrogen absorption and desorption of the alloy have also experienced a multi-fold increase between 0.002 and 0.5 MPa at 303 K. This enhancement is advantageous for expanding the potential applications of this type of alloy. This work presents new ideas for enhancing the hydrogen storage performance of Ca2MgNi9 hydrogen storage alloys.

Experimental and theoretical insights into vanadium-based alloys for room temperature hydrogen storage on the example of Ti16Cr22Zr5V55-xFe2Mnx (x=0–3) alloys

In this work, the microstructures and hydrogen storage properties of the Ti16Zr5Cr22V55-xFe2Mnx (x =0, 1, 2, 3) hydrogen storage alloys were comprehensively investigated toward application under ambient conditions. The X-ray diffraction (XRD) patterns and scanning electron microscopy (SEM) images of the alloys indicated that all of the alloys consist of a BCC main phase and a small amount of C14 Laves secondary phase. All of the studied alloys have a good activation performance and fast absorption/desorption kinetics at 298 K. The flatness of desorption plateau of alloy is improved by the tiny Mn introduction. With the increase of Mn content, the lattice parameter of BCC main phase, electron density and hydrogen absorption/desorption capacity decrease, and the desorption plateau pressure at 298 K increases in the range of 0.1–1 MPa. In addition, the essence of the dependence of high hydrogen capacity on electron density was revealed based on Fermi level. The Tilt, hysteresis, and width of plateau of PCT curve of vanadium-based alloys were clarified on the basis of Sievert's law. And a good quadratic fitting between desorption plateau pressure and Mn content was manifested.

Luminescence Properties of ZrO2: Ti Ceramics Irradiated with Electrons and High-Energy Xe Ions.

Samples of ZrO2 ceramics with different concentrations of impurity titanium ions were synthesized by mixing zirconium and titanium oxide powders in different mass ratios. The X-ray diffraction analysis was used to determine the phase composition, lattice parameters, and crystallite size of the ceramics with varying dopant concentrations. Upon irradiation of the samples with 220 MeV Xe ions to a fluence of 1010 ions/cm2, a decrease in the intensity of the pulsed cathodoluminescence band at 2.5 eV was observed. Additionally, ion irradiation resulted in the emergence of a new thermoluminescence peak at 450-650 K attributed to radiation-induced traps of charge carriers. Further analysis revealed that the thermoluminescence curves of samples irradiated with electrons and ions comprise a superposition of several elementary peaks. Notably, a complex non-monotonic dependence of cathodo- and thermoluminescence intensity on titanium concentration was observed, suggesting the influence of concentration quenching and the presence of tunneling transitions.

Investigating the impact of sodium (Na) dopant on the structural, morphological, optical, and magnetic properties of LaPrSrMnO3 perovskite nanoflakes

Abstract Here we report the structural, optical and magnetic properties of La0.4Pr0.25Na x Sr0.35−x MnO3 (x = 0, 0.05, and 0.1) synthesized using ball milling method. After milling, the precursors are calcinated at 1,200 °C for 12 h. The phase purity, crystal structure, lattice parameter, and crystallite size of the samples were determined using X‐ray diffraction (XRD). The peaks from XRD provide the perovskite hexagonal structure with an R 3 ‾ $\overline{3}$ c space group. Surface morphology shows the recreation of spherical structure to nanoflakes/layered structures. The ultraviolet-visible diffused reflectance spectroscopy (UV–vis DRS) study indicates that the decrease in the band gap is observed with the increase of Na content. The intensity of the luminescence peak decreases progressively with the increase of Na doping. The room temperature (RT) magnetization of the samples reveals weak ferromagnetism and shows a novel vertical shift in magnetization at room temperature.

Structural and optical properties of Zn2.95Ga2−xSnO8:xCr3+: An excellent X-ray charging-based persistent phosphor

This study investigates structural and luminescence properties of Cr3+ doped Zn2.95Ga2SnO8 phosphor. XRD analysis determines the phase purity and lattice parameters, while SEM and TEM analysis were utilized to study the particle size and surface morphology of the sample. UV–visible absorption and PL excitation spectra provided information on the excitation bands and the band-gap of both the undoped and Cr3+ doped Zn2.95Ga2SnO8. The optical band-gap of the material decreases upon doping with Cr3+ ions. Analysis of the Racah parameter and Tanabe Sugano diagram highlights a robust crystal field within Cr3+: Zn2.95Ga2SnO8, causing 2Eg level to become the lowest excited state with sharp emission at 699 nm. Concentration quenching at higher Cr3+ concentrations (> 0.6 mol%) is primarily attributed to the quadrupole-quadrupole interactions. Two distinct traps with trap depths at 0.51 eV and 0.73 eV were identified by using thermoluminescence measurement. The material gives persistent luminescence with a decay time of more than 30 min when charged with blue light (420 nm) and an excellent decay time of more than 16 h when charged with X-rays. Notably, this is the first report on X-ray charging-based persistent luminescence in Zn2.95Ga2SnO8. The outstanding persistent luminescence makes this material highly promising for various applications.

Crystalline structure of 0.65BiFeO3–0.35Ba1-xSrxTiO3 solid solutions in the vicinity of the morphotropic phase boundary

Complex transition metal oxides are distinguished for a close interrelation between their type of crystal structure and electrical and magnetic properties, thus determining their practical importance. Bismuth ferrite based solid solutions contain simultaneously both dipole electric and magnetic ordering thus expanding their potential applications as external impact sensors. The sensitivity of these compositions to external fields is largely dependent on their structural state. 0.65BiFeO3–0.35Ba1-xSrxTiO3 solid solutions (0 ≤ x ≤ 1) the compositions of which are close to the rhombohedral/cubic morphotropic phase boundary have metastable structures and are therefore promising functional materials. The crystal structure and morphology of 0.65BiFeO3–0.35Ba1-xSrxTiO3 solid solutions has been studied using X-ray diffraction, scanning electron microscopy, Raman spectroscopy and energy dispersive X-ray spectroscopy. The chemical substitution of barium ions for strontium ones has been found to reduce the magnitude of rhombohedral distortions and decrease the unit cell parameters for all the substituted compounds. Solid solutions with x ≥ 0,25 have single-phase structure and cubic unit cells, their grain size decreasing with an increase in the concentration of the substituting ions. The results of structural studies obtained using Raman spectroscopy suggest the presence of rhombohedral distortions in the structures of all the compositions studied. The results of structural studies have allowed identifying the sequence of changes in the phase state and lattice parameter of the compounds in the vicinity of the rhombohedral/cubic morphotropic phase boundary. The concentration ranges in which the compounds have single-phase and two-phase structures have been found. The concentration stability range of the polar rhombohedral phase has been corrected on the basis of the structural data obtained using local and microscopic methods.

Preparation of novel Ti–Y/ZrO2 ceramic by two-step of mechanical alloying and microwave-assisted sintering process

Zirconia composite ceramic materials are popular for their many excellent properties. In this study, nTi-3Y–ZrO2 composite ceramics were produced by the mechanical alloying-microwave sintering method with different Ti-doping amounts and microwave sintering temperatures. The sample's phase composition, stability rate, lattice parameters, micromorphology, relative density, and grain size are characterized. The results showed that when the sintering temperature is 1200 °C, the samples with different doping amounts are mainly mixed crystalline structures with tetragonal and cubic phases, and the stability rate remains above 90 %. As TiO2 doping increases, the lattice parameters a(Å) and b(Å)first increase and then decrease, while the lattice parameter c (Å) shows an overall increasing trend. Raman data demonstrated that the increase in Ti content promoted the generation of tetragonal phase zirconia. The average grain size is 61.33 nm, 76.23 nm, 58.77 nm, 63.35 nm, and 68.99 nm, respectively. The increase in doping is also accompanied by a narrowing of the grain size distribution, which increases the sintering activity of the sample. In addition, the relative densities of the samples were 67.85 %, 73.94 %, 84.25 %, 84.87 %, and 77.54 %, respectively, showing a gradual increasing trend overall. When the microwave sintering temperature is 1200 °C, and the doping amount is 5Ti–3Y–92Zr, the performance of the sample is superior to other groups. The preparation of nTi-3Y–ZrO2 composite ceramics can provide certain ideas for preparing ceramic materials with excellent performance in various aspects.

Order-Disorder Phase Transition and Ionic Conductivity in a Li2B12H12 Solid Electrolyte.

Temperature-induced phase transitions and ionic conductivities of Li2B12H12 and LiCB11H12 were simulated with the use of machine learning interatomic potentials based on van der Waals-corrected density functional theory (rev-vdW-DF2 functional). The simulated temperature of order-disorder phase transition, lattice parameters, diffusion, ionic conductivity, and activation energies are in good agreement with experimental data. Our simulations of Li2B12H12 uncover the importance of the reorientational motion of the [B12H12]2- anion. In the ordered α-phase (T < 625 K), these anions have well-defined orientations, while in the disordered β-phase (T > 625 K), their orientations are random. In vacancy-rich systems, its complete rotation was observed, while in the ideal crystal, the anions display limited vabrational motion, indicating the static nature of the phase transition without dynamic disordering. The use of machine learning interatomic potentials has allowed us to study large systems (>2000 atoms) in long (nanosecond-scale) molecular dynamics runs with ab initio quality.

Monitoring the Particle Size Distribution, Phase Quantification and Chemical Composition of Acid-Leached PtCo Electrocatalyst Under Start-up/Shut-Down Conditions Probed By in-Situ SAXS and WAXS Techniques

Large progress has been made towards commercialization of polymer electrolyte membrane fuel cells (PEMFCs) through the development of highly active and robust Pt-Co alloy catalysts for oxygen reduction reaction (ORR).[1,2] However, most ORR catalyst materials suffer from the extremely corrosive conditions occurring during start-up/shut-down (SUSD).[3] Consequently, understanding the degradation mechanisms during SUSD is highly crucial for designing new catalyst materials with enhanced ORR activity and long-term durability.In this work, we show a comprehensive and complementary combination of different advanced techniques such as in-situ small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) as well as ex-situ scanning transmission electron microscopy in combination with electron energy loss spectroscopy (STEM-EELS) to provide deeper insights into the degradation processes of acid-leached Pt-Co catalyst under SUSD conditions.Firstly, Pt-Co nanoparticles supported on high surface area carbon (HSAC) were synthesized using wet impregnation – freeze-drying – thermal annealing method.[4] Compared to our previous works [4-6], an acid-leaching (1 M H2SO4, 15 °C, 2 h) was applied to dissolve the less noble metal from the surface of alloy nanoparticles forming a Pt-enriched skin. STEM-EELS data has also confirmed the formation of the Pt-enriched skin. In addition, ex-situ WAXS data signifies that the acid-leached PtCo catalyst consists of two face-centered cubic (fcc) disordered crystal phases: Pt90Co10 phase with a crystallite size of 3.6 ± 0.4 nm and Pt70Co30 phase with 4.2 ± 0.4 nm size.In terms of ORR performance, the acid-leached PtCo catalyst exhibits a 2.5- & 2-times higher mass activity (0.61 ± 0.12 A mgPt -1) and a 3.5- and 1.3-times higher specific activity (665 ± 84 µA cmPt -2) at 0.9 VRHE compared to commercial ~2 nm Pt/C (0.24 ± 0.05 A mgPt -1, 187 ± 29 µA cmPt -2) and heat-treated 4-5 nm Pt/HSAC (0.30 ± 0.04 A mgPt -1, 297 ± 42 µA cmPt -2), respectively. After SUSD experiments (800 cycles, 0.5 - 1.5 VRHE, 50 mV s-1, 0.1 M HClO4), the mass activity decreases to 0.21 ± 0.06 A mgPt -1 (-65 %) and 0.15 ± 0.03 A mgPt -1 (-38 %) for the acid-leached PtCo catalyst and commercial Pt/C, respectively.To monitor the potential-dependent changes in particle/crystallite size, phase quantification and chemical composition of the acid-leached PtCo catalyst under the SUSD conditions, in-situ SAXS and WAXS experiments were simultaneously performed at the beamline ID31 at European Synchrotron Radiation Facility (ESRF).In-situ WAXS analysis reveals that the lattice parameter of both Pt90Co10 and Pt70Co30 phases increases as a function of the SUSD cycle number, signifying the successive depletion of cobalt mainly from the Pt70Co30 phase. More precisely, the lattice parameter changed from 3.819 ± 0.004 Å (Pt70Co30) to 3.829 ± 0.004 Å (Pt76Co24) during the first 150 SUSD cycles. Only a slight change in lattice parameter for Pt90Co10 phase is observed during the SUSD protocol. Based on the Rietveld quantification, the amount of the Pt70Co30 phase decreases from 61 ± 2 wt.% to 47 ± 2 wt.% during the first 150 SUSD cycles. Afterwards, the Co depletion from this phase is less pronounced with additional cycle number. Furthermore, STEM-EELS investigations on acid-leached PtCo catalyst after first 150 SUSD cycles has confirmed the drastic Co depletion within the nanoparticles. After the SUSD protocol, the chemical composition of the acid-leached PtCo catalyst alters from Pt67±3Co33±3 to Pt81±3Co19±3 (-42 at.%) obtained from the bulk techniques like EDX and µ-XRF.In addition, the Rietveld refinement reveals an increase in crystallite sizes for both Pt-Co crystal phases over the course of the SUSD protocol which is in excellent agreement to the in-situ SAXS and ex-situ TEM results (from 4.1 ± 1.0 nm to 5.2 ± 0.8 nm, +27 %). In detail, the initial larger Pt70Co30 phase shows only a small increase in crystallite size (from 4.3 ± 0.4 nm to 4.8 ± 0.4 nm, +12 %), whereas for the initial smaller Pt90Co10 phase a gradual increase from 3.2 ± 0.3 nm to 4.5 ± 0.4 nm (+41 %) is observed during the SUSD experiment.Based on the in-situ SAXS/WAXS and the ex-situ STEM-EELS data, the Co depletion is the dominant degradation mechanism for the disordered fcc Pt70Co30 phase during the first 150 SUSD cycles. With increasing SUSD cycle number, the particle growth via Ostwald ripening and particle coalescence predominates. Our degradation model can be used to further improve the ORR performance and durability of acid-leached Pt-Co catalysts under the SUSD conditions.Literature:[1] L.R.Borup et al.,Curr.Opin.Electrochem.,2020,21,192-200.[2] C.Wang et al.,Energies,2016,9,603-642.[3] Y.Yu, et al.,J.Power Sources,2012,205,10-23.[4] M.Oezaslan et al.,J.Electrochem.Soc.,2012,159,B394-B405.[5] D.J.Weber et al.,J.Mater.Chem.A,2021,9,15415-15431.[6] P.Weber et al.,ACS Catal.,2022,12,6394-6408.

(Digital Presentation) Sm0.5Sr0.5CoO3- δ -Ce0.9Sm0.1O1.95 Nanocomposites for Reversible Solid Oxide Cells

Electricity production through environmentally friendly energy sources has been one of the main challenges of our society in the last decades. The rapid growth of renewable energy has a large influence in the transport sector and industrial processes. Nevertheless, the irregular and seasonal disposition of renewable energy requires advanced devices for energy storage and conversion into electrical power. In this sense, reversible solid oxide cells appear as a promising alternative to store and produce electrical energy in a more efficient and eco-friendly way than conventional batteries and generators, respectively [1].An important aspect for increasing the efficiency of reversible solid oxide cells is to improve the performance of the air electrode. Although the intrinsic properties of the ceramic material are of great importance, such as electrical conductivity and electrochemical activity, the real performance of the air electrode strongly depends on its microstructure: porosity, particle size, surface area and electrode-electrolyte adherence [2].It is reported that the efficiency of air electrodes may be improved by adding a second phase with high ionic conductivity, such as doped-CeO2, to obtain a composite electrode with more conducting paths for oxide-ions. In addition, composite electrodes have generally higher efficiency than single-phase ones due to the increased electrochemically active area in whole electrode volume [2]. Moreover, they are known to reduce the mechanical stress originated by the different thermal expansion coefficients between the electrode and the electrolyte layers, thus improving the mechanical stability and durability of the cell.Traditionally, composite electrodes are prepared by mechanical mixing of the pristine materials, requiring multiple steps and time-consuming methods. Moreover, it is difficult to control the phase distribution and electrode morphology with this method. In order to overcome this drawback, nanocomposite powders may be synthesized by different co-synthesis methods, showing a more uniform distribution of nanosized crystals with high thermal stability and improved electrochemical properties [3].In this context, Sm0.5Sr0.5CoO3- δ exhibits high mixed ionic and electronic conductivity but relatively high thermal expansion coefficients, ~21.5·10-6 K-1, to be physically compatible with standard electrolyte materials, i.e. 12·10-6 K-1 for doped-CeO2. In this work, Sm0.5Sr0.5CoO3- δ-Ce0.9Sm0.1O1.95 (SSC-CSO) nanocomposite cathodes are successfully prepared in a single process by using the freeze-drying precursor method from a precursor solution containing all cations in stoichiometric amounts. In this way, SSC and CSO phases are formed simultaneously at low sintering temperature, reducing drastically the preparation time. SSC-CSO composite electrodes with different SSC content, ranging from 50 to 100%, are investigated by different structural, microstructural and electrochemical techniques.The XRD patterns show that the composite electrodes at 800 ºC are a mixture of SSC and SCO phases with perovskite and fluorite-type structure, respectively. No secondary phases are detected for any of the samples (Fig. 1a). Moreover, the Rietveld analysis shows a phase fraction and lattice cell parameters similar to the theoretical ones, suggesting minor cation exchange during the co-sintering process.The sintered pellets for electrical characterization show a homogeneous distribution of SSC and CSO phases (Fig. 1b,c). Interestingly, the addition of CGO suppresses partially the grain growth due to cation diffusion limitations during the sintering process. Thus, the grain size decreases from 0.53 µm for 100SSC to 0.32 µm for 60SSC.The lowest values of polarization resistance are found for 50SSC with a value of 0.35 Ω cm2 at 600 °C compared to 0.75 for 100SSC (Fig. 1d). The results suggest that this is a promising strategy to achieve highly efficient ceramic electrodes for reversible solid oxide cells with a notably simplified fabrication process compared to traditional methods.

Manipulation of magnetocaloric and elastocaloric effects in Ni–Mn–In alloys by lattice volume and magnetic variation: Effect of Co and Fe co-doping

The effects of Co and Fe co-doping Ni–Mn–In alloy on the phase stability, lattice parameters, magnetic properties, and electronic structures are systematically investigated by using the first-principles calculations. Results indicate that Fe atoms replace the excess Mn2 atoms by direct and indirect coexistence (Fe→Mn2 and Fe→In→Mn2); Co substitutes the Ni atoms by direct substitution (Co→Ni) for the Ni–Mn–In alloy. The austenites all exhibit the ferromagnetic (FM) state for the studied compositions. The NM martensites are in the ferrimagnetic (FIM-1) state for the Ni2Mn1.5In0.5, Ni2Mn1.25In0.5Fe0.25, Ni1.75Mn1.5In0.5Co0.25, and Ni1.75Mn1.25In0.5Co0.25Fe0.25 alloys, while the other compositions are in the FM state. The phase stability of austenite and martensite decreases with increasing Co and Fe co-doping. A magnetic-structural coupling transition occurs at x < 0.25 and y < 0.25. The Ni1.91Mn1.5In0.5Co0.08 and Ni1.91Mn1.42In0.5Co0.08Fe0.08 alloys exhibit an A→6M→NM transformation, accompanied by a magnetic transition. When Co and Fe are co-doped, the hybridization strength between Co and Fe is greater than that between Co/Fe and Mn. The enhancement of magnetocaloric and elastocaloric effects is favored by larger magnetization difference (∆M) and lattice volume change (∆V/V0). Based on the calculated phase stability, magneto-structure coupling, ∆V/V0 and c/a ratio, one can predict that the Ni2-xMn1.5-yIn0.5CoxFey alloy with Co content 0 ≤ x ≤ 0.25 and Fe content 0 ≤ y ≤ 0.05 is predicted to have good magneto-controlled functional behavior.

Effect of Fe doping on the structural and electrochemical performance of Zn@CuO nanostructures for energy storage device

The demand for supercapacitors increases as the technology grows due to their high-power density and long cycle life. This work presents a hydrothermal approach to synthesize iron-doped zinc copper oxide (Fe@ZnCuO). The XRD technique was used to determine phase identification and lattice parameters. The maximum capacity achieved with Fe@ZnCuO was 938C/g (1563 F/g) at a current density of 1.5 A/g. The asymmetric device Fe@ZnCuO//AC was developed with activated carbon as the negative and Fe@ZnCuO as the positive electrode. At 1.5 A/g current, Fe@ZnCuO//AC had a capacity of 144C/g (90 F/g). Energy and power density achieved with Fe@ZnCuO//AC at 1.5 A/g current were 44.12 Wh kg−1 and 850 W kg−1, respectively. The durability test was also performed with Fe@ZnCuO//AC hybrid device, measuring up to 15,000 consecutive charging/discharging cycles. After completing 15,000 cycles, Fe@ZnCuO can retain 98% of its initial capacity. These findings imply that Fe@ZnCuO can be the best electrode material for asymmetric supercapacitors applications in the future.

The influence of hafnium removal on the microstructure and properties of 8YSZ ceramics

The effects of hafnium removal on the sinterability, phase composition, and microstructural, mechanical, and electrical properties of 8YSZ (8 mol% yttrium stabilized zirconia) were investigated using SEM, XRD, Raman spectroscopy, EBSD, three-point bending, Vickers indentation, and impedance spectroscopy. The 8YSZ and 8YSZ0 (8 mol% yttrium-stabilized hafnium-free zirconia) ceramics were prepared via dry pressing and atmospheric sintering, respectively. The overall mechanical properties of the 8YSZ0 ceramic were poor. However, at a sintering temperature of 1450°C, the relative density of 8YSZ and 8YSZ0 ceramics was almost identical. 8YSZ0 had a slightly smaller grain size and activation energy, and its electrical properties were slightly better than those of the 8YSZ ceramics. The presence of tetragonal secondary phases in the cubic structure of 8YSZ ceramics inhibited crack propagation and led to an increase in the mechanical properties and a decrease in the ion conductivity. In terms of the crystal structure, the increase in the cubic phase lattice parameters and tetragonal phase c/a values of the 8YSZ0 ceramics was attributed to the larger Zr4+radius, reduced local lattice distortion, and increased matrix oxygen vacancy concentration and cubic phase content. The EBSD analysis results indicated that there was no significant difference in grain orientation between the two types of ceramics, but the content of 8YSZ ceramics in large angle grain boundaries was slightly higher, especially in special grain boundaries Σ3 and Σ9. Therefore, this material can be used as a solid-state electrolyte candidate.

Oxygen-Ion and Proton Transport of Origin and Ca-Doped La2ZnNdO5.5 Materials

Oxygen-ionic and proton-conducting oxides are widely studied materials for their application in various electrochemical devices such as solid oxide fuel cells and electrolyzers. Rare earth oxides are known as a class of ionic conductors. In this paper, La2ZnNdO5.5 and its Ca-doped derivatives La2Nd0.9Ca0.1ZnO5.45 and La2ZnNd0.9Ca0.1O5.45 were obtained by a solid-state reaction route. Phase composition, lattice parameters, and hydration capability were investigated by X-ray diffraction and thermogravimetric analyses. The conductivities of these materials were measured by the electrochemical impedance spectroscopy technique in dry (pH2O = 3.5 × 10−5 atm) and wet (pH2O = 2 × 10−2 atm) air. All phases crystallized in a trigonal symmetry with P3m1 space group. The conductivity difference between undoped and calcium-doped samples is more than two orders of magnitude due to the appearance of oxygen vacancies during acceptor doping, which are responsible for a higher ionic conductivity. The La2Nd0.9Ca0.1ZnO5.45 sample shows the highest conductivity of about 10−3 S∙cm−1 at 650 °C. The Ca-doped phases are capable of reversible water uptake, confirming their proton-conducting nature.