Changes In Lattice Parameters Research Articles

Effect of Mn-adding on microstructure, optical and dielectric properties Zn0.95Al0.05O nanoparticles

Pure ZnO and Zn0.95-xAl0.05MnxO (x = 0, 1, 3, 5) nanoparticles (NPs) were successfully produced through co-precipitation method. The doped ZnO nanoparticles were characterized by using X-ray diffraction (XRD), Williamson-Hall plot (W–H Plot) and field emission electron microscope (FESEM) analysis. The XRD patterns revealed that all samples exhibit crystalline hexagonal (wurtzite) structure of the ZnO NPs. The change in lattice parameters (a, c), preferential crystalline orientation for Mn doped samples, change in bond length and micro-strain after doping indicate successful incorporation of Mn2+ in Al-doped ZnO NPs. Further, the increase in average crystallite size directed the improvement in the crystalline nature. FESEM was used to study the morphological analysis of pure and doped ZnO NPs. UV Vis spectroscopy results indicate that the optical transmission improved in the visible region and band gap decreases as a result of doping. The improvement in the dielectric loss due to Mn content doping was observed and is associated with increase in the number of defects. The decrease in ac conductivity (σac) with Mn content is related with increase amount of defects.

Mechanical alloying and characterization of chlorine doped hydroxyapatite nanopowders

Chlorine-doped Hydroxyapatite (ClHA)(Ca10(PO4)6(OH)2-xClx) nanopowders were successfully synthesized using high planetary ball mill. Milling was carried from 1 to 8 h in order to study the effect of milling time on the doped powders. Additionally, a study on the effect of chlorine addition to HA was also done. XRD results confirmed that all the milled powders consisted apatite as main phase. A significant increase in the unit cell parameters of ClHA nanopowders was observed in contrast to pure HA. However, in doped powders the size decreased with an increase in milling time with a minimal change in the lattice parameters. Microscopic observations also revealed an overall increase in the particle size due to Cl− addition. FTIR results confirmed the incorporation of Cl ions into HA lattice. Hemocompatibility of the synthesized powders (pure HA and ClHA8) was investigated using bovine blood. It was seen that hemolysis ratios for both the samples were below 2%, indicating that the synthesized powders of HA and ClHA are hemocompatible and can be used in various biomedical applications.

Rare-earth doped Ni–Co ferrites synthesized by Pechini method: Cation distribution and high temperature magnetic studies

The present work was focused on the effect of rare earth doping on the structural and magnetic properties of Ni–Co ferrite materials with general chemical formula Ni0.5Co0.5Fe1.98R0.02O4 (R = La, Nd, Sm, Gd, Dy). All the ferrites, synthesized by the Pechini method, possess cubic symmetry with Fd3_m space group. A very small change in lattice parameter has been observed with rare earth (R3+) doping. The cation distribution between the tetrahedral (A-site) and octahedral sites (B-site), as estimated by X-ray diffraction analysis (XRD) revealed that the R3+, Co2+ and Ni2+ ions have migrated to the octahedral site. Room temperature magnetization results, obtained from Vibrating Sample Magnetometer (VSM) measurements, showed that saturation magnetization of rare-earth doped ferrites is strongly dependent on magnetic moment of rare earth ion. The coercivity increases with increase in the atomic number of rare-earth ion, which could be justified on the grounds of the stability of spin-orbital coupling that controls the magnetic anisotropy in ferrites. The results further suggest that the Curie temperature is dependent on lattice parameter and hence inter-atomic distance between magnetic ions.

The effect of nickel doped Bismuth Vanadium Oxide on microstructures and electric properties towards BiVO4-NiO composite

The preparation of BiVO4-NiO of microstructures and electric properties has been done using water solution and coated with indium tin oxide (ITO). BiVO4-NiO material was prepared using BiVO4, NiO powders and ITO. Mixing and coating processes were held using water and the resulting paste was coated by screen printing using a small glass stick on an ITO. The heat temperature process was done at 260 °C for 2 h. Samples were characterized using XRD, SEM-EDS and FTIR. The effect of ion Nickel addition did not change the monoclinic structure of bismuth vanadium. The Ni ions have been substituted Bi ion in the bismuth vanadium system which is indicated by the change of lattice parameters and compositions. Then, the additions decrease peak intensity increases due to the bigger microstructures observed. The addition Ni does not affect BiVO4 but decreased the peak band BiVO4 as increases Ni. The linear voltammograms observed an increase BiVO4 with increases Ni because the enhancement of current could improve the oxygen kinetics properties and surface passivation of the electrode in BiVO4-NiO. Therefore, the addition of NiO is reflected in an increase in electrical conductivity.

A Highly Efficient and Stable Photocatalyst; N-Doped ZnO/CNT Composite Thin Film Synthesized via Simple Sol-Gel Drop Coating Method.

The thin film of N-doped ZnO/CNT nanocomposite was successfully fabricated on soda lime glass substrate by a simple sol-gel drop-coating method. The structural, morphological, chemical, and optical properties of as prepared samples were characterized by a variety of tools such as X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Fourier Transform Infrared spectroscopy (FT-IR), and UV-visible spectroscopy. The hexagonal crystalline structure was confirmed from XRD measurement without any other impurity phase detection in samples. The N-doped ZnO/CNT composite showed excellent photo-catalytic activity towards cationic methylene blue (MB) dye degradation with 100% removal rate under UV light irradiation as compared to N-doped ZnO (65%) and pure ZnO (47.36%). The convincing performance has also been observed for the case of visible light irradiation. The enhancement of that photocatalytic activity might be due to narrowing the band gap as well as the reduction of electron–hole pair recombination in ZnO matrix with the incorporation of dopant nitrogen and CNT. It is assumed from the obtained results that N-doped ZnO/CNT nanocomposite thin film can be employed as an economically achievable and ecofriendly method to degrade dye with UV and visible light irradiation. Additionally, density functional theory (DFT) calculations were applied to explore the effect of N-doping on electronic structure of ZnO. The computational study has supported the experimental results of significant band gap contraction, which leads to the maximum absorption towards higher wavelength and no appreciable change of lattice parameters after doping. A conceivable photocatalytic mechanism of N-doped ZnO/CNT nanocomposite has been proposed as well.

Ternary transition metal chalcogenides Ti2PX2 (X = S, Se, Te) anodes for high performance metal-ion batteries: A DFT study

Two-dimensional (2D) materials display special interest as for metal-ion batteries (MIBs) due to they have high specific surface area and unique electrochemical activity. Here, interactions between ternary transition metal chalcogenides Ti2PX2 (X = S, Se, Te) and metal-ion (Li, Na, K and Ca) are theoretically studied via density functional theory (DFT) calculations. Their metal-ion storage capabilities are systematically explored and compared with available experimental and theoretical information. Ti2PX2Li2 and Ti2PX2K2 exhibit the same storage capacity (281 mAhg−1), however K shows lower diffusion barrier (~0.07 eV) than Li (~0.17–0.21 eV). Although Ca shows significant large capacity (842–1685 mAhg−1), its diffusion barrier is higher than other ions. The small change in lattice parameter (Ti2PX2Na6: <1.2%), high capacity (842 mAhg−1 up to Ti2PX2Na6), low open circuit voltage (0.4–0.6 V) and low diffusion barrier energy (~0.1 eV) are found in Ti2PX2 for sodium-ion adsorption. These properties are superior as compared to other available 2D materials, such as graphene, MXenes (Ti3C2), MoS2 and so on. Our results indicate that Ti2PX2 monolayers may be promising for MIBs anode materials, especially for sodium-ion batteries (SIBs) applications.

Patterning enhanced tetragonality in BiFeO3 thin films with effective negative pressure by helium implantation

Helium implantation in epitaxial thin films is a way to control the out-of-plane deformation independently from the in-plane strain controlled by epitaxy. In particular, implantation by means of a helium microscope allows for local implantation and patterning down to the nanometer resolution, which is of interest for device applications. We present here a study of bismuth ferrite (BiFeO3) films where strain was patterned locally by helium implantation. Our combined Raman, XRD and TEM study shows that the implantation causes an elongation of the BiFeO3 unit cell and ultimately a transition towards the so-called super-tetragonal polymorph via states with mixed phases. In addition, TEM reveals the onset of amorphization at a threshold dose that does not seem to impede the overall increase in tetragonality. The phase transition from the R-like to T-like BiFeO3 appears as first-order in character, with regions of phase coexistence and abrupt changes in lattice parameters.

High storage capacity and small volume change of potassium-intercalation into novel vanadium oxychalcogenide monolayers V2S2O, V2Se2O and V2Te2O: An ab initio DFT investigation

A new category of two-dimensional electrode materials, i.e., V2Ch2O (Ch = S, Se and Te) monolayers was explored for K-ion batteries (PIBs) based on principle of chemical exfoliation, density functional theory and ab initio molecular dynamics simulations. The V2Ch2O monolayers show low cleavage energies and excellent thermal, dynamical and mechanical stabilities. Adsorption energies of a potassium atom on the V2Ch2O monolayers are exothermic, which are of benefit to prevent forming dendrites. The existence of electrode potentials substantially decreases the diffusion barriers of potassium atoms on the three V2Ch2O monolayers. The V2Ch2O monolayers are able to maintain their metallic characteristics and single surface phase during the whole K-intercalation process, avoiding the decrease in electronic conductivity and the appearance of potential hysteresis. The theoretical specific capacities of the V2S2O, V2Se2O and V2Te2O monolayers are predicted to be 883.6, 583.1 and 431.0 mAh g−1, respectively, and the corresponding average open-circuit voltages are 0.449, 0.390 and 0.293 V, respectively. The maximum percentage changes in lattice parameters are 4.21%, 6.07% and 7.26% for the V2S2O, V2Se2O and V2Te2O monolayers, respectively. All the calculated properties indicate that the V2Ch2O monolayers are promising electrode materials for PIBs with high capacities and long cycle lives.

Correlative chemical and structural nanocharacterization of a pseudo‐binary 0.75Bi(Fe0.97Ti0.03)O3‐0.25BaTiO3 ceramic

AbstractFast cooling after sintering or annealing of BiFeO3‐BaTiO3 mixed‐oxide ceramics yields core‐shell structures that give excellent functional properties, but their precise phase assemblage and nanostructure remains an open question. By comparing conventional electron energy loss spectroscopy (EELS) with scanning precession electron diffraction (SPED) mapping using a direct electron detector, we correlate chemical composition with the presence or absence of octahedral tilting and with changes in lattice parameters. This reveals that some grains have a three‐phase assemblage of a BaTiO3‐rich pseudocubic shell; a BiFeO3‐rich outer core with octahedral tilting consistent with an R3c structure; and an inner core richer in Ba and even poorer in Ti, which seems to show a pseudocubic structure of slightly smaller lattice parameter than the shell region. This last structure has not been previously identified in these materials, but the composition and structure fit with previous studies. These inner cores are likely to be non‐polar and play no part in the ferroelectric properties. Nevertheless, the combination of EELS and SPED clearly provides a novel way to examine heterogeneous microstructures with high spatial resolution, thus revealing the presence of phases that may be too subtle to detect with more conventional techniques.

Effects of xenon-ion irradiation on the tribological properties and crystal structure of titanium and its alloy Ti6Al4V

Tribological properties of titanium and alloy Ti6Al4V are changed by the irradiation with 160 MeV swift xenon ions. At the beginning of the tribological test, the friction coefficient of titanium is reduced. As the test of titanium proceeds, an unconventional two-step increase in its value is observed. The irradiation causes oscillating changes in the crystal lattice parameters of titanium and Ti6Al4V. These unconventional changes result from the annealing and evolution of radiation defects during irradiation with a high fluence of Xe ions. The two-step changes in the friction coefficient of titanium and the unconventional changes in the crystal lattice parameters of Ti and Ti6Al4V following the swift Xe-ion irradiation have been observed for the first time.

Characterization of “Sandwich” Wulfenite from the Ojuela Mine, Mapimí, Mapimí Municipality, Durango, Mexico: Evidence of Preferred Secondary Nucleation on Selected Wulfenite Faces

This paper describes the formation of “sandwich” wulfenite. Banded wulfenite from the Ojuela Mine, Mapimí, Durango, Mexico, have been found since 2017, but an explanation for the band formation has not been provided. X-ray diffraction (XRD) showed the wulfenite to have a tetragonal unit cell of a = 5.4374(1), c = 12.1123(7) Å. The Raman spectrum was dominated by ν1 (Ag) around 870 cm–1, while the weak shoulder at 859 cm–1 represents the strain activated ν1 (Bu) infrared (IR) band. Two ν2 modes were observed at 318 cm–1 (Ag) and 351 cm–1 (Bg). For the ν3(Eg), the band at 768 cm–1 was assigned to the Bg symmetric mode and the 745 cm–1 band to the Eg vibration. The IR spectrum showed two strong bands at 835 and 779 cm–1 corresponding to v3 modes and a very weak one at 496 cm–1. SEM-EDX (scanning electron microscopy – energy dispersive X-ray analysis) showed that the band does not extend into the main crystal but is limited to the surface as secondary growth. The main thick tabular crystal was dominated by {001}, {110}, and {111}. The {001} surfaces of the wulfenite crystals showed evidence of later dissolution, which may have been part of the source material for this secondary crystallization. The chemical composition of the main wulfenite crystal proved only minor substitution of W for Mo. Contrastingly, a much higher number of substitutions by V, As, and W for Mo – as well as Ca, Fe, Zn, Cu, and Al for Pb – was observed in the secondary band, indicating a change in the fluid composition from which the band crystallized compared to the original wulfenite. Changes in lattice parameters of the secondary wulfenite crystals and the energy involved in nucleation on the surface of the original wulfenite as well as the different bonds exposed on different faces favored the formation of the band on only {110}.

Production of Al based Composites Reinforced with FeAl Intermetallic Particles by Mechanical Alloying

In this research project, Al matrix composite materials reinforced with 5 and 10 (wt.%) of FeAl intermetallic particles were synthesized by Mechanical Alloying (MA) at a speed of 250 RPM for 2, 5, 10 and 15 h of milling time. The results showed that composite materials can be obtained at low energy conditions with improved dispersion of the reinforcement in the Al matrix compared to those obtained by conventional techniques. The composites powders obtained by mechanical alloying at different milling times were studied by Scanning Electron Microscopy (SEM) in order to characterize the morphology and particle size. X-Ray Diffraction (XRD) was used to study the structural evolution of the system as the initial powders were subjected to different milling times, thus obtaining the evolution of the present phases, changes in lattice parameters and crystallite size. This work demonstrates the viability of the MA technique to produce composite materials with a homogenous distribution of the reinforcement particles with a great degree of control in the process, which would be very difficult to reproduce by conventional synthesis methods.

N-doped mixed Co, Ni-oxides with petal structure as effective catalysts for hydrogen and oxygen evolution by water splitting.

Developing electrocatalytic nanomaterials for green H2 energy is inseparable from the exploration of novel materials and internal mechanisms for catalytic enhancement. In this work, nano-petal N-doped bi-metal (Ni, Co) and bi-valence (+2, +3) (Ni1−xCox)2+Co23+O4 compounds have been in situ grown on the surface of Ni foam. The N3− atoms originate from the amino group in urea and doped in the compound during annealing. The as-synthesized N-doped (Ni1−xCox)2+Co23+O4 nano-petals demonstrate commendable hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) bi-functional catalytic efficiency and stability. Electrochemical measurements confirm that the nitrogen doping significantly improves the catalytic kinetics and the surface area. Density functional theory calculations reveal that the improved HER and OER kinetics is not only due to the synergistic effect of bi-metal and bi-valence, as well as the introduction of defects such as oxygen vacancies, but also it more depends on the shortened bond length between the nitrogen N3− atoms and the metal atoms, and the increased electron density of the metal atoms attached to the N3− atoms. In other words, the change of lattice parameters caused by nitrogen doping is more conducive to the catalytic enhancement than the synergistic effect brought by bi-metal. This study provides an experimental and theoretical reference for the design of bi-functional electrocatalytic nanomaterials.

Structural properties of CoxCu1−xFe2O4 solid solution**

Abstract Crystallography information files (CIF) were designed formed CoxCu1−xFe2O4 solid solution with the substitution factor x=0 to 1 with an increment of 0.1 depending on Vegard's law by using crystallography software. The effect of the substitution factor has been studied on some parameters and properties of the Co-Cu ferrite system, such as the effect of substitution factor on the lattice parameter, the volume of unit cell, and the density of the unit cell. Also, XRD patterns were estimated by crystallography software depending on the mathematical models of XRD. The XRD results showed a slight shift in the peak position varying with the substitution factor, these are due to the change in lattice parameter caused by the substitution of ions with different ionic radii. XRD also showed an increment in peak intensity varying with the substitution factor, that's due to an increase in the concentration of Cu which led to an increase in the density of electrons.

Structural and photocatalytic dye degradation properties of Li2Mn0.95Ru0.05O3

In the present study, we have documented the structural and dye degradation properties of Li 2 Mn 0.95 Ru 0.05 O 3 synthesized using solid state synthesis method. X-ray diffraction studies show the single phase composition with Ru doping at Mn site in Li 2 MnO 3 and change in lattice parameters. Raman peaks show the shift in Mn-O stretching mode for Li 2 MnO 3 towards lower wave number and A g stretching mode of Mn – O vibrations show multiple peaks in Li 2 Mn 0.95 Ru 0.05 O 3 . Soft X-ray absorption spectroscopic studies show the presence of mixed valences of Ru +4 /Ru +5 in Li 2 Mn 0.95 Ru 0.05 O 3 . The amount 5 mg of Li 2 Mn 0.95 Ru 0.05 O 3 degrades 5 ml of (10 mg/L) concentrated methylene blue solution in ∼ 8 min of exposure in visible light. In these studies, we have explored new reusable catalyst which uses redox interaction of Ru-Mn to degrade methylene blue dye solutions.

Effect of Static Magnetic Field on Nucleation of Cobalt Nitrate Hexahydrate

Abstract Freezing of cobalt nitrate hexahydrate (CoNHH) under a static magnetic field was studied at three different magnetic field intensities. The results show that the magnetic field has a significant effect when the sample enters the solid phase and reduces the stochastic behaviour of the nucleation. Thermal properties investigated using thermogravimetric and differential thermal analysis revealed the shift to a lower temperature for the onset of decomposition and melting temperature after the freeze-thaw in a magnetic field. Besides that, we observed a significant change in the FT-IR peaks that might indicate the emergence of cobalt nitrate with a lower hydrate number, a phase separation effect, and the evaporation of NO3- ions. Refinement of the XRD spectra shows a single phase of CoNHH with a slight lattice parameter change after the freezing-thawing in a magnetic field. The freezing behaviour of CoNHH was compared to that observed previously for water, a salt solution, and an ethylene glycol solution. We investigated the relationship of the freezing behaviour with hydrogen bonding and magnetic properties and its impact on the change in the Gibbs free energy. The results of this study are important to optimise the performance of CoNHH as latent thermal energy storage.

Structure and thermal diffusivity of SiC-NbC ceramics

The structure and thermal diffusivity of SiC - NbC ceramic materials are investigated. It is shown that with a change in the composition in sintered ceramics, the lattice parameter changes, and also in the near-contact region there is a mutual diffusion of silicon and niobium. This indicates the formation of solid solutions. As the niobium carbide content and temperature increase, the thermal diffusivity of SiC - NbC ceramic materials decreases.

Structural Study of MgyAl(8+x-2y)/3O4-xNx (0 < x < 0.5, 0 < y < 1) Spinel Probed by X-ray Diffraction, 27Al MAS NMR, and First-Principles Calculations.

The deep understanding of the crystal structure and composition-structure relationship is important for modifying and designing solids to obtain functional materials with customized properties. However, because of multiple compositions and complex structures in some spinel solid solutions, the composition-structure relationship is unknown, or becomes very complicated and difficult to be controlled. In this work, the solid-state magic-angle spinning nuclear magnetic resonance (MAS NMR) technique and powder X-ray diffraction (XRD) Rietveld refinement were combined to characterize the crystal structure of quaternary disordered MgyAl(8+x-2y)/3O4-xNx solid solutions in detail, which was supported by the first-principles density functional theory calculations. Diffraction data indicate that Mg ions preferentially enter the tetrahedron structure in MgyAl(8+x-2y)/3O4-xNx solid solutions because the sum of the bond valence in tetrahedron is closer to the atomic valence of Mg. With the compositional change, the coordination polyhedra in the crystal structure will also adjust the volume according to the changes in lattice parameter, anion parameter, and inversion parameter. In addition, the populations, chemical shifts, and quadrupole coupling constants of Al located in different coordinated environments of the solid solutions were detected through the simulation and integration of 27Al MAS NMR spectra, which were related to the structural parameters by the bond valence method. It turns out that 27Al MAS NMR parameters are highly sensitive to the subtle changes in the local environment of Al caused by the preferential occupation of Mg in the tetrahedron. These results provide deep insights into the crystal structural details of novel spinel materials with multiple disorders.

Impact of Local Separation on the Structural and Electrochemical Behaviors in Li2MoO3LiCrO2 Disordered Rock‐Salt Cathode Material

AbstractLi‐excess disordered rock‐salt oxides have emerged as a promising group of cathode materials for Li‐ion batteries. However, the real cation distribution and short‐range order of various disordered oxides have not been fully determined, making it difficult to understand their actual structures and reaction processes. Here, Li1.233Mo0.467Cr0.3O2 (LMCO), as a cathode material that undergoes a unique in situ cation‐disorder is investigated. Through synchrotron‐ and lab‐based multiscale characterizations, it is observed that the as‐prepared material has separate domains resembling Li2MoO3 and LiCrO2 even in a single‐phase bulk crystal structure. The Mo/Li‐rich and Cr/Li‐poor domains are maintained even after significant cation‐disorder. The formation and dissociation of short MoMo bonds along with a unique MoO6 distortion in Mo/Li‐rich domain of disordered LMCO leads to minimal lattice parameter changes during Mo redox reactions. This phenomenon is intensified when the structure becomes more disordered owing to the dissipation of anisotropy. In disordered LMCO, the Mo4+/6+ redox is highly reversible, while Cr3+/4+ redox is not. Finally, based on the local separation that induces different 0‐TM diffusion abilities according to the different domains in disordered LMCO, the mechanisms of the domain‐dependent kinetics, asymmetric Li+ diffusion, and linked hysteresis/degradation processes are explained.

Irradiation response of Al2O3-ZrO2 ceramic composite under He ion irradiation

The dense Al2O3-ZrO2 ceramic composite prepared by spark plasma sintering was irradiated by 500 keV He ions with different fluences and temperatures. The microstructural evolution and mechanical properties were investigated. The results showed that peak broadening and shifts at RT revealed by GIXRD and Raman are associated with damage induced microstrain and formation of point defects. The recovery at 500 °C suggested the reduction of irradiation induced damage. Compared with α-Al2O3, t-ZrO2 exhibited a reverse trend in lattice parameters change and lattice expansion. Many helium bubbles with oblate and ribbon-like shape were mainly formed in α-Al2O3 grains at He concentration peak at 1.0 × 1017 ions/cm2. With increasing of fluence at RT, ribbon-like helium bubbles developed into microcracks at 4.0 × 1017 ions/cm2. Though evident structural changes, no full amorphization was observed at 4.0 × 1017 ions/cm2. Formation of ribbon-like bubbles and microcracks is the main mechanism for degradation of mechanical properties of irradiated Al2O3-ZrO2 composite.