Increase In Lattice Parameter Research Articles

Microstructure evolution and a new mechanism of B2 phase on room temperature mechanical properties of Ti-47Al-2Cr-2Nb alloy prepared by hot isostatic pressing

The formation of B2 phase was adjusted via various hot isostatic pressing processes in Ti-47Al-2Cr-2Nb alloy. The microstructure evolution and a new mechanism of B2 phase on room temperature mechanical properties was investigated by BSE, EBSD and TEM in detail. The result shows that the formation of B2 phase leads to Cr element content decrease in γ matrix phase, which results in lattice parameter increase, namely the c/a ratio of γ matrix phase. Finally, at room temperature the mechanical properties of Ti-47Al-2Cr-2Nb alloy deteriorates.

Strongly Iridescent Hybrid Photonic Sensors Based on Self-Assembled Nanoparticles for Hazardous Solvent Detection.

Facile detection and the identification of hazardous organic solvents are essential for ensuring global safety and avoiding harm to the environment caused by industrial wastes. Here, we present a simple method for the fabrication of silver-coated monodisperse polystyrene nanoparticle photonic structures that are embedded into a polydimethylsiloxane (PDMS) matrix. These hybrid materials exhibit a strong green iridescence with a reflectance peak at 550 nm that originates from the close-packed arrangement of the nanoparticles. This reflectance peak measured under Wulff-Bragg conditions displays a 20 to 50 nm red shift when the photonic sensors are exposed to five commonly employed and highly hazardous organic solvents. These red-shifts correlate well with PDMS swelling ratios using the various solvents, which suggests that the observable color variations result from an increase in the photonic crystal lattice parameter with a similar mechanism to the color modulation of the chameleon skin. Dynamic reflectance measurements enable the possibility of clearly identifying each of the tested solvents. Furthermore, as small amounts of hazardous solvents such as tetrahydrofuran can be detected even when mixed with water, the nanostructured solvent sensors we introduce here could have a major impact on global safety measures as innovative photonic technology for easily visualizing and identifying the presence of contaminants in water.

Pyrochlore structure and spectroscopic studies of titanate ceramics. A comparative investigation on SmDyTi2O7 and YDyTi2O7 solid solutions

Considering the features in changing the structure and properties of rare earth titanates pyrochlores, the substituted Dy2Ti2O7 may be very attractive for various applications. Effect of Sm and Y substitution on the structural properties of Dy2Ti2O7 ceramic was established. These ceramics were prepared by solid-state reaction and characterized by X-ray diffraction and Raman spectroscopy. Both analysis show that YDyTi2O7 with the pyrochlore structure is obtained after heating at 1400°C, but SmDyTi2O7 has already formed after sintering at 1200°C. SEM images revealed that the average grain size was increased with the increase of heating temperature, and an un-homogeneous grain growth was detected. The average size was about 37nm and 135nm for the SmDyTi2O7 and YDyTi2O7 particles, respectively. Structural Rietveld refinements indicate that all prepared ceramics crystallize in cubic structure with space group of Fd3m. The refined cell parameters demonstrate an almost linear correlation with the ionic radius of Ln3+. The vibrational spectra revealed that the positions of bands are sensitive to the Ln3+-ionic radius, and the TiO bond strength decreased linearly with the increase of cubic lattice parameter. Raman spectra indicate that the wavenumber of OTiO bending mode is considerably shifted to lower region with increasing in mass of the Ln atom. This paper provides solid foundations for additional research of these solid solutions, which are very attractive for different fields as promising catalytic compounds for combustion applications or as frustrated magnetic pyrochlore ceramics.

Influence of Ba substitution, Fe doping and annealing effect on magnetic and optical properties of Sr0.9Ba0.1Ti1−xFexO3 nanoparticles prepared by the hydrothermal method

Sr0.9Ba0.1Ti1−xFexO3 (x = 0, 0.05, 0.10 and 0.15) nanoparticles were synthesized by the hydrothermal method. Influence of Ba substitution, Fe doping and annealing effect on magnetic and optical properties of these samples was studied. X-ray diffraction (XRD) results indicated a cubic perovskite structure with the increase of lattice parameter and crystallite sizes of all samples owing to the substitution with a larger ionic radius of Ba and Fe ions at Sr and Ti sites in the crystal structure, respectively. Ba substitution could result in a pure phase of annealed samples. Magnetization of as-prepared samples measured at room temperature by vibrating sample magnetometer (VSM) revealed a diamagnetic and paramagnetic behavior of undoped and Fe-doped samples, respectively. Interestingly, annealing could significantly affect the magnetic behavior of all samples i.e. undoped sample showed paramagnetic behavior, whereas all Fe-doped samples exhibited ferromagnetic behavior with the enhancement of saturation magnetization (Ms) from 0.28 to 0.78 emu/g owing to the increase of Fe content. Ferromagnetic behavior was suggested to originate from Fe3+−VO−Fe3+ coupling in the crystal structure due to the promotion of oxygen vacancy (VO) as confirmed by the X-ray photoelectron spectroscopy (XPS) results. Moreover, coercivity (Hc) and remanent magnetization (Mr) also increased from 110–442 Oe to 0.01–0.15 emu/g, respectively. The determined optical band gaps of annealed samples determined by ultraviolet–visible (UV–vis) spectroscopy were found to decrease from 3.3907 to 3.3469 eV with increasing Fe content.

Stabilization of Sr-rich ultrathin epitaxial films of La2-xSrxCuO4

Varying the level of Sr in La2-xSrxCuO4 produces a wide array of electrical properties, spanning metallic, semiconducting, insulating, and superconducting. While the system has been extensively studied, ultrathin films with high Sr content have not been reported. Using oxide molecular beam epitaxy, ultrathin La2-xSrxCuO4 films (0 < x < 1) were grown to explore the ability to stabilize high Sr content in such films. The resulting crystallinity, surface roughness, and electrical properties of the samples are studied. The films are single crystalline with low surface roughness. Increasing the Sr content from x = 0 to x = 1.0 causes an initial increase and subsequent decrease in the c-axis lattice parameter and the surface roughness as a function of doping. The films exhibit analogous electrical properties to their bulk and thicker film counterparts. The ability to create ultrathin La2-xSrxCuO4 films at high Sr levels shows promise for inducing unexpected electric properties through dopant modulation effects, such as cation ordering, digital superlattices, and atomically precise interfaces.

Structural, magnetic and magnetocaloric properties of Fe17−xMnxPr2 compounds

Polycrystalline Fe17−xMnxPr2 (x = 0–8) compounds were analyzed by x-ray diffraction (XRD) and vibrating sample magnetometer (VSM) measurements. The results show that Fe17−xMnxPr2 compounds exhibited the rhombohedral Th2Zn17-type crystal structure. The lattice parameter and unit cell volume increase with Mn content. The magnetic transition is a typical second-order transition near the TC. The Curie temperature (TC) of Fe17−xMnxPr2 compounds decrease sharply in the range of 300–27 K as the Mn content increase. The maximum magnetic entropy change (∣-ΔSM∣) for Fe17−xMnxPr2 compounds is 6.25 J · kg−1·K−1 in a field of 5 T for the compounds with x = 0. The thermal hysteresis for Fe17−xMnxPr2 are 6.59 K at x = 0 and 1.36 K at x = 8, which reduces with the increase in Mn content.

Synthesis, Short-Range Structure and Hydration Processes of Oxyhalides Ba&lt;sub&gt;2&lt;/sub&gt;InO&lt;sub&gt;3&lt;/sub&gt;X (X = F, Cl, Br) with Ruddlesden-Popper Structure

The oxyhalides Ba2InO3F, Ba2InO3Cl, and Ba2InO3Br were synthesized using the solid state method. It was found that the increasing of halide ion radius leads to the increase of lattice parameters and also caused to redistribution of indium-oxygen bond lengths. The possibility of water uptake was proved by thermogravimetry measurements. The presence of different forms of oxygen-hydrogen groups in the structure of hydrated oxyhalides was indicated by infrared spectroscopy.

Immobilization of selenate in cancrinite using a hydrothermal method

Because of the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, radioactive species were leaked out, including selenium isotopes (79Se). Developing a stable matrix that is suitable for longterm storage is necessary for the decommissioning process of the FDNPP. In the present work, the co-precipitation of SeO42− in cancrinite/sodalite as a potential stable matrix was investigated at various reaction times using a hydrothermal method. Over time, the SeO42− contents in the solid products gradually increased. The XRD patterns revealed that the reaction produced multi-phased precipitates, which were zeolite Na (P), sodalite, and cancrinite. As the SeO42− amount increased, the solid products were transformed to cancrinite. The calculated lattice parameter of sodalite and cancrinite showed an increase in lattice parameter a for sodalite and cancrinite, suggesting SeO42− incorporated into the sodalite/cancrinite structure. XRD, SEM, FTIR, 27Al-NMR, and 29Si-NMR results revealed the phase transformation of the solid products over time. Four stages of the co-precipitation mechanism are proposed, including the formation of zeolite P (Na), hydroxylation of zeolite P (Na), the formation of sodalite, and cancrinite reprecipitation.

Effect of TiB2 nano-inclusions on the thermoelectric properties of boron rich boron carbide

Boron carbide has exceptional thermoelectric properties due to its unique crystal structure. The effects of nano-TiB2 inclusions on the thermoelectric properties of boron rich boron carbide is presented here. Boron rich boron carbide-TiB2 composites were prepared in-situ by sintering of wet ball milled B, B4C and nano-TiO2 powders through Spark Plasma Sintering (SPS) at 1900 °C under 50 MPa pressure. Five different compositions of the composite were prepared- with 1, 2.5, 5, 7.5 and 10 wt.% TiO2. The dependence of densification and thermoelectric properties on TiO2 content were studied. The microstructure was observed through Field Emission Scanning Electron Microscope (FESEM) and phases were analyzed using X-ray diffraction (XRD). Relative densities of 94.8% to 99. 3% were obtained and an almost homogeneous distribution of TiB2 was observed. The electrical property was found to be high for sample with 1 wt% TiO2 and reduced subsequently with higher wt% of TiO2. The overall dimensionless figure of merit was found to be higher than B4C-TiB2 composites, due to the formation of boron rich phase but the effect of TiO2 was not significant. The increase in lattice parameter of boron carbide phase for different TiO2 amounts added showed that the final composition of the composite depends on the amount of TiO2 added.

Effect of Ni+2 Substitution on Structural and Electrical Behaviour of Nano-Size Cadmium Ferrites

This report presents the synthesis of Nickel doped Cadmium Spinel ferrite (Cd1-xNixFe2O4) in which x varies from 0.4 to 0.6 were synthesized by Sol-gel micro oven method. Analysis confirmed the formation of monophasic Cd1-xNixFe2O4 powder with an average particle size in nanometer after synthesis at 800°C with urea, as a reducing agent. The sample powder characterized by using X-Ray diffraction (XRD), Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), Electrical conductivity. The XRD results confirm the cubical spinel phase formation with the partial size 14 nm to 19 nm. The results showed that the lattice parameter increase with increasing Cadmium concentration. TEM confirms the formation of particle size in the range in nm.SEM analysis also support the TEM result. The temperature dependant electrical conductivity of all samples shows semiconducting behavior.

Evidence of extended cation solubility in atomic layer deposited nanocrystalline BaTiO3 thin films and its strong impact on the electrical properties.

Thin films of ≈50 nm thickness with Ba/Ti-ratios ranging from 0.8 to 1.06 were prepared by depositing alternating layers of Ba(OH)2 and TiO2. Annealing at 750 °C promoted the solid-solid transformation into polycrystalline BaTiO3 films containing a mixture of the perovskite and the hexagonal polymorphs with average crystallite sizes smaller than 14 nm and without impurity phases. This, together with an increase of the cubic lattice parameters for Ba-rich films, suggests an extended metastable solubility range for the perovskite-phase in these nanocrystalline thin films on both sides of the stoichiometric composition. Mapping of the cation distribution utilizing energy-filtered transmission electron microscopy corroborates defect accommodation within the BaTiO3 grains. While the cation off-stoichiometry in thermodynamic equilibrium is negligible for BaTiO3, the metastable extended solubility range in the thin films can be directly correlated to the low annealing temperature and nanocrystalline nature. The leakage current behavior can be explained by the formation of Schottky defects for nonstoichiometric films, and the cation ratio has a distinct impact on the dielectric properties: while excess-BaO has a marginal detrimental effect on the permittivity, the dielectric constant declines rapidly by more than 50% towards the Ti-rich side. The present findings highlight the importance of compositional control for the synthesis of nanocrystalline BaTiO3 thin films, in particular for low annealing and/or deposition temperatures. Our synthesis approach using alternating layers of Ba(OH)2 and TiO2 provides a route to precisely control the cation stoichiometry.

Structural, optical, thermoelectrical, and magnetic study of Zn1‐xCoxO (0 ≤ x ≤ 0.10) nanocrystals

AbstractIn this work, we have prepared Co‐doped ZnO nanocomposites by zinc nitrate and cobalt sulfate as new precursors via the coprecipitation method and the samples were followed to identify the morphological, optical, structural, and magnetic properties. The XRD patterns revealed the crystalline nature of nanoparticles with hexagonal wurtzite structures, which meant that Co impurity did not disturb the structure of pure ZnO and the minimum crystallite size of nanoparticles was calculated to be around 37 nm. The XRD patterns also showed the lattice parameter increase owing to the incorporation of a Co dopant. The TEM results revealed the sphere‐like particles whose size varied between 56 and 88 nm in diameter at a 4% level of impurity. DRS analysis identified that the band gap energy decreased from 3.18 eV for the pure substance to 2.36 eV for the 10% impure substance. VSM analysis exhibited that the saturation magnetization value increased to 8.4 × 10−3 emu/g for the highest Co content of 10%, which indicated the ferromagnetic behavior of NPs.

Modulation of structural properties of Sn doped ZnO for UV photoconductors

Sn doped ZnO thin films are synthesized in order to introduce excess charge carriers depending on various doping densities which modifies the surface, particle size and planar orientation of ZnO crystals. From the view of change in optical properties it is observed that with increasing Sn content, the increase in bandgap takes place which results into improved photo response as compared to pure ZnO. A highly-textured orientation in (002) direction has been observed with the relative increase in lattice parameters. Depending on Sn doping, photoconductor performance has been examined and an optimum Sn wt.% doping level is investigated to achieve maximum photo response in terms of sensitivity, ON/OFF ratio, spectral responsivity and detectivity. The maximum ON/OFF ratio and sensitivity are obtained to be 1.2×105 and 1.0×105 for 7 wt.% Sn doped ZnO sample. Similarly, the highest detectivity and spectral responsivity is obtained to be 1.7×1010 Jones and 1.56 A/W for 7 wt.% Sn-ZnO metal-semiconductor-metal photoconductor respectively.

Epitaxial growth of high quality SrFeO3 films on (001) oriented (LaAlO3)0.3(Sr2TaAlO6)0.7

The growth of strontium ferrite SrFeO3 films with a stoichiometry of (1:1:3) is challenging as the unstable Fe4+ oxidation state favors the formation of O vacancies. Here, we report the layer by layer growth of SrFeO3 on (001) oriented (LaAlO3)0.3(Sr2TaAlO6)0.7 using ozone assisted molecular beam epitaxy. Upon cooling from room temperature, the film's resistivity decreased from 750 μΩ cm to 150 μΩ cm, as low as the best single crystals, with two identifiable transition points near 110 K and 60 K in resistivity measurements, being hysteretic between cooling and warming through the 60 K transition. During various annealing steps, the low temperature resistivity changes by orders of magnitude, accompanied by an increase in the c-axis lattice parameter. The hysteresis near 60 K persists for a wide range of annealing conditions. We have identified conditions under which changes due to annealing can be reversed. We attribute changes in resistivity and the out of plane lattice parameter to the reversible movement of oxygen ions in the lattice. SrFeO3 may be a promising material for resistive memory applications based upon the control of oxygen vacancies.

Electrical transport properties of sputtered Nd2−xCexCuO4±δ thin films

Thin films of the electron-doped high-temperature superconductor Nd2−xCexCuO4±δ have been deposited by dc sputtering technique on (100) SrTiO3 substrates. A tuning of the oxygen content in the as-grown non-superconducting samples has been achieved by changing the oxygen partial pressure during the growth in the Argon sputtering atmosphere. All samples show the superconducting transition after a suitable two-step thermal treatment in an oxygen-reducing environment. Structural and electrical transport properties on the as-grown as well as on the superconducting samples have been investigated. We find that the structural properties are consistent with a deficiency of the oxygen content with respect to optimally annealed samples, and that the transition to the superconducting phase is always accompanied by an increase of the c-axis lattice parameter. Measurements of the Hall coefficient RH as a function of temperature and in the normal state of our epitaxial films are presented and discussed. RH results negative for all the films regardless of the oxygen content and it decreases with the temperature. In particular, the Hall coefficient is only about 10% lower than the value measured in the as-grown oxygen-deficient phase, in contrast to the results reported in literature. The removal of the excess oxygen in as-grown samples seems not to be the only requirement for triggering the superconducting transition in electron-doped compounds. The microstructural change associated with the increase of the c-axis parameter in our deoxygenated samples could help in understanding the microscopic mechanism underlying the reduction process of n-type superconductors, which is still under debate.

Ab-initio studies of the structural, electronic, optical and magnetic properties of DyMg intermetallic compound

Abstract Structural, electronic, optical and magnetic properties of DyMg intermetallic compound are calculated by using the full potential linearized augmented plane wave (FP-LAPW) method employing density functional theory (DFT). The obtained optimized equilibrium lattice constant in stable structure of DyMg (B2 phase) with spin polarized calculations is 7.107 Bohr and that without spin polarized calculations is 7.115 Bohr. The electronic band structure and density of states plots show metallic character of DyMg. The energy-dependent components of dielectric function, refractive index, extinction coefficient, absorption spectra, optical conductivity, energy loss spectra and reflectivity are reported in the energy range 0–20 eV. In DyMg maximum absorption is observed in the range 4–11 eV. The highest optical conductivity peak is observed near 0.78 eV (1589.5409 nm) and maximum energy loss occurs at 11.90 eV which corresponds to ~2.8 Hz in ultraviolet region. The obtained total magnetic moment shows that its value decreases with the increase in lattice parameter.

Metal-to-insulator transition and its effective manipulation studied from investigations in V1-xNbxO2 bulks

Nb doping effects on crystalline structure, transport transition and magnetic properties are investigated for V1-xNbxO2 (0 ≤x≤ 5%) bulks. At room temperature, doping does not change structure of monoclinic phase but causes an increase in lattice parameters for the range of x≤ 3%, further doping leads to a structure transition to rutile tetragonal phase. Each sample simultaneously displays a transition to insulating behavior and a sharp decrease in susceptibility below an almost same critical temperature (Tc). The Tc is shown to shift from ~ 340K at x = 0 to ~ 277K at x = 5% at a rate of ~ −13K/at%. It is argued that the observed sharp decrease in susceptibility originates from the formation of V-V dimers with spins in anti-parallel, while the insulating behavior below Tc is due to the electron movement from one dimerized state to another with the help of Variable-Range-Hopping mechanism. Furthermore, it is proposed that doping by larger cations, which would suppress the formation of dimers, can be used to manipulate the metal-insulator transition to lower temperatures.

Effect of Molybdenum Incorporation on the Structure and Magnetic Properties of Cobalt Ferrite

We report on the effect of molybdenum (Mo) incorporation on the crystal structure, surface morphology, Mo chemical valence state, and magnetic properties of cobalt ferrite (CoFe2O4, referred to CFO). Molybdenum incorporated cobalt ferrite (CoFe2–xMoxO4, referred to CFMO) ceramics were prepared by the conventional solid-state reaction method by varying the Mo concentration in the range of x = 0.0–0.3. X-ray diffraction studies indicate that the CFMO materials crystallize in inverse spinel cubic phase. Molybdenum incorporation induced lattice parameter increase from 8.322 to 8.343 A coupled with a significant increase in density from 5.4 to 5.7 g/cm3 was evident in structural analyses. Scanning electron microscopy imaging analyses indicate that the Mo incorporation induces agglomeration of particles leading to larger particle size with increasing x(Mo) values. Detailed X-ray photoelectron spectroscopic (XPS) analyses indicate the increasing Mo content with increasing x from 0.0 to 0.3. XPS confirms that the...

Adsorption of chromium (VI) on bismuth incorporated cobalt ferrite nanoparticles

CoFe2O4 and CoFe1.9Bi0.1O4 nanoparticles are prepared by combustion method utilizing glycine. Pure phase formation is affirmed from the X-ray diffraction and Fourier transform infrared spectroscopy. From the Scanning electron microscopy and Energy Dispersive X-ray spectroscopy, morphology and presence of respective elements in the synthesized compounds are analyzed. Decrease in average crystallite size and increase in lattice parameter is observed due to bismuth substitution. The adsorption capability of CoFe2O4 and CoFe1.9Bi0.1O4 are tested for one of the toxic environmental pollutants chromium (VI). The adsorption efficiency with respect to adsorbent quantity, concentrations of adsorbate and pH are studied. The substitution of the bismuth increased the adsorption capability of cobalt ferrite nanoparticles.

Characterization of Dispersion Strengthened Copper Alloy Prepared by Internal Oxidation Combined with Mechanical Alloying

Cu-3.6 vol.% Al2O3 dispersion strengthened alloy was prepared by mechanical alloying (MA) of internal oxidation Cu-Al powders. The lattice parameter of Cu matrix decreased with milling time for powders milled in argon, while the abnormal increase of lattice parameter occurred in the air resulting from mechanochemical reactions. With a quantitative analysis, the combined method makes residual aluminum oxidized completely within 10-20 h while mechanical alloying method alone needs longer than 40 h. Lamellar structure formed and the thickness of lamellar structure decreased with milling time. The size of Al2O3 particles decreased from 46 to 22 nm after 40 h milling. After reduction, core–shell structure was found in MAed powders milled in the air. The compacted alloy produced by MAed powders milled in the argon had an average hardness and electrical conductivity of 172.2 HV and 82.1% IACS while the unmilled alloy’s were 119.8 HV and 74.1% IACS due to the Al2O3 particles refinement and residual aluminum in situ oxidization.