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Structural, optical and magnetic properties of Fe-doped CeO2 samples probed using X-ray photoelectron spectroscopy
No full textThe present study reports the effect of Fe-doping on the structural, optical, magnetic and electronic properties of polycrystalline CeO2 (for 5 and 10% doping concentration of Fe-cation) samples synthesized by low-temperature solid-state reaction method. Rietveld refinement of the X-ray diffraction patterns establishes fluorite-type face-centred cubic structure of the Fe-doped CeO2 samples and also confirms successful incorporation of Fe ions in the CeO2 lattice. The UV-Vis-NIR absorption spectra displays reduce band gap energy with rising fluency of Fe-ions, which confirm red shifts in the Fe-doped CeO2 samples. The electronic structure of the pure CeO2 and Fe-doped CeO2 polycrystalline samples have been investigated by X-ray photoemission spectroscopy (XPS). The XPS spectra of Ce 3d reveals the reduction of Ce4+ to Ce3+ states Fe-doped CeO2 samples, which are well supported by the Fe 2p and O 1s spectra. Pure polycrystalline CeO2 displays diamagnetic behaviour at room temperature. Interestingly, 5% Fe-doped CeO2 sample displays S-shape hysteresis loop and establishes room temperature ferromagnetism, whereas, 10% Fe-doped CeO2 sample shows weak ferromagnetic behaviour. A decrement is observed in the magnetization on increasing the doping concentration. The possible reason for ferromagnetism in the Fe-doped CeO2 samples may be incorporation of oxygen vacancies, which are further discussed using F-centre exchange mechanism and double exchange interaction. These experimental findings offer potential opportunities for spintronics and optoelectronics applications by integrating them into device structures and evaluating their performance as a function of their material properties
Magnetostructural properties and electric transport in Mn48+xCr3-xNi38Sn11 (x=0, 1) ribbons: Mn/Ni ratio versus Cr doping
No full textWe report the structural, electrical and magnetic properties of Cr substituted Mn48+xCr3-xNi38Sn11 (x = 0 and 1) Heusler ribbons synthesised by melt spinning of the arc-melted bulk alloy. Composition analysis employing EDAX reveals same Ni and Sn concentrations with difference in the Mn/Cr ratio in both the ribbons. Mn48Cr3Ni38Sn11 ribbons have pure cubic-austenite phase whereas Mn49Cr2Ni38Sn11 show a mixture of the dominant cubic-austenite with traces of the orthorhombic-martensitic phase as confirmed by X-ray analysis. Ribbons having higher Cr content show (i) pure cubic austenite structure (L2(1) type) at room temperature (ii) canonical paramagnetic-ferromagnetic transition in the austenite phase and (iii) metallic temperature dependence of resistivity. Small decrease in the Cr content produces dramatic changes in the structure-property profile. Hence ribbons having lower Cr content show (i) a mixture of cubic and orthorhombic phases, (ii) paramagnetic-ferromagnetic transition in the austenite phase above the room temperature which is followed by strongly hysteretic martensitic transition and (iii) metal-like temperature dependence of resistivity followed by typical martensitic resistivity and re-entrant metallic behaviour in the lowest temperature region. AC susceptibility measurements show absence of a spin glass like behaviour in Mn48Cr3Ni38Sn11 while the lower Cr variant demonstrates nearly ideal spin glass like characteristics. The high sensitivity of structure-property correlation towards small compositional variations is attributed to the twin effect of Cr substitution at Mn sites and the Mn/Ni ratio
Investigating the influence of charge transport on the performance of PTB7:PC71BM based organic solar cells
No full textA key challenge for researchers in the field of organic solar cells (OSCs) is to develop a physical model for a device that correctly describes the charge carrier transport phenomenon. In this article, an analytical study on the charge carrier transport phenomenon in an OSC is reported, which expresses a balance between free charge carrier generation and recombination in low mobility PTB7:PC71BM blend layers. First, the current density-voltage (J-V) data for the fabricated OSC were extracted from experiments by varying the incident power light intensity (IPL) and then analysis through theoretical simulation was used to quantify the dominant interface recombination parameters limiting the device's performance. It was found that although the generation of free charge carriers increased at higher IPL values, the performance of the device remained low due to poor electrical transport properties which resulted in a considerable accumulation of generated charge carriers in the active layer. Therefore, it has become important to work out the complex relation between charge carrier mobility, exciton-recombination dynamics and the overall electrical performance parameters in a single framework. This article explains the influence of incident power light intensity and charge carrier mobility on performance parameters, which limits the power conversion efficiency (PCE) of the OSC. The presented analysis could be helpful in optimizing the architecture of future devices to increase the PCE of OSCs
Influence of temperature and A1/N ratio on structural, chemical & electronic properties of epitaxial A1N films grown via PAMBE
No full textThe present article investigates structural, chemical and electronic properties of epitaxial AlN films grown via plasma assisted molecular beam epitaxy on atomically clean Si (1 1 1) substrates. An inclusive optimization process of growth parameters by varying the substrate temperature (790-825 degrees C) and Al/N (III/V) ratio is demonstrated. The AlN film grown with optimized parameters yielded an FWHM of 24.6 arcmin, crystallite size of 11.6 nm, screw dislocation density of 4.43 x 10(9)/cm(2) and a surface roughness of 3.11 nm. Besides, the chemical states and electronic structure analysis displayed absence of remnant metallic aluminium and native surface oxide (-2%) with Fermi level (3.0 eV) pinned near its intrinsic value. A growth mechanism has been proposed for the optimized growth of AlN. Further, the high quality AlN film can potentially be used for the fabrication of smart optoelectronics for deep UV application and field emission devices
Highly efficient field emission properties of radially aligned carbon nanotubes
No full textHere, we report extraordinary field emission properties from one pot synthesized aligned carbon nanotubes endowed with related Fe nanoparticles (NPs). The CNT configuration is in the form of a carbon hollow cylinder (CHC) with CNTs radially aligned towards the CHC axis. The structure generates electron field emission properties such as an ultralow turn on field (0.35 V m(-1) at 10 A cm(-2)), a low threshold field (0.41 V m(-1) at 100 A cm(-2)) and a high field emission current density (7.71 mA cm(-2) at 0.78 V m(-1)). It also exhibits multi-fold improvement in the field enhancement factor (1.34 x 10(4)) with highly stable current emission at 100 A measured for 14 h. No post synthesis treatment is required for enhanced field emission characteristics. The growth related Fe NPs assist in lowering the work function and hence enhancing the field emission properties. The possibility of assembling nano-structured field emitters into macroscale architectures suggests new prospects for next generation three dimensional electron sources
Na incorporated improved properties of Cu2ZnSnS4 (CZTS) thin film by DC sputtering
No full textPolycrystalline CZTS is an emerging candidate for photovoltaic, optoelectronic and gas sensing applications due to its availability and environment-friendly nature and also favorable light harvesting properties. The properties of polycrystalline materials depend upon the grain size. Grain size can be increased by increasing the annealing time, but this may lead to increased cost and also evaporation of certain volatile and low melting materials. Adding some growth enhancing elements is one of the novel methods to improve the grain size of polycrystalline materials. In this study, we studied Na induced CZTS film prepared by sputtering method. Before sulfurization, NaF (similar to 30 nm) thin layer was deposited on deposited CZT film using thermal evaporation method. UV-Visible, XRD and SEM/EDS analysis were used for studying optical, structural, elemental and morphological properties of CZTS films
Bio-functionalization of grade V titanium alloy with type I human collagen for enhancing and promoting human periodontal fibroblast cell adhesion - an in-vitro study
No full textSurface modification of medical grade V titanium alloy (Ti-6Al-4V) with biomolecules is an important and vital step for tailoring it for various biomedical applications. Present study investigates the influence of type I human collagen (T1HC) bio-conjugation through a three stage process. Polished grade V titanium alloy discs were functionalized with free -OH group by means of controlled heat and alkali treatment followed by coating of 3-aminopropyltriethoxy (APTES) silane couplingagent. T1HC were bio-conjugated through 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide hydrochloride N-hydroxysuccinimide (EDC-NHS)coupling reaction. At each stage, grade V titanium alloy surfaces were characterized by atomic force microscopy (AFM), scanning electronmicroscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and Xrayphotoelectron spectroscopy (XPS). FTIR and XPS studies confirms the covalent attachment of APTES with titanium alloy surface while terminalamine groups of APTES remained free for further attachment of T1HC through covalent bond. Aqueous stability of bio-conjugated titanium discsat various pH and time intervals (i.e. at pH of 5.5, 6.8 and 8.0 at timeinterval of 27 and 48 h) confirmed the stability of T1HC bioconjugated collagen on titanium surface. Further human periodontalfibroblast cell line (HPdlF) culture revealed enhanced adhesion on the T1HC bio-conjugated surface compared to the polystyrene and polishedgrade V titanium alloy surface
Carbon material-nanoferrite composite for radiation shielding in microwave frequency
No full textIn sequence to permit electronic gadgets to coexist without maleficent electromagnetic interference (EMI) it is essential to evolve new absorbing and shielding materials with good performance. These technological fields demand not only efficient shields but also materials that meet specific criteria for each engineered design. For example chemical and corrosion resistance, lightweight, flexibility, tunable morphology, processing easiness and inexpensiveness are required. The concerned work present BF/EG composite was appreciated for these applications. The Microwave absorption characteristic were find out in the frequency range 8-12 GHz. Shielding effectiveness of BF/EG composite was obtained 52.4 dB. The material is found to have good microwave absorption materials for EMI shielding applications
Crystal structure, dielectric, magnetic and improved magnetoelectric properties of xNiFe(2)O(4)-(1-x)Na0.5Bi0.5TiO3 composites
No full textMagnetoelectric (ME) composites of NiFe2O4-(1-x)Na0.5Bi0.5TiO3 (NBT) with composition xNiFe(2)O(4)-(1-x)Na0.5Bi0.5TiO3 (x = 0.20, 0.40, 0.60) were prepared successfully by solid state reaction method. The crystal structure analysis was carried by using x-ray diffractometer, field emission scanning electron microscope-energy dispersive analysis of x-rays (FESEM-EDX) and Fourier transform infrared spectroscopy (FTIR). The presence of two individual phases corresponding to ferrite and ferroelectric was confirmed by XRD analysis of composites. Rietveld refinement of XRD data further confirms the existence of both cubic (Fd3m) and rhombohedral (R3c) symmetries. FESEM micrographs and EDX spectra revealed the reduction in grain sizes with increase in ferrite content. FTIR spectra depict two prominent absorption bands around 413 cm(-1) and 618 cm(-1). Dielectric response of these samples was recorded at frequency range 100 Hz-7 MHz for different temperature. Dielectric constant (epsilon') and dielectric loss (tan delta) values found higher at low frequencies, decrease with increase in frequencies and become independent at higher frequencies. epsilon' and tan delta both enhance with rising temperature and become more stable at higher frequencies. Complex impedance spectroscopy (CIS) investigation was used to understand dielectric relaxation and conduction mechanism in composites. Cole-Cole plots for all samples depict two semicircles and the centre of semicircles is depressed below real axis with temperature. Activation energy rises with increase in ferrite content in composites. Magnetic evaluation of the samples discloses the soft magnetic nature of these composites. The maximum value of saturation magnetization (M-s = 22.82 emu g(-1)) and magnetic moment per formula unit (eta = 0.92 mu(B)) is observed for composition having higher NFO content. The highest ME response, alpha similar to 1122 mu V/cmOe is observed for the composite 0.60NiFe(2)O(4)-0.40Na(0.5)Bi(0.5)TiO(3)
Electronic structure and magnetic properties of Ca2IrO4, using first principles
No full textA comprehensive set of electronic structure calculations are performed to understand the origin of the insulating gap and magnetic properties of hexagonal Ca2IrO4. Although, isoelectronic with Sr2IrO4, the spin-orbit coupling driven J(eff) model is anticipated to be less appropriate for Ca2IrO4 following its structural considerations. We find that the local density approximation (LDA), and those including the effects of Coulomb correlations and spin-orbit coupling fail to reproduce the experimental results. Moreover, the calculations employing the modified Becke-Johnson formalism seems to provide sufficiently good results, by predicting Ca2IrO4 to be an antiferromagnetic insulator. The origin of electronic gap is attributed to the antiferromagnetic ordering of Ir spins and the effects of spin-orbit coupling is found marginal. However, due to the anisotropy in the Ir-O bonding within the distorted IrO6 octahedra we deduce large magneto-anisotropic energy in Ca2IrO4. Further, our analysis shows that Ca2IrO4 is an itinerant material, suggesting that band structure effects play an important role in determining the ground state properties of iridates