Search

Pure strontium titanates have been successfully fabricated in this work via sol gel route. The obtained powders were calcined at various temperatures and effects of calcination and sintering on phase development, crystallite size, lattice parameters, microstructure etc. were investigated by XRD and SEM techniques. The development of phase with temperature has been investigated using DTA/TG technique. The dielectric and electrical parameters were analyzed and effects of temperature and frequency variation on these parameters were studied. [ABSTRACT FROM AUTHOR]

A bi-functional chelating sorbent is synthesised by introducing two different functionalities (amine and amidoxime groups) subsequently on the surface of an earlier synthesized cross-linked poly-acrylonitrile beads. The cross-linked base polymer beads are normally synthesised through suspension polymerisation using acrylonitrile and styrene as monomers and divinyl benzene as cross-linking agent. The bi-functionality is introduced by amination of base polymer in the first step by reacting with diethylenetriamine followed by amidoximation reaction with hydroxylamine hydrochloride in the second step. The incorporation of functional groups on beads are identified and confirmed with FTIR spectroscopy while the surface morphology, porosity and pores dimensions are evaluated by SEM and BET techniques. The saturation sorption capacity of synthesized beads for uranyl ion is tested and found ~ 45 mg g−1, which is significantly higher than the beads functionalized with sole amidoxime group. These bi-functional beads are quite efficient over a wide pH (1–10) range. The kinetics measurements indicate that the synthesized sorbents reach its saturation sorption capacity within 2 h at ~25 °C under neutral pH. In this study, the sorbed uranyl ions are eluted out with 1 M HCl efficiently. These beads exhibit excellent reusability up to three cycles without losing much of its capacity, suggesting better usability in real samples. [ABSTRACT FROM AUTHOR]

High-quality GaN layers were grown on sapphire (0001) substrates using laser molecular beam epitaxy (LMBE) by laser ablating a solid GaN target at different laser repetition rates (10–40 Hz) under a constant supply of r.f. nitrogen plasma. The effect of laser repetition rate on the structural and optical properties of GaN layers was systematically studied using high-resolution X-ray diffraction (HRXRD), field emission scanning electron microscopy, atomic force microscopy, Raman spectroscopy and photoluminescence (PL) spectroscopy. High-resolution X-ray rocking curve measurements revealed highly c-axis oriented GaN layers on sapphire grown at 30 Hz with a calculated screw dislocation density of ~1.42 × 107 cm−2, whereas the GaN layers grown at 10 or 40 Hz consisted the screw dislocation density in the range of 108–109 cm−2. Surface morphological analysis revealed a change in grain size as well as surface roughness as a function of laser repetition rate and is explained on the basis of growth kinetics. Vibrational Raman spectroscopy revealed that the GaN layer grown at 10 Hz shows an in-plane compressive stress of ~1 GPa, while the film grown at 30 Hz exhibits a minimum stress of ~0.3 GPa. The PL measurements show a highly luminescent band-to-band emission of GaN at 3.44 eV for the 10 Hz grown highly strained GaN layer and at 3.41 eV for the less strained film grown at 30 Hz along with a broad defect band emission centered around 2.28 eV. It is found that the GaN layers grown at 30 Hz have excellent structural and optical properties. We expect that the less strained thin and highly oriented GaN film grown by LMBE can further be utilized for developing prodigious low-temperature-grown nitride-based multilayer structures and devices. [ABSTRACT FROM AUTHOR]

We present the effect of post-implantation annealing conditions on the structural and optical quality of quantum dots (QDs) grown by combination of focused ion beam (FIB) and molecular beam epitaxy (MBE) approach. A FIB of + ion was employed to pattern a homogeneously buffer layers and then, an in situ annealing step followed by deposition was performed. Three different post-implantation annealing conditions were tested and under well-optimized conditions, a dislocation and defect-free QDs growth on FIB patterned surface was successfully achieved. Furthermore, using photoluminescence (PL) study, we demonstrate that our best sample shows almost similar optical quality as MBE grown QDs on unimplanted surface. The patterning technique described here can presumably be applied to systems other than / and highly interesting for site-controlled nucleation of QDs that finds its potential applications in nanooptoelectronic devices. A collective study on the structural and optical properties of InAs quantum dots (QDs), grown on post annealed focused ion beam (FIB) implanted GaAs surfaces, has been successfully demonstrated. Different post implantation annealing conditions and FIB doses were tested. Under optimal in situ annealing conditions and dose, the growth of high quality InAs QDs on homogeneously implanted GaAs surface was achieved. Thus, FIB patterning and post implantation annealing before QD growth may provide a suitable template for site-controlled nucleation of InAs QDs. [ABSTRACT FROM AUTHOR]

The room temperature multi-ferroic properties of bulk BiFeO3 are not exciting enough for its application in devices. Here, we report the sonochemical synthesis of scandium and titanium codoped BiFeO3 nanoparticles which exhibit improved magnetic and ferroelectric properties at room temperature. The nanoparticles have been checked for phase purity and composition using powder X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). The size and morphology of the nanoparticles have been confirmed using scanning electron microscopy (SEM), and both low and high resolution transmission electron microscopy (TEM/HRTEM). The breaking of the spin cycloid due to the smaller size and slight structural distortion caused by the doping has been found to be instrumental for the enhancement of multi-ferroic properties. The electrical polarization increases significantly in the case of BiFe 0.925 Sc 0.05 Ti 0.025O3 nanoparticles. A marked reduction in the leakage current was seen compared to un-doped BiFeO3. Magnet-oelectric coupling was also observed in the BiFe 0.925 Sc 0.05 Ti 0.025 O3 sample. Our results demonstrate that codoping with Sc and Ti ions is an effective way to rectify and enhance the multi-ferroic nature of BiFeO3. [ABSTRACT FROM AUTHOR]

Nanocrystalline zinc oxide has unique properties and immense application potential toward nanodevice fabrication. Moreover, piezoelectric properties of nanostructural materials can be tuned to meet specific application needs. Nanocrystalline ZnO as well as Cu-doped ZnO was synthesized in our laboratory. Synthesis of samples with dopant concentrations ranging from 1 to 10 atomic% was carried out. Post-synthesis calcinations of these ceramic oxides at 100 °C and 300 °C resulted in formation of nanocrystalline powders with narrow size distribution. Crystallite size increased from 10 to 70 nm when calcination temperature rose from 100 °C to 700 °C for undoped ZnO. Nanorods of ZnO could be clearly seen in SEM and AFM images. Dimensions were found to be 10 nm diameter and 100 nm length at temperature below 300 °C. SEM results revealed that in the case of doped ZnO, the crystallite size varied with increase in dopant concentration. After ascertaining crystallographic phase purity and completing necessary characterization by powder XRD, SEM, and AFM, piezoelectric response of these samples in pellet form was studied at nanometric scale using scanning probe microscopy. In this paper, this enhanced piezoresponse is being correlated with microstructural features. [ABSTRACT FROM PUBLISHER]

Orthorhombic InVO4 was prepared by solid-state reaction method and characterized by powder X-ray diffraction and scanning electron microscopy. The frequency-dependent dielectric and conductivity properties were studied from 300 to 973 K by impedance spectroscopy. A significantly enhanced conductivity was observed at higher temperature whereas almost no conduction was observed below 723 K. Appreciable grain boundary conductivity was observed at higher temperature. The activation energies for grain and grain boundary conductivities are 0.87 and 1.28 eV, respectively. The relative permittivity of ~35 was observed in a wider range of frequencies and temperatures. The frequency dispersion dielectric studies indicated thermally activated hopping conduction process. The high temperature structural studies revealed no significant change in structural parameters except a gradual increasing trend in the unit cell parameters and amplitude of isotropic thermal parameters with increasing temperature. [ABSTRACT FROM AUTHOR]

Abstract: In this study, bactericidal efficacy and mechanism of action of lemon grass oil vapors against Escherichia coli were investigated. Next, in order to develop the application of the vapor as room/surface disinfectant and to study its integration with another antimicrobial agent i.e. negative air ion (NAI), a special set-up was designed and kill time assays were conducted. Zone of inhibition (56mm) due to the vapor phase antimicrobial activity evaluated using disk volatilization assay was compared with direct assay (well diffusion assay) in liquid phase (i.e. 20mm for the same dose of oil). The Chemical analysis of the Essential oil vapor has been done by SPME GC-MS and -Myrcene (3.5%), Limonene (30.3%), Camphene (6.5%), α-Citral (17.6%), β-Citral (11.3%), 6-methyl hepten-2-one (14.6%) and linalool (1.5%) were recorded as major components. The morphological and ultrastructural alterations in vapor treated E. coli cells were studied using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. Results of the kill time assays demonstrated that the combination of NAI with lemon grass oil vapors has a greater bactericidal effect (100% reduction in viability) than NAI alone (42%) or vapors alone (78%) within 8h exposure. Present results indicate that lemon grass oil is highly effective in vapor phase and its efficacy can further be enhanced by integration with Negative air ion (NAI) for reducing the viable microbial load. The integration described here offers a novel technique for reducing the concentration of E. coli on surfaces/indoor spaces. [Copyright &y& Elsevier]

Nanocrystalline La1− x Ca x CrO3 ( x = 0.25, 0.40, 0.50) powders were synthesized by gel-combustion process using aspartic acid as a fuel. Phase identification of the samples was carried out by powder X-ray diffraction. Pore distribution and microstructure of sintered pellets were investigated by small angle neutron scattering ( SANS) and scanning electron microscopy ( SEM). SANS and relative density measurement results indicate better sinterability for products with lower Ca2+ concentration. Four-probe direct current electrical conductivity of LaCrO3 with different Ca2+ concentrations was measured in the temperature range 350°C-1000°C in air as well as in hydrogen atmosphere. Linear behavior of Arrhenius plots of electrical conductivities in both air and hydrogen atmosphere indicates charge carrier transport is due to thermally activated hopping conduction of small hole-polarons. It was observed that the electrical conductivity decreased with increasing substitution of Ca2+ concentration instead of increasing small polaron concentration as expected. This trend in electrical conductivity is attributed to the neutralization of some small polarons due to formation of oxygen vacancies with increase in Ca2+ concentration. [ABSTRACT FROM AUTHOR]

In this study, wood polymer composites (WPCs) were prepared with the impregnation of polymeric monomers methylmethacrylate (5.061moles/L) and acrylonitrile (5.061moles/L) into properly shaped black berry wood specimens in the presence of benzoyl peroxide (0.06moles/L) to initiate the polymerization process forming free radicals in the benzene medium at 74 ± 1°C. Untreated wood and its polymethylmethacrylate (PMMA) and polyacrylonitrile impregnated wood compo- sites were evaluated for stability of wood against thermo-oxidation in terms of differential thermogravimetry, thermogravimetry, differential thermal analysis in air, and wear stability in terms of wear volume. Such prepared WPCs indicated a significant improvement in all the properties investigated. It was also investigated that polyacrylonitrile impregnation imparted more resistance to wood against thermo-oxidation and wear in comparison to PMMA impregnation. Presence of PMMA and polyacrylonitrile impregnation into black berry wood was confirmed through scanning electron microscopy. [ABSTRACT FROM AUTHOR]

Commercially available polycrystalline alumina is implanted at different energies and various ion doses. Microstructural changes, elemental analysis, and evidence of compound formation of AlN and AlON are observed using scanning electron microscopy, electron dispersive X-ray spectroscopy, and GXRD techniques, respectively. Nanohardness increases due to the formation of the hard phase of nitrides. It increases with the increase in ion dose but decreases at higher ion dose. A similar trend is also observed in the corrosion resistance studied in Ringer solution. Corrosion resistance also improves with the increase in ion dose and decreases with the further increasing ion dose. [ABSTRACT FROM AUTHOR]

In this investigation, biodegradable composites were fabricated with polycaprolactone (PCL) matrix reinforced with pine cone powder (15%, 30%, and 45% by weight) and compatibilized with graphite powder (0%, 5%, 10%, and 15% by weight) in polycaprolactone matrix by compression molding technique. The samples were prepared as per ASTM standard and tested for dimensional stability, biodegradability, and fracture energy with scanning electron micrographs. Water-absorption and thickness-swelling were performed to examine the dimensional stability and tests were performed at 23 °C and 50% humidity. Results revealed that the composites with 15 wt % of pine cone powder (PCP) have shown higher dimensional stability as compared to other composites. Bio-composites containing 15–45 wt % of PCP with low graphite content have shown higher disintegration rate than neat PCL. Fracture energy for crack initiation in bio-composites was increased by 68% with 30% PCP. Scanning electron microscopy (SEM) of the composites have shown evenly-distributed PCP particles throughout PCL-matrix at significantly high-degrees or quantities of reinforcing. [ABSTRACT FROM AUTHOR]

Polycrystalline diamond films with a predominant (100) texture were deposited onto silicon substrates using hot-filament chemical vapor deposition. During film deposition, different temperature gradients were created and imposed laterally across the substrate materials. Films grown under a gradient of 100 °C cm-1 displayed large (100) oriented grains. No crystallite (100) orientation was observed in the as-grown films prepared without a temperature gradient. It was observed that the diamond grain size varied as a /unction of the gradient. The lower gradient resulted in smaller grains and vice versa. Furthermore, the size of the grains was a function of the deposition time. The orientation of the diamond grains changed gradually across the substrate from (100) to (110) orientation as we scanned from the high-temperature to the low-temperature zone. The films were characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and Fourier transform infrared (FTIR) spectroscopy. XRD showed strong (400) reflections in the oriented samples. SEM results indicated the presence of smooth diamond surfaces consisting of predominantly (100) oriented platelets. As the (100) oriented diamond grains were grown on top of the (100) oriented silicon substrates, the faces were mostly aligned parallel to the substrate surface resulting in the deposition of a smooth diamond surface. AFM observations revealed the presence of steps located at the boundaries of the oriented grains. FTIR results showed the characteristic difference in hydrogen bonding in the oriented samples and gave useful information about mechanisms responsible for the orientation. Quantitative analysis was carried out to measure the H content in the films, and it was found that the oriented films contained less hydrogen. Our findings suggest that high saturation of carbon and a concentration gradient of sp³ CH2 species can be the key... [ABSTRACT FROM AUTHOR]

Nanocrystalline yttria-doped ceria powder, with the composition Ce0.55Y0.45O1.775, was synthesized by a combustion technique using citric acid as the fuel and the corresponding metal nitrates as oxidants. This process involves mild conditions as the external temperature required to initiate the combustion is only approximately 250 °C. The product was characterized by x-ray diffraction (XRD) to ascertain the phase purity. The crystallite size of these calcined samples, as seen by transmission electron microscopy, was found to be in the range 6 nm to 50 nm. The surface area of the fine powder, as obtained from the Brunauer-Emmett-Teller technique, was about 140 m²/g. The agglomeration behavior as a function of temperature and the lattice thermal expansion studies were carried out using high-temperature XRD. This nanocrystalline powder resulted in nearly theoretical bulk density at a relatively lower temperature, which is attributed to the superior powder properties. The sintered microstructure, as studied by scanning electron microscopy, revealed the presence of fine grains. [ABSTRACT FROM AUTHOR]

Poly (ether block amide) (PEBA) was modified with Mercaptoethanol (ME) to introduce crosslinks in its polymeric structure and emphasis was laid on obtaining non-porous breathable membranes with improved mechanical properties which can be used for various biomedical applications. Pebax MH 1657 (mentioned as PEBA throughout the text) was cast polymerized with ME and the effect of ME on the properties of the membranes (such as water absorption, permeability, tensile strength, elongation & tear strength) was studied. Fourier Transform Infrared Spectroscopy- Attenuated Total Reflectance (FTIR-ATR), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA) and Differential Thermogravimetry (DTG) techniques were used to characterize the membranes. Different amount of ME (10 to 40% w/w) was added to PEBA and 30% of ME was found to be most effective in increasing the mechanical properties of the membrane. Sulfhydryl group played an important role in enhancing mechanical strength of the membranes. PEBA/ME based non porous breathable membrane with excellent mechanical strength is a novel material that can be used for various biomedical applications. [ABSTRACT FROM AUTHOR]

To employ the multiwalled carbon nanotubes (MWCNTs) in electronic devices,  their growth on conductive substrates is a prerequisite. Since electronic properties of MWCNT might be influenced by catalyst and substrate, therefore, to understand their influence on the work function and electrical resistance, individual MWCNT needs to be studied. In this report, we have demonstrated the growth of MWCNTs on conducting substrates such as copper, stainless steel, and insulating SiO2 using thermal CVD technique. First, as-grown MWCNTs on different substrates have been characterized with scanning electron microscopy and Raman spectroscopy. Furthermore, electrical measurements on as-grown individual MWCNT has been performed using electrostatic force microscopy and conductive atomic force microscopy. Performed measurements reveal that work function and electrical resistance of MWCNT vary from 4.32 to 5.32 eV and 4-498 kΩ, respectively, depending on the nature of catalyst as well as substrates. We envision that performed study might boost the on-going research activity in the area of MWCNT-based nanoelectronic devices. [ABSTRACT FROM AUTHOR]

Three solid solutions of pyrochlores in the series Nd2-yearsGdyZr2O7 (y = 0.8, 1.0, 1.2) were synthesized by the gel combustion method using citric acid as fuel. This results in a soft agglomerate powder as verified by dynamic light scattering. The single-phase nature of the products has been confirmed by x-ray diffraction. The increase in full width at half-maxima in the Raman spectra with an increase in Gd3+ content indicates that disorder increases with Gd3+ content. The morphology and particle size of the products were investigated by transmission electron microscopy. Scanning electron microscopy study reveals that the sintered pellets have a density higher than 92% of theoretical densities. The total ionic conductivity measurements in the temperature range 375-800 °C show that with the increase of disorder (Gd3+ content) in the system the activation energy of conduction increases from 0.98 to 1.06 eV and the preexponential factor, which is proportional to the number of mobile species, also follow the same trend of increase. The total conductivity measured in reducing atmosphere shows no change in electrical conductivity, which verifies a negligible contribution of electronic contribution in this system. [ABSTRACT FROM AUTHOR]

Highly sinter-active powders of RE2O3 [rare earth (RE) = Gd, Eu, Dy] have been prepared using the corresponding metal nitrates as the oxidants, and glycine and citric acid as the fuels. Two different oxidant-to-fuel ratios, namely stoichiometric ratio and fuel-deficient ratio were used to explore the possibility of preparing different crystallographic modifications. By a careful control of oxidant-to-fuel ratio, nanocrystalline Eu2O3 and Gd2O3 could be prepared in cubic (C-type) as well as monoclinic (B-type) modifications. However, the high-temperature monoclinic modification could not be obtained for Dy2O3 due to a very high C-to-B-type phase transition temperature. The crystallite size, surface area, and sintering behavior were also studied for powders prepared using different oxidant-to-fuel ratios, and the results showed a remarkable correlation between different fuel contents and powder properties. Some of these powders resulted in pellets of nearly theoretical density. The sintered microstructure was studied by scanning electron microscopy. [ABSTRACT FROM AUTHOR]

Abstract: Diamond windows prepared using hot filament chemical vapor deposition (CVD) were irradiated with Au and Ag ions of energy 100 and 130 MeV, respectively with fluence in the range 1010 to 3×1013 ions/cm2. Scanning electron microscopy (SEM) images showed substantial damage at the surface of the windows irradiated with Au+ of energy 100 MeV and fluence of 3×1013 ions/cm2. At some locations on the diamond windows deposited at 16 kPa, the surface layer appeared to have melted and flowed like a liquid exposing small crystallites underneath. Raman spectra of windows after irradiation showed i) a decrease in the intensity of the one-phonon line at 1332 cm−1 along with an increase in its half width; ii) substantial reduction in the intensity of the graphite G band; and, iii) the appearance of a new band at 667 cm−1. The band at 667 cm−1 did not have a corresponding Stokes line and was therefore identified as a photoluminescence (PL) band. The ion induced damage and localized melting of CVD diamond windows are discussed in terms of the thermal spike model. [Copyright &y& Elsevier]

The present study aims to demonstrate the application of sugarcane bagasse as an excellent field emitter. Field emission property of as-pyrolyzed sugarcane bagasse (p-SBg) before and after the plasma treatment has been investigated. It has been observed that electronic nature of p-SBg transformed from semiconducting to metallic after plasma treatment. Maximum current and turn-on field defined at 10 μA/cm 2 was found to be 800 μA/cm 2 and 2.2 V/μm for as-pyrolyzed sugarcane bagasse (p-SBg) and 25 μA/cm 2 and 8.4 V/μm for H 2 -plasma treated p-SBg. These values are found to be better than the reported values for graphene and activated carbon. In this report, pyrolysis of bagasse has been carried in a thermal chemical vapor deposition (Th-CVD) system in inert argon atmosphere. Scanning electron microscopy (SEM), X-ray Diffraction (XRD), High-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) have been used to study the structure of both pre and post plasma-treated p-SBg bagasse’s sample. HRTEM study reveals that carbonaceous structures such as 3D-nanographene oxide (3D-NGO), graphite nanodots (GNDs), carbon nanotubes (CNTs), and carbon onions are present in both pre-treated and plasma-treated p-SBg. Hence, we envision that the performed study will be a forwarding step to facilitate the application of p-SBg in display devices. [ABSTRACT FROM AUTHOR]

Sugarcane bagasse was exposed to gamma radiation at different doses i.e. 100, 500, 1000 and 2000 kGy at a dose rate of 2.5 kGy/h and characterized for physical, chemical, morphological and structural properties. Results showed that on exposure of sugarcane bagasse, hemicellulose content reduced from 31% to 12.4% at 2000 kGy dose. The cellulose content of bagasse did not get affected much upto 1000 kGy exposure; however at 2000 kGy dose it decreased considerably. XRD study shows an initial increase in crystallinity index of bagasse at a dose level of 100 kGy while on further increase in radiation dose from 100 kGy to 2000 kGy the crystallinity index of bagasse decreases. Pores in the SEM photograph were observed on the surface of irradiated bagasse. UV–Vis spectra of bagasse showed a red shift indicating internal changes caused by radiation exposure. Study shows that the irradiation of bagasse results in disrupton of the lignocellulosic structure of Bagasse which opens up for easy accessibility of acids and hydrolytic enzymes for cellulosic hydrolysis resulting into fermentable sugars. [ABSTRACT FROM AUTHOR]

Transparent, conductive films of poly (3,4-ethylenedioxythiophene) (PEDOT) and poly (3,4-ethylenedioxythiophene)-few walled carbon nanotube (PEDOT-FWCNT) nanocomposite were synthesized by in-situ oxidative polymerization and investigated for their Schottky diode property. The prepared films were characterized by UV-Vis spectroscopy, thermal gravimetric analysis (TGA), surface resistivity, cyclic voltametery, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). SEM reveals the formation of homogeneous and adhesive polymer films while HRTEM confirms the uniform wrapping of polymer chains around the nanotube walls for PEDOT-FWCNT film. Improved thermal stability, conductivity and charge storage property of PEDOT in the presence of FWCNT is observed. Among different compositions, 5 wt. % of FWCNT is found to be optimum with sheet resistance and transmittance of 500 Ω sq-1 and 77%, respectively. Moreover, the electronic and junction properties of polymer films were studied and compared by fabricating sandwich type devices with a configuration of Al/PEDOT or PEDOT-FWCNT nanocomposite/indium tin oxide (ITO) coated glass. The measured current density-voltage characteristics show typical rectifying behavior for both configurations. However, enhanced rectification ratio and higher forward current density is observed in case of PEDOT-FWCNT based Schottky diode. Furthermore, reliability test depicts smaller hysteresis effect and better performance of PEDOT-FWCNT based diodes. [ABSTRACT FROM AUTHOR]

Orthorhombic InVO4 was prepared by solid-state reaction method and characterized by powder X-ray diffraction and scanning electron microscopy. The frequency-dependent dielectric and conductivity properties were studied from 300 to 973 K by impedance spectroscopy. A significantly enhanced conductivity was observed at higher temperature whereas almost no conduction was observed below 723 K. Appreciable grain boundary conductivity was observed at higher temperature. The activation energies for grain and grain boundary conductivities are 0.87 and 1.28 eV, respectively. The relative permittivity of ~35 was observed in a wider range of frequencies and temperatures. The frequency dispersion dielectric studies indicated thermally activated hopping conduction process. The high temperature structural studies revealed no significant change in structural parameters except a gradual increasing trend in the unit cell parameters and amplitude of isotropic thermal parameters with increasing temperature. [ABSTRACT FROM AUTHOR]

A series of Mn-substituted BaMgF4 samples have been synthesized by a hydrothermal route. X-ray diffraction study reveals that the products are monophasic in nature. Scanning electron microscopy (SEM) and energy-dispersive spectrometry (EDS) studies were carried out to investigate the morphology and stoichiometry for these compounds. X-ray photoelectron spectroscoy (XPS) and electron spin resonance (ESR) studies were done to confirm the oxidation state of dopant ion. Room temperature ferromagnetism was observed on Mn substitution at the Mg site in BaMgF4 samples. The saturation magnetization increases initially, shows a peaking effect, and then decreases with further increase in Mn concentration in BaMg1-xMnxF4 (0.0 ⩽ x ⩽ 0.15). However, ferroelectricity was found to decrease with an increase in Mn concentration in the series of investigated BaMg1-xMnxF4 (0.0 ⩽ x ⩽ 0.15) samples. First-principle calculations, using the projector augmented wave potentials on Mn-substituted BaMgF4, confirmed the decrease in magnetic moment with an increase in Mn content beyond certain concentration. These samples exhibit very weak magnetocapacitive coupling, which can be attributed to the very small magnetic signal observed in these samples. [ABSTRACT FROM AUTHOR]

The present work involves the synthesis of a series of Sm2−xDyxZr2O7 compounds (0.0 ≤ x ≤ 2.0) by a controlled gel combustion process. The powders were thoroughly analyzed by powder X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy, and diffuse-reflectance UV−visible spectroscopy. The powder XRD studies revealed the system to be single-phasic throughout with retention of pyrochlore-type ordering until 40 mol % of Dy3+, beyond which the pyrochlore lattice gives way to the defect fluorite structure. Interestingly, Raman spectroscopic studies (as against XRD studies) showed retention of pyrochlore-type ordering throughout the homogeneity range of the compositions studied. This is perhaps the first study that reports retention of a weak pyrochlore-type superstructure in the Dy2Zr2O7 system, which was otherwise known to crystallize in the defect fluorite system. The ionic conductivity measurements showed an increase in the activation energy (Ea) with an increase in the mole percent of Dy3+ owing to the decreased mobility with an increase in the degree of disorder. The system possesses a tunable band gap with varying amounts of Dy3+. First-principles calculations were performed to support a decrease in the band gap of the doped system with an increase in the Dy3+ content. The potential as photocatalysts of some of these compositions was explored, and they exhibited high photocatalytic activity for degradation of xylenol orange, with t1/2 increasing from pure Sm2Zr2O7 to pure Dy2Zr2O7. [ABSTRACT FROM AUTHOR]

Abstract: We report here, a detailed study of the parameter window of the deposition pressures to grow the diamond films on GaN coated quartz substrates using microwave plasma deposition technique. Hexagonal GaN films of 5 µm coated on quartz are used as substrates for diamond deposition in the pressure range of 80–140 Torr, using microwave plasma chemical vapor deposition (MPCVD) technique. The diamond films are characterized by scanning electron microscopy, XRD, photoluminescence and Raman spectroscopy. Scanning electron microscope image shows that the nucleation density of the films is high and we can deposit a continuous film for a deposition time ranging for 6–8 h. Oriented growth of diamond has been observed at higher pressure. [Copyright &y& Elsevier]