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We investigated structural, magnetic and ferroelectric properties and magnetoelectric effect in bulk and nano composites of BiFeO 3 /PMN-PT. Scanning electron microscopy shows that BiFeO 3 and PMN-PT phases makes solid solution in bulk composites while asymmetric grain growth was observed in nano composites. The nano composites show improved ferroelectric properties with well saturated hysteresis loops with saturation polarization (2P s ) ~23.5 µC cm −2 . The magneto electric effect in nanocomposites was revealed by measuring the magnetic hysteresis loops of the same sample before and after electric poling. Magnetization results demonstrate exchange bias phenomenon in the poled composite sample. The observed ME interactions and exchange biasing makes these composites possible candidates for spintronics and sensor applications.

We report the results of our studies on the tailored magnetoelectric response of a polymer based nanocomposite system comprising of varying SmFeO3 filler volume percentage embedded in a poly(vinylidene fluoride) (PVDF) matrix. The ME induced voltage was observed to increase with an increase in the SmFeO3 filler concentration from 1% to 20%. For composite films with 20% SmFeO3 concentration an induced voltage of ∼5.2 mV cm−1 Oe−1 was obtained at 1 kHz. Such a large magnetoelectric response is attributed to intensive interfacial interaction caused by dense packing of magnetostrictive SmFeO3 in the piezoelectric matrix of PVDF. Further, poling of composite films by application of an electric field was observed to lead to a saturated magnetization hysteresis loop caused by reorientation of the magnetization of SmFeO3. This electric field mediated manipulation of magnetic properties in SmFeO3/PVDF holds great potential for low-energy-consuming spintronics devices.

In this work flexible magnetoelectric CoFe2O4(CFO)/(0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3)(PMN-PT)/PMMA nanocomposite films are investigated for non-volatile memory device characteristics. The films exhibit magnetoelectric (ME) effects at room temperature and ME output voltage (α) is found to be ~ 35 mVcm−1Oe−1. The films revealed repeatable switching of a sign of α by applying positive and negative electric pulse during the eighteen cycles for 3500 s. The two states of α can be used to store binary bits in non volatile manner. The nanocomposite films exhibit non-volatile memory characteristics with the α retention time of ~104 s. The electric-field-controlled switching of α in CFO/PMN-PT/PMMA films offers energy-efficient approach for low-power-consumption non-volatile memory devices. The writing and reading operations could be performed in a nondestructive manner.

In this work, we have presented a solid-solution of Sm0.6Dy0.4FeO3 in the form of nano-particles having spin reorientation transition (SRT) at a temperature interval of 220-260 K. The lattice dynamics of Sm0.6Dy0.4FeO3 have investigated by temperature-dependent x-ray diffraction and Raman spectroscopy. A negative thermal expansion at low temperatures has observed, which might be due to the interaction between Sm3+ and Fe3+ sublattice. Anomalous behavior in lattice parameters, octahedral tilt angle, and bond lengths have observed in the vicinity of SRT, which confirms the existence of magneto-elastic coupling in the system. The strong anomaly has observed in linewidth and phonon frequencies of Raman modes around SRT, which may be related to the spin-phonon coupling in Sm0.6Dy0.4FeO3. The contribution of SRT in lattice change and the presence of spin-phonon coupling can help to understand the correlation between the magnetic and structural properties of orthoferrite.

Multifunctional Samarium orthoferrites (SmFeO3) nano-particles have been studying extensively due to their applications in digital memory, ultrafast switching, temperature dependent spin valves and sensor applications. Magnetic properties of SFO were investigated by varying particle size, initial magnetic state of material and applied field under Zero Field Cooling (ZFC) and Field Cooling (FC) protocol. It was found that the remnant magnetization, M−H behavior and coercive field are extremely dependent on particle size. It was also found that the magnetic behavior of single domain SFO nanoparticle is completely different to that of multi domain bulk due to uniaxial magneto crystalline anisotropy. The magnetization vs temperature (M−T) behavior of nano-particle depends on unidirectional anisotropy along with uniaxial magneto-crystalline anisotropy of SFO. The Sm3+ spin ordering in nano-SFO compensates to that of Fe3+ spin ordering at higher temperature (~13 K) compare to that of bulk (~4K). The Sm3+ spin unidirectional magnetic anisotropy is more effective in between ~13 K to ~65 K and Fe3+ spin unidirectional anisotropy is effective at higher temperature beyond ~65 K. Magnetically poled nano-particles show completely different behavior to that of non-poled nano-SFO particles at low temperature. In nutshell, the manuscript shows why one can’t predict the magnetic behavior of the SFO without knowing its particle or grain size, initial magnetic state of the particle, procedure of measurement, the magnitude of applied field and temperature etc., since all these affects the magneto crystalline anisotropy as well as unidirectional anisotropy of SFO.

We studied structural, ferroelectric, magnetic and magneto-electric (ME) properties of (0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3) (PMN-PT)/NiFe2O4 nanocomposite and core shell nanostructures (with ferrimagnetic NiFe2O4 core and ferroelectric PMN-PT shell). Morphology of core shell nanostructures and nanocomposites have been analyzed using transmission electron microscopy and scanning electron microscopy. Both the (PMN-PT)/NiFe2O4 samples reveal magneto electric effect at room temperature. The ME coupling coefficient (α) was found to be two order of magnitude higher for (PMN-PT)/NiFe2O4 nanocomposites in comparison to the core shell nanostructures. The PMN-PT/NiFe2O4 nano composite showed repeatable and reversible switching of α (α > 0 and α 0 and α

The multiferroic properties of La0.7Ba0.3MnO3 (LBMO)/P(VDF-TrFE) (0-3) nano-composite films were investigated for different volume fraction of LBMO particles. The LBMO particles were prepared by sol-gel auto combustion method and these are found to be ferromagnetic at room temperature. The pure P(VDF-TrFE) and La0.7Ba0.3MnO3(LBMO)/P(VDF-TrFE) composite films (30 μm thick) were prepared via solution casting method. It was found that composite films are ferromagnetic at room temperature and the magnetization increases with increase in volume fraction of LBMO. The proper ferroelectric hysteresis loop is observed for P(VDF-TrFE), 0.5% and 1% LBMO/P(VDF-TrFE) composite films. The ferroelectric properties of composite films were deteriorated for higher volume fraction of LBMO. The composite films having less than 2% volume fraction of LBMO in P(VDF-TrFE) exhibit multiferroic properties at room temperature, which can be used for device applications.

We demonstrate the tailoring of anisotropy in magnetic nano-wire element using finite element method based micromagnetic simulation. We calculate the magentostatic properties for the structure by simulating hysteresis for these nano wire elements. The angular variation of remanence for the structures of different dimensions is used as the depiction to establish fourfold magnetic anisotropy. The change of anisotropy strength, which is the ratio of squareness of hysteresis loop in hard axis to easy axis, is demonstrated in this study which is one of the most important parameters to utilize these nanowire elements in multi state magnetic memory application.We demonstrate the tailoring of anisotropy in magnetic nano-wire element using finite element method based micromagnetic simulation. We calculate the magentostatic properties for the structure by simulating hysteresis for these nano wire elements. The angular variation of remanence for the structures of different dimensions is used as the depiction to establish fourfold magnetic anisotropy. The change of anisotropy strength, which is the ratio of squareness of hysteresis loop in hard axis to easy axis, is demonstrated in this study which is one of the most important parameters to utilize these nanowire elements in multi state magnetic memory application.

Single crystals of Yb doped YVO 4 with dopant concentration in the range of 0.75–14.3 at.% were grown by optical floating zone technique. The lattice parameters of YVO 4 remain unaffected up to 2.94 at.% doping of Yb but a contraction in the lattice volume was observed at higher concentrations. Spectral decomposition analysis of the broad absorption at 985 nm suggests that in addition to the contributions from three transitions from the ground state of the crystal field induced Stark multiplets of 2 F 7/2 and 2 F 5/2 , it also has contribution from the transition from the first excited Stark level of 2 F 7/2 to the upper most Stark level of 2 F 5/2 . Further, the absorption spectra exhibited significant polarization dependence. It was found that while for σ- (E⊥c) polarized light the absorption band at ∼972 dominates for π- (E||c) dominant absorption is at ∼985 nm. The absorption cross-section was found to be maximum at 2.94 at.% of doping for both the polarization signifying quenching at higher concentration. The emission spectra of the Yb doped crystals were characterized by two overlapped broad emissions centered at 985 and 1010 nm. The emission at 985 nm dominated over the emission at 1010 nm at lower doping concentrations which reversed at higher doping concentration. It is interesting to note that the PL intensity at 1010 nm is stronger for excitation at 972 nm in comparison to that for 985 nm.

The Bi0.825Sm0.175FeO3 (BSFO) ceramics were prepared by solid state reaction route and the structural, vibrational, and multiferroic properties of these ceramics was studied. The properties of BiFeO3 (BFO) ceramics at higher sintering temperature i. e. 850 °C were compared to that of ceramic at normal sintering temperature (i. e. 830 °C). The Rietveld-refined structure revealed the rhombohedral R3c symmetry in BFO and a mixed phase symmetry (R3c 38.26% + Pnma 61.74%) in BSFO for ceramics sintered at 830 °C. The formation separate phase of SmFeO3 (Pbnm; 12.16%) along with BSFO (Pn21a; 87.84%) phase was observed for ceramics sintered at 850 °C. The small change in sintering temperature led to changes in Raman spectra accompanying abrupt changes in ferroelectric properties. The BSFO shows strong ferromagnetic characteristic due to the spin canting in bulk BFO. The net macroscopic magnetization in bulk BFO due to Sm doping exist due to suppression of spin modulated spiral structure. The BSFO ceramics sintered at 830 °C shows ferroelectric polarization (2Pr) 7.3723 μC/cm2 at an applied field of 15 kV/cm but the BSFO ceramics sintered at 850 °C shows no ferroelectric polarization at room temperature. The presence of magnetization and reasonable ferroelectric polarization at room temperature in BSFO ceramics sintered at 830 °C make this material suitable for multiferroic application.

The influence of La and Nd co-substitution on structure, electric and magnetic properties of epitaxial thin films of BiFeO3 (BFO) was examined. We demonstrate structural phase transition in co-doped La and Nd BFO thin films using Raman spectroscopy. Based on group theoretical analysis of the number and symmetry of Raman lines, we provide strong experimental evidence that the structure has been changed from rhombohedral to monoclinic due to co-doping in BFO. The change in structure was also reflected in morphology of these films. Room temperature magnetic hysteresis curves showed that doped films exhibit enhanced ferromagnetic properties with remnant magnetization of ~10 emu/cm3 and coercive field of 1.2 kOe. The enhanced magnetic properties highlight the potential applications of doped BLNFO thin film for smart devices. Copyright © 2015 John Wiley & Sons, Ltd.

We report impedance characteristics and ac conductivity response of ~1 mm thick pellets made from yttria-stabilized zirconia (YSZ) nanoparticles. Nanoparticles of different average sizes (10–16 nm) and of different yttria (6 mol%, 10 mol% and 16 mol%) contents were obtained via CO 2 laser based laser vaporization method. We employed both the continuous and the pulsed mode of CO 2 laser operation and obtained smallest size nanoparticles under pulsed mode of laser vaporization. Impedance spectroscopic measurements were carried out in frequency range of 10 Hz–1 MHz at various temperatures ranging from room temperature to 500 C. Oxygen ion conductivity response was compared with respect to laser vaporization mode and yttria content in nanoparticles of YSZ. The grain and grain boundary ionic conductivity of pellets made from large sized nanoparticles generated in continuous mode of laser vaporization was two orders of magnitude low compared to pellet made of smallest average size nanoparticles (generated with pulsed mode of laser vaporization). The activation energy of ion hopping in all the samples was estimated using Arrhenius equation and found in the range 0.95–1.34 eV. Possible origin of differences between conductivity in pellets made from nanoparticles generated via pulsed mode and CW mode of vaporization is discussed on the basis of association of oxygen vacancy and Y +3 ion.

Concentration dependent interaction between negatively charged citrate capped gold nanoparticles (GNP) and cationic Rhodamine 6G dye was studied from the change in localized surface plasmon resonance (LSPR) absorption due to dye induced nanoparticles aggregation, fluorescence quenching and surface enhanced Raman scattering (SERS) of the dye. The optical properties resulting from their interaction were found to be highly dependent on dilution of the GNP and concentration of the dye. Composites of up to 1 μM dye concentration, relatively low for monolayer coverage on nanoparticles surface, did not result any noticeable change in LSPR wavelength and bandwidth with respect to the pure GNP solution whereas significantly high quenching of the dye fluorescence was observed. In contrast the composites with higher dye concentration were found to exhibit an additional inter-particle coupled LSPR excitation band at higher wavelengths and the characteristics of this absorption band were found to be highly influenced by the dilution of the GNP. The fluorescence quenching efficiency was found to decrease with either increasing the dye concentration or diluting the GNP. Stern–Volmer plots were found to be non-linear at low dye concentrations and almost linear at higher concentrations. The observed fluorescence quenching was attributed to the resonance energy transfer process substantiated by significant change in the excited state lifetime of the dye in the presence of the GNP. Also dye interacting nanoparticles clusters formed on a substrate via solvent evaporation were found to be highly effective for the SERS based detection of very low concentrations of the dye.

We studied the effect of structural change on the spin–phonon coupling in doped BiFeO3 (BFO) films (Bi0.8La0.1Nd0.1FeO3) grown on SrTiO3 (001) substrate. The temperature-dependent Raman studies show phonon anomalies in the vicinity of magnetic ordering temperature TN owing to the spin–phonon coupling. Doped films exhibit strong anomalies in the line widths of Raman bands around TN revealing the presence of strong spin–lattice coupling. The modification in structure as a result of A-site doping in BFO films plays an important role in controlling the nature of spin–phonon coupling. Copyright © 2014 John Wiley & Sons, Ltd.

Information and Communication Technologies (ICTs) have ushered in the new era and possess the prospective to generate educational and job opportunities, awareness on the basic available health care facilities, legal provisions, government programmes and welfare schemes etc. The benefits amassed from the combination of knowledge and ICT should not be confined to the upper strata of the society but need to liberally flow to all the sections of the female population. The extent of areas in which ICT can put a larger control in the hands of women is extensive and constantly increasing, from managing water distribution at the village-level to standing for local elections and having admittance to enduring learning opportunities. With such an unmatched prowess, ICTs definitely can bring a social change in the rural hinterlands of Odisha, a state in India. A large portion of rural women in the state are reeling under poverty and lack awareness. They are absorbed in the farm sector (which doesn’t promise a hefty return, always) and are unskilled manual laborers. The socio cultural barriers discourage their public participation and decision making ventures. Socially, majority of women in rural Odisha are tied up by age-old traditions. Disparity in women's access to and participation in all communication systems as well as lack of mobilization proves to be a roadblock in their emancipation. It is in this context that this paper wants to examine the underpinning dynamism of culture and technology and if the former fosters or hinders ICT penetration in rural areas of Odisha.

Investigation on structural, vibrational, dielectric and ferroelectric properties of Bi 1− x Pr x FeO 3 ( x = 0.0, 0.15, 0.25) ceramic samples has been carried out. Room temperature Rietveld-refined X-ray diffraction pattern shows the crystal structure of Bi 1− x Pr x FeO 3 is rhombohedral for x = 0 and triclinic for x = 0.15, 0.25. The changes in Raman normal modes with increasing doping concentration infer the structural transformation is due to Pr substitution at A -site in BiFeO 3 . Raman spectra also reveal suppression of ferroelectric behavior due to Pr doping. The dielectric parameters, namely, dielectric permittivity ( e ′) and loss tangent (tan ( δ )) were evaluated as a function of frequency at room temperature. The ferroelectric polarization reduces in Pr doped bulk BFO samples due to structural change.

Single-phase BiFeO3, Bi0.825Pb0.175FeO3 and Bi0.725La0.1Pb0.175FeO3 ceramic samples were prepared via solid state reaction route to study the effects of co-doping (La/Pb) on their crystal structure and ferroelectromagnetic behaviour. X-ray diffraction data accompanied by Rietveld refinement showed that BiFeO3 crystallize in rhombohedral distorted perovskite structure (space group-R3c) while to that BPFO and BLPFO crystallize in tetragonal (P4/mmm) symmetry. Presence of E(TO9) and E(LO9) modes in Raman scattering spectra for BiFeO3 and Bi0.725La0.1Pb0.175FeO3 infers ferroelectric nature. However, absence of both modes in Bi0.875Pb0.175FeO3 indicates the paraelectric nature. The room temperature dielectric constant (10 Hz–1 MHz) of BiFeO3, Bi0.825Pb0.175FeO3 and Bi0.725La0.1Pb0.175FeO3 is about 100, 60, and 200. Ferroelectromagnetic measurements revealed the existence of ferroelectricity with remnant polarization of 0.24 μC/cm2 in Bi0.725La0.1Pb0.175FeO3, paraelectricity in Bi0.875Pb0.175FeO3, and weak (strong) ferromagnetism with remnant magnetizations of 0.25 (1.57) emu/g in Bi0.725La0.1Pb0.175FeO3 (Bi0.825Pb0.175FeO3).

The structural, vibrational, magnetic and dielectric properties of polycrystalline BiFeO 3 and Bi 0.95 Pr 0.05 FeO 3 are investigated by combining X-ray diffraction, Raman scattering spectra, magnetometry and dielectric measurements. Structural symmetry with rhombohedral R 3 c phase is revealed for both parent and 5% Pr substitution at Bi site, serving no chemical pressure and causes no structural transition from R 3 c to any other phase is identified from X-ray diffraction patterns and Raman scattering spectra. The shifting of phonon modes towards higher frequency side is attributed to lower atomic mass of Pr ion as compared to Bi ion. The magnetic measurements at room temperature indicate that Pr substitution induces ferromagnetism and discerns large and non-zero remnant magnetization as compare to pristine BiFeO 3 . Both dielectric permittivity and loss factor of Bi 0.95 Pr 0.05 FeO 3 strongly decreases with increased frequency. Significant role of hopping of oxygen ion vacancies in Bi 0.95 Pr 0.05 FeO 3 is inferred from modulus spectra and ac conductivity analysis.

Emergent technologies based on spintronics demand the unprecedented control on magnetic anisotropy. Here we present the control on magnetic anisotropy of SmFeO3 by the means of Tm3+doping at Sm3+site. A series of nano particles of Sm1-xTmxFeO3 (X = 0, 0.3, 0.5, 0.7, 1) orthoferrite have been synthesized by sol-gel auto-combustion method and phase purity was confirmed by the X-ray diffraction pattern. The crystallographic information obtained from Rietveld refinement and Raman spectroscopy confirmed the changes in oxygen octahedra with the change in doping percentage of Tm3+ ion in SmFeO3. Temperature dependent dc magnetization measurement implies the tuning of spin reorientation temperature from 480 K to 80 K as a function of Tm3+ ion doping concentration. The room temperature magnetic isotherm confirms the canted antiferromagnetic character of nano particles. Sm0.7Tm0.3FeO3 shows the spin reorientation at room temperature which might be used in room temperature spintronics devices.

Tetragonal lead-free Ba0.98Ca0.02Ti0.98Sn0.02O3 (BCST) compound sintered at 1400 °C was investigated for its electrocaloric properties. The large adiabatic temperature variation, ΔT ∼ 0.476 K and isothermal entropy change, ΔS ∼ 1.90 J/kg.K were obtained at ∼ 373 K at an electric field of 20 kV/cm. Further, higher electrocaloric coefficients (ΔT/ΔE ∼ 0.238 K.mm/kV and ΔS/ΔE ∼ 0.952 J.mm/K.kg.kV) with better refrigeration capacity (RC ∼ 152 J/kg) were achieved at the same temperature and electric field. The ΔS/ΔE and RC values for this compound are better than that observed in various other lead-free ferroelectric ceramics.

Nanophosphors of (Sr

Nanoparticles of Yb:Y2O3 have been synthesized by coprecipitation synthesis routes. The (NH4)2SO4 surfactant was added to Y(OH)3 precipitate during synthesis to control the size, morphology, agglomeration and phase of nanoparticles. The dried precipitates were calcined at 900 ° C to obtain the desired cubic phase Yb:Y2O3 nano particles. In the present study we reported the effects of surfactant concentration on size, morphology, agglomeration and phase of Yb:Y2O3 nanoparticles. However the addition of surfactant is not enough to get non-agglomerated nanoparticles. The extracted precipitate should be washed in proper solvent to avoid formation of hard agglomerate during drying. Hence the effects of washing solvent (i.e. water and methanol) on agglomeration and transparency were also reported. The transparency of the sintered pellets, prepared by varying the surfactant concentration and washing solvent, was evaluated. A transparency of 80 % at 1500 nm was achieved in 1 mm thick Yb:Y2O3 ceramic pellet by optimization of the surfactant and washing solvent.

This paper describes the observations of aluminum projectile (or armature) tribomaterial deposition onto copper (stator) conducting rails in an experimental solid-armature railgun system, by optical, and scanning and transmission electron microscopy. The extreme deformation at the aluminum/copper interface creates a solid-state flow regime by dynamic recrystallization which also leads to the erosion-product deposition. Melting of the low-temperature aluminum deposit also contributes to the rail damage and degradation of electromagnetic behavior. The creation of nano-grains by dynamic recrystallization allows for mixing at the aluminum/copper interface, and there is no evidence for traditional alloying.

Erbium (Er) and lanthanum (La) substituted BiFeO3 (BFO) ceramics have been prepared through conventional solid solution route. X-ray diffraction data indicated a gradual phase transition from rhombohedral to monoclinic structure in Bi0·9−x La0·1Er x FeO3 (x = 0·05, 0·07 and 0·1) (BLEFO x = 0·05, 0·07, 0·1) ceramics. Differential thermal analysis (DTA) measurements of BFO samples showed a ferroelectric transition at 835°C, whereas it is shifted to 792°C for BLEFO x = 0·1. The Raman spectra of BLEFO x = 0·05, 0·07, 0·1 samples showed the shift of Raman modes to higher wavenumbers and suppression of A1 modes indicating decrease in ferroelectricity. The Raman spectra also indicated the structural transformation due to Er and La substitution in BFO. On subsequent erbium doping, the intrinsic dielectric constant is found to decrease from 68 (for pure BFO) to 52 for BLEFO x = 0·05 to 43 for BLEFO x = 0·07 but increased to 89 for BLEFO x = 0·1 when compared to pure BFO. The increase in Er content resulted in the increase in spontaneous magnetization (0·1178 emu/g at 8T for BLEFO x = 0·1) due to collapse of spin cycloid structure. Ferroelectric remnant polarization of BLEFO x = 0·05 and BLEFO x = 0·07 decreases when compared to pure BFO while small remnant polarization (close to paraelectric behaviour) is evident for BLEFO x = 0·1.

The gamma-phase poly (vinylidene fluoride) (PVDF) films are usually prepared using dimethyl sulfoxide (DMSO) solvent, regardless of preparation temperature. Here we report the crystallization of both alpha and gamma-phase PVDF films by varying preparation temperature using DMSO solvent. The gamma-phase PVDF films were annealed at 70, 90, 110, 130 and 160 degrees C for five hours. The changes in the phase contents in the PVDF at different annealing conditions have been described. When thin films were annealed at 90 degrees C for 5 h, maximum percentage of beta-phase appears in PVDF thin films. The gamma-phase PVDF films completely converted to alpha-phase when they were annealed at 160 degrees C for 5 h. From X-ray diffraction (XRD), Fourier transform infrared spectrum (FTIR), differential scanning calorimetry (DSC) and Raman studies, it is confirmed that the PVDF thin films, cast from solution and annealed at 90 degrees C for 5 h, have maximum percentage of beta-phase. The beta-phase PVDF shows a remnant polarization of 4.9 mu C/cm(2) at 1400 kV/cm at 1 Hz.

Bismuth ferrite (BFO) and La-substituted BFO with composition Bi 1− x La x FeO 3 ( x =0.05, 0.1 and 0.15) (BLFO x =0.05–0.15 ) ceramics were prepared using the solid state reaction route. A structural phase transition from rhombohedral phase to triclinic phase was observed for BLFO x =0.05–0.15 ceramics. Modulus spectroscopy reveals the deviation of dielectric behavior from ideal Debye characteristics and the dependence of conductivity on ion hopping in BFO and BLFO x =0.05–0.15 ceramics. The conductivity of the BFO ceramics decreases for La content of 5 mol%, followed by a subsequent increase with 10 and 15 mol% of lanthanum doping. The typical values of the activation energies at high temperature reveal the contribution of short range movement of doubly ionized oxygen vacancies to the conduction process in BFO and BLFO x =0.05 ceramics. Both short range and long range motion of oxygen vacancies are responsible for large conductivity in BLFO x =0.1 and 0.15 ceramics.

The precursor glasses in (mol%) 25.53Li2O-21.53Ta2O5-35.29SiO2-17.65Al2O3 (LTSA) and 25K2O-25Nb2O5-50SiO2 (KNS) glass systems were prepared by the melt-quench technique. Ferroelectric LiTaO3 (LT) and KNbO3 (KN) crystallites containing bulk nano glass-ceramics have been prepared by controlled crystallization of these precursor glasses respectively. Second harmonic generations (SHG) at 532 nm in both the glass-ceramics have been realized under fundamental beam of Nd3+ :YAG laser source (1064 nm). The SHG power output has been found to increase up to 14 and 62.4 nJ with variation of rotation angle for LT and KN bulk nano glass-ceramics respectively due to orientation of ferroelectric domains under applied field.

Multilayer lithium tantalate thin films were deposited on Pt-Si Si(111)/SiO2/TiO2/Pt(111)]substrates by sol-gel process. The films were annealed at different annealing temperatures (300, 450 and 650 degrees C) for 15 min. The films are polycrystalline at 650 degrees C and at other annealing conditions below 650 degrees C the films are in amorphous state. The films were characterized using X-ray diffraction, atomic force microscopy (AFM) and Raman spectroscopy. The AFM of images show the formation of nanograins of uniform size (50 nm) at 650 degrees C. These polycrystalline films exhibit spontaneous polarization of 1.5 mu C/cm(2) at an application of 100 kV/cm. The dielectric constant of multilayer film is very small (6.4 at 10 kHz) as compared to that of single crystal. (C) 2010 Elsevier B.V. All rights reserved.

One innovative approach for producing functionally graded tungsten/copper composites involves infiltrating a porous tungsten structure with molten copper. The porous structure is created by sintering tungsten powder to create an initial porous preform and then connecting the preform to the anode of an electrochemical cell. The porosity increases with time as the tungsten oxidizes in the alkaline electrolyte. The rate of porosity increase depends on the local value of electric-potential difference between the electrode and electrolyte, while the local electrical properties are a function of the porosity. Therefore, the porosity distribution, which determines the material-property gradient of the resulting material, can be modeled by a system of coupled equations describing porosity and electric potential. The present work develops a numerical tool capable of predicting the evolution of porosity in the rectangular-slab geometry (the extension to cylindrical-shell and elliptical-shell geometries is straightforward). Analysis of the results suggests that the shape of the gradient can be varied by adjusting parameters such as initial porosity and current density.

The effect of Y and Mn substitution on the structural, magnetic, and dielectric properties of Bi 1 − x Y x Fe 1 − y Mn y O 3 ( x = y = 0 ; x = 0.03 , 0.06 , 0.12 , y = 0.05 ) is investigated. X-ray diffraction and Raman spectroscopy analysis revealed that all the compounds were stabilized in the Rhombohedral structure (Space group: R3c) below Y(6%)-Mn co-doping. A minimal contribution from the Pbam phase was also observed at higher Y (12%). Co-doped compounds exhibit canted ferromagnetic behavior with a significant increase in the saturation magnetization ( M s) of 1.28 emu/g when (Y, Mn) = ( 0.12 , 0.05 ). Dielectric measurements at different temperatures ranging between 30 °C and 210 °C in a wide frequency range of 1 Hz–1 MHz were investigated. Impedance study is useful to understand the correlation of grain and grain boundary with electrical properties. The grain and grain boundary contribution to electrical parameters was presented with equivalent R-C circuit. Furthermore, electrical properties such as complex electrical modulus and electrical conductivity analysis clearly emphasize the substitution of Y and Mn, leading to a significant change in BiFe O 3 ceramic.The effect of Y and Mn substitution on the structural, magnetic, and dielectric properties of Bi 1 − x Y x Fe 1 − y Mn y O 3 ( x = y = 0 ; x = 0.03 , 0.06 , 0.12 , y = 0.05 ) is investigated. X-ray diffraction and Raman spectroscopy analysis revealed that all the compounds were stabilized in the Rhombohedral structure (Space group: R3c) below Y(6%)-Mn co-doping. A minimal contribution from the Pbam phase was also observed at higher Y (12%). Co-doped compounds exhibit canted ferromagnetic behavior with a significant increase in the saturation magnetization ( M s) of 1.28 emu/g when (Y, Mn) = ( 0.12 , 0.05 ). Dielectric measurements at different temperatures ranging between 30 °C and 210 °C in a wide frequency range of 1 Hz–1 MHz were investigated. Impedance study is useful to understand the correlation of grain and grain boundary with electrical properties. The grain and grain boundary contribution to electrical parameters was presented with equivalent R-C circuit. Furthermore,...

In this letter, studies on structural transitions and the effect of electric field poling on magnetoelectric (ME) properties in 0.65Pb (Mg1/3Nb2/3)O3-0.35PbTiO3 (PMN-PT)/NiFe2O4 (NFO) nanocomposites are reported. The composite illustrates dramatic changes in the NFO crystal structure across ferroelectric transition temperature [Curie temperature (Tc) ∼ 450 K] of PMN-PT, while pure NFO does not exhibit any structural change in the temperature range (300 K–650 K). Synchrotron based X-ray diffraction analysis revealed the splitting of NFO peaks across the Tc of PMN-PT in the PMN-PT/NFO composite. Consequently, the anomalies are observed in temperature dependent magnetization of the NFO phase at the Tc of PMN-PT, establishing ME coupling in the PMN-PT/NFO composite. Furthermore, the composite exhibits drastic modification in ME coupling under electrically poled and unpoled conditions. A large self-biased ME effect characterized by non-zero ME response at zero Hbias was observed in electrically poled composites, which was not observed in unpoled PMN-PT/NFO. These results propose an alternative mechanism for intrinsic converse ME effects. The maximum magnetoelectric output was doubled after electrical poling. The observed self-biased converse magnetoelectric effect at room temperature provides potential applications in electrically controlled memory devices and magnetic flux control devices.

Pyroelectric sensor using TGS has been designed and fabricated which can be operated in laser energy meter mode as well as pyroelectric detector mode. The amplifying circuit configuration has very good signal to noise ratio, very high input impedance and low drift. The pyroelectric sensor has been tested using Q-switched Nd: YAG laser and chopped He-Ne laser. The sensitivity of pyroelectric sensor in energymeter mode is 421.7V/J and the voltage responsivity of the pyroelectric sensor is 3.27 V/W in detector mode.

A region across a ferroelectric domain wall has been scanned, using an Nd:YAG laser beam (beam size 440 μm), in a thin crystal of TGS (triglycine sulphate), cut normal to the polar axis and the pyroelectric response of the crystal has been recorded. If a laser pulse of fixed beam size falls on the domain completely, then the output pyroelectric signal is maximum. But when the laser beam (diameter of beam greater than width of domain wall) falls on the domain wall, the pyroelectric signals from two opposite domains tries to cancel each other and net signal depends on the position of laser beam across the domain wall. When the domain wall lies in the middle of the laser beam the output pyroelctric signal will be zero. In our experiment when beam of size 440 μm falls on positive domain the pyroelectric voltage of -2.76 mV recorded and when beam starts crossing the domain wall (i.e from positive domain to negative domain), the pyoelectric signal changes its sign from negative to positive through zero. After 220 μm the signal decreased to minimum and again increases to maximum (+2.46 mV) in opposite direction after 440 μm i.e when beam falls on the negative domain completely. This shows that the polarization in the domain wall region (separating two domains) is zero i.e the paraelectric nature of domain wall. So before detector fabrication the sample must be poled sufficiently to avoid the non uniformity of pyroelectric signal due to the domain wall. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This paper reports the synthesis of lithium tantalate $(LiTaO_3)$ nanoparticles by a sol–gel process involving the use of capping ligands. When the sol was allowed to form gel and then annealed at $600^oC$ for 1 h in the presence of oxygen, hexagonal crystallites of size $2–5 \mu m$ were formed. But when the sol was heat treated at $600^oC$ for 1 h in the presence of oxygen before gelation, agglomerated nanoparticles were formed. The addition of aniline before gelation (a neutral capping ligand with N-donor atom) not only restricted gelation, but also helped in the formation of well-separated and irregular nanoparticles of sizes 40–70 nm, which was confirmed from TEM and XRD studies. The anionic-ligand oleic acid (lipophilic ligand with O-donor atoms) restricted gelation by arresting the surface of $LiTaO_3$, and spherical nanoparticles of size 20–40nm were formed after heating the sol. Comparison of ferroelectric and dielectric properties between bulk particle and spherical nanoparticles (obtained using oleic acid) are reported by characterizing these particles using Raman spectroscopy and differential scanning calorimetry (DSC). The Curie temperature decreases with decreasing the particle size of $LiTaO_3$.

This paper reports the deposition of lithium tantalate (LiTaO3) thin films by sol-gel process. Thin films were deposited on three different substrates, viz. Pt-Si [Pt(111)/TiO2/SiO2/Si(100)], Si(111), and sapphire(006) by spin coating. The influence of lattice mismatch and packing structure of atoms on the orientation of the film was investigated. In order to study the influence of annealing temperature on crystallinity, microstructure, grain size, and roughness, the films were first annealed at 650 degrees C, and subsequently annealed at 1000 degrees C. From XRD and AFM pictures it is confirmed that nano-oriented grain growth occurs only on sapphire substrate at the annealing temperature 650 degrees C, and the grain size increases from 50 to 200 nm when the annealing temperature is increased to 1000 degrees C. The surface roughness of the film increases when the annealing temperature increases. In the case of the Pt-Si substrate, prominent grain growth occurs at 1000 degrees C, but the grains are randomly oriented due to the lattice mismatch and packing structure of atoms. But in case of silicon substrate, packing structure of atoms plays an important role, rather than the lattice mismatch.

This paper reports the fabrication and performance-testing of two types of laser-energy meter based on the pyroelectric effect in a crystal (triglycine sulphate, TGS), namely metal-coated TGS and black-coated TGS. A comparison is made between these two types of sensors in terms of response time and sensitivity. Variation of the output response of the energy meter with laser pulse-width is analysed and verified. When the pulse-width of the laser is greater than the response time of the energy meter, the output signal is found to depend on the input capacitance of the circuit. Experiments done with different laser pulse-widths confirm the mathematical formulation given in this paper. The basic parameters for designing a laser-energy meter are described, and the results are validated against experimental data obtained by measurements with an Nd:YAG laser of variable pulse-width.

It is advantageous to grow crystals of triglycine sulphate (TGS) with a large area in the plane perpendicular to the polar axis (i.e. the (0 1 0) plane), for applications in large-area infrared detectors and laser-energy meters. Growing TGS crystals with such a morphology, using a point seed, has been a difficult task because of a low growth rate along the c -direction. To overcome this problem a cylindrical seed of large dimension along the c -axis is commonly used. This paper reports the growth of TGS crystals by the platform technique, using seeds which need not be long along the c -axis. Crystals were grown from aqueous solution by placing seeds of size 5×5×5 mm 3 in different orientations on the platform. The variation of growth rates of various habit facets with different orientations of seeds was determined. An optimum seed orientation was found such that the platform technique permits one to grow TGS crystals from which large-area (0 1 0) plates can be cut. The grown crystals were characterised by various techniques. A laser-energy meter was designed, fabricated, and tested.

In an electromagnetic (EM) railgun, a thin, unbonded overlay on the rail conductor develops residual strains as evident from its post-shot curvature. Heating due to the transient EM field and a large thermal gradient due to deposition of a molten layer of armature material contribute to the straining of the overlay. In this paper, the authors solved the one-dimensional coupled magnetic and thermal diffusion equations to estimate the thermal gradient in the overlay. Heat sources included both Joule heating and the enthalpy from a resolidified thin layer of molten aluminum deposited by the armature. The thermal gradient so calculated was used in a one-dimensional stress model to compute residual stresses from which residual curvature was calculated. The calculated curvature compares well with the experimental value. Finally, based on the estimated residual stress, they present an estimate for the remaining life of the overlay.

Maximum power point tracking (MPPT) techniques are implemented in photovoltaic (PV) systems to maximize the PV array output power where the latter depends on solar irradiance and temperature. In this paper a typical PV module is modeled mathematically and the PV characteristic curves are dissected under varying temperature and irradiation conditions. The model is then used to compare three popular MPPT techniques namely perturb and observe (P&O) method, incremental conductance (IC) method and the modified P&O method on basis of their dynamic behavior and response to step changes in irradiation levels. The paper further discusses the dynamic simulation model for a Zeta converter in discontinuous current mode (DCM) for step changes in input voltage by Generalized Switch Averaging technique and small signal analysis. The systems are modeled and simulated in a user friendly MATLAB/Simulink environment.

The reaction of indole-3-acetic acid (IAA) with hydrogen peroxide catalysed by 5,10,15,20-tetrakis(2′,6′-dichloro-3′-sulfonatophenyl)porphyrinatoiron(III)hydrate [Cl 8 TPPS 4 Fe(III)(OH 2 ) 2 ] gives indole-3-carbinol (IC) and indole-3-carboxaldehyde (IA) in aqueous buffer solution. The oxidation of IAA with H 2 O 2 in the presence of Cl 8 TPPS 4 Fe(III)(OH 2 ) 2 in AOT reverse micelles gives higher yields of IA than in aqueous solution at the same pH. The yields of different oxidation products in AOT reverse micelles depend on the pH, the water to surfactant ratio (Wo) and concentration of Cl 8 TPPS 4 Fe(III)(OH 2 ) 2 in AOT reverse micelles. The oxidation of IC with H 2 O 2 in the presence of Cl 8 TPPS 4 Fe(III)(OH 2 ) 2 gives IA, indole-3-carboxylic acid (ICA), 2-oxo-indole-3-carbinol and 3-methylene oxindole. The oxidation of indole-3-propionic acid and indole-3-butyric acid with H 2 O 2 in the presence of Cl 8 TPPS 4 Fe(III)(OH 2 ) 2 in aqueous buffer solution as well as AOT reverse micelles do not give the oxidative decarboxylation products. The formation of IC may be explained by the hydrogen abstraction from IAA by high valent oxo-iron(IV) radical cations followed by decarboxylation and subsequent recombination of either free hydroxy radical or hydroxyiron(III)porphyrin. The same abstraction and recombination mechanism has been proposed for oxidation of IC to IA and IA to ICA.

A computer method is developed to generate diffusion impurity profiles for a V-band silicon n + npp + double drift region (DDR) with different values of diffusion length (s) and surface concentration (N H ). The microwave properties of DDRs having different diffusion profiles have been computed by iterative computer simulation programs developed for dc and high frequency analyses of the IMPATT diode. The results indicate that the performance of the DDR optimises for particular values of surface concentration and diffusion length, which in turn provides the optimal impurity diffusion profile and the optimal diffusion fabrication parameters (diffusion time and temperature) for the Si double drift IMPATT.

We have investigated spin phonon coupling in the strain coupled magnetoelectric SmFeO3/0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 (PMN-PT) composite in the temperature range of 300–650 K by Raman spectroscopy and magnetic measurements. The SmFeO3/PMN-PT composite shows sharp rise in magnetic moment across ferroelectric transition temperature (Tc) of PMN-PT. Around this transition temperature (Tc of PMN-PT), the temperature evolution of Raman spectra of the composite also shows anomalies in the phonon frequencies and line width corresponding to the SmFeO3 phase which indicate structural modifications in the SmFeO3 phase around Tc of PMN-PT. The observed structural, magnetic, and phonon anomalies of SmFeO3 around Tc of PMN-PT in SmFeO3/PMN-PT are attributed to spin-phonon coupling providing evidence of strong strain mediated magnetoelectric effects.

Risk of heart attack is a global issue. This paper attempts to mathematically model the influence of eleven predictors on the heart attack risk. The contribution of each predictor and the related risk of heart attack are obtained from a group of medical doctors. Total 300 such cases are structured in a 300 * 12 matrix to conduct the study. Using statistical data mining, significant joint predictors have been extracted and clinically validated. The study also measures the variations in interpretations among doctors.

Alkyl and aromatic mercaptans are among important organic sulfur compounds distributed in petroleum products. The mercaptans cause foul odor and are corrosive toward metals. In addition, mercaptans may cause oxidative deterioration as well as inhibit the performance of various additives (TEL, antioxidants) in finished products. Therefore, it is necessary to remove them, either by extractive processes or by converting them into innocuous disulfides. Such processes are usually referred to as “sweetening.”

Alkyl and aromatic mercaptans are among important organic sulfur compounds distributed in petroleum products. The mercaptans cause foul odor and are corrosive toward metals. In addition, mercaptans may cause oxidative deterioration as well as inhibit the performance of various additives (TEL, antioxidants) in finished products. Therefore, it is necessary to remove them, either by extractive processes or by converting them into innocuous disulfides. Such processes are usually referred to as “sweetening.”

Moderate yields of benzaldehyde, benzyl alcohol and benzylamine are obtained by the biomimetic oxidation of N-nitrosodibenzylamine with molecular oxygen catalysed by water soluble anionic manganese(III) 5,10,15,20-tetraphenylporphyrin acetate/sodium dithionite/methylene blue in aerosol-OT (AOT) reverse micelles, under phase transfer conditions with AOT concentration higher than 10−3M. The formation of α-hydroxy-N-nitrosodibenzylamine and its decomposition products, benzaldehyde and benzyl alcohol in reverse micellar systems are governed by the ratio of water and AOT, pH and other changes in the microenvirpnment.