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A series of dimeric gemini surfactants on the study of DL-alanine (Ala) with ninhydrin reaction was carried out using the UV–vis spectroscopic technique. A study has been made under a pseudo 1st-order experimental situation by fixing ninhydrin ≥ 10 times over Ala. Rate constants (kψ) on kinetics of Ala with ninhydrin reaction were determined by varying pH, temperatures, concentrations of ninhydrin, and Ala and gemini surfactants. The outcomes of the present study disclose that the experiment obeys the respective first and fractional order of rate paths in [Ala] and [ninhydrin]. The role of temperature on kψ was employed to calculate various thermodynamic parameters. The infrequent role of gemini surfactants was observed upon addition of different concentrations to reaction. The observed enhancement in kψ values at different surfactant concentrations could be deduced by the pseudo-phase model. From experimental results, different constants and parameters including micelle-substrate-binding constant (KA), micelle-ninhydrin-binding constant (KB), and rate constant in micelle (km) were calculated.

High temperature electrical properties of morphotropic phase boundary BiScO3-PbTiO3 compositions, exhibiting high piezoelectric coefficient, saturation polarization, field induced strain and low dielectric loss have been presented in detail. Dielectric loss and various electrical parameters have been comprehensively utilized to identify multiple dipolar relaxation dynamics in the regime where conductivity effects are low. Dielectric data confirms presence of various polymorphs exhibiting lower (higher) symmetry configuration, which extends to wider (narrower) temperature regime. Effect of conductivity associated with the charge transport is not dominant up to 600 K, which shows that this material is a promising candidate for high temperature applications.

Study of evolution of ferroelectric correlations in a system which intrinsically exhibits short range polar order in the form of polar-nano regions (PNRs), is the goal of the present work. For this purpose, well-known Relaxor ferroelectric i.e. P b M g 1 / 3 N b 2 / 3 O 3 (PMN) and its solid solutions with P b T i O 3 (PT) has been systemically synthesized by varying composition, precursors and synthesis parameters. Dynamics associated with the PNRs and structural phase transitions of various polymorphs have been traced through temperature and frequency dependent dielectric permittivity profile. Formation of solid solutions with PT generates ferroelectric correlations associated with the tetragonal polymorphs, suppresses thermal fluctuations, overcomes diffused character of phase transition, effects polarization switching, stabilizes ferroelectric hysteresis characteristics and shifts dielectric permittivity maxima toward higher temperatures. Addition of PT led to relaxation dynamics associated with the multiple polymorphic phase transitions for T

To identify the generation of various contributions in the electrical response of EuTiO3, a series of pure and doped, morphologically different and crystallographically oriented thin films prepared through RF magnetron sputtering and polycrystalline samples prepared through solid state reaction method have been investigated. Effect of stoichiometry, morphology and crystallographic orientation on the electrical response have been traced. Interestingly, in case of thin films, synthesis in more reducing atmosphere led to an in-plane crystallographic re-orientation from [110] to [100], accompanied by the observation of a prominent intrinsic antiferrodistortive phase transition. At temperatures above the antiferrodistorive phase transition, potential barriers to conduction at grain boundary are found to be directly proportional to the oxygen vacancy concentration, and inversely proportional to the average grain size. The relaxation times obtained from the frequency dependent dielectric response show an anomalous non-monotonic variation with temperature, which arises due to the variation of octahedral tilt angle.

Visible light-activated Ag-doped spindle-like BiFeO3 (Ag-BFO) magnetic nanocomposite using different Ag loadings was synthesized via hydrothermal synthesis methods. The structural, morphological, optical and magnetic properties of as-prepared nanocomposite was analyzed by various characterization techniques. Field emission scanning electron microscopy images revealed the distribution of metallic Ag on the surface of spindle-like BFO with the widths ranging from 30 to 60 nm and the lengths from 200 to 250 nm. The X-ray photoelectron spectroscopy spectra showed that the electronic states of Bi3+, Fe3+ and Ag0 existed in the Ag-BFO nanocomposite. UV–Vis diffuse reflectance spectra showed a red-shift on the light absorption edges after the loading of metallic Ag. Fourier transform infrared spectroscopy studies confirmed the presence of metallic Ag and Fe−O bond of FeO6 octahedral perovskite structure. The photocatalytic results presented that the Ag-BFO nanocomposite exhibited boosted visible light photoactivity on the degradation of malachite green (MG) dye. Especially, the 3 wt% Ag-BFO nanocomposite displayed excellent photoactivity than that of the pure BFO. The boosted photoactivity of Ag-BFO nanocomposite can be credited to the high electron-hole pairs separation efficiency and hydroxyl (•OH) radicals generation capability as witnessed by photoluminescence and terephthalic-photoluminescence (TA-PL) measurements. The Ag-BFO mineralization of MG dye under different light sources suggested that around 90.5% COD removal was achieved under sunlight irradiation, while 20.9% and 33.9% of COD were removed under visible and UV light irradiation, respectively. Other organic substances such as methylene blue, sunset yellow, phenol and 2,4-dichlorophenoxyacetic acid were also successfully degraded under the identical condition. Moreover, the Ag-BFO nanocomposite retained its photoactivity and morphological stability even after five recycling runs. The separation of Ag-BFO nanocomposite from the aqueous suspension was also relatively easy due to its strong ferromagnetism property. The radical scavengers study also showed that hole (h+), hydrogen peroxide (H2O2) and •OH radicals were the core active species for the Ag-BFO nanocomposite catalytic system. Furthermore, the Ag-BFO nanocomposite showed much improved antibacterial activities towards the Escherichia coli and Micrococcus luteus in comparison with the pure BFO. These findings presented that the Ag-BFO magnetic nanocomposite can be utilized as photocatalytic and antimicrobial agents for the prospective practical applications in the wastewater treatment.

We present the study of structural, morphological, dielectric, transport and ferroelectric properties of (1-x)BFO–xPTO solid solutions, with 0.3 ≤ x ≤ 0.6, prepared via non-conventional synthesis methods. These methods include Sol-gel and Single-step solid state method. Structural analysis revealed presence of mixed phases i.e. monoclinic (CC) and tetragonal (P4mm) phases, for all compositions showing a Morphotropic Phase Boundary. For the compositions with higher concentration of PTO, an increase in tetragonal phase fraction has been observed. Quantitative analysis showed, in general, higher value of c/a (i.e. tetragonality) for all samples as compared to the bulk PTO. The morphological analysis shows small grain size irrespective of synthesis method and composition. The low temperature frequency dependent tangent loss shows dielectric relaxation with small magnitude of dielectric constant indicating absence of extrinsic contributions. High temperature dielectric anomaly is observed around 400–500 K corresponding to magnetic phase transformation of BFO at Neel temperature which suggest the presence of magneto-electric coupling in specific compositions. Sol-gel prepared composite appeared to be more resistive than the Single-step synthesized composite and shows Arrhenius type dependence of high temperature ac conductivity. Ferroelectricity was observed in all ceramic samples which sustained high applied electric field up to 190 kV/cm. Finally, a correlation between polarization, tetragonal phase fraction and c/a ratio, has been drawn and discussed. It is concluded that c/a ratio (i.e. tetragonality) is more important parameter which can be tuned to achieve enhanced ferroelectric response as compared to the tetragonal phase fraction in (1-x)BFO–xPTO solid solutions.

Visible light–responsive Pt-loaded coral-like BiFeO3 (Pt-BFO) nanocomposite at different Pt loadings was synthesized via a two-step hydrothermal synthesis method. The as-synthesized photocatalyst was characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), UV–vis diffuse reflectance spectroscopy (UV–vis DRS), photoluminescence (PL) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and magnetic hysteresis loop (M-H loop) analyses. The FESEM images revealed that Pt nanoparticles were evenly distributed on the coral-like BFO. The UV–vis DRS results indicated that the addition of Pt dopant modified the optical properties of the BFO. The as-synthesized Pt-BFO nanocomposite was effectively applied for the photodegradation of malachite green (MG) dye under visible light irradiation. Specifically, 0.5 wt% Pt-BFO nanocomposite presented boosted photocatalytic performance than those of the pure BFO and commercial TiO2. Such a remarkably improved photoactivity could be mainly attributed to the formation of good interface between Pt and BFO, which not only boosted the separation efficiency of charge carriers but also possessed great redox ability for significant photocatalytic reaction. Moreover, the strong magnetic property of the Pt-BFO nanocomposite was helpful in the particle separation along with its great recyclability. The radical scavenger test indicated that hole (h+), hydroxyl (·OH) radical, and hydrogen peroxide (H2O2) were the main oxidative species for the Pt-BFO photodegradation of MG. Finally, the Pt-BFO nanocomposite was revealed high antibacterial activity towards Bacillus cereus (B. cereus) and Escherichia coli (E. coli) microorganisms, highlighting its potential photocatalytic and antibacterial properties at different industrial and biomedical applications.

Because of excellent physical properties and wide range of applications in electrodes, electrical connections, microelectronic packaging, and heating mineral, Tungsten–copper (W–Cu) composite powders have been significantly remarkable. The substantial differences in the density and lack of fusion of copper and tungsten in both solid and liquid phases, led to occur some problems in W–Cu composite powders. Among the various methods of preparing tungsten–copper composites, the electroless plating process is one of the conventional methods as it is easy to use, efficient, and inexpensive. In this paper, the copper electrolyte solution containing copper sulfate as the main salt, formaldehyde as the reducing agent, sodium ethylene diamine tetra-acetate as the sophisticated agent, has been employed in the electroless copper plating process of tungsten powder. The effects of main parameters of electroless copper plating including NaOH concentration, time and operating temperature, and pre-activation of tungsten powder on the amount of deposited copper layer were investigated. Then, the phase behavior, morphology, mechanical, and corrosion behavior were evaluated using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy(EDS), Vickers hardness tester, and electrochemical impedance spectroscopy (EIS), respectively. Results demonstrated an improvement in the morphology and amount of the copper, which was deposited on the surface of the activated tungsten powder. Indeed, the defects formed on the surface of the tungsten powder increased the sites for nucleation and growth of copper particles. In agreement with the Fick's 2nd law, the maximum deposition rate of 7.9 vol% was obtained at 14 g/l NaOH, 100 °C and processing time of 90 min, with a (111) orientation on the activated tungsten powder surface. The higher capacitance and the charge transfer resistance along with the highest ndl at the 14 g/l NaOH concentration demonstrated the homogeneity and integrity of W–Cu composite, the lowest hardness of 149.0 ± 2.8 Hv and a compressive strength of 187 ± 11 MPa.

Coral-like palladium-doped BiFeO3 (Pd/BFO) nanocomposite was synthesized via a simple two-step hydrothermal route. X-ray diffraction, UV–visible diffuse reflectance spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray and vibrating sample magnetometer were used to investigate the crystallinity, morphology, optical and magnetic features of the samples. The synthesized samples exhibited enhanced visible light photoactivity for the degradation of malachite green dye as compared to those of pure BFO and commercial TiO2. The enhancement in the photoactivity was attributed to the formation of heterojunction between the Pd and BFO, which was beneficial for yield of highly reactive hydroxyl radicals as confirmed by photoluminescence-terephthalic acid test. Owing to the magnetic behavior of coral-like Pd/BFO, this nanocomposite can also be easily recovered by a magnetic field along with good reusability.

The effects of ammonium hydroxide (AH) concentration in the hydrothermal reaction precursors and time on growth, morphological, optical and spectroscopic properties of TiO2 nanostructures have been investigated in detail. The dandelion nanostructures were also observed on the top surface of vertically aligned nanorods whose density increases with increase in AH concentration and reaction time. Dandelion nanostructures were also observed on top of vertically aligned nanorods surface whose density increases with increase in AH concentration and reaction time. The average nanorod length increases with an enhancement in the second generation of nanorods with AH addition. In the case where C-layer was deposited on FTO, the dandelion structures grown via hydrothermal technique were denser exhibiting transformation to flower like morphology. Hence, with AH addition, the formation of 1D/3D (aligned nanorods/dandelion structures) structure has been observed. AH plays crucial role by facilitating second generation crystallite growth and significantly effects resultant morphology. Specifically, the structures grown with AH addition; i.e. primary, first generation and second generation crystals have been observed to be different. Both Raman and XRD studies revealed that nanorods were crystalline (rutile phase) while the C-layer exhibited anatase phase and no extra phase appeared in the spectra. The reflectance increase has been observed with increasing concentration of AH and temperature which is attributed to the increased scattering by dandelion-like structures.

We present detailed comparative study of effect of isovalent i.e. Eu+3 substitution at A-site and tetra (Ti+4, Zr+4), penta (V+5) and hexavalent (W+6) substitutions at B-site in BiFeO3. Eu+3 substitution led to phase transformation and exhibited mixed phases i.e. rhombohedral and orthorhombic, while tetravalent substituents (Ti+4 and Zr+4) led to stabilization of cubic phase. In higher valent (i.e. V+5 and W+6) cases solubility limit was significantly reduced where orthorhombic phase was observed as in the case of parent compound. Phase transformation as a consequence of increase in microstrain and chemical pressure induced by the substituent has been discussed. Solubility limit of different B-site dopants i.e. Zr, W and V was extracted to 5%, 2% and 2%, respectively. Extra phases in various cases were Bi2Fe4O9, Bi25FeO40, Bi14W2O27, and Bi23V4O44.5 and their fractional amount have been quantified. Ti was substituted up to 15% and has been observed to be completely soluble in the parent compound. Solubility limits depends on ionic radii mismatch and valance difference of Fe+3 and dopant, in which valance difference plays more dominant role. Solubility limit and phase transformation has been explained in terms of change in bond strength and tolerance factor induced by incorporation of dopant which depend on its size and valence state. Detail optical, dielectric, ferroelectric, magnetic and transport properties of Eu and Ti co-doped samples and selected low concentration B-site doped compositions (i.e. 2%) have presented and discussed. Two d-d transitions and three charge transfer transitions were observed within UV-VIS range. Both change in cell volume for the same phase and transformation in crystal structure affects the band gap. Increase in room temperature dielectric constant and saturation polarization was also found to increase in case of Eu-Ti co-doped samples with increasing concentration of Ti. Substitution of Eu at A-site and Ti at B-site led to observation of weak ferromagnetism. Effect of extra phases on ferroelectricity and transport properties have also been discussed.

The aim of this study is to develop processing maps based on two models and compare them with conventional processing maps. The hyperbolic sinus constitutive equation and artificial neural network (ANN) approaches were used in this investigation to predict flow stress and to develop processing maps in various conditions. The hot compression tests of InX-750 superalloy were carried out above the gamma prime phase temperature and within the temperature range of 1000–1150 °C and strain rate of 0.001–1.000 s−1. The processing maps were conducted based upon dynamic material model (DMM) for data by experimental, constitutive equation and ANN approaches. The processing maps drawn by either of the prediction methods show that the method developed by ANN data does not significantly differ from the experimental processing map. The ANN approach is thus a suitable way to predict the flow stress as well as hot working processing map of engineering metals and materials.

BiFeO3 is a well-known room temperature multiferroic material. However, the presence of antiferromagnetic magnetic order and high leakage current limit its utilization in magnetoelectric devices. This study deals with conclusive identification of the presence of magnetoelectric coupling by carefully selecting higher bond strength cationic substitution and using contactless measurement. Complementary to the magnetic studies, detailed structural analyses are carried out to determine the B-site bond length, B-site bond angle, ionic size mismatch and electronic structure of the substituent. The structural modification due to cationic substitution leads to release of latent magnetization that is locked within the cycloid. Non-monotonic temperature dependence of magnetic coercivity is observed and the results are confirmed for various compositions. These results are explained using Ginzburg-Landau Mean field model. Crossover from anomalous to usual trend of magnetic coercivity as a function of temperature is presented covering the temperature regime beyond Neel temperature of BiFeO3. Results are explained in terms of effective anisotropy which includes contribution associated with the electric polarization. This proves the existence of magnetoelectric effect. Magnetic switching is shown to be affected by the presence of ferroelectric order. The inclusion of normal ferromagnetic response in the high temperature regime makes this a unique study. The importance of this study lies in the fact that such magnetoelectric characteristic cannot be explored through the conventional electrical response measurements as the presence of high leakage current in BFO makes such measurements extremely difficult.

Post sintering studies of BaTiO 3 (BTO) nanoparticles are presented in detail. Bulk nanostructures were prepared via three different compaction processes, namely, uniaxial cold pressing (UCP), Cold Isostatic Pressing (CIP) and Spark Plasma Sintering (SPS). Effect of compaction technique on microstructures have been investigated and correlated with electrical response for each sample. In addition to the transport properties, temperature and frequency dependent dielectric response of variously sintered samples and bulk counterpart was recorded. Several aspects have been identified that are essential to be taken into account in order to completely understand physical processes. Drastically distinct features were observed in paraelectric (PE) regime well above ferroelectric (FE)-PE transition temperature. These features include intra grain conduction with a reduction in the magnitude of PE to FE peak dielectric constant magnitude. Role of strain, grain boundary conduction associated with observation of Maxwell Wagner relaxation and hopping conduction in dielectric and ferroelectric response have been observed and discussed. Densification with presence of oxygen vacancies, significantly enhances conductivity associated with the hopping of the carriers, in turn deteriorated ferroelectric response.

This study analyses the impact of twin-headed gemini surfactants on the interaction between glutamic acid (Glu) and a ninhydrin (Nin) in an acetate buffer. Analyses were observed using a UV–vis spectrophotometer and values of absorbance were recorded at fixed time intermissions. The impact of parameters such as pH, temperature, [Glu], and [Nin] was examined on reaction in gemini surfactants. Using a conductometric technique, electrical conductivities of pure geminis and their mixed systems were noted. Using these data, thus, cmc values of pure geminis and their mixed system were measured. By varying different parameters, the rate constant (kψ-value) was evaluated on finishing each kinetic run using a computer-based procedure. The study showed that twin-headed gemini surfactants demonstrated an excellent impact on the titled reaction over the aqueous system although 16–4–16 catalyzed the study more among geminis and followed the abilities to catalyze at each concentration as 16–4–16 > 16–5–16 > 16–6–16. Our goal was to assess the impact of varied gemini surfactants on rate constant and thus, a pseudo-phase model for micellar activity was applied. A low positive value of ΔH# with a large negative ΔS# was obtained in geminis than for aqueous solutions. A probable reaction mechanism is discussed.

Single phase BiFeO3 (BFO) is difficult to synthesize due to the volatile nature of Bi and the formation of impurity phases which restrict its use in commercial applications. Presence of free charge carriers in the system due to the formation of oxygen vacancies leads to an increase in the leakage current and suppresses intrinsic ferroelectric response of the system. In this paper, we present a detailed study of the structural phase transformation triggered by the substitution of rare-earth (RE) ions at A-site of BFO. We report that the chemical pressure induced by the substitutional ions stabilizes lower symmetry polymorphs. A detailed phase diagram showing connection between chemical pressure, ionic radii mismatch, dopant concentration and rare ions is also extracted on the basis of the structural analysis. Change in peak position and intensity of Raman vibrational modes and transformation of structure from rhombohedral to orthorhombic phase are identified to be a function of the concentration of RE ions substituted at the A-site. Five electronic transitions, two d-d and three charge transfer (CT) transitions, are observed in optical measurement within the spectral range of 1–5 eV. Shifts in d-d and CT transitions as a function of substitution are also observed. Dependence of the direct band gap on the concentration of substituent ion is also studied. Presence of spin spiral structure results in net cancellation of magnetic moments in BFO and, as a result, antiferromagnetic hysteresis loop is observed. Substitution of RE ions at A-sites induces chemical pressure which affects Fe-O-Fe bond angle and results in the destruction of spiral spin structure. Consequently, weak ferromagnetism is observed beyond certain concentration of RE in BFO.

Two-dimensional (2D) transition metal carbides and nitrides (MXenes) have arisen as a robust class of nanomaterials with many applications. Properties such as higher metallic conductivity, high surface area, ease of functionalization, active metallic hydroxide sites, hydrophilicity and biocompatibility make MXenes ideal candidates for environmental remediation, energy storage, catalysis and sensors. Despite the growing interest in MXene materials, there are relatively few reports on MXenes. Thus, there is a need for a comprehensive, up-to-date review concerning its recent development in environmental remediation, focusing on addressing future challenges and prospects. This study systematically reviews the recent progress in the MXenes preparation, characterization, and their applications as adsorbents in membrane filtration and photocatalytic agent for various organics, heavy metal ions, radionuclides and gaseous contaminants remediations. The results suggested that MXene-based materials are promising alternatives to conventional materials such as activated carbon and graphene for environmental applications. Finally, various future research challenges were also highlighted to better understand the current research and development of MXene-based materials. This review aims to encourage and attract engineers and material scientists to explore the use of MXenes in environmental remediation technologies.

In classical ferroelectric BaTiO3, inclusion of Pb at A-site, forms a unique system in terms of improvement in the physical properties and for investigation of several interesting aspects associated with the physical chemistry and materials science. Manipulation of ferroelectric instability with high tetragonality arises due to Pb-O bond which exhibits strong covalent nature along with the presence of the stereochemically active lone pair of Pb (i.e. 6s2). In contrast, Ba-O chemical bond is ionic in nature. In the present work, Pb is progressively substituted with Ba, to observe the intrinsic effects on the physical properties such as tetragonality, phase transition temperature, vibrational modes, piezoelectric coefficient, ferroelectric domain configuration etc. Phase transition temperature significantly increases with substitution of Pb, which is a manifestation of the effect of chemical bond modification. Sintering temperature effects both intrinsic as well as extrinsic contributions to the physical properties of the system.

A 6Gb/s per lane ultra-definition display interface (UDDI) system is presented to reduce the production cost and to improve the form-factor of Quad-UHD TV panels. The receiver (RX) is implemented in a 0.18um Source IC process. The transmitter (TX) is fabricated in a low-leakage 65nm process for integration with a Timing Controller (TCON) ASIC. The analog front-end of the receiver is equipped with a continuous-time linear equalizer and a 5-tap decision feedback equalizer. Continuous calibration and adaptation engines in the receiver ensure reliable communication over an extended operation period. The transmitter employs 3-tap pre-emphasis for channel equalization and a dual-VCO LC PLL for low jitter transmission. System link layer employs a low-overhead error correction code to protect video data against random errors and to limit worst-case run-length. The system also deploys scrambling to reduce EMI. Noise-free video quality was achieved at 6Gb/s over 65” display Source PCBs and at 4Gb/s over 105” display Source PCBs. The UDDI system improves the highest existing intra-panel interface speed by nearly a factor of 2.

We studied the effect of the presence of inner surface on polycrystalline hollow single oxide nanoparticles of NiFe2O4 via extensive field and temperature dependent magnetic. Hollow morphology was obtained by post-synthesis annealing of Ni33Fe67/NiFe2O4 core/shell particles, prepared in an inert gas condensation system. High resolution electron microscopy studies revealed that the hollow nanoparticles were polycrystalline. Particles, as well as voids, exhibited size distribution. High values of up to 2522 Oe coercivity (HC) and 444 Oe exchange bias (EB) fields were measured at low temperatures. Through observation of low saturation magnetization, larger HC and the presence of EB show drastically different magnetic response when compared to the bulk counterpart and solid single oxide nanoparticles. Results showed presence of strong coupling between the ferrimagnetic (FiM) and the disordered surface spins that arises due to enhancement in the surface to volume ratio associated with the morphology of the particles. Coercivity and exchange bias were found to decrease as a function of temperature and persisted up to 80 K, where their magnitudes were 1128 Oe and 16 Oe, respectively.

In this work we present synthesis and extensive characterization of Cerium oxide (CeO2) nanocrystals. Comparison between the properties of as-prepared and air annealed nanoparticles has been carried out, with a goal to clearly identify the effect of oxygen vacancies on crystal, electronic and band structure. Detail crystal and electronic structural analysis was employed to quantify oxygen vacancies. Structural analysis confirmed that the formation of single phase cubic Fluorite structure for both as-prepared and annealed samples. Crystal and electronic structural studies confirmed that Ce ions exists in two oxidation states, Ce+3 and Ce+4. Concentration of oxygen vacancies was larger in as-synthesis nanocrystal. A drastic decrease in oxygen vacancy concentration was observed for the sample annealed in air at 550 °C. For the as-prepared sample, the Raman allowed F2g mode shifted towards lower wavenumber, exhibiting mode softening with broader and asymmetric peak. Observation of absorption edge revealed presence of 4f band within the band gap. Absorption with different band edge, confirmed different energy position of 4f level for the sample possessing oxygen vacancies. Blue shift of the band edge for as-prepared sample has been discussed in terms of increase in lattice parameter, formation of Ce+3 ions, quantum confinement effect etc. Photoluminescence emission studies revealed presence of F-centers with corresponding energy level located below 4f band as a result of oxygen vacancies. It was found that within the measured experimental energy window, transitions associated by the F-center are mainly associated with 4f0 to 4f1, F++ to 4f1 and 4f0 to F+.

We have systematically investigated the effects of divalent dopants (Sr2+, Pb2+, Ba2+) of varying ionic sizes on the structural and electronic properties of BiFeO3. These include multiferroic, magnetic, Mossbauer and optical measurements, and, in particular, the temperature dependence of the magnetic coercivity. Mossbauer results showed that Fe ions retained their trivalent state, and divalent ion substitution at the trivalent site results in generation of oxygen vacancies. Optical measurements showed that the d–d transition energies develop a small blue shift (90–100 meV), consistent with decreased crystal field splitting while the direct band gap also showed blue shift as a consequence of decreased chemical pressure. The saturation magnetization of the system increases with increasing size of the dopant. This enhancement is ascribed to the local lattice distortions induced by the size difference between the host and the dopant, generation of oxygen vacancies and the suppression/destruction of the antiferromagnetic spiral spin structure. We found an anomalous but systematic decrease in the magnetic coercivity (Hc) at low temperatures, which is explained in terms of an effective magnetic anisotropy that includes the effects of magnetoelectric coupling. The almost linear decrease in Hc with decreasing temperature is qualitatively explained within the effective anisotropy model and the Landau mean field formulation. Our findings give further insight into the coercivity mechanism of Bi0.75A0.25FeO3 (A = Sr2, Ba2+, and Pb2+) bulk ferromagnets and suggest that the coercivity of such multiferroics can be tailored by the combination of magnetic anisotropy and magnetoelectric interaction.

Intrinsic dielectric relaxations associated with the domains in dense single-phase Barium Titanate (BaTiO3), covering entire ferroelectric regime and various polymorphs, has been investigated. Existence of frequency dispersion in dielectric loss in the three phases where system exhibits low symmetry, has been recorded and analyzed. Formation and reorientation of the mesoscopic ferroelectric sub-domains/domain boundaries because of applied ac electric field, generates relaxation dynamics between consecutive phase transitions. Relaxation dynamics have been observed due to the presence of multiple domain variants associated with the low symmetry configurations such as orthorhombic, rhombohedral and tetragonal. Frequencies which effectively triggers these effects have been traced for various structural phases and activation energy has been extracted. Such intrinsic response of the system has been found to be sensitive to the processing of the ceramics and intentional incorporation of that defects by ionic substitution.

In this report, gold nanoparticle-decorated on the coral-like magnetic BiFeO3 (Au-BiFeO3) composite has been successfully fabricated by facile two-steps hydrothermal technique. Incorporation of Au nanoparticles on the BiFeO3 enabled effective harvesting sunlight for 2,4-dichlorophenoxyacetic acid (2,4-D) photodegradation and Escherichia coli (E. coli) inactivation on the heterojunction structures. The Au-BiFeO3 composite exhibited ameliorated photoactivities toward pollutant photodegradation and bacterial disinfection as compared to that of bare BiFeO3. The findings of these studies implied that decorating of Au on the coral-like BiFeO3 can greatly delay the recombination process of the charge carriers produced by photon absorption and thus enhanced the photoactivity of the BiFeO3. The possible photocatalytic mechanism was also postulated and supported by photoluminescence and electronic investigations. The radical trapping and electron spin resonance outcomes supported the role of the oxidative active species and its interaction for the degradation of 2,4-D. The intermediates responsible for the photodegradation have also been detected. Additionally, the prepared composite can be easily recovered through an external magnet and demonstrated good reusability within minimal release of deposited Au after six runs.

In this paper a comprehensive study that includes structural, magnetic, ferroelectric, dielectric and electrical characterizations of as-prepared and quenched MPB 1-x(BiFeO3)-x(PbTiO3)(BF-xPT) solid solutions prepared by wet chemical method has been presented. Qualitative and quantitively structural analysis revealed coexistence of rhombohedral/monoclinic, tetragonal and orthorhombic phases. Sensitivity to the experimental variables such as composition, synthesis conditions, sintering temperature and particle size, confirms the existence of a complex energy phase diagram where minima associated with various polymorphs lies almost at same level for MPB compositions. Magnetic characterizations reveal the presence of three anomalies, i.e., originating from the Neel transition, iso-structural transition and ferroelectric phase transition. Second anomaly detected to be the most sensitive to the quenching. Enhancement of magnetic moment in quenched compositions is a manifestation of strong interaction between spins of Fe2+ ions with the pinned point defect dipoles. Interestingly, thermal quenching enhanced the ferroelectric properties by removing the domain wall pinning. Saturated ferroelectric loops were observed only for quenched samples which is a consequence of strong domain wall de-pinning. Low temperature dielectric relaxation has been observed while the high temperature dielectric data of as-prepared composition exhibited Maxwell-Wagner and iso-structural phase transition. In contrast, along with these two features, quenched samples showed additional Curie transition. Enhancement in large polaron hoping in the low frequency region for the quenched composition has been confirmed via frequency dependent profile of the ac conductivity. Low value of activation energy of charge carriers for quenched compositions indicates large polaron hoping characteristics in BF-xPT solid solution.

Automation of greenhouses has proved to be extremely helpful in maximizing crop yields and minimizing labor costs. The optimum conditions for cultivating plants are regularly maintained by the use of programmed sensors and actuators with constant monitoring of the system. In this paper, we have designed a prototype of a smart greenhouse using Arduino microcontroller, simple yet improved in feedbacks and algorithms. Only three important microclimatic parameters namely moisture level, temperature and light are taken into consideration for the design of the system. Signals acquired from the sensors are first isolated and filtered to reduce noise before it is processed by Arduino. With the help of LabVIEW program, Time domain analysis and Fast Fourier Transform (FFT) of the acquired signals are done to analyze the waveform. Especially, for smoothing the outlying data digitally, Moving average algorithm is designed. With the implement of this algorithm, variations in the sensed data which could occur from rapidly changing environment or imprecise sensors, could be largely smoothed and stable output could be created. Also, actuators are controlled with constant feedbacks to ensure desired conditions are always met. Lastly, data is constantly acquired by the use of Data Acquisition Hardware and can be viewed through PC or Smart devices for monitoring purposes.

Manganese oxide nanoparticles were prepared in an inert gas condensation system. X-ray Diffraction (XRD) studies revealed presence of multiple manganese oxide phases while high resolution transmission electron microscopy (HRTEM) showed polycrystalline hollow nanoparticle morphology. The additional inner surface of the hollow nanoparticle directly affect the magnetic properties of these particles. Combined physical structure, electronic structure and magnetic susceptibility analyses led to the conclusion that the prepared nanoparticles are polycrystalline and composed of γ -Mn 2 O 3 and MnO crystallites. Magnetic study found a sharp peak around 38 K with no frequency dependence in the AC susceptibility measurement. Large coercivity ( H C ) and exchange bias ( H EB ) fields, up to 11 kOe and 7 kOe, respectively, were observed below the order temperatures. H C and H EB were found to increase and decrease, respectively, as a function of cooling field. Both H C and H EB were found to decrease monotonically as the temperature approached paramagnetic phase transition of the ferrimagnetic component.

Investigation of intrinsic response and proper selection/tailoring of perovskite oxides is challenging and essential to understand the origin of various instabilities. For this purpose, Eu0.7Ba0.3TiO3-δ is shown to be a prime candidate. Coexistence of quantum paraelectric and ferroelectric instabilities with Ba substitution and variation of oxygen vacancies has been demonstrated in a specifically chosen composition. Random distribution of Ba2+ ions in a stoichiometric composition brings the system toward phase boundary. Interestingly, in the space charge unactivated temperature regime, the role of intentionally introduced oxygen vacancies is to induce ferroelectric character through the formation of local defect dipoles.

We present detailed magnetic properties of (1-x)BaTiO3–xCoFe2O4 (x = 1, 0.5, 0.4, 0.3, 0.2, 0.1, 0.75, 0.05, 0.025) nanocomposites, synthesized through multiple-step chemical synthesis technique. Stepwise synthesis and structural optimization of composites include oxalate route synthesis of BaTiO3 with specifically chosen tetragonality followed by mixing in citric acid solution, and a final addition of the precursor for CoFe2O4. Heat treatment temperature were appropriately chosen to obtain composites with distinct spinel and tetragonal perovskite phases. Peak broadening has been observed in composites being a consequence of presence of strain. Main goal of the present work is to investigate magnetic response as a function of temperature for various compositions and to compare them with the magnetic properties of CoFe2O4 nanoparticles. BaTiO3 acts as a barrier for the growth of the CoFe2O4 due to the phase separation between these constituent phases in the composites. The nanoscopic features are consistently observed in the magnetic properties of the composites. These features include increase in coercivity, stronger temperature dependence of coercivity and magnetic irreversibility. CoFe2O4 and BaTiO3 composites exhibit strong temperature dependence with a more than an order of magnitude increase in coercivity at low temperatures.

In this study, the Cu-Lu2O3-Cu metal-insulator-metal (MIM) structure was fabricated by electron beam evaporation method on the glass substrate with symmetric electrode configuration. The dominant conduction mechanism in fabricated MIM diode was analyzed using temperature dependent current-voltage (I-V) characteristics in temperature range 323–403 K. Schottky emission, Fowler-Nordheim (F-N) and Poole-Frankel (P-F) conduction mechanisms were tested by analyzing the I-V data according to these theories. P-F emission and Schottky emission conduction mechanisms were found to be dominant conduction mechanisms in low and high applied electric field range respectively. The Schottky emission mechanism was further studied in detail by plotting the Ln(I/T2) Vs V1/2 and Ln(I/T2) Vs 1000/T plots at different applied fields and temperatures respectively. The dielectric constants were extracted from the conduction plots at various temperatures and were found to be close agreement with experimental dielectric constant of Lu2O3 (11). The metal-insulator barrier height and trap energy were also calculated at various measurement temperatures and discussed according to Schottky emission theory.

The effect of thermal quenching on physical properties of morphotropic phase boundary BiFeO3-0.35PbTiO3 composition, composed of Pnma, R3c and P4mm phases, has been investigated in detail. We detected and quantified role of quenching through investigation of magnetic, dielectric and ferroelectric anomalies. Quenching significantly i) enhances the tetragonal phase percentage (hence affects domain structure), ii) reduces domain wall clamping with a large increase in electrical polarization, iii) increases magnetization at the structural phase transition temperature (tunable magneto-electric coupling), iv) magnifies intrinsic property i.e. intra grain relaxation dynamics (which are otherwise suppressed due to the pinning of the defect dipoles), etc. All these findings clearly verify the role of quenching which noticeably enhances multiferroic properties at the well-known morphotropic phase boundary.

We present a detailed dielectric response of EuTiO3 to identify the role of Eu3+, Ti3+ ions, and oxygen vacancies in the generation of hopping conduction by varying oxygen stoichiometry. The dielectric response clearly reveals a transition from single relaxation to multiple relaxation mechanisms (excluding grain boundary contribution) as a function of a decrease in oxygen content. Systematic evaluation of dielectric and electric responses with the aid of magnetic measurements has been utilized to differentiate between Eu3+ doped EuTiO3 and EuTiO3-δ compounds in least and moderate reducing conditions. A rise in AC conductivity correlates well with the onset temperature of relaxation mechanisms, and the corresponding activation energies calculated through the Arrhenius law indicate that the observed mechanisms are thermally activated charge carrier hopping between Ti ions present in multiple valent states. A schematic model is presented for EuTiO3, and the possible conduction mechanisms are determined considering the Eu2+/Eu3+, Ti3+/Ti4+, and oxygen vacancy defects. The presented model fits well with the experimental results and implies that in a moderately reduced EuTiO3 sample, the low temperature relaxation mechanism is associated with hopping between Ti3+ and Ti4+ ions formed due to unreduced Eu3+ ions. While for highly reduced samples, oxygen vacancies also contribute to the electrical conduction and generate two more relaxation mechanisms, which are identified to be associated with singly and doubly charged oxygen vacancies. The polydispersive nature of charge carrier hopping has been quantified through the phenomenological Debye model and is discussed in detail in terms of variation in the bond length and the lattice parameter.We present a detailed dielectric response of EuTiO3 to identify the role of Eu3+, Ti3+ ions, and oxygen vacancies in the generation of hopping conduction by varying oxygen stoichiometry. The dielectric response clearly reveals a transition from single relaxation to multiple relaxation mechanisms (excluding grain boundary contribution) as a function of a decrease in oxygen content. Systematic evaluation of dielectric and electric responses with the aid of magnetic measurements has been utilized to differentiate between Eu3+ doped EuTiO3 and EuTiO3-δ compounds in least and moderate reducing conditions. A rise in AC conductivity correlates well with the onset temperature of relaxation mechanisms, and the corresponding activation energies calculated through the Arrhenius law indicate that the observed mechanisms are thermally activated charge carrier hopping between Ti ions present in multiple valent states. A schematic model is presented for EuTiO3, and the possible conduction mechanisms are determined consi...

We have systematically investigated the effects of Eu substitution on chemical pressure, bond lengths, microstrain, bond angles, octahedral tilting, vibrational modes and phase transformation, in BiFeO3. Correlation between concentration, phase, local structure and magnetism has been explained. Substitution of Eu ions with contrasting magnetic moment and dissimilar size, affects the local structure by changing bond angles and hence modifies spin structure through weakening of Dzyaloshinsky-Moriya (DM) interaction which lead to destruction of spiral spin configuration. Intriguing as well as anomalous magnetic response such as weak ferromagnetism with high coercivity, stair step like loops with significant drop in coercivity and systematic decrease in the magnetic coercivity at low temperatures has been observed as a function of Eu concentration (x). These results are explained on the basis of weakening of DM interaction, field induced melting of antiferromagnetic clusters and modification in effective magnetic anisotropy including contribution of magnetoelectric coupling, for various values of x. These results were used to generate the magnetic phase diagram.

Spindly bismuth ferrite oxide (BiFeO3, BFO) nanoparticles were fabricated by Bi(NO3)3, Fe(NO3)3, NaOH and urea solutions at 125° C. The BFO nanoparticles have a spindle-shaped of ~120 m in length and ~50 nm in width. Such nanoparticles could be used in the photocatalytic degradation of Malachite Green (MG) dye under irradiation by a 105 W compact fluorescent lamp. They were very stable and could be easily recovered by an applied magnetic field. There was an optimal photocatalyst amount of 1.0 g/L, at which the degradation efficiency of MG was improved to 72.6% under exposure of visible light for 240 min. The active hydroxyl (•OH) radicals formed during the photocatalytic process were tested using a photoluminescence–terephthalic acid (PL–TA) measurement, which were validate to be significantly affected by the photocatalyst amount. Other organic pollutants including phenol, bisphenol A and methylparaben could also be photodecomposed in the presence of similar conditions. These features demonstrated the BFO nanoparticles practical applications in environmental remediation.

Noncompensated cation-anion codoping in TiO2 nanoparticles has been achieved by a chemical synthesis route. Significant reduction in the optical bandgap and enhancement in the absorption of visible light have been observed. Structural phase transformation has been tracked in detail as a function of doping and heat treatment temperature. Anatase to rutile phase transition temperature for doped samples was higher in comparison to the pure TiO2 nanoparticles. Nitrogen and chromium addition increases the phase transformation barrier, where the effect of the former dopant is of more significance. The Raman results showed an increase in the oxygen content with higher post annealing temperatures. With Cr incorporation, the peak associated with the Eg mode has been found to shift towards a higher wave number, while with nitrogen incorporation, the shift was towards a lower wave number. A decrease in reflectance with N co-doping for all samples, irrespective of phase and annealing temperatures, has been observed. In compositions with nitrogen of the same content, bandgap reduction was higher in the rutile phase in comparison to the anatase phase. In general, overall results revealed that with a higher loading fraction of ammonia, the N content increases, while Cr addition prevents nitrogen loss even up to high post annealing temperatures, i.e., 850 °C.

Bi1−x Pb x FeO3 (0 ≤ x ≤ 0.3) has been characterized in detail with an aim to identify role of defect such as dopant, various vacancies, grain boundaries etc, and their effect on structural, optical and multiferroic properties. Structural analysis revealed that Pb substitution transforms the rhombohedral phase of BiFeO3 to the pseudocubic phase for x ≥ 0.15, consistently all vibrational Raman modes associated with the rhombohedral phase are found disappeared. Optical response revealed weakening of the d–d transitions with Pb addition indicating change in the Fe atoms environment consistent with the transition from non-centrosymmetric to the centrosymmetric structure. Transport and dielectric responses are explained in terms of hopping due to the presence of defects like oxygen vacancies and grain boundary conduction. In the high temperature regime, grain boundary conduction led to decrease in resistivity with the presence of a hump that is associated with hopping conduction. Extrinsic contributions in the transport properties correlate well with dielectric response. Magnetic and ferroelectric responses are also presented where role of oxygen vacancies defects has been clearly identified.

Structural phase transition temperature and its associated hysteresis in VO2 have been controlled by high valent dopant induced local structural modification which acts as phase nucleation site during phase transformation. Monoclinic phase intensity loops plotted against temperature has been observed to exhibit thermal hysteresis. It is shown that the size, shape and central position of hysteresis loop depend on stoichiometry and doping concentration. Highest reduction in phase transformation temperature and thermal hysteresis width has been observed in case of W+6-Mo+6 co-doping and W+6 doping, respectively. Hence energy barrier associated with the structural phase transition has been successfully manipulated to vary Tc and hysteresis width. These findings have implications for designing the phase switching devices and smart window applications.

We present the frequency- and temperature-dependent dielectric response of Eu1-x Ba x TiO3 (0 ⩽ x ⩽ 0.5) in detail. Excluding grain boundary effects, four relaxation mechanisms were observed. Relaxation dynamics were observed to arise due to hopping conduction associated with defects, namely oxygen vacancies as well as Eu3+ and Ti3+ ions. Dielectric relaxation analysis led to the identification of Ti ions in two different environments with different relaxation rates in the overall EuTiO3 perovskite structure. The emergence of another relaxation mechanism associated with ferroelectric order as a consequence of the formation of polar regions was also observed for higher Ba concentrations. The addition of Ba led to the identification of relaxation dynamics associated with hopping conduction between Eu ions, Ti ions (in the regions with and without oxygen vacancies) and with the formation of ferroelectric polar regions. Furthermore, the polydispersivity and relaxation times were extracted within the framework of the modified Debye model. Relaxation times have been observed to increase with a decrease in temperature while larger values of polydispersivity reveal a wide distribution of relaxation times due to the presence of lattice parameter and energy barrier distributions.