Effect of CuO on Dielectric Properties of Perovskite Titanate and Hexagonal Manganite

Giant dielectric material CuO is chosen suitably to make composite with insulating SrTiO3 and semiconducting SrMnO3 by solid state reaction route. Ceramic samples of 30 & 40 wt% CuO with above parent matrix ceramics were prepared. From the XRD results it confirms the formation of perfect composites with semiconducting CuO as a secondary phase. Surface morphology study from SEM confirms the presence of both types of grains. Dielectric studies were carried out at four selected frequencies (1 kHz, 10 kHz, 100 kHz, 1 MHz). The result has shown the extraordinarily improved dielectric constant. Maxwell-Wagner polarization (interfacial polarization) was made responsible for the improved result. Dielectric loss also increased by a considerable manner

Ferroelectric ceramic dispersion to enhance the beta phase of polymer for improving dielectric and ferroelectric properties of the composites

Ferroelectric ceramic-polymer composites consisting of Poly Vinyledine Fluoride-Hexa Fluoro Propylene (PVDF-HFP) as polymer host and 0.5Ba(Zr0.2Ti0.8)O-3-0.5(Ba0.7Ca0.3)TiO3(BZT-BCT) ceramics as filler were prepared using solution casting technique. These composites are characterized for structural, microstructural, vibrational, optical, dielectric and ferroelectric properties at various experimental conditions. The electroactive beta phase fraction (observed from XRD and FTIR analysis) increases as the filler concentration increases up to 20 wt% of BZT-BCT and above that its value decreases. FTIR results were analyzed to understand the mechanism of enhancement of beta phase by the interaction between negatively surface charged ions of filler with the CH(2)dipole of polymer matrix. UV-visible spectroscopy also employed to confirm polymer-ceramic filler interaction. Variation of the dielectric constant with different filler concentrations is explained using the percolation theory. Finally, the interplay between the functional properties and the beta phase is discussed in detail

Multi-criteria assessment to screen climate smart rice establishment techniques in coastal rice production system of India

Introduction: Conventional rice production techniques are less economical and more vulnerable to sustainable utilization of farm resources as well as significantly contributed GHGs to atmosphere. Methods: In order to assess the best rice production system for coastal areas, six rice production techniques were evaluated, including SRI-AWD (system of rice intensification with alternate wetting and drying (AWD)), DSR-CF (direct seeded rice with continuous flooding (CF)), DSR-AWD (direct seeded rice with AWD), TPR-CF (transplanted rice with CF), TPR-AWD (transplanted rice with AWD), and FPR-CF (farmer practice with CF). The performance of these technologies was assessed using indicators such as rice productivity, energy balance, GWP (global warming potential), soil health indicators, and profitability. Finally, using these indicators, a climate smartness index (CSI) was calculated. Results and discussion: Rice grown with SRI-AWD method had 54.8 % higher CSI over FPR-CF, and also give 24.5 to 28.3% higher CSI for DSR and TPR as well. There evaluations based on the climate smartness index can provide cleaner and more sustainable rice production and can be used as guiding principle for policy makers.publishedVersio

Structural, Vibrational, Dielectric, Ferroelectric and Electrical Properties of (1-x) Na0.5Bi0.5TiO3–x BaTiO3 Solid Solutions and The Effect of Ion Irradiations on Functional Properties of Ferroelectric Ceramic-Polymer Composites

Dielectric oxides are an important class of materials, which are widely used in modern electronic and optoelectronic device applications. Ferroelectrics are the non-linear dielectrics, which possess piezoelectric, pyroelectric, and ferroelectric properties. Ferroelectric ceramic oxides are extensively utilized in various devices such as piezoelectric sensors, actuators, IR detectors, capacitors, energy storage, energy harvesting, and memory devices due to their outstanding physical properties. Among the different structural families, ferroelectric oxides belonging to the perovskite structure are widely used due to the possibility of tuning the physical properties as per the requirement of device applications. In order to further enhance the electromechanical, dielectric and ferroelectric properties, the fabrication of solid solutions with different types of perovskites are one of the suitable approaches. Around the morphotropic phase boundary (MPB) compositions of the ferroelectric solid solutions, anomalous enhancement of dielectric permittivity, polarization, electromechanical and piezoelectric properties are observed. In view of the processing and environmental issues pertaining to leadbased ferroelectric materials, investigations on lead-free ferroelectrics are carried out intensively in recent years. The 1st part of this work is mainly focused on the synthesis and characterization of high quality lead free ferroelectric ceramic oxides having general formula: (1-x) Na0.5Bi0.5TiO3–x BaTiO3 (NBT-BT) solid solutions (x = 0.00, 0.02, 0.04, 0.05, 0.06, 0.07, 0.08 and 0.10). Among the available lead free ferroelectric ceramics, the A-site distorted perovskite (Na0.5Bi0.5)TiO3 (NBT) system has drawn immense attention due to their excellent dielectric, and ferroelectric properties. However, it has some limitations such as (i) high coercive field, (ii) high conductivity, (iii) high dielectric loss and (iv) high leakage current, which is against the use of this system in various device applications. In order to overcome these limitations, fabrication of solid solutions of NBT with BaTiO3 (BT) system has been studied. The NBT-BT ceramics are prepared by sol–gel auto combustion method followed by the sintering using microwave sintering technique. Structural, vibrational, dielectric, ferroelectric, and electrical properties of NBT-BT solid-solution are investigated using a wide variety of experimental techniques. The formation of single phase material with perovskite structure is confirmed from the X ray diffraction (XRD) patterns. A compositional driven structural phase transition from R3c (x = 0.0 to 0.05) to P4mm (x = 0.08 to 0.10) through an intermediate co-existence of R3c + P4mm (x = 0.06 and 0.07) is observed from X-ray Rietveld refinement and Raman spectroscopic studies. Existence of MPB composition has been observed in (1-x) Na0.5Bi0.5TiO3–x BaTiO3 solid solutions at x = 0.06. The same observation is also clearly seen in Raman spectroscopic studies. The scanning electron micrographs confirmed the presence of grains and grain boundaries with dense microstructure. It has been found that the grain size decreases with increasing of BaTiO3 (BT) concentration. The ferroelectric property has been studied by measuring P-E hysteresis loop after electrical poling and observed enhanced and welldeveloped ferroelectric loops after poling the ceramic samples. The highest polarization (2Pr O is observed for x = 0.06 sample. This enhancement of the ferroelectric properties could be resulted due to the presence of the MPB, i.e. the presence of both the rhombohedral and tetragonal phases. The temperature variation of dielectric properties shows two types of phase transitions such as (i) Relaxor ferroelectric to ferroelectric (TFR) and (ii) ferroelectric to paraelectric (FE-PE) phase transition (Tm or TC), for all compositions. It has been observed that the value of Tm is decreased with the increasing x, whereas there is a decrease in value of TFR with increase in composition up to x = 0.06 and thereafter it increases again. On the other hand, the value of dielectric permittivity at Tm (εrmax) increases with an increase in the composition up to x = 0.06 but with further increasing x, it decreases. The observed maximum value of dielectric permittivity at Tm and a minimum value of TFR for x = 0.06 may be due to the existence of MPB. Complex impedance, complex electrical modulus formalism, and frequency dependent ac conductivity analysis have also been carried out to study the relaxation and conduction mechanism. The presence of grain- and grain boundary contribution to impedance spectra in NBT–BT ceramics are analyzed using complex impedance plot (Nyquist plot) in association with complex modulus plot. The experimental data of these materials are fitted using suitable equivalent circuit to explain the electrical response of the materials. The frequency dependent of ac conductivity of these materials fits well with the double power law. The demand for miniaturized, flexible and light weight devices, leads to the development of flexible dielectric materials. There are two types of dielectric materials namely ceramics and polymers are widely used for storing the capacitive energy in capacitor. In view of this, ferroelectric polymer ceramic composites are one of the important R & D activities in the field of materials science. The polymer matrix in the polymer composites has the functionalities such as flexibility, easy processing, low cost and exhibit high breakdown strength. However, polymers are the materials having low dielectric permittivity. On the other hand, ferroelectric ceramic oxides have high dielectric permittivity but low breakdown strength. Therefore, the fabrication of ceramic-polymer composites can be a suitable solution for the problems associated with the ceramics and polymers, when considered separately for the energy storage. Solution-casting technique is used to prepare the free standing and flexible ferroelectric ceramic- polymer composite having general formula PVDF (Polyvinylidene fluoride) + ϕ wt.% of 0.94(Na0.5Bi0.5TiO3)-0.06BaTiO3 (BNBT) (ϕ = 0, 5, 10, 15, 20, 25, 30, 35, 40 and 50) with 0-3 connectivity. This MPB composition BNBT has been chosen as filler as it possesses high dielectric permittivity and maximum polarization in the entire BNBT series. The semicrystalline nature and formation of composite due to the addition of BNBT filler to PVDF is confirmed from XRD analysis. The surface morphology of the prepared samples is studied using Field Emission Scanning Electron Microscope (FE-SEM), which shows the presence of spherulite and homogeneous distribution of ceramic filler particles in PVDF confirming the semicrystalline nature of the samples. In the polymeric chain of PVDF, systematic packing of parallel dipoles of fluorine atoms on one side yields higher electronegativity and hydrogen atoms on the other side (less electronegativity as compared to fluorine) with carbon as a backbone results in polar β-phase. FTIR and XRD results suggest that the fraction of the electro active β-phase increases with increase in filler concentrations and peaked for 35 wt.% of the ceramic filler. The increase in the fraction of β-phase has been explained based on ion (negatively charged surface ion of the ferroelectric ceramic filler)-dipole (-CH2 dipole of the polymer matrix) interactions, as evidenced from FTIR spectra. It has been observed that dielectric permittivity keep on increasing with addition of ceramic filler up to 35 wt.%. However, above 35 wt.% a decrease in the dielectric permittivity value has been observed for all the frequencies. Swift Heavy Ion (SHI) irradiation is one of the most effective, powerful and emerging techniques for tailoring the physico-chemical properties of the material suitable for a particular application. The effect of Swift Heavy Li3+ ion beam (50 MeV) irradiation with different fluence (ranging from 1×1011 to 3.3×1013 ions/cm2) on the structural, morphological, vibrational, dielectric and ferroelectric properties of PVDF and PVDF + 35 wt.% BNBT (PVDF-BNBT) composite are studied. XRD patterns show an increase of β-phase and degree of crystallinity upon irradiation for the respective films. The scanning electron microscopic study showed a systematic increase in the spherulites size with irradiation. Dielectric permittivity and ferroelectric polarization of PVDF and PVDF-BNBT composite is increased with increase of fluence and the highest value is observed for the highest fluence. So the interaction of Li3+ ions with polymer composite leading to the enhancement β-phase, which plays the decisive role for the enhancement of the functional properties such as dielectric and ferroelectric propertie

Impedance spectroscopic study on microwave sintered (1-x) Na0.5Bi0.5TiO3-x BaTiO3 ceramics

Complex impedance spectroscopic technique has been implemented to study the detailed electrical transport properties of Lead free ferroelectric ceramic solid solutions of (1 - x) Na0.5Bi0.5TiO3-x BaTiO3 (NBT-BT) (0.00 <= x <= 0.10). The NBT-BT ceramics have been synthesized by sol-gel auto combustion method and sintered via microwave sintering technique. Room temperature X-ray diffraction patterns confirmed the formation of the single phase materials with perovskite structure. The surface morphology of the samples has been studied using field emission scanning electron microscopic (FESEM) technique. The FESEM micrographs confirm that the grain size decreases with increasing BaTiO3 (BT) concentration. Complex impedance, complex electric modulus formalism, and frequency dependent ac conductivity analysis have been used to study the relaxation and conduction mechanism in these materials. The presence of grain- and grain boundary contribution to impedance spectra in NBT-BT ceramics were analyzed using complex impedance plot in association with complex modulus plot. The grain- and grain boundary contributions were discerned in NBT-BT ceramic through least-squares fitting of the experimental data with a suitable equivalent circuit model. Complex impedance and complex electric modulus spectroscopic analysis indicate that the dielectric relaxation in these materials are of non-Debye type. A negative temperature coefficient of resistance (NTCR) behavior of our NBT-BT ceramics was seen from the temperature dependent conductivity studies. We have obtained similar activation energies from the conduction and relaxation process

Impedance spectroscopic study on microwave sintered (1-x) Na0.5Bi0.5TiO3-x BaTiO3 ceramics

Complex impedance spectroscopic technique has been implemented to study the detailed electrical transport properties of Lead free ferroelectric ceramic solid solutions of (1 - x) Na0.5Bi0.5TiO3-x BaTiO3 (NBT-BT) (0.00 <= x <= 0.10). The NBT-BT ceramics have been synthesized by sol-gel auto combustion method and sintered via microwave sintering technique. Room temperature X-ray diffraction patterns confirmed the formation of the single phase materials with perovskite structure. The surface morphology of the samples has been studied using field emission scanning electron microscopic (FESEM) technique. The FESEM micrographs confirm that the grain size decreases with increasing BaTiO3 (BT) concentration. Complex impedance, complex electric modulus formalism, and frequency dependent ac conductivity analysis have been used to study the relaxation and conduction mechanism in these materials. The presence of grain- and grain boundary contribution to impedance spectra in NBT-BT ceramics were analyzed using complex impedance plot in association with complex modulus plot. The grain- and grain boundary contributions were discerned in NBT-BT ceramic through least-squares fitting of the experimental data with a suitable equivalent circuit model. Complex impedance and complex electric modulus spectroscopic analysis indicate that the dielectric relaxation in these materials are of non-Debye type. A negative temperature coefficient of resistance (NTCR) behavior of our NBT-BT ceramics was seen from the temperature dependent conductivity studies. We have obtained similar activation energies from the conduction and relaxation process

Dielectric/ferroelectric properties of ferroelectric ceramic dispersed poly (vinylidene fluoride) with enhanced beta-phase formation

Free standing and flexible ferroelectric ceramic-polymer composites (PVDF + Phi wt% of BNBT (0.94Na(0)(.)(5)Bi(0)(.)(5)TiO(3)-0.06BaTiO(3))) with 0-3 connectivity were synthesized by solution-casting technique. Composite nature and homogeneous distribution of ceramic filler particles in PVDF were confirmed with x-ray diffraction and scanning electron microscopic analysis. The intensity ratio of beta-phase with respect to alpha-phase i.e., I-20(.2)./I-18.4. (obtained from XRD analysis) and the fraction of electro-active beta phase i.e., F(beta)% (obtained from FTIR analysis) are enhanced with increase in filler concentrations and peaked for 35 wt% of the ceramic filler. An enhancement of the % of crystallinity (calculated from XRD analysis) has been observed with increase in the filler concentrations. The increase of the fraction of beta-phase has been explained on the basis of ion (negatively charged surface ion of the ferroelectric ceramic filler) -dipole (-CH2 dipole of the polymer matrix) interactions, as evidenced from FTIR and UV-VIS absorbance spectra. Relative dielectric permittivity (dielectric constant) and ferroelectric polarization were found to be highest for the composite with 35 we% of ferroelectric ceramic filler. Percolation theory has been successfully employed to explain the observed trend in the dielectric properties with the compositional variation. Significant enhancement in the electro active beta-phase has been correlated with the improved dielectric and ferroelectric properties of the composite

Sintering dependent Ca2+ solubility in barium titanate synthesized by sol-gel auto combustion method

We report the preparation of ferroelectric Ba0.7Ca0.3TiO3 (BCT) ceramics by sol-gel auto combustion technique and its specific functional properties. The structural, dielectric and ferroelectric properties of BCT are strongly depending on the sintering temperature which also improves the phase purity and crystalline quality of the system. The formation of single-phase BCT is realized by sintering at 1450 degrees C for 4h. suggesting the solubility limit of Ca2+ cation. Grain size and relative density are increased as the sintering temperature increased. The Rietveld refinement technique is employed for the detailed crystal structural analysis. The temperature and frequency dependent dielectric properties are investigated; the measured dielectric constant is epsilon(r)=2680at the transition temperature T-c=120 degrees C for the single phase ferroelectric BCT. Sintering and electrical poling improved the shape of the hysteresis curve and reduced the leakage current. Electrical conduction mechanism is also discussed

Enhanced functional properties of soft polymer-ceramic composites by swift heavy ion irradiation

The physical and chemical properties of soft polymer-ceramic composites with 50 MeV swift heavy, Li3+ ion irradiation were studied. A solution-casting technique was employed to synthesize free standing, flexible composite films of ferroelectric polymer PVDF and ferroelectric ceramic BNBT mixtures with 0-3 connectivity. However, only 35 wt% ceramic was chosen for the study as it showed the highest dielectric constant and enhanced ferroelectric properties without irradiation. The effects of ion irradiation on the structural, microstructural, morphological, dielectric and ferroelectric properties of this particular composition were systematically investigated and conclusions were drawn. The mechanism for the enhancement of the electroactive beta-phase due to the swift heavy ion irradiation was discussed and the enhancement was well correlated with its ferroelectric and dielectric properties