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There is a growing interest in BiFeO3-based alloys because of the possibility it offers for developing high-temperature high-performance piezoelectric materials and for their interesting multiferroic properties. Often such ceramics are synthesized with additives either to reduce/suppress leakage current that the system inherits from the parent compound BiFeO3 or to promote sintering via formation of the liquid phase. We demonstrate here the propensity for stabilizing ferromagnetism in the ferroelectric solid solution BiFeO3–PbTiO3 (BF–PT) when synthesized with additive MnO2. Detailed investigation revealed that the ferromagnetic property of the ceramic is extrinsic and caused by the additive enabled precipitation of trace amount of the ferrimagnetic Pb-hexaferrite phase, not easily detected in conventional x-ray diffraction measurements. We also show that the ferromagnetic property is induced in Co-modified BF–PT. However, in this case, the additive stabilizes the CoFe2O4 spinel ferrite phase. While our findings offer a strategy to develop particulate magnetoelectric multiferroic composites using additive assisted precipitation of the ferrimagnetic phase(s) in BiFeO3-based ferroelectric alloys, it also helps in better understanding of the electromechanical response in BFO-based alloys. [ABSTRACT FROM AUTHOR]

The use of additives as a sintering aid for promoting densification is well-known in processing structural ceramics. In leaky ferroelectric ceramics (e.g., BiFeO 3 -based systems), additives are also used to reduce the leakage current, improve the poling efficiency and the piezoelectric response of a material. A less investigated aspect is how additives affect the multiferroic (ferroelectric and magnetic) features of BiFeO 3 -based ceramics. In this work, we report a systematic study of the effect of different additives viz, MnO 2 , CuO, K 2 CO 3 and KMnO 4 on the microstructural, electromechanical, and magnetic properties of Dy-modified BiFeO 3 –PbTiO 3. We found that all the additives help in the precipitation of the ferrimagnetic dysprosium iron garnet phase. The additives containing potassium (K) tend to suppress the grain size. We found that the best combination of ferroelectric and ferromagnetic behaviour was found in a mixture of additives. [ABSTRACT FROM AUTHOR]

We report here the synthesis of a self-grown 0–3 particulate multiferroic composite by controlled precipitation of the ferrimagnetic garnet phase using additive (MnO2) assisted sintering of a multi-cation ferroelectric system (Bi, Pb, Dy)(Fe, Ti)O3. The particulate multiferroic composite derived in this manner exhibits a favorable microstructure, wherein, although the volume fraction of the garnet phase is kept low (6%), which helps in retaining the electrical insulating character of the specimen, the number fraction of the garnet grains vis-à-vis the ferroelectric grains is ∼1:1. The composite shows a nearly ∼50% increase in saturation polarization at room temperature under a modest magnetic field of 1 T, suggesting a considerable improvement in ferroelectric domain switching due to the efficient strain transfer from the minority garnet grains to the majority piezoelectric grains. [ABSTRACT FROM AUTHOR]

Polymer Solar cells being flexible, light weight, inexpensive, colorful and large area devices, portend potential for large scale grid power generation. The first major breakthrough in organic solar cell performance came in 1986 when Tang discovered that much higher efficiencies about 1% can be attained when electron donor (D) and electron acceptor (A) are brought together in one cell. With the discovery of photo induced electron transfer from a conjugated polymer to fullerene molecules in 1992, the bulk heterojunction (BHJ) polymer solar cell has become the most successful device structure developed in the field till date. Poly(3-hexyl thiophene) (P3HT) has been the subject of intensive investigations upto 2008 yielding power conversion efficiencies (PCEs) around 5-6%. OPV technology has grown during the past decade with cell efficiencies quadrupling. As alternative route of higher performance, two or more single cells can be combined in tandem structure. The most efficient tandem organic solar cell reported by Yang Yang's group has 8.62% power conversion efficiency (PCE) which has been further improved with an NREL - certified PCE of 10.6%. An overview of the above will be presented in this paper. [ABSTRACT FROM AUTHOR]

Abstract: Novel flocculant based on amphoteric amylopectin for wastewater and industrial effluents treatment has been developed in authors’ laboratory. Amphoteric flocculants have anionic and cationic moieties on the same macromolecule and is used to remove both positively and negatively charged contaminant particles in suspensions. Amylopectin based flocculants have been found to be highly efficient flocculant and hence it has been chosen as base polysaccharide. By grafting of polyacrylamide and subsequent hydrolysis, anionic amylopectin has been synthesized. Afterwards, a cationic moiety has been inserted both by chemical/microwave processing. The flocculation efficiency of the amphoteric amylopectin has been tested in kaolin and iron ore suspensions. The results indicate its high efficiency in comparison with anionic, grafted, and base amylopectin. The amphoteric amylopectin prepared via microwave irradiation showed best flocculation efficiency. [Copyright &y& Elsevier]

One of the important requirements for piezoelectric materials for use as high strain actuators is that they exhibit large unipolar electrostrain with minimum hysteresis. While large unipolar electrostrain >1% is generally achievable in good quality single crystals, most polycrystalline piezoelectric show low values < 0.4%. Unipolar electrostrain 0.5%–0.7% in polycrystalline piezoelectrics has often been reported in Na0.5Bi0.5TiO3-based compositions at the non-ergodic ergodic boundary. Not amenable to poling, such materials exhibit almost nearly zero direct piezoelectric coefficient (d33 ∼ 0 pC/N) and cannot be simultaneously used as a sensor. In this paper, we report a combination of large unipolar electrostrain of ∼0.6% with small strain hysteresis of 25% in a Sn-modified relaxor ferroelectric system PbTiO3–Bi(Ni1/2Zr1/2)O3. It exhibits d33 ∼ 340 pC/N, which is stable up to 130 °C, and large signal converse piezoelectric coefficient d33* ∼ 1200 pm/V. A combination of large d33 and d33* in the same material makes it an important candidate for simultaneous use as a sensor and high strain actuators. X-ray diffraction study in situ with the electric field suggests that large electrostrain with low strain hysteresis in this system is because of the increased reversible switching of the field stabilized tetragonal ferroelastic domains. [ABSTRACT FROM AUTHOR]

The synthesis of novel cationic flocculants based on amylopectin (AP), acrylamide (AM) and (3-acrylamidopropyl) trimethylammonium chloride (ATMAC) were done by free radical polymerization using ammonium persulphate (APS) as an initiator. Three different grades of novel cationic flocculants (AP- g -C 1 to AP- g -C 3) were synthesized by varying the proportion of acrylamide and (3-acrylamidopropyl) trimethylammonium chloride monomers. Through the hydrolysis of these flocculants, in presence of NaOH, three different grades of amphoteric polymers (AP-AT-C 1 to AP-AT-C 3) were synthesized. The synthesized polymers were characterized by various methods, namely, infrared spectroscopy, NMR spectroscopy, thermal analysis, viscosity measurement, scanning electron microscopy and X-ray diffractometry. The flocculation performance of AP- g -C and AP-AT-C were studied in kaolin suspension using jar test and settling test methods at neutral pH. Dye (Methylene blue) removal tests were performed using polymer beads and analysed by UV–vis spectroscopy. [ABSTRACT FROM AUTHOR]