Until now, lead zirconate titanate (PZT)-based ceramics are the most widely used in piezoelectric devices. However, the use of lead is being avoided due to its toxicity and environmental risks. Indeed, the attention has been moved to lead-free ceramics, especially on potassium sodium niobate (KNN)-based materials, due to growing environmental concerns. These materials are technologically interesting. For applications such as actuators, an electromechanical coupling providing high strain with high force, e.g, fuel injection, ultrasonic motor, etc., is required, Moreover, in the current context, the new technologies evolve toward the miniaturization of the conventional electronic devices. Herein, we have developed microfiber ceramics of KNN-based composition, which yield a high strain value with S max as high as 0.17% at 3 kV mm −1 . According to our results, this phenomenon can be explained by an extrinsic effect that favors the internal relaxation of the system. To reach this breakthrough, a sintering mechanism has been established, which allows for correlating the extrinsic factors of the system with electromechanical properties of the ceramic fibers. We believe that the general strategy and design principles described in this study will open new avenues in developing of (K,Na)NbO 3 -based lead-free piezoelectric fibers with enhanced properties for high-precision sensor and actuator applications.

Lead-free piezoelectric materials have grown in importance through increased environmental concern and subsequent EU and worldwide legislation, with the aspiration to reduce the use of Pbbased materials in all sectors. Integration of the next generation of lead-free piezoelectric materials with substrates to form functional micro devices has received less attention. Low temperature synthesis methods for K 0.5 Na 0.5 NbO 3 powder were developed to overcome the issue of poor purity of the final product during high temperature sintering. Molten hydroxide synthesis (MHS), derived from molten salt synthesis (MSS), has been developed to overcome a Na ion preference in the molten salt synthesis reaction that leads to NaNbO 3 production instead of K 0.5 Na 0.5 NbO 3 when stoichiometric amounts of precursors are used. MHS makes use of a KOH molten reaction aid in place of the NaCl/KCl molten salt mix of the MSS. In a two stage reaction K rich intermediate niobates are produced and subsequent reactions with Na species produce KNN.

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Abstract:In this paper, we report on the reaction of phenol benzoylation with benzoic acid, which was carried out in the absence of solvent. The aim of this reaction is the synthesis of hydroxybenzophenones, which are important intermediates for the chemical industry. H-beta zeolites offered superior performance compared to H-Y, with a remarkably high conversion of phenol and high yields to the desired compounds, when using a stoichiometric amount of benzoic acid. It was found that the reaction mechanism did not include the intramolecular Fries rearrangement of the primary product phenyl benzoate, but indeed, the bimolecular reaction between phenyl benzoate and phenol mainly contributed to the formation of hydroxybenzophenones. The product distribution was greatly affected by the presence of Lewis-type acid sites in H-beta; it was suggested that the interaction between the aromatic ring and the electrophilic Al 3+ species led to the preferred formation of o-hydroxybenzophenone, because of the decreased charge density on the C atom at the para position of the phenolic ring. H-Y zeolites were efficient than H-beta in phenyl benzoate transformation into hydroxybenzophenones.

This paper describes the production of spherical-shaped lead zirconate titanate (PZT) nanoparticles by the electrohydrodynamic atomisation (EHDA) process in order to make inks suitable for ink jet printing applications. PZT sols with different concentrations (0?1-0?6 M) were used as starting materials. Two different heating systems, gas heating and direct heating, were used in order to remove the solvent, reduce the particle size and stabilise the PZT particles. Several aspects have been considered, such as liquid flow rate, sol concentration and heat system temperature, and their influence on the particle dimension is determined. Using optimised processing parameters of direct heating at 520uC, 0?2 M precursor sol, flow rate of 0?2 mL h -1 and field of 3 kV cm -1 , particles of 100-300 nm in diameter were synthesised. Following stabilisation at 300uC, the particles were suspended in a PZT sol to produce an ink suitable for ink jet printing.

Ferroelectric fibers based on a commercial lead zirconium titanate powder were investigated by a new characterization method to measure single fiber properties, such as large signal polarization and longitudinal free strain, and small signal properties, such as piezoelectric constant. To verify the measurements, the free strain data were compared with dynamic mechanical analyzer measurements. For this investigation, lead zirconate titanate fibers were sintered in lead-rich atmosphere at different temperatures. Microstructure and phase composition were analyzed by scanning electron microscope and X-ray diffraction. By increasing the temperature from 1150°C to 1200°C, the electromechanical behavior of the fibers could be improved: an increase in remnant and saturation polarization occurred. A d 33 as of ;430 and ;400 pm/ V could be measured for 1150°C and 1200°C, respectively. These d 33 values are very close to the one reported on the data sheet of the material.