Dense and fine-grained (Na 0.535 K 0.485 ) 1Àx Li x (Nb 0.8 Ta 0.2 )O 3 (x 5 0.02-0.07) (abbreviated as NKL x NT) lead-free piezoceramics were fabricated by spark plasma sintering (SPS), followed by postannealing in air. All the NKL x NT ceramics showed single perovskite structures with a phase transition from an orthorhombic symmetry to a tetragonal one across a composition region of 0.04oxo0.05. The sample with a composition of x 5 0.05 had the maximum values of piezoelectric coefficient (d 33 5 243 pC/N) and planar electromechanical coupling coefficient (k p 5 46.1%), and other good properties such as Q m 5 85, e r 5 1240, and tg d 5 0.023. Because of the enhanced densification and refined microstructure, the SPSprocessed NKL x NT ceramics also had better fracture strength than that prepared by normal sintering.

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Piezoelectric nanostructures have many important applications in nanodevices and micro‐electro‐mechanical systems. This work developed a topochemical method based on Molten‐Salt Synthesis for synthesizing one‐dimensional nanoscale single crystals of lead‐free (K,Na)NbO3 (KNN) piezoelectric oxides. The synthesis process started from molten‐salt reaction between Nb2O5 powders and KCl to produce high‐aspect‐ratio K2Nb8O21 bar‐shaped particles which were transformed to Nb2O5 nanobars via ion‐exchange and thermal decomposition steps, and finally, KNN nanobars were formed also by molten‐salt reaction among Nb2O5 nanobars as templates, and K2CO3 and Na2CO3 in KCl salts. The as‐synthesized KNN nanobars were proved to be single crystals by transmission electron microscopy. The piezoelectricity of an individual KNN nanobar was confirmed by scanning probe microscopy, as the effective piezoelectric coefficient d33* was measured to be 113 pm/V.

Monodisperse hematite (α-Fe2O3) nanoparticles were synthesized by forced hydrolysis of acidic Fe3+ solution. Rietveld analysis was applied to the X-ray powder diffraction data to refine the lattice constants and atomic positions. The lattice constants for a hexagonal unit cell were determined to be a ∼ 0.50327 and c ∼ 1.37521 nm. High resolution transmission electron microscopy was employed to study the morphology of the particles. Atomic scale micrographs and diffraction patterns from several zone axes were obtained. These reveal the high degree of crystallinity of the particles. A series of observations made on the particles by tilting them through a range of ±45° revealed the particles to be micaceous with stacking of platelets with well defined crystallographic orientations. The Morin transition in these nanoparticles was found to occur at 210 K, which is lower temperature than 263 K of bulk hematite. It was ascertained from the previous Mössbauer studies that the spin orientation for nano-sized hematite particle flips from 90° to 28° with respect to the c-axis of the hexagonal structure during the Morin transition, which is in contrast to that observed in bulk hematite where spin orientation flips from 90° to 0°.

Magnetic nanoparticle (MNP)-based solder composites can facilitate solder reflow in AC magnetic fields. We compare power loss in a solder composite sample with MNP loading of different particle size distribution. Scaling of solder composite samples shows that, for smaller samples, power loss is not sufficient to realize solder reflow temperature. Additional heating can be derived from eddy current losses in Cu planes in the substrate board. Eddy current heating in Cu sheets of various thickness were evaluated to quantify their effect for low-temperature electronic assembly.