The field of lead-free piezoceramics, which aims to replace lead zirconate titanate (PZT) and related perovskite materials, has been vibrant for almost 15 years. Once the science in this field attained a certain stage of maturity, materials with properties better than PZT have appeared, and the first products are about to reach the marketplace. This article describes the three most promising lead-free piezoceramics currently under discussion to replace PZT. Each has a pronounced property profile geared for specific applications. Guidelines for directions for fundamental future research on as well as technology transfer to industry of lead-free piezoceramics are provided.

Sodium bismuth titanate (NBT) and its solid solutions with other ABO3 perovskites are of great interest for lead-free ferroelectric and piezoelectric applications. In this article, we provide an introduction to the complex structure of NBT, including atomic displacements and nanoscale defects. We also review poling effects and properties as well as NBT-ABO3 phase equilibria. The interesting relaxor properties, frequency dispersion in dielectric permittivity, and field-induced structural phase transitions of these systems are discussed. Finally, we describe other functional, mechanical, and electrical properties of NBT.

This article reviews a grounding in thin-film science and technology, an interest in combining materials science with applied physics and electrical engineering, and the active pursuit of collaborations with experts in other disciplines. That basis has enabled participation in the beginnings of integrated-circuit technology, the invention of new solar cells, the understanding of hydrogenated amorphous silicon for solar cells and thin-film transistors, the development of the principles of flexible, conformable, and stretchable electronics, and the devising and demonstration of large-area electronic systems.

Coherent cuboidal B2 nanoprecipitation in body-centered cubic (BCC)-based high-entropy alloys (HEAs) is important for the improvement of mechanical strength. The present work primarily investigated the effect of Ti substitution for Al on the cuboidal B2 nanoprecipitates in BCC Al0.7NiCoFeCr2 HEAs. A series of (Al,Ti)0.7NiCoFeCr2 HEAs with different Al/Ti ratios were prepared by suction-cast processing, and their microstructures and mechanical properties were then characterized comprehensively. It was found that the substitution of Ti for Al can change the phase structures of ordered precipitation, from the B2-AlNi to a highly ordered L21-Ni2AlTi phase. Especially, a small amount addition of Ti (≤4.2 at.%, Al/Ti ratio ≥2/1) renders the HEAs with cuboidal L21 nanoparticles coherently precipitated into the BCC matrix, which is attributed to the moderate lattice misfit (ε = 0.5–0.6%) between BCC and L21 phases. HEAs with such coherent microstructures exhibit high compressive yield strength of about 1700–1800 MPa. When the Ti content reaches up to 6.25 at.%, the matrix of the alloy will be turned into the σ phase, rather than BCC, leading to a heavy brittleness.

The search for lead-free alternatives to Pb(Zr,Ti)O3 (PZT) piezoelectric ceramics has become a major topic in functional materials research due to legislation in many countries that restricts the use of lead alloys and compounds in commercial products. This article examines both the necessity for regulation and the impacts those regulations have created in the context of piezoelectric materials. It reviews the toxicity of lead, describes current legislation to control the spread of lead in the environment, and attempts to define the risks associated with the manufacture, use, and disposal of lead-based piezoelectric materials. The consequences of current legislation, both intended and unintended, are examined.

We investigate the impact of increasing number density of self-catalyzed GaAs nanowires (NWs) on their crystal structure, grown by molecular beam epitaxy. To this end, we employ an iterative, lithography-free approach for varying the number density of self-catalyzed GaAs NWs grown on Si(111) covered with native oxide. We use scanning electron microscopy and x-ray diffraction in combination with simulations based on the extended Markov model for the morphologic characterization of the so obtained NWs. Our findings show how both the shape of the Ga-droplet and the NW crystal structure are affected even by relatively small changes of the wire number density, allowing for a quantification of its influence on the local NW growth conditions at nominally identical growth parameters.

Activation of persulfate (PS) by ultraviolet light or transition metal catalysts has been extensively studied. However, little is known about the activation of PS by iron oxychloride (FeOCl) in the presence of visible light irradiation. Herein, the catalytic activity of FeOCl was developed for oxidative degradation of rhodamine B (RhB) with the FeOCl/PS/Vis process. The characterization of FeOCl for reaction kinetics, degradation mechanism, and catalyst stability was investigated. It is found that the redox cycle of iron species and photoinduced electrons formed on the FeOCl catalyst surface can effectively activate PS, to generate radicals. Based on quenching experiments and electron paramagnetic resonance, the photogenerated holes (h+) and sulfate radicals (SO4−•) are the predominant reactive oxidants for RhB decolorization, while superoxide radicals (•O2−) and hydroxyl radicals (•OH) are also involved. Moreover, FeOCl shows good catalytic performance in a wide range of pH values (pH = 3–10) and excellent reusability and stability, as well.

The flow of particles through confined volumes has appeared under different contexts in nature and technology. Some examples include the flow of red blood cells or drug delivery vehicles through capillaries, or surfactant-based particles in nano- or microfluidic cells. The molecular composition of the particles along with external conditions and the characteristics of the confined volume impact the response of the particle to flow. This review focuses on the problem of phospholipid vesicles constrained to flowing in channels. The review examines how experimental and computational approaches have been harnessed to study the response of these particles to the flow.

Effective degradation of organic pollutants in wastewater is of great importance to the environment and human society. TiO2-based electrospun nanofibrous materials combining the properties of the large specific surface area, high aspect ratio, tunable compositions and structures, as well as easy to recycle, show great promise for the efficient removal of organic pollutants. In this Prospective paper, the recent progress in the degradation of organic water contaminants over visible-light-responsive TiO2-based nanofibrous materials is summarized, with emphasis on the strategies for improving the visible-light photocatalytic activity of TiO2-based nanofibrous materials. Finally, the current challenges and future outlook in this field are discussed.

Lithium (Li) dendrite formation in Li-metal batteries (LMBs) remains a key obstacle preventing LMBs from their widespread application. This study focuses on the role of the stress field in the Li electrodeposits formation and growth. Coupled electrochemical and mechanical phase-field model (PFM) is used to investigate electrodeposited Li evolution under different conditions. The PFM results, using both the anisotropic elastic properties of Li and the random delivery of Li-ions through the solid electrolyte interface, show a significant local stress development indicating a direct correlation between the stress field and the origin of the undesired Li filaments initiation.

The use of copper hydroxyphosphate (Cu2PO4OH), also called libethenite, as a near-infrared (NIR) absorbing additive has been investigated. Samples were synthesized by using a hydrothermal treatment or simple wet chemical processing, which was later easily upscaled. All synthesized samples showed a strong absorption in the NIR region. Trials were conducted to produce laser-marked plastic plates and security IR ink printing tests. It was found that when incorporated in plastic and ink formulation, Cu2PO4OH added good NIR absorption properties without influencing other finished product properties too much, which confirms that it is a suitable additive that can be readily manufactured at room temperature and without pressured equipment.

In this study, Au-based nanoglasses in the form of thin films deposited by magnetron sputtering are comparatively dealloyed. The films have either nanograined or nanocolumnar microstructure, depending on the working pressure of Ar in the sputtering chamber. Nanocolumnar thin films exhibit much higher dealloying rate reducing effectively the dealloying time with respect to nanograined and homogenous thin films. Electrocatalysis experiments indicate that the resulting nanoporous films are active for the methanol electrooxidation, with promising results in term of stability especially for the dealloyed nanocolumnar film.

The topological insulator/superconductor heterostructure is one of the most promising platforms to create and manipulate Majorana bound states. Here, we used molecular beam epitaxy to grow high-quality (Bi0.5Sb0.5)2Te3 films on Nb surfaces. To promote proper (Bi0.5Sb0.5)2Te3 film nucleation in the early growth stage, we developed a two-step growth method. Bi, Sb, and Te clusters were first evaporated at a low temperature of 180 °C, which is below the typical growth temperature and then annealed to form a crystalized passivation layer. Second, a standard (Bi0.5Sb0.5)2Te3 film was grown under the normal deposition temperature of 280 °C. We used reflection high-energy electron diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction to further characterize the (Bi0.5Sb0.5)2Te3 film and passivation layer quality. Finally, the top Nb film was laid down by magnetron sputtering at room temperature. The hetero-Nb/epitaxial (Bi0.5Sb0.5)2Te3/Nb stacks were further fabricated into micro-Josephson junctions and showed clear Josephson currents demonstrating an excellent material quality.